CLIMATE WISE BOILER AND STEAM EFFICIENCY WISE RULES 

Pamela Hennan Milmoe 

Director, Climate Wise Program 

U.S. Environmental Protection Agency 

ABSTRACT 

Climate Wise is an industrial energy efficiency 

program sponsored by the U.S. EPA, and supported 

by the U.S. DOE, working in partnership with more 

than 400 industrial companies. Many Climate Wise 

Partners are evaluating or implementing boiler and 

steam system efficiency measures and have requested 

assistance in quickly estimating the impacts of these 

projects through the Wise Line. Climate Wise has 

developed the Wise Rules for Industrial Efficiency 

(Wise Rules Tool Kit) to provide companies with 

simple rules of thumb, or Wise Rules, for estimating 

potential energy, cost, and greenhouse gas emissions 

savings from key industrial energy efficiency 

measures for a broad range of end uses, including 

boilers and steam systems. This paper presents 

excerpts from the Wise Rules Tool Kit on boiler and 

steam system efficiency measures. 

INTRODUCTION 

The Wise Rules are a compilation of some of the 

best industrial energy efficiency infonnation from a 

variety of industrial, academic and government 

sources. The Wise Rules were developed from 

infonnation sources including the DOEIIAC database 

(8), the Rutgers University Office of Industrial 

Productivity and Energy Assessment, the Association 

of Energy Engineers and the Bonneville Power 

Administration, the Energy Efficiency and Renewable 

Energy ClearinghouselNetwork (ERECIEREN), the 

Centre for the Analysis and Dissemination of 

Demonstrated Energy Technologies (CADDET), and 

Climate Wise Partners' own estimates. These data 

sources are quite comprehensive and may be new to 

many Climate Wise Partners. We have extracted core 

information from these materials to provide Climate 

Wise Partners with ready-to-use Wise Rules. 

Thorough references are included to direct Partners to 

the original sources for more detailed treatment of the 

issues. The Wise Rules can help companies develop 

a first cut estimate of project impacts and provide 

guidance on how to analyze efficiency measures in 

more detail. 

Steven R. Winkelman
 

Senior Associate
 

ICF Kaiser Consulting Group
 

This paper presents excerpts from the Wise Rules 

Tool Kit on boiler and steam system efficiency 

measures. This will include a discussion of boilers 

and steam systems, and sample Wise Rules presented 

in text, tabular, and graphical fonnats. The Wise 

Rules provide a range of estimates of energy savings 

for broad categories of efficiency measures, (e.g., 

boiler maintenance), and more specific measures 

(e.g., adjusting air to fuel ratio). Savings estimates 

are expressed both as a percent of boiler fuel use and 

as a percent of an average facility's fuel consumption. 

BOll..ERS 

Boilers are one of the most important energy uses 

in manufacturing, typically comprising over 25 

percent of total manufacturing energy demand. A 

boiler generates hot water or steam, typically from the 

combustion of coal, oil or natural gas. A network of 

pipes delivers steam (or hot water) to provide heat for 

a variety of process and space heating applications. 

Once the heat has been extracted from the water or 

steam, another network of pipes returns the 

condensed water back to the boiler where it is 

cyclically reheated. There are several different types 

of boilers including natural draft, forced draft, hot 

water or steam, and fire tube or water tube. The 

typical boiler used in small-to-medium sized 

industrial operations is a forced draft steam boiler at 

120-150 psi and approximately ISO hp (equivalent to 

5.0 MMBtulhr) (4). Typical boiler efficiencies range 

from about 70 to 85 percent depending on fuel type, 

configuration, and heat recovery capability (3). 

Boiler Savings by Industry Group 

Figure 1 illustrates the potential energy savings 

from boiler efficiency measures based on IAC audit 

recommendations (8). Boiler efficiency measures 

with an average savings of 3% of facility energy use 

and a simple payback of 9 months were 

recommended at 20% of the 4,300 facilities audited 

from 1990 to 1997. 

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ESL-IE-98-04-47 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, TX, April 22-23, 1998
Recommendation 

Rate 

50% 6 month 

payback 

45% 

40% 

35% 

30% 

25% 

20% 

15% 

10% 

5% 

0% 

4 month 

payback 

• Recommendalion Rale 

6 month 

payback 

Energy Savings 

9 month 

payback 

Figure I. Boiler Savings by Industry Group (8) 

The Wise Rules Tool Kit provides a brief 

Ener 

Saving 

70/< 

60/1 

50/1 

40/1 

30/1 

20/1 

10/1 

00/1 

overview of the efficiency measures considered. 

Following is a discussion of boiler tune-up and 

air/fuel ratio optimization measures and associated 

Wise Rules 

Boiler Tune-Up and AirlFuel Ratio Optimization 

Using the following instruments allows plant 

engineers to properly monitor and adjust boiler 

operating conditions: stack thermometers, fuel 

meters, make-up feed water meters, oxygen analyzers, 

run-time recorders, energy output metering (steam 

flow, Btu output), and return condensate 

thermometers (6). Periodic measurement of flue gas 

oxygen, carbon monoxide, opacity, and temperature 

provides the fundamental data for a boiler tune-up. A 

typical tune-up might include a reduction of excess 

air (and excess oxygen, 02), boiler tube cleaning, and 

re-calibration of boiler controls. 

•	 A good tune-up with preclSlon testing 

equipment can detect and correct excess air 

losses, smoking, unbumed fuel losses, 

sooting, and high stack temperatures, and 

result in boiler fuel savings of 2% to 20% 

(6). 

Each fuel type and firing method has an opti al 

air/fuel ratio. For example, optimum excess air fo a 

pulverized coal boiler is 15 - 20% (3 - 3.5% exc ss 

02), and optimum excess air for a forced draft as 

boiler is 5 - 10% (l - 2% excess 02) (7). The air/f¥el 

ratio should be adjusted to the manufacturer's 

recommendations. Because it is difficult to reach ~d

maintain optimal values in most boilers, actual exctss 

air levels may need to be set higher than optimal !). Manual or automatic oxygen trim can insure that e 

proper air/fuel mixture ratio is maintained (2). 

•	 A 3% decrease in flue gas 02 typic lly 

produces a 2% increase in boiler efficie cy 

(I). 

•	 Using over fire draft control systems to 

control excess air can result in boiler el 

savings ranging from 2% to 10% ( ith 

typical equipment costs around $1,500) ( ). 

When boilers are operating at low loads excessair requirements may be greater than the opti~al

levels and efficiency may be lower (7). 

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•	 Using a characterizable fuel valve to match 

the airlJuel ratios across the load range can 

lead to fuel savings ranging from 2% to 

12% at low cost (6). 

The Wise Rules also include DOElIAC data on 

specific efficiency measures. For example, air/fuel 

ratio optimization was recommended at 16 percent of 

facilities audited. The average energy savings across 

all industry sectors was 2,100 MMBtu or 2.4 percent 

of annual facility energy use. The average 

implementation cpst for these measures was $5,600 

with a simple payback period of three months. 

Summary of Boiler Wise Rules 

The Wise Rules in Table 1 can be used to 

identify and estimate potential energy saving from 

boiler efficiency measures. In selecting alternative 

efficiency options and eliminating less attractive 

measures, consider the potential costs, savings, 

payback times and any secondary effects. When using 

the Wise Rules, remember that several of the 

measures may overlap, or complement each other 

(e.g., tune-up and flue gas 02 reduction) and energy 

savings rates of overlapping measures may not be 

additive. In addition. multiple Wise Rules may 

address the same measure from multiple perspectives. 

For example Boiler Wise Rule I expresses savings 

from boiler load management as a percent of the 

boiler's energy use. while Boiler Wise Rule 2 

expresses savings as a percent of the facility's total 

energy use. Wise Rules may not be comparable 

because they rely on different sources with different 

assumptions. 

Adjust the Wise Rules to match your 

circumstances. For example, you may want to scale 

the gross fuel cost savings to match your boiler size. 

To calculate savings for a 10 MMBtu/hr natural gas 

boiler, multiply gross fuel cost savings by a factor of 

ten. This scaling is applicable only to gross fuel cost 

savings expressed per MMBtulhr, e.g., Rule 2, but 

not Rule I in Table I. Implementation costs may not 

scale in a linear manner. Similarly, you can adjust the 

savings numbers on the basis of your fuel prices and 

operating hours. For example. if your boiler uses coal 

at a price of $1.50IMMBtu, divide the cost savings 

values in Table I by the per MMBtu price of natural 

gas. e.g., $2.30, and multiply by $1.50. 

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ESL-IE-98-04-47 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, TX, April 22-23, 1998
Measure 

(lAC Recommendation Rate) 

Summary: Typical Efficiency Improvements, Which May
 

Include Many or All of the Measures Below (20%)
 

Boiler Load Management 

I.	 Operate on high fire setting or install smaller boilers 

(1%) 

2.	 Optimize boiler size and boiler load
 

Tune-Up and AirlFueI Ratio Optimization
 

3.	 Implement boiler maintenance (air/fuel ratio
 

optimization, burner maintenance, boiler tube
 

cleaning) (16%)
 

4. Implement comprehensive tune-up 

5. Decrease flue gas 0') by 3% 

6. Utilize over fire draft control 

7. Utilize characterizable fuel valve 

8.	 Convert to atomizing burners
 

Stack Losses and Waste Heat Recovery
 

9. Reduce net stack temperature by 40 of 

10. Utilize stack dampers 

II. Direct contact condensation heat recovery 

12.	 Pre-heat combustion air (3%) 

Blowdown Control and Heat Recovery 

13.	 Minimize boiler blow down (1%) 

14.	 Remove 1/32" to 1/8" deposit from heat transfer 

surfaces 

15.	 Utilize blowdown heat recovery 

16.	 Increase boiler feed water by I10 F 

J7. Utilize automatic blowdown control 

Table I. Summary of Boiler Efficiency Measures 

Average Energy Savings* 

2.8% of total facility energy
 

use**
 

7.4% of total facility energy
 

use**
 

2% to 50%
 

2.4% of total facility energy
 

use**
 

2% to 20%
 

2%
 

2% to 10%
 

2% to 12%
 

2% to 8%
 

I % to 2% 

5% to 20% 

8% to 20% 

2.6% of total facility energy
 

use**
 

1.6% of total facility
 

energy**
 

2% to 8%
 

2% to 5%
 

1%
 

2% to 20%
 

Average Annual Cost
 

Savingsper MMBtuJhr
 

and (Paybackt
 

$7,200 (9 months) [total
 

dollars, not on a per
 

MMBtufhr basis]**
 

$19,900 (23 months)
 

[total dollars, not on a per
 

MMBtu/hr basis]**
 

$230 to $5,750***
 

$2,460 (5 months)
 

[total dollars, not on a pe
 

MMBtu/hr basis]**
 

$230 to $2,300***
 

$230***
 

$230 to $1,400***
 

$230 to $1,400***
 

$230 to $920***
 

$ 140 to $230***
 

$580 to $2,300***
 

$920 to $2,300***
 

$5,200 (8 months)
 

[total dollars, not on a per
 

MMBtu/hr basis]** 

$8,500 (11 months)** 

$230 to $920*** 

$230 to $580***
 

$140***
 

$230 to $2,300***
 

! 

, 

Table Notes:

• Percenl of boiler energy use, unless noted 

•• Energy savings are as a percent of total facility energy use. Cost savings (fuel, O&M, etc.) are expressed in dollars, not in 

dollars per MMBruIhr of boiler size. 

•••	 Based on a natural gas boiler with 80% efficiency, operating 5.000 hrsIyr, with a gas price of ~$2.30IMMBtu.These are gross 

fuel savings only and do not include capital, maintenance or other costs (savings). 

STEAM SYSTEMS maintenance, repairing steam leaks, insulation. 

Steam	 system efficiency improvements are a condensate measures, and va p p or recom ression ~"r

logical complement to boiler efficiency measures. 

Useful energy escapes from steam distribution 

systems from malfunctioning steam traps, steam 

leaks, and radiative losses from steam lines, 

condensate lines, and storage tanks. Each of these 

areas presents opportunities for energy savings. 

Based in data from the DOElIAC database (8), steam 

system efficiency measures were recommended a 

13% of the 4,300 facilities audi ted with an averag 

anticipated savings of 2% of a facility's total energ 

use and a simple payback of 6 months. 

The Wise Rules Tool Kit provides a brier 

Steam system efficiency measures that may be of overview of the efficiency measures considered' 

interest to Climate Wise Partners include steam trap 

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ESL-IE-98-04-47 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, TX, April 22-23, 1998
Following is a discussion of steam leak repair and 

insulation measures and associated Wise Rules. 

Repairing Steam Leaks 

Repairing leaks in steam pipes, condensate return 

lines, and fittings can yield significant energy and 

cost savings. Steam leaks increase boiler fuel use 

because additional steam must be generated to make 

up for the wasted steam. Leaky condensate return 

lines increase make-up water requirements and 

increase boiler fuel use because make-up water is 

cooler than condensate return water and more energy 

is required to heat the boiler feed water. Savings will 

depend on factors such as boiler efficiency, annual 

operating hours, and boiler pressure (4). 

•	 The cost of high pressure steam leaks (125 

psi) can range from $660 to $2,200 per leak 

per year (8,760 hrs). The cost of low 

pressure steam leaks (15 psi) can range 

from $130 to $480 per leak per year (8,760 

hrs) (5). 

Steam leak repair was recommended at two 

percent of the DOElIAC facilities audited (8). The 

average energy savings across all industry sectors was 

2,200 MMBtu or 0.9 percent of annual facility energy 

use. The average implementation cost for these 

measures was $6,100 with a simple payback period of 

three months. 

Improved Insulation 

Often insulation is removed to make repairs and 

is not replaced. Uninsulated surfaces in boiler and 

steam systems can reach 450 OF. These high 

temperatures can threaten employee safety and can be 

fire hazards. Table 2. presents annual costs of heat 

loss per 100 feet of uninsulated steam pipe. 

Steam Pressure Cost per 100 ft of pipe per year 

(8760 hr) 

25DSi $1,600 

50DSi $1,900 

75 psi $2,100 

100DSi $2,300 

Table 2. Annual Costs of Heat Loss per 100 feet of 

Uninsulated Steam Pipe (5) 

Sector-Specific Savings Estimates from Steam 

System Efficiency Measures in the lAC Database 

Table 3 provides sector-specific savings 

estimates from steam system efficiency measures in 

the lAC Database (8). As indicated in Table 3, the 

average savings across all industries (SIC 20-39) 

from measures such as steam trap replacement, leak 

repair, insulation, and improved operations was 2.1 

percent of total facility energy use with an average 

simple payback of 6 months. At a fabricated metals 

plant (SIC 34), system efficiency measures might 

reduce total facility energy use by 3.0 percent. Steam 

system efficiency measures recommended in the 

DOEIIAC audits had the largest relative impact in the 

fabricated metals industry (SIC 34), but were most 

frequently recommended in the textile mill products 

industry (SIC 22). 

Summary of Wise Rules for Steam Systems 

The Wise Rules in Table 4 can be used to 

identify and estimate potential energy saving from 

steam system efficiency measures. When identifying 

attractive options and eliminating weak ones, 

consider potential costs, savings, payback periods and 

any secondary effects. When using the Wise Rules, 

remember that some measures may overlap or 

complement each other (e.g., steam trap maintenance 

and steam pipe insulation) and energy savings rates 

may not be additive. Multiple Wise Rules may 

address the same efficiency measure from different 

perspectives. For example, Steam Rules I and 2 

express savings from steam trap maintenance as a 

percent of a facility's total energy use, and as a 

percent of boiler energy use. 

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ESL-IE-98-04-47 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, TX, April 22-23, 1998
51 

2 

2 

2 

2 

2 

2 

3 

3 

20­

TabIe 3. Sector-Specific Savings Estimates from Steam System Efficiency Measures in the lAC Database (8) 

Note: Includes traps, rondensate, leaks, insulation, and operations (1990-1997). 

C Industry Average Energy Savings 

Recomme 

ndation 

Rate (%) 

(% of total 

facility energy 

use) 

Annual 

(MMBtu) 

0 Food 27% 1.7% 1,540 

2 Textile Mill Products 32% ].6% 2,480 

3 Aooarel & Textile Products 26% 1.7% 620 

4 Lumber & Wood Products 15% 1.5% 3,930 

6 Paper 25% 1.3% 2,220 

8 Chemicals 26% 2.7% 7,170 

0 Rubber and Plastics 10% 2.4% 1,850 

4 Fabricated Metals 8% 3.0% 1,800 

39 Average Across Industries 14% 2.1% 2,420 

Average
 

Irnplementation
 

Costs
 

$2,600 

$6,890 

$990 

$2,940 

$3,870 

$3,370 

$2,860 

$2,610 

$3,350 

Average
 

Annual
 

Cost
 

Savings
 

$5,530
 

$7,940
 

$1,950
 

$5,480
 

$8,020
 

$13,550
 

$9,190
 

$5,510
 

$7,120
 

Averae:e 

Simple 

Payback 

(months) 

6 

10 

6 

6 

6 

3 

4 

6 

6 

Measure 

(IAC Recommendation Rate) 

Summary: Typical Efficiency Improvements, Which May 

Include Many or All of the Measures Below (13%) 

Steam Trap Maintenance 

I. Implement steam trap maintenance program (I %) 

2.	 Steam trao maintenance 

Leak Repair 

3. Repair steam leaks (2%) 

4. Repair high pressure (125 psi) leaks 

Repair low pressure ( 15 psi) leaks
 

Insulation
 

5. Improve insulation of steam lines (7%) 

Other Measures 

6. Recompress low pressure vapor 

7. Reduce heat loss from condensate (4%) 

Average Energy Savings* 

2% of total facility energy use 

3.4% of total facility energy
 

use
 

10-20% of boiler fuel use
 

1.0% of total facility energy
 

use
 

1.0% of total facility energy
 

use
 

90-95% of energy needed to
 

raise the steam in a boiler
 

1.3% of total facility energy
 

use
 

Average Annual Cost 

Savin~s and (Pavback) 

$7,100 (6 months) 

$17,400 ( 2 months) 

10-20% of boiler fuel costs 

$6,100 (3 months) 

$660 - $2,200 per leak $130 

- $480 oer leak 

$1,600 - $2,300 oer 100 ft 

$2,800 (10 months) 

$6,700 (8 months) 

Table 4. Summary of Steam System Efficiency Measures
 

Table note:
 

* Percent of stearn system energy use, unless noted. 

REFERENCES	 5. Rutgers University Office of Industrial Productivity 

1. 3M Company, "Rules of Thumb: Quick Methods of Energy Assessment, "Useful Rules of Thumb for Resourc 

Evaluating Energy Reduction Opportunities," 1992. Conservation and Pollution Prevention," March 1996. 

2. Garay, P.N., Handbook of Industnal Power and Steam 6. TaplIn, H.R., BOIler Plant and DlStnbutlOn System 

Systems, Fairmont Press. Optimization Manual, Fairmont Press, 1991. 

3. O'Callaghan, P., Energy Management, McGraw-Hill, 7. Turner, W.e., Energy Management Handbook, 3rl 

England, 1993, p. 198. Edition, Fairmont Press, 1997. 

4. Rutgers University, Office of Industrial Productivity and 8. U.S. Department of Energy, Industrial Assessment 

Energy Assessment, Modem Industrial Assessments: A Database, July 1997. 

Training Manual, Version LOb, December 1995. 

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