{"operation":"document","citation":"PI-79-034","title":"Memo: Internal — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1979-09-20","effective_on":null,"summary":"PI-79-034 response to Memo: Internal concerning 192.747.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1979/PI79034.pdf","body":"<<<PAGE 1>>>\n\nInterpretation of §192.747\nAssociate Director for Pipeline Safety Regulation, DMT-30\nChief, Southern Region, DMT-16\nIn your memorandum of December 19, 1978, you point out problems you find in trying to enforce\n§192.747 \"Valve maintenance; distribution systems\" concerning the number of valves that must be\nmaintained as required in a given piping system having a well defined business district and class 1,\n2, and 3 areas. You asked if one key valve will suffice as the emergency valve, assuming that the\nvalve controls the system supply and that multiple main valves do exist within the system. If one\nvalve will not suffice, what minimum number of key valves should suffice, and what systems areas\nshould they control?\nAfter a thorough review, we have concluded that:\n(a) Section 192.747 does not specify how many valves are necessary for the safe operation\nof a distribution system. The regulation requires that any valves necessary for the safe operation\nof a distribution system (key valves) \"...be checked and serviced at intervals not exceeding 1\nyear.\" Section 192.181 which prescribed design standards for installation of key valves in pipeline\nsystems can be used as a guideline for identifying key valves in existing systems installed prior to\n1971. On such existing systems, new valve installations can be required only if the existing\nsystem is hazardous to life or property or as necessary to meet the requirements of the operators'\nInspection and Maintenance or Emergency Plans. In addition, the manual used by the\nTransportation Safety Institute (TSI) in conducting the course on \"Safety Regulation for Gas\nPipeline Systems\" includes additional guidance in determining if one key valve will suffice as the\nemergency valve on such a distribution system. The TSI manual states that key valves be\nconsidered at each pressure regulating station, principal lines to business districts, and class 4\nlocations, as well as other criteria. Since the system to which you refer has a well defined\nbusiness district, class 1, 2, and 3 areas, as well as multiple main line valves. it appears that more\nthan one key valve may be required for the safe operation of that distribution system.\n(b) We cannot establish the minimum number of key valves that would suffice\"...for a\ntypical distribution system having a well defined business district, and class 1, 2, and 3 areas\"\nbecause the number would depend on the specific system design. Because if the various dwelling\ndensities of the system, it appears that several key valves can be identified using criteria set forth\nin §192.181, such as the operating pressure, the size of the mains, and the local physical\nconditions. Some additional criteria to ne considered in determining the location of key valves are\nDB\nC:\\WP51\\INTERPRT\\192\\747\\79-09-20\n1\n\n<<<PAGE 2>>>\n\nthe size of the system, accessibility of each valve, and the capability of the operator to handle an\nemergency. The TSI manual states that the key valves should be considered at the following\nlocations:\n1. 2. 3. 4. Control valve(s) at each pressure regulator station.\nPrincipal feed(s) to business districts and class 4 locations.\nAll single valves on mains within (2) above.\nValves that meet the following criteria.\n(a) Reasonable for sectionalizing plan.\nConsider - Number of customers\n- Volume of gas\n- Environment\n- Response time/valve accessibility\n(b) Necessary because of unsatisfactory maintenance\nHistory of pipeline section\nConsider - Leak history\n- Types of failures\nCesar DeLeon\nDB\nC:\\WP51\\INTERPRT\\192\\747\\79-09-20\n2","truncated":false,"body_characters":3561}