Virginia State Corporation Commission — Pipeline Safety Interpretation

Page 1July 23, 1992 Mr. Massoud Tahamtani Utilities Manager Division of Energy Regulation Virginia State Corporation Commission P.O. Box 1197 Richmond, VA 23209 Dear Mr. Tahamtani: This responds to your letter of June 29, 1992, asking questions about Part 192. First, you asked if gas storage vessels used with a valve actuator are bottle-type holders subject to §§ 192.175 and 192.177. These two standards are based on comparable provisions of the 1968 edition of ASME B31.8 Code. That Code contains the following definitions: Bottle-type holder is any bottle or group of interconnected bottles installed in one location, and used for the sole purpose of storing gas. Bottle * * * is a gas-tight structure completely fabricated from pipe with integral drawn, forged, or spun end closures and tested in the manufacturer's plant. Based on these definition, we believe the vessels are not bottle-type holders. Although they may be bottles that store gas, gas storage is not their sole purpose. The fact, their primary purpose is to provide power to actuate the valve when necessary. Thus, they are not subject to §§ 192.175 and 192.177. Next, you asked whether a city gate station must have overpressure protection. If it is required, you asked whether the station operator may reply on an interstate transmission operator's devices to protect the station against overpressure. If such reliance is permissible, you asked if you may request from the station operator information about the devices to demonstrate compliance with applicable standards, such as § 192.743. Under Part 192, distribution systems readied for service after March 12, 1971, or replaced, relocated, or otherwise changed after November 12, 1970, must have overpressure protection devices under § 192.195. Other distribution systems are not required to have such protection unless their maximum allowable operating pressure is established under § 192.619(b) or § 192.621(b). If a distribution operator seeks to satisfy these requirements by relying on overpressure protection devices it does not own or operate, it is still responsible for compliance of the devices with Part 192. In this case, you may ask the operator to produce evidence that the devices comply with applicable Part 192 requirements.jt 1 192.175/92-07-23#

Page 2Finally, you asked if § 192.625(a) may be met by collecting gas samples throughout a system, testing the samples for odorant concentration with a gas chromatograph, and reporting concentrations of odorant in gas as lbs./MMCF. If so, you asked at what odorant concentration (lbs./MMCF) would a gas in air concentration of one-fifth of the lower explosive limit be readily detectable by a person with a normal sense of smell. Section 192.625(a) provides that a combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell. Also, § 192.625(f) provides that each operator shall conduct periodic sampling of combustible gases to assure the proper concentration of odorant. Section 192.625 does not specify how an operator must test the samples to assure that a pipeline contains the proper concentration of odorant, or the concentration required by § 192.625(a). So any testing procedure may be used that is capable of demonstrating the sufficiency of odorant concentration. If a gas chromatograph is used, the operator must compare the measured odorant concentrations with the proper concentration, which must be determined separately. Since the proper odorant concentration can vary among systems, we cannot give you a specific value in lbs./MMCF that meets the standard. I hope you find this information useful. If you need any further clarification, please call me. Sincerely, Cesar De Leon Director, Regulatory Programs Office of Pipeline Safety jt 2 192.175/92-07-23#