Tennessee Public Service Commission — Pipeline Safety Interpretation

Page 1Mr. John Searcy Engineering Division Tennessee Public Service Commission Cordell Hull Building Nashville, TN 37219 Dear Mr. Searcy: This responds to your letter of February 21, 1974, concerning uprating requirements for steel pipelines operated at 100 psig, or more, with hoop stresses less than 30 percent of SMYS. You ask whether "the pressure must be increased in the increments required to the desired maximum allowable operating pressure times the appropriate factor in the table in 192.619(a)(2)(ii)?" Subject to the requirements of section 192.621, the maximum allowable operating pressure (MAOP) for the pipelines to which you refer may not be increased above the lowest pressure determined in accordance with action 192.619(a). In uprating to a pressure permitted by section 192.619(a)(2)(ii), a strength test must be performed. The increments prescribed by section 192.557(c) apply to the increase in pressure between the existing MAOP and the test pressure or the desired MAOP multiplied by the appropriate factor in section 192.619(a)(2)(ii). Thank you for your interest in pipeline safety. Sincerely, s/Cesar DeLeon Joseph C. Caldwell Director Office of Pipeline Safety DB C:\WP51\INTERPRT\192\619\74-03-11.2 1#

Page 2TENNESSEE PUBLIC SERVICE COMMISSION CORDELL HULL BUILDING NASHVILLE, TENNESSEE 37219 February 21, 1974 Mr. Joseph C. Caldwell Director Office of Pipeline Safety Department of Transportation 2100 2nd Street, SW Washington, D. C. 20590 Dear Mr. Caldwell: 192.557(c) states that ". . .the increase in maximum allowable operating pressure must be in increments that are equal to 10 p.s.i.g. or 25% of the total pressure increase,. . ." 192.557 does not refer in particular to test requirements, which may be used as a criteria for determining maximum allowable operating pressure, as does 192.555. 192.553(d) does, however, refer generally to limitations on maximum allowable operating pressures. Therefore, using test pressure as the criteria for determining maximum allowable operating pressure for steel pipelines operating at 100 p.s.i.g. or more, is it a correct interpretation that to uprate, the pressure must be increased in the increments required to the desired maximum allowable operating pressure times the appropriate factor in the table in 192.619(a)(2)(ii)? Sincerely, John Searcy Engineering Division DB C:\WP51\INTERPRT\192\619\74-03-11.2 2#