Tennessee Public Service Commission — Pipeline Safety Interpretation

Page 1PI-74-0133 August 13, 1974 Mr. John Searcy Tennessee Public Service Commission Cordell Hull Building Nashville, TN 37219 Dear Mr. Searcy: Thank you for your letter of July 26, 1974, asking whether 49 CFR 192.197 (a) provides for protection against overpressure due to failure of a regulator. Sections 192.197(a) and (b) protect against unsafe operation of gas utilization equipment due to overpressuring by a distribution system. Paragraph (a) sets forth criteria for a service regulator to provide this protection. Under paragraph (b), where a regulator does not meet that criteria, the operator must install suitable devices to protect against overpressure when the regulator fails. The problem of providing protection against overpressure due to failure of a regulator which meets the criteria of paragraph (a) is not addressed by the regulation. We trust our response is helpful to you. Sincerely, SIGNED EDWARD F. CYGAN Joseph C. Caldwell Director Office of Pipeline Safety#

Page 2Tennessee Public Service Commission Cordell Hull Building Nashville, Tennessee 37219 July 26, 1974 Mr. Joseph C. Caldwell, Director Office of Pipeline Safety Department of Transportation 2100 Second Street, SW Washington, D.C. 20590 Dear Mr. Caldwell: Both 192.197(a) and (b) intend the same end result, which is prevention of unsafe appliance pressure. (b) must be complied with when (a) is not. However, in (a), the conditions under which unsafe appliance pressure must be prevented are normal operating conditions, and in (b), the condition is regulator failure. This appears to be inconsistent, since compliance with (a) does not provide for regulator failure, yet is the first of two alternatives "...to prevent a pressure that would cause the unsafe operation of any...gas utilization equipment." Is it correct that the intent of 192.197(a) is to also provide for regulator failure? Sincerely, John Searcy Engineering Division#