Pipeline Safety: Safety of Liquefied Petroleum Gas (LPG) Distribution Systems

AGENCY:

Research and Special Programs Administration (RSPA), DOT.

ACTION:

Notice; issuance of advisory bulletin.

SUMMARY:

This advisory bulletin urges owners and operators of liquefied petroleum gas (LPG) distribution systems to review their compliance with all leak detection, corrosion monitoring, and emergency response procedures, including training of emergency response personnel and liaison with emergency responders. Heavy rains and frozen soils can cause leaking propane to migrate to low areas, such as basements, and impede measurement of the presence of combustible gas.

FOR FURTHER INFORMATION CONTACT:

Richard Huriaux, (202) 366-4565; or by e-mail, richard.huriaux@rspa.dot.gov. This document can be viewed at the OPS home page at http://ops.dot.gov.

SUPPLEMENTARY INFORMATION:

I. Background

On September 1, 2002 a propane gas explosion leveled a house in Snow Hill, MD. An employee of the local gas distribution company was killed and 17 emergency responders and others were injured, four critically. The accident is under investigation by the Maryland Public Service Commission. Initial observations indicate that the propane gas explosion occurred as the basement was being mechanically ventilated. The propane gas may have leaked into the house from a corroded service line.

The Federal pipeline safety regulations for gas pipeline systems (49 CFR part 192) provide safety requirements for corrosion control, leak detection, operations and maintenance, and emergency response for LPG systems. Leak detection on LPG systems is complicated because LPG is heavier than air and has a lower explosive limit (LEL) of 2 percent in air. Leak detection equipment must be calibrated to detect this lower concentration. Leak detection may also be complicated by extremely wet or frozen soils and by ineffective leak detection procedures. Wet or frozen soils can effectively cap an area of leaking gas and cause gas that had been venting through the soil into the air to be redirected along underground utility lines or through loosely compacted soils into structures, especially basements. Both these conditions require leak detection procedures that emphasize measurement of gas below the surface of the soil or pavement. Usually this is accomplished by “bar holing” and examination of below ground areas, such as manholes, storm drains, and basements.

In addition, the gas pipeline safety regulations require an operator to establish and follow written procedures for responding to an LPG pipeline emergency (49 CFR 192.615). The operator's emergency plan for LPG must recognize its different characteristics. The operator must establish effective communications between utilities and appropriate fire, police, and other public officials. The regulations require a continuing educational program to enable customers, the public, and appropriate government organizations to recognize an LPG pipeline emergency and to take action to notify the gas operator and local emergency responders (49 CFR 192.616).

Prompt and effective response is required when gas is detected in or near a building. All actions should be directed to protecting people through a prompt evacuation of the affected buildings and securing the area.

RSPA and its state pipeline safety program partners have recently issued a manual to assist LPG pipeline operators in safely operating their systems and effectively responding to emergencies. The Training Guide for Operators of Small LP Gas Systems, which was prepared for RSPA by the National Association of Regulatory Utility Commissioners, includes information on LPG pipeline system operations and maintenance and on preparing the required emergency response manual. Chapter X addresses gas leakage control guidelines for LPG systems. It includes guidelines for the detection, grading, and control of gas leakage for systems handling LPG and other heavier-than-air gas mixtures.

Another excellent source of information on complying with the gas pipeline safety regulations is the Guide for Gas Transmission and Distribution Piping Systems ^© (ANSI GPTC Z380.1-1998), which is published by the Gas Piping Technology Committee. The document provides useful detail on written emergency procedures, including making the area safe through evacuation, access control, elimination of sources of ignition, ventilation, and coordination with emergency responders. It also addresses procedures for establishing liaison and emergency planning with public officials.

II. Advisory Bulletin (ADB-02-05)

To: Owners and Operators of Liquefied Petroleum Gas (LPG) Distribution Systems.

Subject: Safety of Liquefied Petroleum Gas (LPG) Distribution Systems

Purpose: To advise owners and operators of liquefied petroleum gas (LPG) distribution systems

Advisory: Owners and operators of liquefied petroleum gas (LPG) distribution systems should review their compliance with all leak detection, corrosion monitoring, and emergency response procedures, including training of emergency response personnel and liaison with other agencies.

LPG system operators should ensure that their procedures are adequate to detect leaks of heavier-than-air gas. LPG leaks do not dissipate as readily as does the natural gas, which is lighter than air and tends to rise through the soil. Leak detection may also be complicated by extremely wet or frozen soils that effectively cap an area of leaking gas and cause gas that had been venting through the soil into the air to be redirected along underground utility lines or through loosely compacted soils into structures, especially basements. Both these conditions require a leak detection procedure that emphasizes measurement of gas below the surface of the soil or pavement. Usually this is accomplished by “bar holing” and examination of below ground areas, such as manholes, storm drains, and basements.

In addition, the gas pipeline safety regulations require an operator to establish and follow written procedures for responding to LPG pipeline emergencies (49 CFR 192.615). This includes establishment of communications systems between utilities, and appropriate fire, police, and other public officials. The regulations also require an operator to establish a continuing educational program to enable customers, the public, and appropriate government organizations to recognize a gas pipeline emergency and to take action to notify the gas operator and local emergency responders (49 CFR 192.616).

Prompt and effective response is required when gas is detected in or near a building. All actions should be directed to protecting people first through a prompt evacuation of the buildings, followed by establishing access control, elimination of sources of ignition, ventilation, and coordination with emergency responders.