Safety Spotlight: Cleaning Gas Piping

Friday, March 29, 2019 @ 02:03 PM gHale

EDITOR’S NOTE: This is the second in a three-part series that excerpts the Chemical Safety Board’s (CSB) spotlight on the importance of safety guidelines, codes and standards to the manufacturing automation industry. This segment talks about gas piping cleaning.

Almost 10 years ago, on June 9, 2009, four workers died, three were critically burned, and 67 others injured in a natural gas explosion at the ConAgra Foods Slim Jim meat processing facility in Garner, North Carolina.

At the time of the explosion, natural gas was being purged indoors from piping connected to a newly installed water heater.

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Similarly, on February 7, 2010, six workers were killed during a planned activity to clean debris from natural gas pipes at Kleen Energy in Middletown, Connecticut.

To remove the debris, workers forced natural gas through the piping at a high pressure and volume (known as a “gas blow”). At predetermined locations, the natural gas and debris released directly to the atmosphere. During this process, the natural gas found an ignition source and exploded.

In light of those two incidents, it is clear industry safety guidelines, codes, and standards play a key role in protecting the safety and health of workers, the public, and the environment.

As part of its mission, the Chemical Safety Board (CSB) makes recommendations to standards developing organizations (SDOs), when industry-wide safety gaps or weaknesses are identified during an incident investigation.

After an investigation, the CSB concluded that relevant industry codes and standards did not address safe practices for cleaning fuel gas piping and did not require fuel gas piping to be vented safely outdoors.

Along those lines, the CSB made a recommendation to the National Fire Protection Association (NFPA) to revise the scope of its National Fuel Gas Code, NFPA 54/ANSI Z223.1, a consensus standard that provides requirements for fuel gas piping system safety. The recommendation called for the NFPA to: Enact a Tentative Interim Amendment and permanent changes to the National Fuel Gas Code (NFPA 54/ANSI Z223.1) that address the safe conduct of fuel gas piping cleaning operations.

At a minimum:
1. Remove the existing NFPA 54 fuel gas piping exemptions for power plants and systems with an operating pressure of 125 pounds per square inch gauge (psig) or more.
2. For cleaning methodology, require the use of inherently safer alternatives such as air blows or pigging with air in lieu of flammable gas.

In response, NFPA developed and issued a new gas process safety standard via an expedited rulemaking process. As a result, NFPA 56, Standard for Fire and Explosion Prevention During Cleaning and Purging of Flammable Gas Piping Systems was developed and approved in less than 24 weeks. The typical NFPA code development process lasts roughly 104 weeks. The 2014 edition of the standard was approved in July 2013. NFPA 56 prohibits the use of flammable gas to clean piping and provides guidance for the use of non-flammable alternatives.

The standard also includes detailed safety requirements for purging fuel gas piping systems into and out of service, a common practice which inevitably involves some release of flammable gas. Notably, the standard requires that discharged gases be released to an outdoor location or captured for further processed before release.



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