Re: “Natural Gas Piping: It’s Time for Better Risk Control,” by John Puskar, PE (May 2010)

Mr. Puskar’s recommendations to address the hazards associated with purging and blowing natural gas from large industrial piping systems are a significant contribution to the dialogue that is taking place on this important subject. Mr. Puskar correctly identifies two codes that can inform the designer, constructor, and operator of fuel gas piping systems in preparation for a safe purge of natural gas into and from the piping: 29 CFR 1910.147, concerning the lockout/tagout control of hazardous energy, and the National Fuel Gas Code (NFPA 54). POWER magazine readers should also know of the limitations of NFPA 54 and of the other statutes and codes that may apply to this activity.

First, while NFPA 54 does govern the design, construction, inspection, and purging requirements for many commercial fuel gas systems, that code does not apply to fuel gas piping in electric utility power plants. A 2009 revision to Section of NFPA 54 explicitly excludes those piping systems from the reach of that code. Instead, ASME B31.1, Power Piping Code, applies to the design, construction, and inspection of power plant fuel gas piping systems. The applicability of ASME B31.1 to these piping systems is made explicit in paragraph 100.1.2 of that code. Also, the NFPA 54 defines a purge as follows: “To free a gas conduit of air or gas, or a mixture of air or gas.” The cause of the 2009 explosion at the ConAgra plant in North Carolina, as reported by the U.S. Chemical Safety Board (CSB), was the result of one or more unsafe gas purges. In contrast, the CSB reports that the 2010 explosion at the Kleen Energy plant in Connecticut was the result of a “gas blow.” The CSB reports that a “gas blow” is an operation in which natural gas is used to clean debris from new fuel gas piping. A “gas blow” is not a “purge” as that term is used in NFPA 54. Southwest Gas does not perform gas blows, and is unaware of any other natural gas utility that cleans debris from its pipelines by gas blowing.

Next, for those employers that are bound by the U.S. Occupational Safety and Health Act, 29 USC 654(a)(1) applies to gas purging and blowing operations. This federal statute is the "general duty" clause, and it provides that: "Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees." The 2009 Field Operations Manual, published by the Occupational Safety and Health Administration (OSHA) of the U.S. Department of Labor, describes the operation of the general duty clause as follows:

“In general, [U.S. Occupational Safety and Health] Review Commission and court precedent have established that the following elements are necessary to prove a violation of the general duty clause:

  • The employer failed to keep the workplace free of a hazard to which employees of that employer were exposed;
  • The hazard was recognized;
  • The hazard was causing or was likely to cause death or serious physical harm; and
  • There was a feasible and useful method to correct the hazard.”

Finally, the OSHA Hazard Communication Standard (HCS) can apply to gas purging and blowing operations. Identical versions of this code are found at 29 CFR 1910.1200 and at 29 CFR 1926.1200. Natural gas is a “hazardous chemical” as that term is used in the HCS, and as such, employers that move or displace natural gas during any purging or gas blowing operations are required by the HCS to obtain the material safety data sheets (MSDSs) for the natural gas that they are using, to develop a written hazard communication plan, to make this MSDS available to their employees, and to provide training to employees in relation to the MSDS.

Following the tragic accidents identified in Mr. Puskar’s article, Southwest Gas Corporation drafted and published an MSDS that identifies a number of hazards associated with odorized natural gas that can cause serious injuries, including purge-related hazards ( This MSDS also includes a number of precautions, engineering controls, and safe work practices that address purge-related natural gas hazards. Southwest Gas has alerted all of its commercial customers of the availability of this MSDS. Readers of POWER magazine are encouraged to review this MSDS and to compare their practices to those in the MSDS. In addition, several natural gas utilities have published similar safety information bulletins that can be found on their websites.

—Craig Roecks, Assistant General Counsel/Legal Affairs, Southwest Gas Corp.