E PLURIBUS UNUM

NATIONAL TRA SPORTATIO

N

B OARD

SAFE T Y

N

National Transportation Safety Board 

Washington, D.C. 20594 

Marine Accident Brief 

Accident No.: DCA-03-MM-032 

Accident Type: Boiler rupture 

Vessel: Bahamas-registered passenger vessel S/S Norway

Location: Piers 1 and 2, Miami, Florida 

Date: May 25, 2003 

Time: 0637 eastern daylight time1

 

Owner/Operator: Norwegian Cruise Line 

Property Damage: $20-$23 million 

Complement: 911 crew 

2,135 passengers 

Fatalities/Injuries: Passengers: none 

Crew: 8 fatalities; 10 serious injuries; 7 minor injuries 

Introduction 

At 0637 on May 25, 2003, the Bahamas-registered passenger vessel S/S Norway

(figure 1), with 911 crewmembers and 2,135 passengers on board,2 suffered a boiler 

rupture in the aft boiler room. The accident occurred about an hour after the vessel had 

moored in Miami, Florida, at the end of a 7-day Caribbean cruise. As a result of the 

accident, 8 crewmembers sustained fatal injuries, 10 suffered serious injuries, and 7 

received minor injuries.3 No passengers were injured. 

1

 Times in this report are eastern daylight time, according to the 24-hour clock. 

2

 The crew was composed of Norwegian officers in the deck and engine departments. As is the case 

on most foreign-flag cruise ships operating in U.S. waters, members of the other shipboard departments 

comprised a variety of nationalities. 

3

 Title 49 Code of Federal Regulations section 830.2 defines a fatal injury as any injury that results in 

death within 30 days of an accident. It defines a serious injury as one that (1) requires hospitalization for 

more than 48 hours, commencing within 7 days from the date the injury was received; (2) results in a 

fracture of any bone (except simple fractures of fingers, toes, or nose); (3) causes severe hemorrhages, 

nerve, muscle, or tendon damage; (4) involves any internal organ; or (5) involves second- or third-degree 

burns, or any burn affecting more than 5 percent of the body surface. In the Norway accident, all the 

deceased sustained second- and third-degree burns on 50 to 100 percent of their body area and died from 

 NTSB/MAB-07/03
Figure 1. In 2003, the 43-year-old Norway (originally the S/S France) was one of the last 

of the steam-driven cruise ships operating out of U.S. ports. After the accident, the ship 

was removed from service and later sold for scrap. 

The Norway, owned and operated by Norwegian Cruise Line (NCL), was a 

conventional welded, steel-hulled liner, certificated for unrestricted international 

voyages. The ship met the regulations of the International Convention for the Safety of 

Life at Sea, 1960 (SOLAS 60), and the International Convention on Load Lines, 1966. 

After various upgrades in 1980, the vessel met the standards of the 1974 SOLAS 

Convention (SOLAS 74). 

The Norway was built by Chantiers de l’Atlantique (Penhoët-Loire) in SaintNazaire, France, and originally sailed under the French flag as the S/S France. When 

launched in 1960, the France was the longest oceangoing liner in the world. The France

operated primarily in the trans-Atlantic trade from the time of its construction until 1974. 

In 1979, the liner was sold to Klosters Rederi A/S,4

 one of Norway’s oldest shipping 

companies. Klosters had the vessel overhauled for its Caribbean cruising operations, 

which was run by its subsidiary, Norwegian Caribbean Lines.5

 Klosters renamed the 

vessel the S/S Norway in 1979 and registered it in Norway. Beginning in 1980, the 

Norway operated on Caribbean cruises that originated at Miami, and in 1987, the vessel 

was reflagged to the Bahamas flag. In October 2000, Star Cruises,6

 NCL’s parent 

company, announced that the Norway would be relocated to the Asian market, a decision 

that was later reversed. 

 thermal injuries or from complications from thermal injuries. Four crewmembers died the day of the 

accident; three died within 4 days; and the eighth man died 26 days later. 

4

 Klosters Rederi A/S/ became Kloster Cruise A/S in 1986. 

5

 The subsidiary was renamed Norwegian Cruise Line in 1987. 

6

 In 2000, Star Cruises, PLC, a Malaysian corporation, acquired NCL from Klosters. 

: 2 NTSB/MAB-07/03
The National Transportation Safety Board investigated the Norway accident under 

the authority of the Independent Safety Board Act of 1974 and according to Safety Board 

rules. The designated parties to the investigation were the U.S. Coast Guard; NCL; 

Bureau Veritas (BV), the classification society that inspected the Norway;

7

 Bahamas 

Maritime Authority, the vessel’s flag state; Siemens, the manufacturer of the vessel’s 

boiler control and monitoring system; and Lloyd Werft Shipyard, which performed or 

contracted out boiler repairs in Bremerhaven, Germany, in 1987 and 1990. 

In investigating the cause of the boiler rupture, the Safety Board reviewed the 

boiler repair history recorded in various company and classification society documents 

over the last 40 years (see “Boiler History” section). The Board also examined the 

operating practices and inspection procedures that affected boiler safety (see “Factors 

Affecting Boiler Life”). Representatives of the parties cooperated with the Board in its 

postaccident investigation (see “Postaccident Investigation and Findings”). 

Accident Description 

About 0400 on May 25, 2003, while the Norway was inbound through the 

channels leading to the Port of Miami (figure 2), the engineering watch changed. The 

second engineer, who was going off duty, said that he told his relief that there was 

nothing out of the ordinary to report about the boilers and that “all conditions were 

normal.” 

At 0529, the Norway moored at its berth at piers 1 and 2 on Dodge Island, the 

bridge watch ordered “finished with main turbines,” and the engineroom watch began to 

shut down the propulsion system in preparation for the ship’s port stay. The vessel’s four 

 7

 Classification societies such as BV are private, independent organizations that establish and apply 

technical standards for the design, construction, and survey (inspection) of ships. Classification societies 

are one of the elements of the maritime safety network. Other elements include ship owners, ship builders, 

national and international regulatory bodies, and insurance underwriters. The standards developed by 

classification societies are published in documents referred to as the classification society’s “Rules.” 

Currently there are over 50 classification societies in the world, and the 10 major classification societies, 

collectively representing about 94 percent of the world commercial tonnage, are members of an association 

known as the International Association of Classification Societies (IACS). International standards and 

regulations promulgated by the International Maritime Organization, the United Nations agency concerned 

with maritime safety and the prevention of marine pollution from ships, require ships to be designed, 

constructed and maintained in compliance with structural, mechanical, and electrical requirements of a 

recognized classification society or with applicable requirements of the flag administration, giving 

classification societies a prominent role in the international regulatory regime of vessel safety (SOLAS 

regulations at chapter II-1, part A-1, regulation 3-1). In addition, many countries (including the Bahamas 

and the United States) delegate responsibility for some regulatory functions to classification societies, such 

as inspection for compliance with certain national and international regulations and issuance of some safety 

certificates, and may also adopt class society rules as their own national standards. Ship classification is 

usually a requirement for a ship owner to obtain and maintain insurance coverage. 

: 3 NTSB/MAB-07/03
main propulsion boilers were located on the engine deck (deck No. 2; see figures 3 and 

4), in the next-to-aftermost main vertical zone.8

By 0600, the Norway was secured alongside the pier and crewmembers were 

starting the in-port routine, which included rigging gangways, discharging garbage, 

fueling, provisioning, offloading passenger baggage, and disembarking passengers. In the 

aft engine/boiler room, the watch was reduced from seven to six crewmembers when one 

of the second engineers received permission to leave before the end of the watch.9 On the 

Biscayne deck (deck No. 5), the second engineer was monitoring the boiler gauges and 

instruments in the engine control room aft of the boiler room (figure 5). He later stated, 

“All was normal.” No alarms were indicated, and he heard only “normal engine/boiler 

room sounds.” At the time, boiler No. 21 was not operating and boiler Nos. 22, 23, 

and 24 were operating and providing steam to vessel systems. The remaining five boiler 

room watchstanders were in the aft boiler room or in spaces next to it. 

Figure 2. Overall schematic of Port of Miami. 

 8

 A vessel meeting the standards of SOLAS 74 is divided along its length into main vertical zones by 

“A-60 class divisions,” that is, bulkheads that are insulated steel barriers designed to prevent the passage of 

smoke and flame from a fire for 60 minutes. 

9

 The 0400-to-0800 watch included three licensed crewmembers (one third engineer and two second 

engineers) and four unlicensed crewmembers. The third engineer was in charge of the boiler room and was 

there at the time of the accident. 

: 4 NTSB/MAB-07/03
: 

5 NTSB/MAB-07/03 NTSB/MAB-07/03
Figure 4. Plan view of decks 2 through 5 on Norway. 

: 6 NTSB/MAB-07/03
Figure 5. Layout of Norway’s aft boiler room, where boiler No. 23 ruptured (from copy of 

original drawing of S/S France boiler arrangement provided by NCL). Boilers were 

numbered to indicate whether they were in the forward (1) or aft (2) boiler room. Thus, 

No. 23 indicated the third boiler in the aft boiler room. The forward boilers were removed 

when the France was overhauled and renamed the Norway. 

About 0637, a boiler ruptured in the aft boiler room. The second engineer in the 

engine control room and other crewmembers said that they heard a “bang” and felt the 

vessel shake. Some crewmembers said they thought that something had struck the side of 

the vessel; others said they thought that a bomb had detonated. The second engineer who 

had gone off watch said that he was outside on the Olympic deck (deck No. 11) when he 

heard the bang, looked up to see “lots of black smoke from the aft smoke stack,” and 

knew that “something had gone very wrong in the boiler room.” 

Boiler No. 23, located on the starboard side of the boiler room, had ruptured. The 

boiler contained about 20 tons of water operating at a temperature of about 528o F under 

a pressure of about 60 bar (870 pounds per square inch [psi])10). In the normal 

atmospheric pressure of the aft boiler room (14.7 psi), the pressurized hot water rapidly 

expanded in volume about 1,260 times into steam.11 The expanding steam, mixed with 

smoke, soot, and debris, swept through the engineering spaces, fatally injuring four 

 10 One bar = 0.98692 atmospheric pressure at sea level = 14.504 psi. 

11 Water at that pressure and temperature will expand about 1,260 times into hot vapor/steam when 

the pressure is released to atmospheric pressure (Michael R Lindeburg, Mechanical Engineering Reference 

Manual for the PE [professional engineer] Exam, 11th ed. [Belmont, California: Professional Publications, 

Inc., 2001], appendix 24B, p. A-46). 

: 7 NTSB/MAB-07/03
engineering crewmembers who were on watch or on duty in or near the boiler room, as 

well as four other crewmembers who were in the crew living spaces on the starboard side 

of the Caribbean deck, next to the boiler room. 

Because of the height of the boilers (about 30 feet), the aft boiler room space 

extended from deck No. 2 to deck No. 4 (Caribbean deck). The Caribbean deck was the 

first level having living quarters—in this case, crew rooms forward, immediately 

outboard, and aft of the boiler room (figure 4). The boiler casing continued upward 

through the remaining decks, allowing the exhaust from the boilers to vent to the outside 

air through the aft smokestack. 

As the steam rose through the aft boiler room, it broke through the bulkheads on 

the starboard side of the Caribbean deck (No. 4) and the Biscayne deck (No. 5), 

breaching the crew accommodation areas and scalding six crewmembers in their rooms 

or in the corridors of the accommodation spaces. Seven crewmembers were preparing to 

rig a garbage gangway out the side port12 of the Biscayne deck when the steam entered 

the corridor near them. They sustained thermal burns on 6 to 20 percent of their bodies 

before escaping the scalding vapor by jumping overboard toward the pier, which was 

about 8 feet below the Biscayne deck. Three crewmembers who jumped from the side 

port landed in the water and four landed on the pier; one suffered a broken leg when he 

landed on the dock. A crewmember on vessel security detail at an aft gangway on the 

Biscayne deck suffered minor burns from the smoke and steam before he escaped down 

the gangway to the pier. In the 15 minutes immediately after the boiler rupture, about 125 

crewmembers exited the ship using the Biscayne deck gangway. 

At the time of the boiler rupture, a Miami-Dade police officer on routine patrol of 

the pier was within 100 feet of the Norway’s side port. He said that the blast momentarily 

stunned him, but that he recovered and immediately reported the accident and the injured 

crewmembers on the pier and in the water to his command, which alerted area response 

agencies. The police subsequently secured the pier area and did not allow anyone other 

than city response personnel to board the Norway, including crewmembers who had fled 

the ship and later attempted to reboard. 

In the meantime, on board the Norway, some of the injured crewmembers made 

their way to safety, including two men who took shelter in the main galley on the Atlantic 

deck (deck No. 6). The galley staff on duty immediately called the bridge to request 

medical help, thus alerting the bridge watch about the crew injuries. Within 5 minutes of 

the rupture, the bridge watch ordered the fire watch and emergency teams to muster.13

Ten minutes later, the master made a public address directing the passengers to their 

lifeboat muster stations. Table 1 chronicles the documented emergency response actions 

by shoreside agencies and shipboard personnel. 

 12 An opening in the hull through which a gangway can be rigged for the passage of cargo, luggage, 

provisions, garbage, or fuel hoses. When not in use, such ports are secured by hinged, watertight doors. 

13 To muster is to assemble at a prearranged place. 

: 8 NTSB/MAB-07/03
Table 1. Chronology of emergency activities. 

Time Event 

0637 Rupture occurs in boiler No. 23 in aft boiler room. 

Rupture activates sprinkler system in areas around boiler room as well as smoke alarms locally 

in affected areas and remotely in wheelhouse. 

Pier-side Miami-Dade police officer radios report of accident to his command. 

0638 Boiler automation system shuts down operating main boilers, which stops steam turbine 

generators and causes loss of main electrical power. Ship’s battery-operated emergency 

systems activate and function as designed. 

0640 Emergency diesel generators automatically activate to provide emergency electrical power. 

Miami-Dade County Rescue Fire Department (MDFD) dispatches units to Norway. 

0641 City of Miami Department of Fire-Rescue (Miami Fire-Rescue) receives notice of accident and 

dispatches one unit at 0642. 

0643 After receiving report that injured people are in main galley, bridge watch broadcasts “Code 

Alpha in the main galley,” an alert for medical staff to muster there. 

0647 MDFD vehicles arrive at piers 1 and 2 and meet with Norway’s chief of security. MDFD 

responders perform pier-side triage of injured crew. 

0648 

to 

0654 

Shoreside response agencies continue to dispatch additional units to scene. Fire department 

assets total 41 units and one rescue boat. 

0650 Bridge announces “Code Alpha in the West Indies galley,” alerting medical staff to attend to 

more injury victims in that kitchen. 

0651 Bridge watch announces “Code Bravo” (alert for fire teams to muster). Bridge also sounds 

emergency alarm and orders all available crew to muster at emergency stations. Chief engineer 

organizes fire teams to check boiler room and engineroom for injured crewmembers. 

0652 Master makes public address system announcement informing passengers of accident and that 

everything is under control. Directs them to lifeboat muster stations on International deck (deck 

No. 10). 

0653 On-scene MDFD and Miami Fire-Rescue commanders confer, declare accident a mass casualty 

incident, and establish incident command post under direction of MDFD. 

0654 Miami Beach Fire Department (MBFD) rescue boat retrieves three crewmen from water. 

0657 Vessel’s chief firefighter briefs fire department’s on-scene commander and guides four MDFD 

firefighters on board Norway. 

0658 Master radios situation report to Coast Guard and calls his company by cellular telephone. 

0731 First passenger count at muster stations indicates 41 passengers unaccounted for. Cruise 

director makes announcements every 5 to 10 minutes on public address system from bridge to 

have passengers report to stations. 

0800 All passengers accounted for. Master assures passengers that everything is under control and 

that it is safe to return to staterooms. 

0820 Shoreside fire-rescue incident commander declares condition under control. 

0800 Bridge watch begins announcements advising passengers to disembark using gangway on 

Norway deck (deck No. 7). All passengers ashore by 0900. 

0901 Master orders abandon ship signal sounded. Several crewmembers are already ashore, and 

some depart the vessel on hearing abandon ship alarm. Several crew musters taken; final count 

indicates 103 unaccounted for. 

1045 All crewmembers accounted for. 

: 9 NTSB/MAB-07/03
After the accident, the shoreside response agencies and NCL critiqued the 

emergency response activities of their personnel and made procedural changes based on 

the findings of their reviews. A discussion of their actions is found in the “Postaccident 

Actions by Parties” section of this brief. 

The damaged Norway was towed to Germany, arriving in Bremerhaven on 

September 23, 2003. The ship remained moored at Bremerhaven awaiting a decision on 

whether it would be repaired and returned to service or taken out of service. In March 

2004, NCL announced that the Norway would not be returned to service and transferred 

ownership of the vessel to its parent company, Star Cruises, for eventual scrapping. The 

Norway was the only steam vessel operated by NCL. 

Boiler Information 

Operation 

The Norway’s boilers were water-tube, modified D-type14 units (figure 6). The 

boilers produced steam at about 60 bar (870 psi) pressure from water that was heated by 

oil-fired furnaces. The water was carried in tubes surrounding the furnace area 

(combustion chamber). Combustion air was routed from forced-draft fans to the five 

burners (fed with heavy fuel oil) fitted on the front of each burner. 

The Norway’s boilers had an upper steam drum, a lower water drum, and a 

waterwall header. The waterwall header (where the failure occurred in the accident) was 

about 29 inches in diameter and had manholes at each end. The drums and header 

connected the various banks of tubes surrounding the furnace area. The outer surfaces of 

the boiler were kept cool by waterwall tubes and refractory materials suitable for high 

temperatures,15 all of which were enclosed in an air-cooled steel casing. 

The steam drum served as the upper interface between the steam and the water. 

Steam traveled from the steam drum through an outlet pipe at the top to another set of 

tubes called the superheater. The superheater further raised the steam’s temperature and 

thus its energy level.16 Superheated steam went to the ship’s main propulsion turbines 

and auxiliary turbines. The turbines converted the thermal energy of the steam into 

mechanical energy and drove the Norway’s propellers and electrical generators. Steam at 

lower pressures and temperatures also heated the boiler’s fuel oil, produced distilled 

water, and warmed the ship’s living and work spaces, among other uses. 

 14 D-type boilers are so called because the position of the drums and the header appears to form the 

letter D. The Norway’s boilers were modified in that the waterwall headers were larger than in a normal Dtype boiler and the floor tubes were inclined rather than horizontal. 

15 Refractory materials retain their strength at high temperatures and are therefore used to line 

furnaces, kilns, and incinerators. 

16 The superheater also evaporated water that could damage the turbine blades. 

: 10 NTSB/MAB-07/03
Figure 6. Boiler cross section. The Norway’s boilers had three separate drums that were 

interconnected with steel tubes to exchange heat with the furnace to produce steam—

the steam drum, the water (or mud) drum, and the waterwall header. The waterwall was 

a series of vertical tubes that lined the furnace wall. At the base of the waterwall was its 

header (drum). Each boiler measured about 30 feet high, 25 feet wide, and 20 feet deep. 

Most of the steam was produced in the generating tubes, which surrounded the 

furnace and absorbed heat from the burning fuel. The generating tubes were arranged in 

rows at high angles of inclination to accelerate the natural circulation of water in the 

boiler between the steam drum and the water drum. The system also contained other 

tubes, including screen tubes (which protected the superheater tubes and generating tubes 

from direct exposure to the radiant heat of the burners), waterwall tubes and floor tubes 

(which cooled the boundaries of the furnace), and downcomer tubes (which ran outside 

the furnace area to ensure downward circulation of lower-temperature water between the 

drums). Most of the tubes were 1 to 3 inches in diameter. The largest tubes were the 

downcomer tubes, about 4 inches in diameter. 

: 11 NTSB/MAB-07/03
The steam output flow rate was regulated by controlling the fuel oil pressure to 

the burners and by varying the number of burners in operation. Combustion gases leaving 

the furnace were routed across screen tubes, superheater tubes, generating tubes, and 

economizer tubes before passing upward through the exhaust duct and away from the 

ship at the top of the smokestack. 

The boilers were fitted with an electronic automatic control system and an 

electronic boiler management system. Besides automatically lighting and shutting down 

the boilers and burners (the burners could also be started and stopped manually), the 

boiler management system would automatically shut down the boiler or burners when 

critical parameters (such as steam pressure or steam drum water level) exceeded safe 

limits or when a burner failed. The boilers were also equipped with a remote monitoring 

and alarm system, and each boiler had three safety valves—two at the top of the steam 

drum and one at the superheater outlet—to protect against overpressurization.17 

The Norway’s boilers operated as part of the steam cycle—a closed cycle in 

which used steam is condensed and returned to the boilers as feedwater to generate more 

steam. The steam cycle has four phases: generation, expansion, condensation, and feed 

(figure 7). 

In the generation phase of the steam cycle, the chemical energy of fuel oil is 

converted into thermal energy (steam). In the expansion phase, the steam enters the 

turbines, which convert its thermal energy to mechanical energy. Having lost most of its 

energy, the steam leaves the turbines at a very low pressure and a much lower 

temperature than when it entered. 

The low-pressure steam then enters the condensation phase, in which a seawatercooled condenser converts it from a vapor to a liquid at nearly vacuum pressure. The 

liquid goes to a condensate pump, which increases the pressure of the fluid and delivers it 

to a deaerating feedwater heater. Direct contact with steam heats the water and removes 

oxygen. 

The heated and deaerated water (feedwater) goes to a feedwater pump, then 

through economizer tubes in the boiler’s exhaust duct. The economizer tubes heat the 

feedwater before it passes into the steam drum, and the steam cycle begins again. 

 17 The safety valves at the top of the steam drum were set to release at 71.5 and 71.3 kilograms per 

square centimeter (kg/cm2

), or 1,017 and 1,014 psi. The valve at the superheater outlet was set to release at 

66 kg/cm2

 (939 psi). The superheater safety valve could either release spontaneously at its set pressure or 

be initiated by a pilot valve mounted on the steam drum that was set at 71 kg/cm2

 (1,010 psi). 

: 12 NTSB/MAB-07/03
Deaerating

Feedwater

Heater

Steam Turbine

Feedwater

 Pump

Condensate

Pump

Condenser

Superheater Generating 

Tubes

Condensation 

Feed Phase

Phase

Economizer

Steam

Drum

Water

Drum

Expansion Phase

Generation Phase

Exhaust

Mechanical

Output

Figure 7. Schematic of the steam cycle, showing the main steps in which steam flowed 

from the Norway’s boilers to the turbines, after which it was condensed and returned as 

feedwater to the boilers, where it was reused to generate more steam.

Boiler History 

Modification. As constructed, the vessel had eight main steam boilers (four in the 

forward boiler room and four in the aft boiler room) that powered four main propulsion 

turbines and steam auxiliaries and four propeller shafts. Between 1974 and 1979, the 

France was in lay-up status, during which the eight boilers in the forward and aft boiler 

rooms were preserved as stipulated by BV, its classification society. During the vessel’s 

1979 overhaul for use on Caribbean cruises, the four boilers in the forward engineroom 

and two of the propellers were removed, in anticipation of voyages not requiring high 

transoceanic operating speeds. 

Some boiler features were also upgraded and other features installed to enhance 

the safety of operations, including a remote monitoring and alarm system to alert 

engineers of abnormal conditions, an electronic automatic control system, and an 

electronic boiler management system. The management system had chart recorders that 

continuously captured several monitored parameters, including steam drum water level, 

steam drum pressure, burner fuel oil pressure, fuel oil flow rate, superheater steam 

pressure, and superheater steam flow rate. In addition, various automatic safety 

shutdowns, in case of low water level in the boiler steam drum or high steam pressure, for 

example, were fitted to protect personnel and equipment from damage. 

About September 1997, NCL contracted for a propulsion study to determine 

methods of achieving a 27-knot ship speed and the steam demanded by 80,000 shaft 

: 13 NTSB/MAB-07/03
horsepower. The propulsion study report recommended that new, higher-capacity boilers 

and new booster propulsion units be installed to achieve the desired horsepower. About 

the same time, NCL also contracted with Harris Pye Marine, Ltd., a leading specialist in 

repairing marine boilers and associated steam systems, to assess the Norway’s boiler 

equipment. The contractor reported: 

Although these boilers are around 40 years old and are currently suffering from 

on-going tube failures, there is no report of the main components—i.e., headers 

or drums–having any Conditions of Class18 put on them. It is known that various 

defects have been noted in and attended to in the past, but we would not suggest 

that this precludes these components from many more useful years work, once 

the deteriorating tubes have been addressed. . . . 

In November 1997, the port engineer at the time wrote to the NCL executive vice 

president, cruise operations: “The boilers on the S/S Norway have reached a state where a 

decision must be made.” He recommended a number of options for addressing the 

problems, including, but not limited to, replacing the old boilers, completely retubing the 

old boilers with new economizers, and installing new automation. 

On November 19, 1997, NCL’s executive vice president, cruise operations, wrote 

in an interoffice memo that the company would begin a retubing program on the Norway

“next year.” Major overhauls of the boilers began in November 1998 with the retubing of 

both the upper and the lower economizers. In May 1999, the tube bank in the furnace area 

was retubed, and in 2002, the secondary superheater was retubed. 

Defects and Repairs. To determine the nature and scope of past problems with 

the boilers, Safety Board staff obtained copies of various company and classification 

society documents over the previous 40 years to review the repair history of the boilers. 

Company reports and classification society surveys documented instances of cracking, 

corrosion, pitting, and tube failures throughout the history of the ship’s boilers (tables 2 

and 3).19 The documents indicate that as early as December 1970, cracks were observed 

in the longitudinal welds of the waterwall headers, water drums, and steam drums of all 

four boilers. The documents also indicate that the longitudinal welds on the header of 

boiler No. 23 (the boiler that ruptured) were last weld-repaired in 1990. 

 18 “Conditions of class” or “recommendations” are synonymous terms used by class societies for 

requirements that specific measures, repairs, or requests for surveys are to be carried out by the owner 

within a specified time to retain the ship’s class certificate. A vessel is said to be “in class” when the rules 

and regulations, in the opinion of the classification society, have been complied with. 

19 Boiler repairs were described in the following documents: BV survey for April 14 through July 5, 

1982; BV survey for September 2 through 24, 1984; Deutsche Babcock inspection report 18-8702-999, 

dated September 18, 1985; Lloyd Werft Bremerhaven instructions written by Deutsche Babcock dated 

October 26, 1987; BV survey report covering period September 7 through 23, 1987; Kloster Cruise 

interoffice memorandum dated October 8, 1987; BV survey report for period November 7 through 21, 

1987; Deutsche Babcock repair document 18-9790-999, dated February 18, 1988; Deutsche Babcock repair 

document 94-8351-998, September 1990; BV survey report covering period September 3 through October 

2, 1990. 

: 14 NTSB/MAB-07/03
The boiler drums were periodically monitored by visual and nondestructive 

testing20 methods, and detected cracks were removed by grinding. When cracks extended 

below the minimum allowable wall thickness, they were ground off, and weld repairs 

built the walls back up. The engineering company Deutsche Babcock specified the 

welding procedure, which BV approved. Lloyd Werft or its subcontractor performed the 

weld repairs while the ship was in drydock in Bremerhaven in 1987 and 1990. 

Table 2. Documented boiler cracks and corrosion during vessel history. 

Date Source Condition 

Dec. 

1970 

Deutsche Babcock 

report 

Small flaws [cracks] in welded seams in water part of steam drums, 

maximum depth 1.5 millimeters (mm). 

Dec. 

1973 

Deutsche Babcock 

report 

1- to 3.5-centimeter cracks found in water drum boiler No. 24; cracks were 

ground off up to 3 mm depth. 

Feb. 

1974 

Deutsche Babcock 

report 

Corrosion flaws found in way of internal longitudinal welded seams of 

water drums. Corrosion defects ground off. Maximum depth of defects 

∼3 mm. 

1982 NCL study Microcracks found in tubes. Conclusion: frequent boiler cycling very 

damaging to boilers. 

May/June 

1982 

Deutsche Babcock 

report 

Corrosion cracks in longitudinal and circumferential welds of boiler Nos. 

21-24; defective areas rectified by grinding. 

July 1982 BV survey report Cracks found as follows: lower small header [waterwall header] boiler No. 

23—whole length of outer longitudinal seam and about one-third of length 

of inner longitudinal seam, maximum depth about 1 mm. All cracks ground 

off. 

Sept. 

1984 

BV survey report Upper and lower drums found without new cracks. Lower small drum: 

cracks found in way of outer and inner longitudinal weld seams, maximum 

depth ∼2.5 mm. All cracks ground off. 

June 

1985 

BV survey report Erosion seen in lower areas of drums on circumferential weld seams. BV 

recommends rectifying defects by grinding. All drums of boiler No. 23 

show strong corrosion pitting. Conclusion: heavy oxygen corrosion 

present. 

Sept. 

1987 

BV survey report Cracks and pitting in most drums of all boilers. Cracks repaired by 

grinding, except boiler No. 21, which was at minimum wall thickness and 

could not be ground further. Boiler No. 21 operation restricted until upper 

and side drum (header) cracks could be repaired. 

Nov. 

1987 

BV survey report Cracks on longitudinal seam and wastage in boiler No. 21 upper drum and 

side drum permanently repaired by welding. 

Sept. 

1990 

Deutsche Babcock 

test report 

Corrosion and pitting in almost all drums. Boiler No. 23 lateral drum had 

“crack-like” indications in longitudinal welds, but none in circumferential 

welds. Welding done on lateral drum of boiler Nos. 22 and 23. 

Longitudinal weld on boiler No. 21’s upper drum not reworked. 

Nov. 

1990 

Letter from 

Babcock Material 

Test Division to 

NCL 

Corrosion chip tested from upper drum of boiler No. 22. Corrosion 

attributed to oxygen corrosions during boiler standstill with lack of 

preservation coating, or during boiler operation with unsatisfactory water 

quality. 

 20 Testing that does not damage or destroy the object. 

: 15 NTSB/MAB-07/03
Date Source Condition 

Jan. 

1991 

Letter from Lloyd 

Werft to Kloster 

Cruise 

Lloyd Werft points out problem with increased corrosion: “Regarding the 

increased occurrence of corrosion pittings inside the boiler drums and 

Babcock's report on this matter, we hereby point out to you again that the 

preservation of the boilers in shutoff condition should be given the utmost 

attention.” 

Sept. 

1993 

Deutsche Babcock 

service report 

Corrosion in all drums of boiler No. 24, including “severe corrosion pitting 

on both longitudinal welds” of intermediate drum. 

Oct. 1993 BV survey report Survey of boiler No. 24 finds corrosion in all drums. BV recommends “on 

shutdown of the boiler, it is however absolutely necessary to inspect the 

longitudinal welds of boiler 24 again." 

Aug. 

1996 

BV memorandum Miami BV office advises London BV office to check main boilers for 

cracks: "A particular attention has to be paid to the Main and Aux[iliary] 

Boilers. Some cracks were found since 87 on the various drums of the MB 

[main boiler] as indicated hereafter. Particular attention to be paid to 

monitor these details.” 

Sept. 

1996 

BV survey report Cracks and pitting in boiler Nos. 22 and 24. Scanning reveals cracks to be 

5 to 6 mm deep and 1 to 1.5 mm wide. 

Nov. 

2002 

Harris Pye report Inspection of boiler No. 21 finds oxygen tubercles [areas of mineral 

buildup] in [generating] tubes. Report states: “[W]hat gives us cause for 

concern is the fact that we do not know what active corrosion is 

underneath the tubercles.” 

Jan. 

2003 

Harris Pye report Inspection of boiler No. 24 finds: “The amount of tubercle growth and 

pitting . . . indicates that oxygen corrosion is active in this boiler.” 

No documents were found indicating that cracks were found or repaired after 

1996. A former port engineer told investigators that his practice had been to have the 

boilers periodically inspected for cracks, but that such inspections did not take place 

during the 1999 shipyard period, his last year of employment with NCL. NCL’s Miami 

port engineer at the time of the accident declined on the advice of legal counsel to be 

interviewed by the Safety Board. 

Table 3. Documented tube defects and corrective action during vessel history. 

Year Month Condition 

1980 Apr. Leaks in two water tubes (boiler No. 21); contractor finds pitting in all water tubes of all 

boilers. 

May Leaks in five water tubes (boiler No. 21). 

1981 -- All boilers have significant tube failures when sulfamic acid from evaporator leaks into 

boiler feedwater system. 

1982 Sept. Break in economizer tube (boiler No. 23); two holes in waterwall tube (boiler No. 21). 

Oct. Evaporator tube on boiler No. 21 leaks and sprays water on a tube, damaging it.

Nov. Tube bursts (boiler No. 21).

Dec. Two tubes burst (boiler No. 21).

1983 Sept. Tube cracks in “main” boiler. 

1985 June Two tube failures (boiler No. 21). 

1986 Jan. Tube failure (boiler No. 22). 

1987 Feb. Tube failure (boiler No. 22). 

: 16 NTSB/MAB-07/03
Year Month Condition 

July Economizer tube failure (boiler No. 23). 

Nov. Tube failure [boiler not identified]. 

1988 June Tube failure (boiler No. 23).

Sept. Tube failure (boiler No. 23).

Oct. Two tube failures (boiler No. 22).

1990 Dec. Tube failure (boiler No. 22). 

1996 Feb. Tube failure (boiler No. 21). 

May Leaks in superheater tubes of two boilers. 

June Tube failure (boiler No. 21). 

July Tube failures on internal desuperheater and two tube leaks on economizer (boiler No. 

22). 

July During BV occasional survey (boiler No. 21), 23 generating tubes and riser tubes are 

plugged. 

Sept. Drew Marine analyzes cause of tube failure. Attributes failure to “dual contributions of 

internal stress-assisted corrosion damage and creep void and crack formation, which 

was related to long-term metal overheading.” 

1998 Oct. Harris Pye retubes economizer (boiler No. 23). 

Nov.-Dec. Crew plugs main condenser tubes. 

Nov. Harris Pye retubes economizer (boiler No. 22). 

Dec. Crew plugs tube (boiler No. 22). 

1999 Feb. Crew plugs superheater tube (boiler No. 22). 

1999 Apr.-May Harris Pye retubes boiler Nos. 22 and 23. 

2000 Jan. Tube leaks in boiler No. 24. 

Feb. Tube leak in economizer (boiler No. 24). 

June Crew plugs tubes on superheater and riser (boiler No. 24). 

July-Aug. Crew plugs surge pipe and secondary superheater (boiler No. 24). 

Aug. Crew plugs tube on riser (boiler No. 24). 

Oct. Tube leaks in boiler Nos. 22 and 23 plugged. 

Oct.-Nov. Tube leaks in boiler Nos. 21 and 23 plugged. 

2001 Jan. Tube leak in boiler No. 23 plugged. 

Feb. Economizer tube leak in boiler No. 23 plugged. 

May Tube leak in boiler No. 21. 

July Superheater tube leaks in boiler No. 24 plugged. 

Aug. Economizer tube leak in boiler No. 21 plugged. 

Oct. Superheater tube leaks in boiler No. 24 plugged. 

Oct. Superheater tube leaks in boiler No. 21 plugged. 

Dec. Superheater tube leaks in boiler No. 24 plugged. 

2002 Feb. Superheater tube leaks in boiler No. 21 plugged. 

Feb. Superheater tube leaks in boiler No. 24 plugged. 

: 17 NTSB/MAB-07/03
Factors Affecting Boiler Life 

Marine boilers have an estimated design life,21 and the degree of material fatigue 

they sustain is affected by how they are operated, how well they are maintained, and how 

often and how well they are inspected and repaired. The Safety Board reviewed the 

written operating practices of NCL and BV and interviewed past and present company 

representatives to determine the effectiveness of stated and actual operations. 

Investigators addressed a number of practices; the discussion below summarizes findings 

in the areas of written guidance, startup and shutdown protocols, cycling, water testing 

and treatment, maintenance and cleaning, and inspections. 

Written Guidance. The original boiler manuals issued by the vessel 

manufacturer22 included detailed instructions for operation and maintenance designed to 

minimize thermal stresses and the potential for material degradation, such as cracking 

and corrosive pitting, and component breakdown, such as water tube failures and leaks. 

NCL’s procedures for managing the Norway’s engineering equipment were 

formalized in 1998, as required by the International Management Code for the Safe 

Operation of Ships and for Pollution Prevention (International Safety Management Code, 

or ISM code).23 The stated objective of the NCL safety and environmental management 

system (SEMS) was “to ensure that conditions, activities, and tasks both ashore and 

onboard essential for the safety and protection of the passengers, crew, ship and the 

environment, are carried out under controlled conditions.” NCL SEMS procedure J100 

stated: 

This ship is to be maintained in compliance with applicable Flag State, 

Classification, International and Local Rules and Regulations at all times. A 

Planned Maintenance System, AMOS-D, forms the basis for the onboard 

maintenance program for equipment and systems, additionally, there shall be an 

ongoing maintenance program kept up to date both for corrosion control 

purposes and to present the vessel in a first class condition at all times. 

NCL used AMOS, a computer-based preventive maintenance program, to plan 

and document maintenance actions for all equipment, including the boilers. The 

computer-based program did not contain a procedure for boiler inspection and cleaning. 

The original boiler manual states that the “frequency of cleaning cannot be laid down in 

any precise manner” but recommends that cleanings should not be carried out more often 

 21 The estimated design life of a marine boiler the size of those on the Norway was 150,000 hours 

under normal cycling conditions, based on an estimate provided by a representative of Siemens AG, a 

global corporation that provides a variety of technical services, including electrical engineering, for 

companies. The Safety Board could not determine the number of hours the Norway’s boilers had operated. 

22 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers” (no 

date). 

23 After a number of serious marine accidents in the late 1980s that were due to human error and poor 

management oversight, the International Maritime Organization adopted resolutions that led to the 

implementation the ISM code. Since July 1998, compliance with the ISM code is mandatory under SOLAS 

chapter IX, “Management for the Safe Operation of Ships.” 

: 18 NTSB/MAB-07/03
than every 3,000 hours.24 At the shipboard level, the chief engineer and his staff managed 

the Norway’s engineering equipment. The senior first engineer was responsible for 

maintaining AMOS.25 

Startup and Shutdown Protocols. During the startup, also called “light-off,” 

and shutdown of a steam boiler, pressure and temperature changes cause bending and 

alternating stresses in the various boiler components, such as drums and headers. All 

marine boilers are designed to accommodate thermal and mechanical stresses. In the case 

of the Norway boilers, the waterwall header, the water drum, and the inboard side of each 

boiler had structural supports at the front and the rear. In addition, the structural 

foundation of each boiler was supported by a “sliding foot,” a design arrangement that 

allowed the boiler to expand as it heated up during light-off and to contract when it was 

cooling off during shutdown.26 

Maintenance records indicate that the boilers had experienced problems with the 

condition of the sliding feet on at least two occasions before the accident. In January 

2003, the Harris Pye inspector reported that “the sliding feet [of boiler No. 24] showed no 

indication of movement” and “no signs of lubrication.” A sliding foot that cannot move is 

termed a “frozen foot” and can cause high stresses on the boiler and the ship’s structure 

because it restricts boiler expansion. NCL records show that maintenance was performed 

on “not working” feet of unidentified boilers 2 weeks before the rupture. 

Major marine industry entities involved with steam boilers, including the U.S. 

Navy, classification societies, and boiler manufacturers, have published instructions 

indicating that care must be taken during light-off and shutdown to mitigate thermal 

stresses on a boiler. The machinery operation and maintenance guide issued by the vessel 

manufacturer specified proper procedures for starting up and shutting down its boilers.27

During light-off, the manufacturer’s manual indicated that one or more of the unit’s 

burners should be fired at intervals until the pressure reached 8 bar (116 psi), after which 

continuous firing was allowed until the boiler reached a pressure of 60 bar (870 psi).28

The manual states that reaching the recommended operating pressure requires “about 3 

hours,” and that it is “advisable not to accelerate the procedure, and to allow the 

 24 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers”: 

“frequency of cleaning cannot be laid down in any precise manner; it depends on the percentage of 

impurities in the fuel, the quality of combustion, on the effectiveness of fuel additives, etc. It is 

recommended that washes be spaced out as much as possible, being carried out at the earliest after 3000 

hours of operation, but perhaps occurring only after 6000 hours, provided that intermediate inspections of 

the elements prove satisfactory” (p. 40). 

25 The engineering department crew numbered between 83 and 87. 

26 The holes for the bolts connecting the boiler foundations to the ship’s structure were elongated to 

permit expansion. 

27 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers,” 

pp. 26 and 36. 

28 Each boiler was designed by the manufacturer and rated by the classification society to operate at 

70 bar (1,015 psi) drum pressure, but both the original owner/operator and NCL elected to operate the 

boilers at 60 to 62 bar (870 to 900 psi). 

: 19 NTSB/MAB-07/03
temperature to rise gradually.” The manual’s specified procedures for shutting down a 

boiler indicate that the superheater should not be filled with water until “the boiler has 

cooled down, about 48 hours after extinction [of fires].” 

The Norway’s chief engineer had posted the company’s light-off and shutdown 

procedures in the boiler room for the engineering crew’s reference. The posted 

procedures did not specify a period for raising the steam pressure or for cooling down a 

boiler. 

Safety Board investigators talked with several second engineers on the Norway. 

Their comments indicated that, in general, they followed the light-off procedures 

recommended by the manufacturer. A second engineer who had worked on board the 

Norway for about 4 years stated that he allowed a boiler to heat up “very slowly” by 

switching a burner on for 5 minutes and then off for 5 or 10 minutes during “the first 

hours,” and that this light-off process took about 10 hours. He stated, in part: 

We used to start heating the boiler when we are in St. Thomas . . . about 8:00 in 

the morning . . . We start the process for . . . eight to nine hours, till we have full 

pressure. We do it very slowly. So, I may . . . switch on the burner for five . . . 

minutes and switch off 10 minutes the first hours. Normally, we . . . have 60 bar 

on the boilers about 6:00 in the evening. . . . . 

Statements from several second engineers revealed, however, that none of them 

followed the manufacturer’s procedures for shutting down the boilers. They each 

employed one or more measures, such as opening vents and drains and running one or 

more of the boiler’s forced-air fans, in an attempt to speed the cooling of the boiler so 

that it could be shut down in less time, in some cases, in as little as 1 to 2 hours. One 

second engineer said that by using the forced-draft fans and opening the drain on the 

bottom of the water drum (the boiler bottom blow valve) for about 20 minutes “so [that] 

it loses a lot of pressure,” he estimated that the boiler pressure could be reduced from 60 

bar (870 psi) to 0 bar in 1 to 2 hours. 

The boiler monitoring system had several strip chart recorders29 that recorded 

various boiler operating parameters, including steam pressure (for boiler data, see 

appendix A). The pressure chart data could be used to estimate the time it took for a 

boiler to warm up and cool down during light-off and shutdown, respectively. 

Investigators noted that the charted light-off profiles were consistent with intermittent 

firing of the burners. The data indicate that the boilers went from zero pressure to a full 

pressure of 60 to 62 bar (870 to 900 psi) in 1.5 to 5.5 hours; the average was 3.4 hours. 

According to the charts, the boilers were fired at 10-minute intervals and shut down for 

10 minutes until the boilers reached pressure. 

 29 A strip chart recorder consists of a roll of paper that is passed beneath one or more ink pens. If the 

signal representing the monitored parameter remains constant, a straight horizontal line is drawn on the 

chart. If the parameter changes, the pens deflect, producing a charted display resembling sawtoothed or 

sloping curved lines. 

: 20 NTSB/MAB-07/03
The charted shutdown profiles showed a steadily decreasing curve, representative 

of a falling pressure rate over time—in most cases, a reduction from full pressure to zero 

pressure in about 3 hours. The rate of pressure drop from full to zero pressure ranged 

between 45 minutes and 4 hours, with an average of 2.8 hours.30

Between the late 1990s and 2002, several port engineers and chief engineers 

expressed concern about the effects on the boilers caused by the frequent light-offs and 

shutdowns required by the vessel’s operational schedule and route. In a 1998 e-mail to 

the NCL’s vice president of ship operations, an NCL port engineer stated: 

Since the S/S Norway started the itinerary to St. Maarten, St. John, St. Thomas, 

Great Stirrup Cay, the ship has been sailing on 2-3 boilers. This operation is 

causing a lot of stress to the boilers, because we are forced to shut them down 

frequently. After a few years of operating in this condition, and being the boiler 

shut down for more than 100 times, and light off every year, we can see that the 

steel is getting brittle and the reoccurrence of tube failures. If we want to 

continue the safe operations of the vessel with no mechanical interruptions, the 

retubing of all 4 boilers should be done soonest. 

During the last few years, we experienced numerous boiler tube failures, which 

caused shutting down the boilers for repairs. We must realize that we have 

reached a point where the operation of the vessel is not safe. Also we should take 

in consideration that the interior of the boilers [is] worn out due to sulfur-dioxide 

corrosion. 

In January 2002, a different port engineer (the port engineer at the time of the accident) 

sent an e-mail to NCL management, advising: 

Leaks on the boiler will happen again, and is–once in awhile, not particular[ly] 

abnormal. But with the frequency of leaks we have had lately, particular on 

boiler 24, it is all reasons for concern, and it has to be addressed. The reason for 

boiler-tube leaks on the Norway is well known; in and out with the third boiler 

every single week gives heavy thermal stresses of the boiler-tubes, economizers 

and brickwork. With the present itinerary, delays and/or cancellation of ports 

must be expected. 

Later that year, in July 2002, the port engineer e-mailed NCL management: 

The planned re-tubing of the superheaters [has] had some impact on the 

consumption; with only 3 boilers in operation, the chief engineer has been 

uncomfortable in shutting down the boiler on Saturdays, knowing he must light it 

up again before S. Martens. So three boilers have been in line until safe restspeed to St. Martens has been obtained. Knowing how much stress this lighting 

up and shutting down has on the boiler, I support this when one boiler is out of 

service. 

 30 In some cases, the recordings were interrupted, meaning that a full reading could not be obtained. 

Either the recorders were stopped before pressure dropped to zero or the boilers were started back up in the 

middle of a cycle. 

: 21 NTSB/MAB-07/03
Cycling. One boiler cycle is defined as the unit going from zero pressure to full 

pressure and back down to zero pressure. At the time of the accident, the Norway’s 

itinerary was a 7-day voyage that departed the Port of Miami, sailed to stops in St. 

Maarten (Netherlands Antilles), St. Thomas (U.S. Virgin Islands), and the Great Stirrup 

Cay (Bahamas), and then returned to Miami. After the Norway began that itinerary, the 

ship’s boilers were subject to more frequent cycling than when the vessel made transAtlantic voyages while under French flag. The Norway normally sailed using two or three 

boilers, depending on the speed needed to reach a port on the cruise schedule. Typically, 

one or more boilers were idle for periods lasting from a day to several weeks (see 

appendix A). 

Investigators examined the stoker (boiler operator) logbooks to determine the 

number and the duration of the cycles and the shutdown periods for the four boilers. For a 

1-year period (July 1997 to July 1998) taken at random, the boilers had between 11 and 

29 cycles, or an average of 23 cycles per year. For the 17-month period before the 

accident (January 2002 through May 2003), the boilers had between 18 and 26 cycles, or 

an average of 15.2 cycles per year. The logbooks show that a boiler’s cycle frequently 

lasted 1.5 days or less, and in many cases, less than half a day. 

The logbooks showed that between July 1997 and July 1998, the boilers were shut 

down for 10 or more days between two and seven times (appendix A, table 2). Pressure 

chart data confirmed that the Norway’s engineering crew typically brought a boiler’s 

pressure down to zero shortly after they shut it down. Three of the four boilers each were 

idle for periods lasting 20 or more days.31 Boiler No. 22 was shut down once for more 

than 20 days, boiler No. 23 was shut down twice for more than 20 days, and boiler No. 24 

was shut down six times for more than 20 days. In the 17-month period before the 

accident, a boiler was shut down for 10 days or more between three and seven times. 

Boiler No. 23 was shut down once for more than 20 days, boiler No. 21 was shut down 

twice for more than 20 days, and boiler No. 24 was shut down for more than 20 days 

three times. The boiler records did not indicate whether the boilers were in a wet or dry 

condition32 during periods of idleness or what techniques, if any, were used to prevent 

oxygen corrosion during lay-up (see below). 

Water Testing and Treatment. An essential maintenance task associated with 

steam boilers is ensuring that the water in the system is free of contaminants and has the 

appropriate chemical and oxygen levels to prevent scale formation and corrosion. As 

discussed in the “Boiler History” section, the Norway’s boilers were found to have pitting 

and oxygen corrosion on multiple occasions during their lifetime. As noted in the 

“Postaccident Investigation and Findings” section, the fatigue cracks found on the water 

wall header fracture surface appeared to have originated at the base of corrosion pits. 

 31 From July 1997 to July 1998, the longest shutdown period of boiler No. 21 was 19.5 days 

(appendix A, table 2).

32 The wet condition was when a boiler was shut down but still sealed and full of water. The dry 

condition was when a boiler was completely drained of water. 

: 22 NTSB/MAB-07/03
NCL had a chemical treatment program that included required procedures for 

water testing by onboard engineering personnel and a contract with Drew Marine 

Division of Ashland Chemical to supply test and treatment chemicals for the boiler water 

and to provide technical services. The water treatment manual used by Drew Marine 

recommends that the level of hydrazine33 in a boiler’s water be 0.03 to 0.01 parts per 

million (ppm) for normal operations and that it be increased to 150 to 200 ppm during 

periods of wet lay-up. The Drew Marine guidance also states that a wet lay-up (as 

opposed to dry lay-up) be used for “all but very extended lay-up periods.” However, the 

manual does not define “very extended lay-up periods.” The original operating manual 

from the French manufacturer recommended that if a boiler was to be “shut down for a 

prolonged period (5 days or more), completely fill the upper drums [with water] up to the 

air releases [drum vents], injecting hydrazine.”34 

The NCL water treatment procedures required a second engineer to draw and test 

the water from the boilers each day and, if needed, to either add the appropriate chemical 

to control phosphate levels, alkalinity, pH levels, chloride levels, dissolved solids, and 

oxygen levels (as indicated by the amount of oxygen scavenger present in the water) or to 

skim the water to remove contaminants. An NCL second engineer documented the test 

findings. Although the water test and treatment logs indicated whether a boiler was in a 

steaming condition or shut down, they did not record whether it was in a dry or a wet layup status when idle. Consequently, the logs do not indicate whether the level of hydrazine 

was increased as part of the lay-up procedures for a boiler being idled (appendix A). 

The contract services with Drew Marine included a visit about once a month from 

one of its engineers, who would review the records of tests done by the vessel’s second 

engineer, independently test the boiler water, and, if necessary, train the crew in boilerwater-testing procedures. The service engineers also submitted reports of findings to the 

Norway’s chief engineer and to the port engineer. Available historical service reports 

indicate that a Drew Marine engineer repeatedly commented about deviations from the 

standard levels of chemicals and the need to maintain the levels within prescribed limits. 

However, the service technician did not state that NCL’s administration of the chemical 

program was deficient. 

According to a Drew Marine representative in Miami, the service engineers relied 

primarily on their reviews of tests done by the crew and on their own monthly tests to 

evaluate the effectiveness of the water treatment program. The service engineers did not 

examine the interiors of the boilers to determine whether or how well the chemical 

treatments controlled scaling, sludge, and corrosion inside the drums and tubes. 

Safety Board investigators examined the water chemistry logbook for the boilers 

and noted that the second engineers had recorded daily readings of parameters such as 

phosphate, hydrazine, conductivity, chloride, pH, and alkalinity. The logbook also 

 33 Hydrazine (chemically N2H4), a highly toxic carcinogenic chemical, is used in the treatment of 

boiler water. When injected into the boiler feedwater system, it acts an “oxygen scavenger” to remove 

excess oxygen from the feedwater and thereby prevent corrosion. 

34 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers,” p. 36. 

: 23 NTSB/MAB-07/03
showed the amounts of other chemicals, including the oxygen-scavenger hydrazine, that 

reportedly had been added to adjust the water chemistry.35 Investigators noted that no 

entries were logged for some boilers for several days at a time and subsequently 

determined that water chemistry readings were not taken when a boiler was not steaming. 

Closer examination of the data for a randomly selected year (January through December 

2000) revealed the following about the levels of hydrazine: 

• In some cases, the levels of hydrazine were low during operation. For 

example, in boiler No. 24 from July 27 to September 28, 2000, hydrazine 

levels were almost always below the specified minimum, at approximately 

0.01 ppm. 

• Almost every time a boiler came out of an idle period (lay-up), the hydrazine 

level was zero or near-zero for 1 or more days. After reaching the specified 

range, the levels typically stabilized and then were generally maintained 

within operational limits. 

• No records indicate that after a boiler was taken out of service, the hydrazine 

was increased to the level recommended by Drew Marine for idle conditions 

(150 to 200 ppm). 

• Boiler water chemistry readings were not taken on idle boilers in the wet 

condition to assess the levels of hydrazine present.36

Among the documents that Safety Board investigators reviewed were shipyard 

memoranda warning that action needed to be taken to address the suspected cause of the 

active corrosion found in the boilers, including the maintenance of idle boilers. A 

memorandum dated January 25, 1991, from a shipyard that had performed an inspection 

of the boilers stated: 

Regarding the increased occurrence of corrosion pittings inside the boiler drums 

and Babcock’s report on this matter, we hereby point out to you again that the 

preservation of the boilers in shutoff condition should be given the utmost 

attention. It would be recommended to make a provision for transfer pumping of 

the boiler water from the smaller side drums to the upper drum. Maybe, there 

should also be discussions with Drew Chemical about the dosage of hydrazine in 

boiler water and condensate. 

In July 1991, the same shipyard stated in a memo: 

 35 Besides hydrazine, the chemicals were GC (a concentrated alkaline liquid that neutralizes acid and 

controls corrosion); Adjunct B (a phosphate boiler water treatment chemical that works in conjunction with 

GC to control scale formation due to hardness); and SLLC-A (condensate corrosion inhibitor made from a 

volatile liquid organic amine designed to minimize corrosion in steam and condensate systems by 

providing a pH environment that neutralizes the effects of carbon dioxide). 

36 Based on interviews and logbook records of water chemistry readings. 

: 24 NTSB/MAB-07/03
Please find enclosed the report of the boiler water analysis for the S/S Norway 

. . . No major trace elements have been found in the analysis results. So there is 

every indication to suppose that the increase in corrosions is nothing else but the 

effect of shutdown corrosion. We would suggest the following measures to solve 

this problem: Installation should be done of a connecting steamline from the 

atomizer steam groups on each boiler to the respective two lower drums in each 

case . . . The steam as nozzled this way will keep the boiler under pressure and 

maintain temperature . . . The overall situation about the problems with 

combustion air and corrosion should be discussed in detail between Siemens, 

Babcock, the Owner, and Lloyd Werft. 

Investigators found no evidence that the shipyard’s recommendations were 

followed. In late 2002 (table 2), a contractor inspected boiler No. 21 at the request of 

NCL and found “oxygen tubercles present in the [generating] tubes.”37 The report further 

stated, “[W]hat gives us cause for concern is the fact that we do not know what active 

corrosion is underneath the tubercles.” 

Maintenance and Cleaning. On the basis of statements from the vessel’s 

engineering crew and other maintenance records for the 3 years preceding the accident, 

all four boilers had been cleaned and inspected about every 3,000 hours. The 3,000-hour 

maintenance tasks included cleaning the water economizer and water-washing the 

superheater and generating tubes. The original boiler manual noted that “if the treatment 

of the boiler water is correct, then as a rule no significant deposit should occur within the 

boiler tubes.” If necessary, a scaling device driven by compressed air could be used, but 

the manual advised against using it “frequently or regularly, unless large deposits are 

detected, as the mechanical scaling of the tubes destroys the protective coating formed by 

the phosphates.” The manual states that the drums should be cleaned at every inspection 

by washing with fresh water to remove mud deposits that “may have a rapid corrosive 

effect.”38 

For boiler No. 23, the 3,000-hour cleanings and inspections had occurred in 

February 2000, November 2000, March 2001, September 2001, May 2002, July 2002, 

January 2003, and April 2003. Boiler No. 23 was off-line from April 19, 2003, until May 

15 (10 days before the accident) while engineers repaired the furnace’s refractory 

material (blue-ram39). 

Inspections. As noted in the “Written Guidance” section, NCL had formalized 

the process for managing the Norway’s engineering equipment, listing the required 

procedures in the company’s SEMS and establishing a computerized preventive 

maintenance system (AMOS). Investigators reviewed the SEMS manuals and other 

 37 Tubercles (also spelled tubercules) are local mounds of corrosion products (or oxide crust) that 

promote accelerated corrosion underneath. Tubercles appear to grow above the surface of the metal and are 

indicative of oxygen corrosion or other forms pitting mechanisms, such as chloride pitting and galvanic 

corrosion. 

38 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers,” 

pp. 42-43. 

39 Blue-ram is a high temperature plastic (moldable) refractory material. 

: 25 NTSB/MAB-07/03
materials and found no references to requirements or procedures addressing periodic 

inspection of the boiler interior areas for corrosion and cracks. 

Because of the limited access to the interiors of the waterwall headers (a manhole 

at each end of the 13-foot-long cylinders), inspection was best accomplished by the 

inspector actually entering the headers. However, access was difficult because the access 

manholes measured only about 12 by 16 inches (30 by 40 centimeters) and the drum was 

only 29 inches in diameter. In interviews, the second engineer in charge of boiler 

maintenance said that he could and did enter the waterwall headers to check the inside of 

the drums.40 The relief chief engineer, who was 6 feet 7 inches tall and weighed 340 

pounds, said that it was impossible for him to enter the drums and headers.41 

BV rules required a complete (internal) survey of boilers twice in 5 years, or 

about every 2 1/2 years. BV had internal procedures that provided guidance to its 

surveyors in the inspection of boilers. When questioned about his inspection of the 

internal areas of the drums and headers, the BV surveyor at the time of the accident stated 

that BV did not require its surveyors to enter the drums and that he could not get into the 

steam drum, the water drum, or the waterwall header because the access manholes were 

too small. He said, “You can look in . . . for corrosion or whatever, but it’s limited.” 

The previous BV surveyor stated that he had entered the steam and water drums 

of the boilers, but that he had not entered the waterwall header and had only viewed the 

interior of the header from the outside. He also stated that the BV guidelines required the 

surveyors to enter only the steam drum; the requirements did not stipulate that they 

should enter the water drum or the waterwall header. 

According to NCL’s previous Norway port (Miami) engineer, the BV surveyor 

who performed boiler surveys during the 1980s and until 1991 went inside the drums and 

headers during inspections. He indicated that a surveyor could not examine the drum by 

simply putting his head through the access opening and shining a flashlight inside the 

drum. He stated, “You have to go in . . . And it’s a very, very cramped space. Not 

everybody can get in there.” He said that he was aware that other BV surveyors had 

entered the drums to inspect them. 

According to BV survey rules and internal guidance provided to its surveyors 

before the accident and still in effect, if a boiler has not been fully surveyed internally, 

hydraulic tests are required.42 No specific test pressure is specified for the hydraulic tests, 

but 115 to 140 percent of working pressure is the typical pressure specified for such tests. 

Because the Norway boilers were certified to operate at 70 bar (1,015 psi), a 115 percent 

 40 The second engineer was of average physical size. 

41 The relief chief engineer was not part of the Norway crew at the time of the accident but was in 

Miami and available for interviewing during the on-scene investigation; he was scheduled to begin his 

4-month duty 2 weeks after the accident. 

42 A hydraulic test is commonly called a hydrostatic or hydro test. The test involves completely filling 

the boiler with water, sealing it of from other connected systems, and applying the specified test pressure 

using the ship’s feedwater pump or a small special-purpose hydrostatic pump. 

: 26 NTSB/MAB-07/03
test pressure would have been about 80 bar (1,160 psi). According to BV survey 

documents, boiler No. 23 was last internally inspected in July 2002, at which time it was 

subjected to a 70 bar (1,015 psi), or working pressure, hydraulic test. During its previous 

internal examination in November 2001, the boiler was not subjected to a hydraulic test, 

and at its May 1999 internal examination, it was subjected to a hydraulic test of 80 bar 

(1,160 psi). Thus, BV did not appear to follow its own rules regarding hydraulic testing. 

Postaccident Investigation and Findings 

NCL assigned a metallurgist to assist a Safety Board metallurgist during the onscene examination of the boiler room. The NCL metallurgist also participated in the 

follow-up examination and analysis of boiler sections that were removed and sent to the 

Board’s materials laboratory in Washington, D.C. 

On-Site Examination and Testing 

On June 6, 2003, Safety Board investigators conducted an on-site examination of 

boiler No. 23 and observed that a large outboard section of the waterwall header was 

liberated where fracture had occurred (figure 8). The waterwall header had been 

manufactured by longitudinally welding together two half-cylinder components—the 

tube sheet, so called because it contains openings for the waterwall tubes, and a thinner 

sheet called the wrapper sheet. Investigators noted that weld repairs had been made at the 

longitudinal welds between the two sheets and that large portions of the header fracture 

occurred at or next to the repair regions. Later laboratory tests found that the repairs 

appeared to have been made using the temper bead welding technique.43 

The entire waterwall header, including the caps (“dished heads”), was about 16.5 

feet long. The cylindrical portion of the header was about 13 feet long. The fracture along 

the upper longitudinal weld extended about 11 feet, and the fracture along the lower 

longitudinal weld extended about 8 feet. The weld repairs were approximately 1.5 inches 

wide along almost the entire length of the original longitudinal weld seams. The fractures 

along the weld seams were connected by overstress fractures through the wrapper sheet.

The header’s upper longitudinal fracture had dark areas, indicating preexisting cracks that 

extended from the inner surface through about 40 percent of the wall thickness toward the 

outer surface of the header. 

 43 For more information, see “Analysis of Boiler Rupture” section and appendix B.

: 27 NTSB/MAB-07/03
Figure 8. Schematic (left) showing location of fracturing along the longitudinal welds, 

and partial view (right) of damaged waterwall header, looking aft. The waterwall header 

was constructed by longitudinally welding together two half-cylinders and then welding 

caps (dished heads) on either end. The two half-cylinders were of different thicknesses. 

During the manufacture of the header, the tube sheet was tapered down to the wrapper 

sheet and the two were welded together at the bottom of the tapered region. The header 

fractured where weld repairs had been made along the original longitudinal welds joining 

the tube sheet and the wrapper sheet. 

The header’s lower longitudinal fracture surface also had dark areas, again 

indicating the presence of preexisting cracks from the inner surface through about 60 

percent of the wall thickness. The preexisting crack region extended along the length of 

the fracture. Investigators observed isolated thumbnail-shaped regions, indicative of 

metal fatigue, at both ends of this fracture. The weld repair region contained both 

longitudinal and transverse cracks not observed in other areas of the boiler. The 

transverse cracks varied from 0.5 to 2 inches long. 

The liberated section of the header (a single piece of the wrapper sheet) showed 

the presence of the preexisting cracks and copper nuggets covering portions of the 

fracture surface near the inner surface. The significance of the copper nuggets is 

discussed below. 

Laboratory Examination 

To determine the nature of the fracture, Safety Board investigators had eight 

sections from the header and the liberated piece sent to the Safety Board’s materials 

laboratory for examination. Safety Board investigators examined the fracture surfaces 

along the longitudinal welds of the boiler No. 23 header under high magnification in the 

laboratory. The fractures were found to have begun along the side of the weld repair 

: 28 NTSB/MAB-07/03
region, with the upper fracture on the tube sheet side of the weld repair region and the 

lower fracture on the wrapper sheet side of the weld repair region. Fatigue cracks on 

multiple longitudinal planes joined to form a larger crack front. 

The fracture features indicated that fatigue cracking began at the base of large 

corrosion pits and then propagated alongside the weld repair. The header material next to 

welded areas is known as the heat-affected zone. Heat from welding operations and 

subsequent recooling causes changes in the microstructure and mechanical properties of 

the base metal in the heat-affected zone. The welding process can also create residual 

stresses in and next to the weld areas. Residual stresses can lead to accelerated corrosion 

and cracking. Controlled welding procedures approved by the classification society are 

used for welds in stress-critical structures such as boilers to minimize the effects of 

welding. Industry codes for boilers also use substantial safety factors in design to account 

for uncertainties such as residual stresses. 

Visual examination of the fracture surface along the lower longitudinal weld 

repair showed fatigue cracks that reached a maximum depth of 0.55 inch in a section 

0.933 inch thick. The remainder of the wall thickness fractured in overstress and was 

necked down (narrowed), reducing the overall wall thickness at the fracture to between 

0.7 and 0.8 inch.44 Investigators prepared a transverse metallographic section through the 

forward end of the fracture at the wrapper sheet and lower longitudinal weld for 

examination in detail. This section showed cracking or pitting up to 0.1 inch deep in the 

wrapper sheet and up to 0.15 inch deep in the center of the weld repair, both on the 

header interior surface. Laboratory examination of part of the original weld (an area 

without weld repair) showed that portions of the original weld had been ground and the 

thickness of the wrapper sheet reduced. Where grinding had removed the most material, 

the wall was approximately 0.788 inch thick, slightly below the minimum thickness 

(0.791 inch) allowed before weld repair was required.45

Investigators found copper fragments on the surface of the fatigue crack portion 

of the fracture, next to the inner surface of the header. Fragments were not found 

elsewhere in the header material. The fragments were about 0.070 to 0.190 inch long, 

flat, and flush with the inner surface of the header, up to about 0.1 inch wide and 

0.09 inch deep in the crack. The side of the copper fragments deepest into the cracks was 

rounded and contained longitudinal cracks. The fracture halves were put together to 

determine how well they matched. The shape of the fragments of copper closely matched 

the fracture contours (figure 9). 

 44 The deformation associated with the fracture made it impossible to determine the precise thickness 

of the wrapper sheet at the fractured areas when the boiler ruptured. 

45 BV specified in its September 1984 boiler survey that the design thickness of the header at the 

longitudinal seams was 24 mm (0.995 inch) and the minimum allowable thickness was 20.1 mm (0.791 

inch). The permissible reduction in header thickness was an allowance for wastage as a result of corrosion. 

: 29 NTSB/MAB-07/03
Figure 9. View of matching fracture halves (above) and enlarged image of copper 

nuggets (below) at the edge of the fracture. Arrow points to area of enlarged image. 

: 30 NTSB/MAB-07/03
Investigators determined the elemental composition of the copper fragments to be 

almost pure copper, with a wrought (hammered) structure similar to the composition of 

hammered copper refrigeration tubing. The inside surface of the nuggets had transverse 

marks associated with grinding, consistent with the copper material having been ground 

flush with the inner diameter of the header after being introduced into the open crack. 

Investigators considered the possibility that the copper had entered the boiler as the result 

of chemical reactions such as deposition induced by excess hydrazine.46 They discounted 

this mechanism as the source because of the mechanical features and shape of the copper 

nuggets. 

Safety Board investigators consulted with several experts in boiler operation and 

maintenance, none of whom could propose any theories that could adequately explain the 

origin of the copper nuggets. Investigators therefore concluded that the copper had most 

likely been deliberately introduced into the boiler waterwall header during a misguided 

maintenance action. A likely result of the introduction of the copper into the cracked 

areas of the water wall header would have been to mask the cracks, making their 

detection more difficult during inspections.

Tests of Associated Equipment 

The Safety Board tested or arranged for the testing of various safety and control 

devices associated with the boiler system to determine whether their operation or failure 

might have caused or contributed to the rupture. Tests of the four safety valves on boiler 

No. 23 revealed no significant defects, indicating that they probably functioned properly 

at the time of the accident. 

The fuel burner management system was designed to detect abnormal operating 

parameters in the boiler and automatically shut it down if necessary. The control console 

for the system was located in the engine control room. The boiler rupture and release of 

steam therefore did not affect the system’s control components. However, the local 

actuators, sensors, and cabling were damaged to such a degree that a full system check 

was not possible. The Safety Board arranged for Siemens, the manufacturer of the 

system, and an independent systems specialist acting on behalf of the Board to do a 

functional check of the burner management system using simulated inputs. The check 

determined that the system worked as intended. 

NCL engineers conducted tests, witnessed by a Coast Guard representative, of the 

burners, retractable igniters, and fuel valves at the front of boiler No. 23. The tests 

indicated that the front hardware of boiler No. 23 operated properly. 

 46 As noted earlier, hydrazine is used to prevent corrosion by removing excess oxygen from boiler 

feedwater. Any hydrazine that does not react with oxygen decomposes at higher temperatures into 

ammonia. Ammonia, which leaves the boiler with the steam output, causes corrosion of components in the 

condenser and feedwater system containing copper alloys, removing copper from the metal and suspending 

it in the feedwater. The suspended copper then enters the boiler and can be deposited on the inside of the 

boiler or carried over with the steam output and deposited on other components, such as turbine blades. 

: 31 NTSB/MAB-07/03
Investigators sent fuel oil samples taken from the storage tanks to a fuel-testing 

laboratory for analysis to determine whether the oil was contaminated. Depending on the 

type and amount of contamination in fuel oil, its flashpoint can be lowered to the point 

that it can prematurely ignite and cause an explosion. The test results for the fuel samples 

(380 centistokes [cSt] viscosity grade) showed that the flashpoint of the oil was above 

200° F, well above the specification for this grade of fuel and for the boiler. 

Nondestructive Testing of Boilers 

After the accident, NCL contracted with Det Norske Veritas (DNV), another 

classification society, to evaluate the condition of the drums and headers of the three 

boilers not involved in the accident. The tests were visual inspection, plastic replica 

testing, hardness testing, and magnetic particle inspection. The tests were used to 

determine the presence and severity of cracks and the metallurgical condition of the drum 

and header material. 

The visual inspections found moderate to significant pitting and corrosion in the 

drums and headers. The nondestructive testing found cracks that required extensive repair 

before the boilers could be returned to service. The plastic replica examination of the 

material microstructure of the steam and water drums of boiler No. 24 found “significant 

material degeneration due to carbide coarsening and the formation of creep pores,” and 

concluded that the “drums [were] not suitable for further safe operation.” 

The Safety Board also contracted with Engineering and Inspections Unlimited, 

Inc., for nondestructive testing of the same three boilers. The contractor’s report states: 

Fluorescent Magnetic Particle examination located cracks in the welds of headers 

21, 22, and 24, and in the welds of water drums 22 and 24. No cracking was 

observed in water drum 21 or steam drum 22. 

The contractor conducted ultrasonic testing to measure the depth of the cracks. The depth 

ranged from 0.010 to 0.250 inch. 

Postaccident Actions by Parties 

Norwegian Cruise Line Changes 

NCL’s standing Risk Management Committee met in October 2003 to address 

safety issues that the cruise line itself had identified in the Norway accident. As 

prescribed by the ISM code, the objectives of the committee were as follows: 

• Provide for safe practices in ship operation and a safe working environment. 

• Establish safeguards against all identified risks. 

: 32 NTSB/MAB-07/03
• Continuously improve safety management skills of personnel, including 

preparing for emergencies. 

NCL adopted most of the committee’s recommended improvements or preventive 

measures fleetwide by the end of 2004 and included them as review items to be verified 

annually during internal audits. Most of the changes, several of which are described 

below, have been incorporated in the company’s SEMS. 

In the Norway accident, about 125 crewmembers exited the ship within minutes 

of the boiler rupture, and area police did not allow them to return to the vessel. As a 

result, some members of the vessel response teams and some crew monitors for the 

passenger muster were not on board the ship, which affected the timely accomplishment 

of some emergency tasks. NCL therefore added training and quarterly drill requirements 

for shoreside evacuations to all ship emergency plans. In some cases, the quarterly drills 

are conducted in cooperation with local response authorities, including those serving the 

Port of Miami. 

According to company officials, having multiple gangways rigged when the 

boiler ruptured facilitated evacuation from the Norway. NCL therefore reviewed other 

ships and ports to determine the feasibility of rigging multiple gangways so that 

emergency evacuation could be accomplished away from potentially hazardous ship 

areas. Ship emergency plans now include ongoing reviews of shoreside muster 

procedures following a ship evacuation. 

An NCL spokesperson indicated that the Norway accident highlighted the need 

for better hazardous material (hazmat) awareness, handling, and containment. In this 

instance, the Miami responders may not have been aware of the asbestos on the vessel.47

NCL has since removed vessels with asbestos from service. The company also reviewed 

and mapped onboard areas such as chemical lockers that pose potential explosion or 

release dangers and upgraded its training and response procedures for hazmat incidents. 

Emergency drills now include control of damaged areas after an accident, identification 

of hazmat contamination and personnel exposure, and other site safety measures. In 

addition, the company has arranged service agreements with hazmat incident response 

contractors at all U.S. ports where its ships call. 

Emergency preparedness measures now include ensuring that for emergency 

follow-up and investigation, responders and others can obtain extra copies of fire plans, 

either from a ship that has onboard plotting capability or from a port agent. For the safety 

of personnel, company officials researched what clothing and personal protective 

equipment (PPE) could safeguard crew (regular and response personnel) against hazards 

such as those that prevailed in the Norway accident and protect them from injury. In 

addition, ships are now required to carry additional PPE and portable communications for 

postaccident follow-up. 

 47 Before 1976, asbestos was commonly used as a high-temperature insulating material in the marine 

industry. 

: 33 NTSB/MAB-07/03
NCL evaluated the various areas of its ships to identify structural and technical 

considerations for different types of emergencies. In the Norway accident, the steam 

lifted and propelled several deck plates (although the plates struck no one). The 

company’s technical superintendent now must evaluate as part of his semiannual 

inspection whether deck plates pose “missile hazards.” Officials reviewed the location 

and adequacy of shut-off valves for piping that might be blown away or damaged and 

included bulkhead valve inspection and testing in internal audits. The evaluations 

determined that the risk associated with machinery-space doors that opened onto crew or 

passenger accommodation or work areas was limited to older ships; however, as an 

ongoing measure, the company will evaluate all new-build designs for such risks. 

Company officials considered whether watertight doors in machinery areas should be 

kept closed in case of an explosion, but decided against any procedural change after 

realizing that in the Norway accident, closed doors would have funneled the steam and 

debris to upper accommodation areas. 

In the Norway accident, not all the ship’s hospital spaces had emergency lighting. 

NCL officials have now identified secondary medical stations on all their ships. In 

addition, evaluating postaccident crew care facilities has been added to the action log for 

NCL’s shoreside officials. 

NCL officials reviewed all records of vessel modifications and vessel drawings 

for completeness and accuracy. All new vessel drawings, technical reports, and manuals 

have been translated into English. A spokesperson said that digitizing the files has 

improved record-keeping fleetwide, and a project is under way to convert all files to 

electronic format. In addition, each ship’s technical superintendent has been tasked with 

taking digital photographs of machinery spaces when doing semiannual inspections of 

ships so that company and investigative officials will have a preincident record of 

conditions, if necessary. 

Other than the Norway, the NCL fleet had diesel engine-based propulsion 

systems. However, steam continues to be used for purposes other than propulsion on 

NCL motor ships as well as in virtually all other motor vessels, with the steam being 

generated by either oil-fired or waste heat boilers. Often termed auxiliary boilers, they 

provide low-pressure steam (7 to 10 bar or 100 to 145 psi) for a variety of uses, including 

fuel oil heating, hot water heating, laundry and galley services, and heating in HVAC 

(heating, ventilation, and air conditioning) systems. The steam generators used for 

auxiliary steam services pose a much lower threat to safety than those used for 

propulsion, principally because of their smaller size and the much lower pressure, 

temperature, and energy levels at which the boilers supply steam. Consequently, the 

hazards posed by low-pressure steam, while not trivial, are much lower than those of 

high-pressure propulsion steam boilers. 

The company’s review of operating procedures resulted in several changes. NCL 

standardized its routine maintenance program and associated documentation and included 

areas that were not controlled in the past. The company’s SMS now includes 

maintenance, document control, and audits of formerly unofficial logs such as stoker and 

incinerator logs. After a review of welding procedures for normal and emergency repairs, 

: 34 NTSB/MAB-07/03
NCL’s SMS was changed to put greater emphasis on qualifications, credentials, and 

third-party inspections. The review of boiler inspection procedures resulted in standing 

orders for staff to submit reports if any pitting is identified and if class surveyors do not 

enter a boiler’s internal spaces when carrying out their examinations. Also, the condition 

of each boiler must be mentioned in periodic reports. 

After it enacted its procedural and systemic changes, NCL asked the Coast Guard 

to audit its SMS. Coast Guard inspectors and auditors reviewed NCL headquarters, as 

well as two cruise ships (Norwegian Majesty and Norwegian Sun) that were selected at 

random. According to NCL, the Coast Guard now routinely audits its SMS as part of the 

certification process for U.S-flag vessels. 

Classification Society Changes 

Shortly after the Norway accident, the classification society DNV, which had 

evaluated the condition of three of the Norway’s boilers for NCL after the rupture, issued 

a notice to its surveyors to pay special attention to the survey of all boilers over 9 years 

old. The notice advised surveyors to 

perform a general internal examination of both water- and fire/gas side, with a 

special focus on the drums and headers, welding seams for possible cracks, 

corrosion, pitting and wastage. If conditions described above are found, thickness 

measurements and/or other non-destructive testing methods will be performed. 

DNV intended to use the experience surveyors gained through this increased focus to 

help in its continuous efforts to improve rules and survey procedures. 

In 2006, BV revised its rules for boiler surveys to include requirements for the 

surveyor to review the operation, maintenance, repair history, and feedwater chemistry 

records since the last boiler survey. The revision was in response to changes to the IACS 

unified requirements concerning classification and survey (section Z18), which became 

effective in January 2007. 

City of Miami Changes 

As part of their standard operating policies, the fire departments and police 

departments involved in the Norway accident critiqued the response effort to identify 

whether and when problems occurred. One report stated: 

There appeared to be much confusion by the Miami fire units as to which 

department had responsibility for the incident and who was in command. There 

were [two] different operations going on at the same time in two different 

locations with no real formal command structure in place. . . . 

Representatives of the departments subsequently met to address the deficiencies 

identified in the Norway accident and to develop procedures for improving interaction 

and communication. The Miami response agencies also agreed to participate in shoreside 

drills that NCL added to its emergency preparedness procedures after the accident. 

: 35 NTSB/MAB-07/03
Analysis of Boiler Rupture 

During the course of the investigation, it became clear that the header in boiler 

No. 23 ruptured because of extensive fatigue cracking and that a number of factors 

contributed to the initiation and propagation of the cracking. Cracks were detected at 

original welds beginning in the 1970s, and additional cracks were observed on later 

occasions. The cracks were monitored and ground away until the minimum allowable 

wall thickness was reached, at which time weld repairs were made to build up the 

material thickness. The cracks initiated at the base of corrosion pits at the original 

longitudinal welds when the boiler was exposed to excessive cycling (thermal and 

mechanical loading), with severe transients (rates of temperature change) from startup to 

cooldown and constraint from frozen support feet. The pitting most likely resulted from 

improper water chemistry (oxygen pitting) during lay-up periods. 

In 1987 and 1990, weld repairs were performed when the cracks extended below 

the minimum allowable grinding thickness. Cracking began again a few years later. The 

width and length of the weld repairs probably accelerated the pitting and cracking 

because of residual stresses in the weld repairs. 

The cracks then grew to critical size, causing the header in boiler No. 23 to 

rupture. Documents analyzed by the Safety Board showed no nondestructive testing or 

appropriate internal visual inspections after 1996 for the headers of boiler Nos. 22 and 24 

and after 1990 for the headers of boiler Nos. 21 and 23. 

Fatigue Cracking 

The metallurgical analysis found that the material properties of the header steel 

were normal. In addition, the pressure readings at the time of the accident were within 

normal operating range. Therefore, the boiler was subjected to typical loads at the time of 

the rupture. Nevertheless, the boiler ruptured because preexisting cracks extended 40 to 

60 percent through the wall thickness, which was already reduced by grinding. At the 

time of the rupture, there was insufficient cross-sectional area in the header to withstand 

the pressure, and the header failed catastrophically. It is thus clear that fatigue cracking 

ultimately led to the rupture of the header. 

Postaccident examination detected fatigue cracking in both the original welds and 

the weld repairs. The cracking initiated at the base of corrosion pits on the inner surface 

of the drums. The presence of pits localized stresses at the surface and favored the 

initiation of fatigue. The reduced wall thickness also contributed to fatigue initiation by 

concentrating local stresses. After the fatigue cracks initiated, they produced local stress 

concentrations at the crack tips, which most likely propagated with every firing cycle of 

the boiler. 

In a pressure vessel, cracking is expected to occur along the longitudinal weld 

seams because the hoop stress48 is twice the longitudinal stress, based on the internal 

 48 Mechanical stress in the circumferential direction of a cylinder. 

: 36 NTSB/MAB-07/03
pressure load (for a cylindrical vessel). Both longitudinal and transverse cracking was 

discovered in boiler No. 23, suggesting either that stress was elevated enough to initiate 

cracking in both directions or that additional stresses in the longitudinal direction, such as 

in reaction to the frozen boiler supports, were superimposed on the pressure loads to 

cause transverse cracking. 

Improper Water Chemistry 

Poor control of water chemistry is known to contribute to corrosion fatigue 

damage. According to the American Society of Mechanical Engineers (ASME) boiler 

code, corrosion in a boiler can occur either while the boiler is in service or while it is 

idle.49 When a boiler is idle, proper precautions need to be taken. Boilers are typically 

passivated, that is, protected from corrosion by an internal film of magnetite (Fe3O4). The 

film can be broken by oxygen pitting, acid dissolving the coating (acid attack), or 

concentrated alkali (caustic) conditions, all of which cause localized loss of boiler metal 

(corrosion). Localized corrosion has been noted to be the primary cause of boiler failure 

and can result from high chemical concentrations or uncontrolled oxygen in the system. 

Water chemistry records, the metallurgical characteristics of the damage, and historical 

documents indicate that oxygen corrosion was the most likely mechanism for the 

corrosion pitting observed in boiler No. 23. 

Oxygen corrosion, by definition, results from excess oxygen in the water system 

and is controlled by the use of deaerating equipment50 and chemicals such as hydrazine. 

According to the Drew Marine water chemistry dosing chart, the hydrazine levels for the 

Norway were to be maintained between 0.03 and 0.01 ppm during operation. If the levels 

of hydrazine were not sufficiently high, excess oxygen would be present in the water to 

facilitate or enable corrosion. Records show that oxygen pitting had plagued the 

Norway’s boilers for several decades and that the boilers had an ongoing problem with 

maintaining the proper hydrazine levels to prevent corrosion. The Safety Board therefore 

closely examined the historical levels of hydrazine in the boilers, as discussed earlier in 

the “Water Testing and Treatment” section (see also appendix A). Investigators found 

low levels of hydrazine for long periods during both operation and lay-up. 

Several warnings were given that oxygen corrosion was a problem and was likely 

the result of incorrect water chemistry during both operational and lay-up periods. It is 

apparent that efforts to address this issue were ineffective, since active oxygen corrosion 

was present, as documented in the Harris Pye reports on boiler Nos. 21 and 24 from 

November 2002 and January 2003. Active oxygen corrosion, as evidenced by tubercles, 

was also discovered during the postaccident examination of the boilers. The accident 

investigation determined that the Norway’s boilers were often shut down for longer than 

10 days and sometimes for more than 40 days without proper water treatment.51

 49 ASME Boiler and Pressure Vessel Code, section VII, “Recommended Guidelines for the Care of 

Power Boilers,” subsection C8.5 (American Society of Mechanical Engineers, 2004). 

50 Equipment that removes oxygen and carbon dioxide from boiler feedwater. 

51 The boilers were possibly in the dry state during some maintenance periods. 

: 37 NTSB/MAB-07/03
According to the Drew Marine documents, hydrazine levels were to be increased during 

idle or lay-up periods, but the documents did not specify how many idle days had to pass 

before the boiler was considered in lay-up condition. 

The documents point to numerous boiler tube failures over the years. Boiler tube 

failure can occur because of direct pitting of the internal surfaces or because of sludge 

buildup on the interior surfaces. When deposits build up inside the tubes, heat transfer 

reduces and the tubes operate at higher temperatures because less energy is transferred to 

the water or steam in the tubes. Operation at higher temperatures can eventually lead to 

loss of material properties (creep damage), fracturing, and burn-through, requiring that 

the tubes be plugged at the ends and put out of commission. Deposits typically form 

because of improper water chemistry that leads to precipitation of minerals from the 

boiler feedwater or from internal corrosion of the boiler and steam system, leading to rust 

deposits. It is likely that the oxygen corrosion that was observed in the headers and 

elsewhere contributed to the observed boiler tube failures. 

Boiler Stresses 

Cycling. The greatest contributors to the initiation and propagation of the fatigue 

cracking in boiler No. 23 were the thermal and pressure stresses associated with starting 

up and shutting down the boilers. As described earlier (see also appendix A), the number 

of boiler cycles (pressure going from zero to full then back to zero) and the rate of 

pressure buildup in the Norway’s boilers were as follows: 

• From July 1997 to July 1998, the boilers averaged 23 cycles per year. 

• From January 2002 through May 2003, the boilers averaged 15.2 cycles per 

year. 

• The boilers took an average of 3.4 hours to go from zero to full pressure (60 

to 62 bar). 

• The boilers took an average of 2.8 hours to drop from full pressure to zero. 

According to NCL’s former port engineer, the ship often had to shut down a 

boiler for some reason (such as leaking tubes), and when the engineers would restart the 

boiler, they would often raise the pressure too fast. The rate of drop from full to zero 

pressure ranged between 45 minutes and 4 hours, with an average of 2.8 hours. The time 

necessary to reduce boiler pressure was not specified in the operating manual or other 

records.52 Depending on how quickly they were started and cooled, the boilers could 

have suffered significant additional stresses from thermal transients. Multiple documents 

show that the boilers had frequent and significant damage to the boiler refractory 

materials, an indication that the boilers were heated and cooled too quickly. 

 52 The boiler manual stated that boiler cooling should take about 48 hours. 

: 38 NTSB/MAB-07/03
As noted earlier, when the ship was converted to Caribbean sailing, the four 

boilers in the forward engineroom were removed. The evidence indicates that two to 

three boilers operated at a time, with one usually being idle for maintenance. The original 

design documents were not available to show how the boilers were intended to be cycled. 

However, the actions taken by the classification society in 1987 when cracks were found, 

the statements from several of the engineers, and the numerous tube failures indicate that 

boiler cycling was damaging to the boilers and was known to be a problem on the 

Norway. 

Frozen Sliding Feet. Additional stresses on the boilers could have come from 

frozen sliding feet, which would have impeded the movement of the water drums and 

headers. Thermal stresses would have resulted when the pressure vessels sought to 

expand or contract during heating and cooling but were held in place by the frozen 

sliding feet. A January 2003 inspection by Harris Pye found that the feet of boiler No. 24 

did not appear to be lubricated. According to NCL maintenance records, repairs were 

made to the frozen feet of unidentified boilers 2 weeks before the rupture. 

The Norway’s original boiler manual contains the following guidance regarding 

the sliding feet: “The free movement of the boiler feet should be checked periodically. If 

necessary, introduce grease through the oval holes.”53 The Navy’s inspection manual54

states that maintenance personnel should inspect the sliding feet movement indicators 

before each light-off, during warmup, and after a boiler comes on line. The manual 

further states that a boiler whose sliding feet cannot be verified as functional should be 

shut down for repair. The Navy document suggests that the presence of frozen feet is a 

serious condition that can stress the boiler and that should be corrected immediately. 

Welding Procedure 

The evidence (weld appearance, examination of metallurgical sections through 

various welds, and NCL documents) indicates that a temper bead welding technique was 

used to repair cracking and corrosion in the longitudinal welds of the header of boiler 

No. 23. Temper bead welding is used to reduce the detrimental effects of exposure to the 

very high temperatures associated with the welding process. Temper bead welding 

creates a weld that has a reduced hardness and lower residual stresses compared with 

welds created using conventional welding processes. Appendix B describes the temper 

bead welding technique, the weld procedure used by Lloyd Werft on the Norway’s 

boilers, and the procedure used by the Navy on its boilers. 

BV had approved the welding process used by Lloyd Werft. However, Lloyd 

Werft’s procedure was not specific and did not indicate that a qualification plan was used 

to show that the welders were capable of the job. Nevertheless, because boiler operations 

were sufficient to create cracking in the header of boiler No. 23 before the weld repairs 

 53 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers,” p. 43. 

54 Navy Technical Manual, S9221-D2-MMA-010, “Technical Manual for Steam Generating Plant 

Inspection (Non-Nuclear),” section 4-2.3.2, b, 3; October 1990. 

: 39 NTSB/MAB-07/03
were made, even if the weld repair had properties similar to the original weld, additional 

cracking would have still occurred because NCL did not take the steps necessary to 

eliminate the conditions that had originally caused the cracking. In addition, the weld 

location showed changes in geometry, grain size, and structure. Those factors, in 

particular the residual stress, created conditions that allowed subsequent cracks to initiate 

sooner and propagate faster than the original cracks. 

The fracture along the upper longitudinal weld in boiler No. 23 extended about 

11 feet, and the fracture along the lower longitudinal weld extended about 8 feet. No 

evidence or substantiation of a welding procedure was found to show that weld repairs 11 

feet long were acceptable and would not affect the life of the boiler. According to the 

Navy’s procedure (appendix B), weld repairs exceeding 6 inches in length require special 

approval. 

Inspection and Maintenance 

Boilers are typically inspected by a combination of internal visual inspection and 

nondestructive testing such as fluorescent magnetic particle inspection or ultrasonic 

inspection. The evidence suggests that lack of proper internal inspections, lack of 

appropriate nondestructive inspections, poor guidelines, and poor training of its surveyors 

by BV may have caused the cracks in the Norway’s boilers to remain undetected. 

Documents show that cracks were first detected in 1970 on the original welds and 

were monitored through a combination of internal visual inspections and nondestructive 

testing by boiler repair specialists and BV. From interviews, investigators found that from 

1996 on, the surveyors changed their method of internal visual inspections of the headers. 

They began opening the manholes and looking inside with a flashlight rather than 

crawling inside and doing a thorough inspection (the condition of the boiler was assessed 

primarily by entering only the steam drum). 

According to the classification society rules, internal inspections were not 

required as long as pressure tests were performed. If visual internal inspections were 

performed, according to the guidelines to surveyors, inspectors did not need to enter the 

headers, only the steam drums. The visual inspection guide was vague and did not point 

out any specific areas to be inspected. The entire contents of the BV guidelines for 

inspecting the lower boiler drums consisted of the following:55

An internal inspection will not usually show much but any signs of pitting in the 

upper drum or tubes should be followed up by a further examination of the tubes 

via the lower drum. 

Manhole doors, their landings, joints and dogs should be carefully checked. 

 55 By comparison, the Navy’s technical manual for inspection of boiler drums and headers devotes an 

entire chapter to the inspection of boiler drums and headers (chapter 5 in Navy Technical Manual S9221-

D2-MMA-010). 

: 40 NTSB/MAB-07/03
After weld repair of the drums in 1987 and 1990, it appears that no further 

nondestructive testing was performed, except for the work done on boiler Nos. 22 and 24 

in 1996, which indicated that cracking continued. From 1990 through 2003, it appears 

that no nondestructive testing was done on the weld seams of boiler Nos. 21 and 23, even 

though the history of cracking was well-documented and cracking was rediscovered on 

the weld seams of boiler Nos. 22 and 24 in 1996. 

The Safety Board’s metallurgical examination found large, isolated copper 

nuggets on the fracture surfaces near the surface of the header. The nuggets closely 

matched the contours of both fracture halves. Analysis of the nuggets revealed that the 

material was highly worked, with elevated hardness, and that its composition was pure 

copper. Similar characteristics were produced in the materials laboratory using highly 

worked copper tubing. 

The copper nuggets were found in only two areas of the fracture surface next to 

the weld repairs and not in other areas of the fracture surfaces or in the other boiler 

drums. The boiler contained no sources of pure, highly worked copper. Pure copper could 

have been produced by corrosion of the copper materials elsewhere in the steam system, 

such as in the condenser, but it would not have had the same size, microstructural 

features, ground-flat areas, and elevated hardness as exhibited by the nuggets. The Safety 

Board’s metallurgist concluded that the nuggets were not produced by corrosion. The 

metallurgist also discounted the possibility that the copper had been deposited in the 

boiler as a result of chemical reactions between excess hydrazine and copper alloys in the 

condenser and feedwater system. 

The width, overall shape, structure, and ground surface of the copper nuggets 

clearly indicate that the copper was worked into the cracks after they were largely 

formed. This means that when the copper was introduced into the fatigue crack portion of 

the fracture in boiler No. 23, the crack was approximately 0.1 inch wide. None of the 

several boiler experts interviewed had ever heard of a temporary fix using copper. From a 

metallurgical point of view, copper would offer no structural benefits and would not be 

considered a repair.56 The only explanation for the presence of the copper is that it was 

introduced to mask the crack, impede inspection, and avoid necessary repairs. 

In recent years, no formal inspection program appears to have been carried out for 

the boilers, even though it was known that they were susceptible to cracking and were in 

fact cracked in 1996. For the Norway’s last 6 to 7 years of operation, there is no record 

that either classification society surveyors or NCL personnel entered the headers to 

inspect them. Although NCL personnel apparently opened the drums and headers and 

looked into the boilers to assess their cleanliness during the required 3,000-hour 

inspections, it does not appear that they actively inspected the drum and header interiors 

for cracks. The presence of copper on the fracture surfaces indicates that NCL shipboard 

 56 Forcing copper into the crack might have increased the tendency for the crack to propagate farther 

into the wall thickness. At any rate, the copper would have done nothing to reduce the concentration of 

stress at the tip of the crack when the boiler was pressurized. 

: 41 NTSB/MAB-07/03
: 42 NTSB/MAB-07/03

engineers were aware of the cracking condition but did not take appropriate action to fix 

the problem. 

Summary 

The Safety Board determined that the following factors contributed to the rupture 

of boiler No. 23 on the Norway: 

• Lack of adherence to water chemistry composition limits and procedures by 

both the water chemistry subcontractors and NCL during wet lay-up periods, 

leading to pitting from oxygen corrosion. 

• Failure to take number of boiler cycles into account during maintenance. 

• Severe thermal transients from heating and cooling the boilers too quickly 

and from constraints created by frozen boiler support feet. 

• Use of questionable weld repair procedures. 

• Lack of appropriate nondestructive testing by the BV surveyors and NCL 

inspectors to determine whether cracks were present. 

• Inadequate survey guidance from BV to its surveyors. 

• Failure to repair cracks into which copper had been inappropriately 

introduced. 

Probable Cause 

The National Transportation Safety Board determines that the probable cause of 

the boiler rupture on the Norway was the deficient boiler operation, maintenance, and 

inspection practices of Norwegian Cruise Line, which allowed material deterioration and 

fatigue cracking to weaken the boiler. Inadequate boiler surveys by Bureau Veritas 

contributed to the cause of the accident. 

BY THE NATIONAL TRANSPORTATION SAFETY BOARD 

MARK V. ROSENKER ROBERT L. SUMWALT 

Chairman Vice Chairman 

DEBORAH A. P. HERSMAN STEVEN R. CHEALANDER

Member Member

Adopted: October 29, 2007 

Member KATHRYN O’LEARY HIGGINS voted to disapprove this brief. 
 43

 

Appendix A 

Boiler Data 

The raw data from several boiler logbooks (water chemistry logbook from 

January 2000 to May 2001,1

 stoker’s logbook2 from July 1997 through May 2003, four 

printouts from pressure recorders for boiler Nos. 22 and 23) were examined and 

converted to tables and graphs for ease of analysis. The following describes the findings. 

Water Chemistry. The water chemistry logbook included daily readings on 

parameters such as phosphate, hydrazine, conductivity, chloride, pH, and alkalinity 

levels. The logbook also contained the amounts of GC,3 adjunct-B,4 Amerzine 

(hydrazine),5 and SLLC-A6 that were added to adjust the water chemistry. 

Only the levels of hydrazine were tabulated for this report. Table 1 shows the 

levels of hydrazine in all boilers for a randomly selected year (January through December 

2000). The green cells at the top of the table show where no data were available from 

January 1 to 26, 2000. No data were also available for several individual days (March 13, 

May 13, July 17, and November 29) and for 6 consecutive days in December (December 

13 to 18). The blank areas in days where data were collected show where water chemistry 

readings were not taken because specific boilers were idle or under repair. The required 

level of hydrazine was between 0.03 and 0.1 parts per million (ppm).7

 Table 1 shows 

hydrazine levels within the specification limits in black, those above the limit in blue, and 

those below the limit in red. The far right column shows the monthly readings of water 

chemistry8 taken by Drew Marine personnel during their on-site examination at the ship. 

The green cells in the monthly data again indicate months for which no records were 

found. Reviewing the data, the following was noted: 

• Almost every time a boiler came out of an idle period (lay-up), the hydrazine 

level was zero or near zero for one or more days. After reaching the specified 

1

 Norwegian Cruise Line (NCL) logbook containing water tests from January 2000 through May 2001. 

2

 A record book containing information about when boilers are started, shut down, cleaned, skimmed, 

or blown-down and the fuel nozzles cleaned. Entries are made at each watch. 3

 GC is a concentrated alkaline liquid that neutralizes acid and controls corrosion. 

4

 Adjunct B is a phosphate boiler water treatment chemical that works in conjunction with GC to 

control scale formation due to hardness. 5

 Amerzine (hydrazine) is a liquid catalyzed oxygen scavenger used to minimize oxygen corrosion in 

boiler steam and condensate systems. Amerzine also promotes the formation of protective iron and copper 

oxide films. 6

 SLLC-A is a condensate corrosion inhibitor made from a volatile liquid organic amine designed to 

minimize corrosion in steam and condensate systems by providing a pH environment, which neutralizes the 

effects of carbon dioxide. 7

 Drew Marine Control and Dosing chart, BW-CS-4 (May 2003). 

8

 Drew monthly water chemistry service reports. 
 44

 

range, the levels typically stabilized and then were generally maintained 

within operational limits. 

• In some cases, continued low levels of hydrazine were observed during 

operation. For example, in boiler No. 24 from July 27 to September 28, 2000, 

hydrazine levels were almost always below the specified minimum, at 

approximately 0.01 ppm. 

• No records were found to show that hydrazine levels were built up before idle 

periods (for idle conditions, 150-200 ppm hydrazine was recommended). 

• It appeared that boiler water chemistry readings were not taken on idle boilers 

in the wet condition9

 to assess the levels of hydrazine.10 

According to interviews and documents,11 typically two boilers were operated on 

a routine basis, with the third boiler operated during peak demand. The fourth boiler was 

typically idle for maintenance. Examination of the data in table 1 (yellow areas) 

confirmed that two boilers were operated on a routine basis, with a third coming on line 

as needed. 

Cycles. The number of boiler cycles in a given period was quantified by 

collecting data from the stoker’s logbook for several periods: one was chosen randomly 

and was from July 10, 1997, to July 15, 1998 (1 year), and the other was from January 

2002 to the failure date of May 25, 2003 (17 months). One boiler cycle was defined as 

going from zero load to a full load of 60-62 bar and back to zero. Tables 2 and 3 

summarize the data for these two periods, showing the number of boiler cycles and the 

amount of time the boilers were on and off. Tables 4A through 4C, which show raw data 

from the stoker’s logbook in visual form, contain the following cycle data: 

• All boilers from July 1997 to July 1998 (table 4A). 

• Boiler No. 23 from April 2001 to December 2001 (table 4B). 

• All boilers from January 2002 to May 2003 (table 4C). 

Table 2 shows that, for a 1-year period from 1997 to 1998, the boilers 

accumulated between 11 and 29 cycles, with the average being 23 cycles that year or 

approximately one cycle every 2 weeks. Table 3 shows that from the beginning of 2002 

through May 2003, the boilers accumulated between 18 and 26 cycles, with an average of 

21.5 in about 17 months, or 15.2 per year. Pressure charts and interviews with personnel 

indicated that when the boilers were shut down, they were typically brought to zero 

pressure. Therefore, the boiler pressure cycles were from zero pressure to the operating 

9

 The wet condition was when the boiler was shut down but still sealed and full of water. 

10 Based on when water chemistry readings were taken in the logbook and interviews. 11 NCL interoffice memo, March 16, 1998. 
 45

 

pressure of 62 bar (900 psi) and back to zero. It should be noted that the boilers were 

often started and shut down within 1.5 days or less, frequently in less than 0.5 day. 

Idle Periods. Tables 2 and 3 also show the amount of time the boilers were on 

and off. The red data indicate periods when the boilers were shut down for 20 or more 

days, and the blue data indicate periods when the boilers were shut down for 10 to 20 

days. Table 2 (1997-1998) shows that the boilers were shut down for 10 or more days 

between two and seven times each in this period. Boiler No. 21 was not shut down for 20 

or more days, boiler No. 22 had one instance where it was off for more than 20 days, 

boiler No. 23 had two instances, and boiler No. 24 had six instances. Table 3 (2002-2003) 

shows that in 17 months, the boilers were shut down between three and seven times each 

for 10 days or more. Boiler No. 23 had one instance where it was shut down for more 

than 20 days, boiler No. 21 had two instances, and boiler No. 24 had three instances. 

Startup and Cooldown. Four printouts from the boiler pressure recorders were 

examined to determine the rate of pressure buildup and dropoff. Table 5 summarizes the 

data. The question marks signify interrupted recordings, meaning that a full reading could 

not be obtained: either the recorders stopped before dropping to zero pressure or the 

boilers started back up in the middle of the cycle. 

The data indicate that the boilers went from zero pressure to a full pressure of 

60-62 bar in 1.5 to 5.5 hours. The average ramp-up rate was 3.4 hours. According to the 

charts, the boilers were fired at 10-minute intervals and shut down for 10 minutes until 

the boilers reached pressure. That practice is consistent with the boiler startup procedure 

in the original operating manual.12 

The rate of pressure drop from full pressure to zero ranged between 45 minutes 

(0.75 hours) and 4 hours, with an average of 2.8 hours. No expected pressure cooldown 

time was found in the original operating manual or other records. 

12 Liner France, Propulsion Machinery, Operation and Maintenance Guide, vol. 3, “Boilers,” p. 26. 
2000 

January 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 

22 023 024 

February 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.1 0.1 0.07 0.07 0.1 0.1 0.07 0.07 0.1 0.1 0.0722 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.05 0.1 023 0 0 0.03 0.07 0.07 0.07 0.07 0.1 0.07 0.05 0.1 0

24 0 0.01 0 0.03 0.01 0.01 0.01 0.03 0.07 0.07 0.07 0.07 0.1 0.1 0.05 0.07 0.07 0.07 0.07 0.07 0.07 0.03 

March 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.01 0.01 0.01 0.01 0 0.03 

22 0.3 0.07 0.07 0.07 0.07 0.07 0.1 0.1 0.07 

23 0.2 0.07 0.07 0.1 0.07 0.07 0.1 0.1 0.05 0.3 0.2 0.05 ? 0.2 0.05 0.03 0.05 0.1 0.05 0.05 0.2 0.03 0.03 0.1 0.1 0.07 0

24 0 0.03 0.05 0.03 ? 0.1 0.07 0.05 0.05 0.1 0.05 0.05 0.03 0.03 0.07 0.1 0.07 0

April 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0 0 0.03 0.03 0.05 0.05 0.07 0.1 0

22 0.01 0.01 0.03 0.01 0

23 0.1 0.1 0.1 0.3 0.2 0.05 0.07 0.3 0.03 0.03 0.1 0.1 0.03 0.1 0.2 0.07 0.07 0.1 0.07 0.07 

24 0.1 0.1 0.1 0.2 0.2 0.05 0.07 0.2 0.03 0.03 0.1 0.1 0.03 0.1 0.1 0.07 0.07 0.07 0.05 0.02 0.1 0.07 0.07 0.1 0.07 0.1 0

May 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.03 0.07 0.07 0.07 0.1 0.07 0.05 0.05 0.1 0.05 0.03 0.03 ? 0.01 0.03 0.07 0.05 0.03 0.07 0.07 0.05 0.03 0

22 0.05 0.1 0.07 0.05 0.07 0.07 0.07 0.05 0.1 0.07 0.05 0.05 ? 0.07 0.07 0.07 23 0.01 0.01 0 0.01 0.03 ? 0.07 0.07 0.07 0.07 0.05 0.05 0.01 0.03 0.03

24 0.01 0.01 0.01 0.01 0.03 0.01 0.05 0.05 0.03 0.03 0

June 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.05 0.05 0.01 0.03 0.05 0.07 0.07 0.05 0.05 0.05 0.03 0.03 0.03 0.05 0.05 0.07 0.05 0.05 0.05 0.07 0.05 0.05 0

22 0.05 0.05 0.07 0.05 0.05 0.05 0.03 0.05 0.05 0.07 0.07 0.05 0.05 0.05 0.03 0.03 0.03 0.05 0.05 0.07 0.05 0.05 0.05 0.01 0.07 0.05 0

23 0.01 0.08 0.07 0.05 0.05 0.03 0.07

24 0.01 0.03 0 0.01 0.03 0.03 

July 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.07 0.07 0.07 0.07 0.07 0.03 0.07 0.07 0.07 0.07 0.07 0.1 0.05 0.1 0.2 0.05 ? 0.05 0.07 0.03 0.05 0.1 0.05 0.07 0.07 0.07 0

22 0.07 0.07 0.07 0.07 0.07 0.05 0.07 0.07 0.07 0.07 0.07 0.07 0.05 0.1 0.1 0.05 ? 0.07 0.1 0.05 0.05 0.1 0.01 0.07 0.1 0.07 0

23 0.01 0.02 0.01 0.03 

24 

August 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.05 0.1 0.05 0.03 0.1 0.05 0.05 0.1 0.05 0.03 

22 0.03 0.05 0.1 0.05 0.03 0.03 0.01 0.01 0.05 0.07 0.05 0.1 023 0.05 0.03 0.01 0.02 0.05 0.07 0.1 0.1 0.1 0.07 0.05 0.1 0.1 0.1 0.15 0.1 0.2 0.07 0.07 0.1 0

24 0.01 0.01 0.01 0.01 0.01 0 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.03 0.02

September 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.03 0.05 0.1 0.07 0.0722 0.07 0.2 0.03 0.07 0.1 0.07 0.07 0.1 0.07 0.05 0.07 0.03 0.07 0.07 0.1 0.07 0.05 0.07 0.07 0.03 0

23 0.07 0.15 0.05 0.03 0.1 0.07 0.07 0.1 0.07 0.05 0.07 0.1 0.03 0.07 0.07 0.1 0.05 0.05 0.07 0.07 0.03 0.07 0.07 0.07 0.05 0.07 0

24 0 0.01 0.01 0.01 0 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0

October 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

2122 0.01 0.03 0.07 0.07 0.07 0.07 0.07 0.03 0.05 0.07 0.05 0.05 0.05 0.05 0.05 0.03

23 0.05 0.05 0.07 0.07 0.05 0.05 0.07 0.07 0.07 0.07 0.07 0.03 0.05 0.07 0.05 0.05 0.05 0.05 0.05 0.03 0.05 0.07 0.05 0.07 0.07 0.07 024 0.03 0.03 0.05 0.07 0.03 0.03 0.01 0.03 0.01 0.01 0.01 0.05 0.05 0.07 0.07 0.05 0

November 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.01 0.01 0.01 0.01 0.01 0.01 0.03 0.03 0.05 0.05 0.05 0.07 0.07 0.05 0.03 0.03 0.03 0.03 0.05 0.05 0.05 0

22 0.01 0.01 0.03 0.07 0.05 0

23 0.05 0.05 0.05 0.05 0.05 0.05 0.1 0.07 0.05 0.07 0.01 0.03 24 0.07 0.05 0.05 0.05 0.05 0.05 0.1 0.07 0.05 0.01 0.05 0.05 0.05 0.05 0.05 0.05 0.07 0.03 0.05 0.03 0.03 0.03 0.01 0.05 

December 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2

21 0.06 0.06 0.06 0.05 0.06 0.05 0.05 0.05 0.06 0.06 0.07 0.07 ? ????? 0 0.01 0.01 0.1 

22 0.07 0.06 0.05 0.05 0.07 0.06 0.06 0.06 0.06 0.06 0.07 0.07 ? ????? 0.05 0.05 0.03 0.05 0.07 0.05 0.05 0.07 023 0.04 0.04 ? ????? 0.03 0.05 0.03 0.05 0.07 0.05 0.05 0.07 024

Hydrazine ContentLimits 0.03-0.1 ppm

Hydrazine 2000
ON OFF ON OFF ON OFF ON OFF

cycle 1 0.5 2.5 1.5 12.5 >17 10.5 >37

2 0.5 9.5 16.5 8 21 8.5 8.5 41

3 1.5 1.5 33.5 0 2 3.5 20 4.5

4 12.5 5.5 8 9 8.5 5.5 44.5 26.5

5 1.5 4.5 0.5 1.5 1.5 1.5 15.5 12.5

6 1.5 6.5 1.5 5.5 12.5 6.5 8 7.5

7 16 5 6 22 0.5 11 6.5 27

8 2 0 1.5 1.5 6.5 1.5 39.5 8.5

9 9.5 1.5 2.5 1.5 0.5 7.5 0.5 4

10 0.5 7.5 1.5 2 22.5 12.5 1 23.5

11 19.5 0 2 14.5 8.5 3 3.5 31

12 0.5 1 23.5 13.5 0.5 1.5 >0.5

13 1.5 1.5 14.5 6.5 12.5 1.5

14 12.5 19.5 7.5 6 5.5 0.5

15 15.5 5.5 27 5.5 2.5 3

16 8.5 3 1 1 0.5 1.5

17 1 5 1.5 5.5 1.5 10.5

18 5 3.5 1.5 5.5 0.5 1.5

19 0.5 1.5 2 3 1.5 2.5

20 13.5 0 0.5 4.5 1.5 1.5

21 23 5.5 2 5.5 1.5 5.5

22 1.5 3.5 39 3 22.5 3.5

23 0.5 1.5 9 0.5 0.5 20.5

24 1.5 3.5 22 >0.5 28.5 3.5

25 0.5 1.5 5.5 22.5

26 58 5 12 11

27 23 12.5 3 0

28 11 3 4 >2

29 0 4

Summary Data

AVG DAYS ON

AVG DAYS OFF

Cycles

July 10, 1997 to July 15, 1998

29 24 28 11

4 6 6 19

8 9 7 15

BOILER OPERATION TIME (DAYS)

BOILER 21 BOILER 22 BOILER 23 BOILER 24

CYCLE COUNT 97-98
January 2002 ON OFF ON OFF ON OFF ON OFF

cycle 1 >12 4 >48 1 1.5 5.5 >15

2 3.5 2 27.5 2.5 16 1.5 0 13

3 7.5 1 46.5 16.5 12 3 0.5 13.5

4 3.5 5.5 58.5 1 29 1 0 6.5

5 43.5 3.5 33.5 0 46 16.5 0 35.5

6 3.5 3.5 14.5 3.5 1.5 2 0 13.5

7 3.5 12.5 12.5 10 5 2.5 35.5 0.5

8 75 3.5 8.5 2.5 32.5 16.5 0.5 44.5

9 1 2 18.5 9.5 18.5 5.5 16 4.5

10 8 16.5 11.5 2.5 5.5 5 1.5 0.5

11 6.5 5.5 4.5 2.5 30 2.5 0.5 0.5

12 6.5 15.5 4.5 2.5 13.5 9.5 2.5 1.5

13 8.5 4.5 4.5 2.5 1.5 1.5 2 0.5

14 3 8 12 2 57.5 2 0.5 0.5

15 19 9.5 33 2 5.5 1 2 1.5

16 2 42 5 17.5 2.5 0.5

17 35 1.5 19.5 0.5

18 21 1.5

19 11.5 8.5

20 5.5 0.5

21 13.5 4.5

22 30.5 2.5

23 8.5 16.5

January 2003 1 5.5 0.5 40.5 1.5 3.5 2.5 18.5 19.5

2 12.5 2.5 13 2.5 1.5 1.5 1 5

3 2.5 29.5 25 12.5 85.5 26.5 29 23.5

4 50.5 0 >37 >9 >51

57 0

6 9.5 >8

Summary Data

AVG DAYS ON

AVG DAYS OFF

2002-2003 cycles

January 1, 2002 to May 25, 2003

19

7

19

11

9

26

14

8

23

24

4

18

Failure 5/25/2003

BOILER OPERATION TIME (DAYS)

BOILER 21 BOILER 22 BOILER 23 BOILER 24

CYCLE COUNT 02-03
1997

jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 21 1805 1130 1630 800 1830 1125 2135

Boiler 22 1800 1155 

Boiler 23 2150Boiler 24aug 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1200 1800 1150 2020 440 

115 610

1750 

100 1135

sep 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1830 1800 1300 1620 

1245 

730 940 2010 1120 1755 1100 

oct 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

910 1750 

1400 1500 720 1915 1200 1750 

1200 1610/2250 

1400 1120 

nov 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1740 1235

1800 1040 2340 710 1800 

650 1625 925 1800

dec 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1800 1040 1805

705 1700

1030 1750 1020 

1015

1998jan 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1010 800 728 745 1040 2245 725 1805

1050 415

715 1810 855 1802 1110 1525 

1820 430

feb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

915 930 

1120 1515 1200 1110

1700 720 1750 1110 2330 450 1800 1145 1810

1825 1530 750 2210

mar 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1800 1030 1725 715 1850 1100 2010 555 1800

1150 

1030 1745 725

1805

apr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1755 1025 1800 1125 1800 1500 1410 730 1800 

1526

may 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

2100 155

340

700 1530 215

630 2100 700 430 725

jun 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

655 2245

140 440 820 1600

2145 2255

120 1100

jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1835 1850/2045 2300

1630

1825 1900 2030 2320

1615

Boiler cycles 97-03 
2001

apr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 21Boiler 22Boiler 23 400Boiler 24may 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1305jun 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1800 1105jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1530 1155aug 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1755 1010 955 1215 sep 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1110oct 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 1955 nov 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

NOVEMBER 2001 DRYDOCK BREMERHAVEN

1700

dec 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 23 945 2105 

Boiler cycles 97-03 
2002

jan 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Boiler 21 930 530 1610 1605 

Boiler 22 

Boiler 23 1820 1010 1800 1915 Boiler 24 2000/2300 

feb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1135 1735

2400 

1000 920

2010/2235 1200/1630

mar 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1100 1630 

end? 1950

600/80

apr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1610 1145 1735

1100

1950

may 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1810

1745 1135 1000 1200 

345 1350 325

jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

Jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1710 10 645 830 800

2140

1130 1750 1245 194550 1710 250 1525 

aug 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

2010 415 2210 750

1300 1820 230 1640

1140 345 2220 2300

1700 500 1735 1040 2100

sep 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1740 1030 300 230 

520 415 1120 2220

310 1910

240 1900 

oct 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1030 

1110 2130

1125 1630 700 1700

530 1305 1730 1250 

nov 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1130 1900 1015 1830 1115 1830 1100 1645

dec 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

2000

1210 1100

1245 1600 550 655 

1445 900 

jan 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

40 1645 905 1545

1125 800

30 1010 1630 735 1700

900

Feb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

935 1730 545

305 2200

410 930 955

Mar 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

2020

140 1255

745

Apr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

1045 1700

605

1650

May 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

830 1000 2300

1715

Boiler cycles 97-03 
Roll Boiler Ramp-Up Time (hrs) Cool-Down Time (hrs)

NTSB D023 22 0.75

15-Dec-02 ? 1

? ?

3 ?

3.5 2.5

3 3

2.75 ?

3 2.5

3

NTSB D024 23 4 ?

19-Oct-02 ? 2.75

? 3

3 ?

3.5 2.75

? ?

?

NTSB D025 23 4

17-Mar-03 4 ?

? ?

3.5 ?

3 ?

5.5 ?

?

NTSB D026 22 ?

31-Mar-02 ? 2.5

3 ?

1.5 2

3.5

Average 3.4 2.8

Boiler Transients
Appendix B 

Temper Bead Welding 

Temper bead welding is used to reduce the detrimental effects of exposure to the 

very high temperatures associated with the welding process. Using temper bead welding 

creates a weld that has a reduced hardness and lower residual stresses compared with 

welds created using conventional welding processes.1

 Reducing hardness improves 

resistance to brittle fracture, stress corrosion, and fatigue. Temper bead welding does not 

reduce residual stresses in a welded joint as well as full postweld heat treatment. 

However, if postweld heat treatment cannot be performed, some of its benefits can be 

obtained by using the temper bead welding technique. 

In a typical weld bead, grain coarsening occurs in the parent metal2

 next to the 

weld, while the parent metal slightly beyond experiences grain refining. The temper bead 

welding method was developed to reduce or eliminate the coarse-grain regions in the 

parent metal. Coarse-grained structures have poor resistance to fracture. Coarse-grained 

structures in the weld metal also reduce toughness, but not to the same extent as in the 

parent metal. 

In the temper bead welding method, first a layer of small weld beads with low 

heat input is laid to ensure minimum penetration of the parent metal. The technique 

entails using small electrodes, welding in the horizontal position, and adjusting the angle 

of the electrode or torch to minimize penetration, taking care to avoid cracking the metal 

from exposure to hydrogen and lack-of-fusion defects (incompletely fused spots). 

Successively larger weld beads are placed on top of smaller ones, such that the refined 

zone overlaps the coarse areas created by the original runs. Sometimes the first layer is 

slightly ground so that the refined zones of the successive layers line up correctly. The 

use of successive layers not only refines the grain structure of the parent metal, but each 

successive layer of weld beads tempers the previous weld bead. Often the top layers 

above the parent layer are ground off. 

The author of the “Gowelding” website states, “Unfortunately, whilst this may 

appear easy in theory, in practice it can be difficult to achieve. It requires the production 

of many test weld simulations and metallographic examinations, before sufficient 

confidence can be gained to perform the actual production weld.” According to the Navy 

repair manual,3

 

 1

 Further information on temper bead welding is found on the “Gowelding” website, which is 

maintained by a welding professional <www.gowelding.com/met/ temper.htm>, and also on the website of 

the Welding Technology Institute of Australia <wtia.com.au/>. 

2

 The metal of parts to be welded is referred to as the “parent metal.” 

3

 Navy Technical Manual S9221-C1-GTP-010, 0910-LP-331-5300, “Repair and Overhaul Main 

Propulsion Boilers,” vol. 1, revised February 1991, section 1-4.5.5, p. 1-6. 

 53
Whenever stress relief is required by MIL-STD-278, the proper application of 

stress relief procedures will produce weld metallurgical properties superior to 

those resulting from the stringer bead or temper bead procedures allowed by this 

manual for some of the welding on boilers. Repair activities should also be aware 

that, considering the requirements for temper bead procedure qualification and 

welder mock up trials, stress relief may in some cases be the more cost effective 

and timely alternative. 

The Navy’s temper bead welding procedure for low-carbon steel material up to 

1.5 inches thick (weld repair thickness 0.25 to 0.5 inch) is described in its technical 

manual (chapter 5) as follows: 

• Preheat joint to 350° F. 

• Use temper bead method, where no postweld heat treatment is required. If the 

repair area is over 6 inches in length, special approval is required. The 

procedure is as follows (see figure): 

Step 1: Perform first pass using 3/32-inch electrodes over entire joint that was 

ground and grind welds to produce smooth layer. 

Step 2: Deposit second full layer with 1/8-inch rods. 

Step 3. Deposit third and subsequent layers with 5/32-inch rods, making sure 

not to overlap tie-in points. 

Step 4: Grind off reinforcement until flush. 

Step 4 

Figure. Navy’s temper bead welding procedure, steps 1-3 (left), step 4 (right). 

According to Lloyd Werft working instructions dated October 26, 1987, the weld 

procedure used on the Norway’s boilers was as follows: 

The area of weld and a surrounding area of at least the drum wall thickness to be 

preheated to approximately 150° C [302 °F]. Such preheating will be done by 

 54
 55

means of resistance heating. Temperature control will be effected with 

thermocouples at inner side of drum. 

Welding additive will be a welding rod “E Mo B” to DIN 8575 of the trade mark 

“SH Schwarz 3 MK.” Welding to be done in string layers. 

Once the prepared area has been filled up, so-called hardening layers will be 

welded using material different from the base metal. These hardening layers will 

subsequently be worked off again.

The Lloyd Werft procedure does not mention the size of the rods, the heat input, 

or how the layers are to be deposited. Further, there is no indication that a qualification 

plan was used to show that the welders were capable of welding the boiler geometry, or 

that actual weld coupons were made to show that the welders could do the job. By 

comparison, when the boiler tubes were welded in place (in 1999 and 2002), the weld 

procedures were very specific, with evidence that qualifications trials were performed 

and passed. No evidence or substantiation of a welding procedure was found to show that 

repair welds 11 feet long were acceptable and would not affect the life of the boiler. 

(According to the Navy’s procedure, repair welds exceeding 6 inches in length require 

special approval.) Although the headers of boiler Nos. 21, 22, and 23 were welded, only 

header 21 appeared to have been ground flush.