Tennessee Public Service Commission — Pipeline Safety Interpretation

Page 1July 28, 1975 Mr. John Searcy Engineering Division Tennessee Public Service Commission Cordell Hull Building Nashville, Tennessee 37219 Dear Mr. Searcy: The following is in response to your numbered inquiries of July 1, 1975: 1. Yes. 2. Yes, Section 192.619(c) applies subject to the requirements of Section 192.621. 3. For a steel or plastic high-pressure distribution system, the maximum allowable operating pressure is governed by Section 192.619, subject to the applicable limitation of Section 192.621. Under these requirements, a person may not operate a pipeline at a pressure permitted by Section 192.619(c) if that pressure would exceed the applicable limitation of Section 192.621. Sincerely, Cesar DeLeon Acting Director Office of Pipeline Safety Operations dal\192\619\75-07-28 1#

Page 2July 1, 1975 Mr. Joseph Caldwell, Director Office of Pipeline Safety Department of Transportation 2100 2nd Street, SW Washington, D.C. 20590 Dear Mr. Caldwell: 1. 2. 3. Is it correct that 192.619(b) and 192.621(b) apply only when 192.619(a)(6) and 192.621(a)(5) respectively are the applicable criteria for determining maximum allowable operating pressure; and that when a maximum allowable operating pressure has been determined in accordance with 192.619(a)(6) or 192.621(a)(5), that 192.619(b) or 192.621(b) respectively require over-pressure protection devices to prevent that maximum allowable operating pressure from being exceeded? 192.619(c), under certain conditions, allows an operator to disregard the other provisions of 192.619 in determining a maximum allowable operating pressure in steel and plastic pipelines. 192.619(a)(1) and (a)(6) contain provisions identical to those in 192.621(a)(1) and (a)(5) respectively. Is it correct that while 192.619(c) allows these two provisions in 192.619 to be disregarded, that they cannot be disregarded in 192.621, thereby in effect causing 192.621 to preclude 192.619(c) where these two provisions are concerned? In effect, is it correct that for high pressure steel and plastic distribution systems, the maximum allowable operating pressure is the lowest of a combined list of the pressures in 192.619(a)(1) through (a)(6) and 192.621(a)(1) through (a)(5), except, depending on the answer to Question 2, as provided in 192.619(c)? Sincerely, John Searcy Engineering Division dal\192\619\75-07-28 2#

Page 3Q-3. IH Mr. Searcy asks, in effect, if MAOP for hi-press. distribution system is determined by list of items from 192.619(a)(1-6) and 192.621(a)(1-5), except as provided by 192.619(c). Mr. DeLeon replies that 192.621 limits 192.619 and that 192.619(c) is not applicable if pressure exceeds that allowed by 192.621. Unless 192.619, including provision of 192.619(c), results somehow in a MAOP lower than that established by 192.621, 192.621 will govern hi-press. distr. syst. of steel or plastic. dal\192\619\75-07-28 3#

Page 4RE: Interpretation by C. DL. of Searcy letter of 7/1/75 Remarks: Q-1 IH Q-2 IH Mr. Searcy asks if the relief devices must prevent exceeding that particular MAOP determined by 192.619(a)(6) or 192.621(a)(5). Mr. DeLeon says yes. This is not what 192.619(b) states (§192.???) It states that relf.dev. must prevent the MAOP form being exceeded, in accordance with 192.195 which eventually allows the relf. dev. to be set per 192.201 (i.e. 10% above MAOP or 1.5 X Op. Pr. as applicable.) Mr. Searcy asks if 192.619(c) is nullified by 192.621, regarding 192.619(a)(1) & (a)(6) Mr. DeLeon says yes. 192.621 would nullify 192.619(c) only for hi-press distribution systems. dal\192\619\75-07-28 4#