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RULE 4451 VALVES, PRESSURE RELIEF VALVES, FLANGES, THREADED 

CONNECTIONS AND PROCESS DRAINS AT PETROLEUM REFINERIES 

AND CHEMICAL PLANTS (Adopted April 11, 1991, Amended December 17, 

1992; Amended April 20, 2005) 

1.0 Purpose 

 The purpose of this rule is to limit leaks from valves, flanges, threaded connections and 

process drains that may result in fugitive emissions of VOC at petroleum refineries and 

chemical plants. Inspection, repair and maintenance schedules, recordkeeping and 

administrative requirements, and test methods are specified. 

2.0 Applicability 

 This rule applies to all valves, pressure relief valves, flanges, threaded connections and 

process drains at petroleum refineries and chemical plants that may be the source of 

fugitive VOC emissions. The provisions of this rule shall expire on April 19, 2006. 

3.0. Definitions 

 3.1 Background: a reading on a portable hydrocarbon detection instrument which is 

taken at least three (3) meters upwind from any valve, pressure relief valve 

(PRV), flange, threaded connections, or process drain to be inspected and which 

is uninfluenced by any specific emission point. 

 3.2 Chemical plant: an establishment that produces organic chemicals and/or 

manufactures products by organic chemical processes. 

 3.3 Commercial natural gas: a mixture of gaseous hydrocarbons, chiefly methane 

and less than ten (10) percent VOCs excluding ethane as determined in 

accordance with ASTM Methods E168-67, E169-63, or E260-73, used as a fuel 

and obtained from a company licensed to dispense such gases. 

 3.4 Component Type: any one (1) of the following groups: valves, pressure relief 

valves, flanges, threaded connections, and process drains. 

 3.5 Essential Device: any device which cannot be taken out of service without 

reducing by more than 33 percent the throughput of the process unit which it 

serves. 

 3.6 Essential Refinery Operation: any operation which cannot be taken out of 

service without reducing by more than 33 percent the throughput of the process 

unit which it serves. 
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 3.7 Flange: a projecting rim on a pipe used to attach it to another pipe or any other 

component in a piping system. 

 3.8 Inaccessible: a location that is over 15 feet above ground when access is 

required from the ground; or a location that is over six (6) feet away from a 

platform when access is required from the platform. 

 3.9 Leak: 

 3.9.1 for valves, flanges and threaded connections: 

 3.9.1.1 the dripping of liquid organic compounds at a rate of more 

than three (3) drops per minute; 

 3.9.1.2 a reading of methane on a portable hydrocarbon detection 

instrument in excess of 10,000 ppm above background 

when measured at a distance of one (1) centimeter of the 

potential source with an instrument calibrated with 

methane. 

 

 3.9.2 for pressure relief valves (PRVs) a reading of methane on a portable 

hydrocarbon detective instrument in excess of 10,000 ppm above 

background when measured in the plane at the centroid of any 

atmospheric vent with an instrument calibrated with methane. 

 3.9.3 for process drains a reading of methane on a portable hydrocarbon 

detection instrument in excess of 10,000 ppm above background when 

measured at a distance of one (1) centimeter of the potential source with 

an instrument calibrated with methane. 

 3.10 Maintenance Operation: a routine program of inspection and repair of 

equipment designed to detect and eliminate conditions which may result in a 

breakdown. 

 3.11 Portable Hydrocarbon Detection Instrument: a hydrocarbon analyzer which 

uses the flame ionization detection or thermal conductivity methods and satisfies 

Method 21, 40 CFR Part 60. The instrument shall be equated to calibrating on 

methane and sampling at one (1) liter per minute. 

 3.12 Pressure Relief Valve (PRV): an automatic pressure relieving device associated 

with a process vessel or piping system which is activated by static pressure 

upstream of the device and relieves to the atmosphere. 

 3.13 Process Drain: any open portion of a non-continuous piping system, including 

open origination portion(s) of such a system used for collection and transport of 
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liquids discharged from process vessels. Drains used exclusively during 

breakdown conditions pursuant to Rule 1100 (Equipment Breakdown) or 

exclusively for maintenance operations are not process drains for the purposes 

of this rule. 

 3.14 Refinery: an establishment that processes petroleum as defined in the Standard 

Industrial Classification Code under 2911 (Petroleum Refining). 

 3.15 Unsafe: those components which are operating at temperatures or pressures 

which make inspection of these components hazardous to inspection personnel. 

 3.16 Valve: any device that regulates the flow of fluid in a piping system by means 

of an external actuator acting to permit or block passage of fluid. 

4.0 Exemptions 

 4.1 Valves, PRVs, flanges, and threaded connections handling only commercial 

natural gas are exempt from the provisions of this rule. 

 4.2 Valves, PRVs, flanges, threaded connections, and process drains handling 

material which has less than ten (10) percent by weight VOCs (as determined in 

accordance with ASTM Methods E-168-67, E-169-63, E-260-73), are exempt 

from the provisions of this rule. 

 4.3 The requirements of Section 5.2.1 and 5.2.2 shall not apply to valves, flanges, 

threaded connections and PRVs that are unsafe to inspect due to conditions of 

operation (e.g. high temperature). Prior written concurrence of the APCO shall 

be obtained and such valves, threaded connections and PRVs shall be inspected 

for signs of leakage during turnaround. 

 4.4 The requirements of Section 5.2.1 and 5.2.2 shall not apply to valves, flanges, 

threaded connections and PRVs which are in inaccessible locations provided the 

prior written concurrence of the APCO has been obtained and such valves, 

threaded connections and PRVs are inspected for leakage during each process 

unit shutdown or annually, whichever is more frequent. 

 4.5 The requirements of this rule shall not apply to components handling exclusively 

heavy liquid streams which have less than ten (10) percent evaporation at 150o

 C 

as determined by ASTM Method D-86-78 and provided the operator so 

identifies such components as outlined in Section 6.1 or prior to changing 

service of existing components. 

 4.6 Except in Kern County, the requirements of Section 5.1.1 shall not apply to 

components handling VOCs with a TVP less than or equal to 1.55 pounds, 

process drains and threaded connections, until November 1, 1991. In Kern 
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County, the requirements of Section 5.1.1 shall be effective upon date of 

adoption. 

 4.7 The requirements of Sections 5.1.4 and 5.2.1 shall not apply to threaded 

connections provided that the operator inspects each threaded connection after 

assembly with a portable hydrocarbon detection instrument to establish such 

connections do not have VOC emissions under operating conditions, and 

provided such connections are visually inspected at least quarterly and no 

leakage is detected. This section shall also apply to threaded connections in 

service prior to the adoption of this rule. 

 4.8 Ethane shall be excluded from the requirements of this rule if the ethane content 

of the stream being handled is less than 20 percent by volume. A facility 

operator requesting exemption of ethane shall demonstrate for each leak 

detected, that such stream has an ethane content less than 20 percent. Analysis 

of ethane content shall be by gas chromatographic (qualitative and quantitative 

determination in accordance with ASTM Method E-260-73) analysis. 

5.0 Requirements 

 5.1 General 

 5.1.1 A facility operator shall not use any valve, PRV, flange, threaded 

connections, or process drain at a petroleum refinery or chemical plant 

for handling VOCs unless such valve, PRV, flange, threaded connection, 

or process drain does not allow the material being handled to leak into 

the atmosphere. 

 5.1.2 Emissions from components which have been tagged by the facility 

operator for repair within fifteen calendar days or which have been 

repaired and are awaiting re-inspection pursuant to Section 5.2 shall not 

be in violation of the prohibition in Section 5.1.1 providing the total 

number of leaking components of any component type does not exceed 

two (2) percent of the total number of components of that type that were 

inspected and that are subject to the prohibitions of this rule. 

 5.1.3 In a petroleum refinery or chemical plant a facility operator shall inspect 

every valve, PRV, flange, threaded connection, and process drain 

handling VOCs in accordance with Section 5.2. Any such device that 

leaks shall be repaired in accordance with Section 5.3, such that each 

device shall not leak. 

 5.1.4 A facility operator shall not use any valve, other than a valve on a 

product sampling line, a safety pressure relief valve, or a double block 

and bleeder valve, which is located at the end of a pipe or line containing 
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VOCs unless such valve is sealed with a blind flange, plug or cap. This 

shall not include loading spouts and water drain valves. 

 5.1.5 Every leaking valve, PRV, flange, threaded connection, and process 

drain shall be affixed with a record of inspection which shall bear a 

legible record of all inspections for at least a fifteen month period or 

coded with the records kept in a centralized location. 

 5.2 Inspection 

 5.2.1 All valves, threaded connections and PRVs handling VOCs shall be 

inspected for leakage at least once every three (3) months. If less than 

two (2) percent of the components of any component type subject to the 

prohibitions of this rule, except PRVs, are found to leak during each of 

five (5) consecutive quarterly inspections, the inspection frequency for 

that component type may be changed from quarterly to annual. If any 

annual inspection shows that two (2) percent or more of all of a specific 

component type subject to the prohibitions of this rule are leaking, then 

quarterly inspections of that component type shall be resumed. 

 5.2.2 All flanges and process drains handling VOCs shall be inspected at least 

once every 12 months. 

 5.2.3 Within three (3) days after any PRV vents to atmosphere the operator 

shall inspect with a portable hydrocarbon detection instrument any such 

PRV and shall repair any leak in accordance with Section 5.3.1. 

 5.2.4 Inspection shall be accomplished by sampling for vapors with a portable 

hydrocarbon detection instrument and by visual examination for 

indication of liquid leakage. 

 5.2.5 Any leaking component shall be identified by affixing a weatherproof, 

readily visible tag bearing the date on which the leak is detected. The 

tag shall remain in place until repair and reinspection documents 

compliance with the requirements of this rule. 

 5.2.6 Each leak detected shall be recorded on the inspection record along with 

the date of inspection, component identification number, actual 

instrument reading, and the inspector's initials. 
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 5.3 Repair 

 5.3.1 Within 15 days after detection any valve, PRV, flange, threaded 

connection, or process drain found to leak shall be repaired or vented to 

a flare satisfying the requirements of 40 CFR 60.18 or to a vapor control 

device that is at least 95 percent efficient as measured by EPA Method 

25. 

 5.3.2 The following repair schedule shall apply to any valve, PRV, flange, 

threaded connection, or process drain that is found to leak and that 

cannot be repaired to a no-leak condition without requiring the shutdown 

of essential refinery operations: 

 5.3.2.1 If the leak rate is less than ten (10) drops per minute the 

following shall be required and the APCO shall be 

notified of: 

 5.3.2.1.1 the expected date of repair, not to exceed 

one (1) year or the date of the next process 

unit turnaround whichever is less, for each 

valve, PRV, flange, threaded connection, 

and process drain, and 

 5.3.2.1.2 the actual date of repair for each valve, 

PRV, flange, threaded connection, and 

process drain. 

 5.3.2.2 If the leak rate is greater than nine (9) drops per minute or 

10,000 ppm measured one (1) centimeter from the source, 

the following shall be required and the APCO shall be 

notified of: 

 5.3.2.2.1 an emergency repair, within 15 days after 

detection, to reduce the leak to less than ten 

(10) drops per minute or 10,000 ppm as 

methane measured one (1) centimeter from 

the source, or 

 5.3.2.2.2 the venting, within 30 days after detection, 

of the emission to a flare or vapor control 

system that satisfies the requirements of 

Section 5.3.1, or 

 5.3.2.2.3 a demonstration, within 30 days after 

detection, that measures in Sections 5.3.2.1 
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and 5.3.2.2 are infeasible. The 

demonstration shall include documentation 

that the component is an essential device 

and that no vapor control device that 

satisfies the requirements of Section 5.3.1 

exists. 

 5.3.2.3 Repair an essential device to eliminate the leak during the 

next process unit shutdown, but in no case later than one 

(1) year from the date of the original leak detection. 

6.0 Administrative Requirements 

 6.1 Operator Management Plans 

 6.1.1 Each operator shall, not later than November 1, 1991, submit a 

management plan to the APCO. The management plan shall describe 

how the operator will comply with the requirements of this rule. 

 The management plan must include: 

 6.1.1.1 description of any hazard which might affect the safety of 

an inspector; 

 6.1.1.2 identification of process units which cannot be 

immediately shutdown for repair of leaks; 

 6.1.1.3 identification of components for which an exemption in 

accordance with Sections 4.1 through 4.6 of this rule is 

requested; 

 6.1.1.4 specific identification of the resource commitment to a 

program to implement, inspect, and repair components; 

 6.1.1.5 schedule of quarterly inspections to be conducted in 

accordance with EPA Method 21.; and 

 6.1.1.6 repair procedures to be used within 15 calendar days 

following leak detection which results in compliance with 

the requirements of this rule. 

 6.1.2 The operator of a new facility or a facility to be modified shall submit a 

new or modified operator management plan to the APCO prior to 

implementation of an Authority to Construct. 
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 6.1.3 Each management plan shall: 

 6.1.3.1 specify whether contractor or employee inspection will be 

used; 

 6.1.3.2 specify training standards for personnel performing 

inspections, and 

 6.1.3.3 provide leak detection training (using a portable 

hydrocarbon detection instrument) for new operators, and 

for experienced operators as necessary. 

 6.1.4 Changes to the management plan must be submitted to the APCO before 

implementation. If the APCO fails to respond to the plan in writing 

within 30 days, it shall be deemed approved. 

 6.2 Recordkeeping 

 6.2.1 Each facility operator shall maintain an inspection log containing, at a 

minimum, the following: 

 6.2.1.1 name, location, type of components, and description of 

any unit where leaking components are found. 

 6.2.1.2 date of leak detection, emission level (ppm) of leak, and 

method of detection. 

 6.2.1.3 date and emission level of recheck after leak is repaired. 

 6.2.1.4 identification of leaks that cannot be repaired until next 

process unit turnaround. 

 6.2.1.5 total number of components inspected, and total number 

and percentage of leaking components found. 

 6.2.2 Copies of the inspection log shall be retained by the operator for a 

minimum of two (2) years after the date of an entry. 

 6.2.3 Copies of the inspection log shall be made available upon request to 

District personnel. 

 6.3 Test Methods: 

 6.3.1 Analysis of halogenated exempt compounds shall be by ARB Method 

432.
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Administrative Change 12/5/05

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 6.3.2 Efficiency of VOC destruction device shall be measured by EPA Method 

25, 25a, or 25b, as applicable, and analysis of halogenated exempt 

compounds shall be analyzed by ARB Method 422. 

 6.3.3 The TVP of organic liquids, including light crude and petroleum 

distillates, shall be measured using Reid vapor pressure ASTM Method 

No. D-323-82 modified by maintaining the hot water bath at storage 

temperature. Where storage temperature is above 100°F, TVP may be 

determined by Reid Vapor pressure at 100°F and ARB approved 

calculations. Organic liquids listed in Table 1 shall be deemed to be in 

compliance with the appropriate vapor pressure limits for the material, 

provided actual operating temperature does not exceed the corresponding 

maximum temperature listed. 

 6.3.4 Leak detection shall be performed with a portable hydrocarbon detection 

instrument in accordance with EPA Method 21. 
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 Table 1 

 TEMPERATURE VERSUS VAPOR PRESSURE 

ORGANIC LIQUID Reference Properties Maximum Temp °F 

Not to Exceed 

Gravity 

°API 

IBP 

°F 

0.5 (psia) 1.5 (psia) 

Middle Distillates 

Kerosene 42.5 350 195 250 

Diesel 36.4 372 230 290 

Gas Oil 26.2 390 249 310 

Stove Oil 23 421 275 340 

Jet Fuels 

JP-1 43.1 330 165 230 

JP-3 54.7 110 --- 25 

JP-4 51.5 150 20 68 

JP-5 39.6 355 205 260 

JP-7 44-50 360 205 260 

Fuel Oil 

No. 1 42.5 350 195 250 

No. 2 36.4 372 230 290 

No. 3 26.2 390 249 310 

No. 4 23 421 275 340 

No. 5 19.9 560 380 465 

Residual 19.27 --- 405 --- 

No. 6 16.2 625 450 --- 

Asphalts 

60-100 pen. --- --- 490 550 

120-150 pen. --- --- 450 500 

200-300 pen. --- --- 360 420 

IBP = Initial Boiling Point