{"operation":"document","citation":"PI-79-046","title":"Memo: Internal — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1979-12-24","effective_on":null,"summary":"PI-79-046 response to Memo: Internal concerning 192.197.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-046.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-046.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-046","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1979/PI79046.pdf","body":"<<<PAGE 1>>>\n\nDecember 24, 1979\nMonitoring Regulator System\nAssociate Director for Pipeline Safety Regulation, DMT-30\nChief, Southwest Region, DMT-17\nIn your memorandum of August 2, 1979, relating to monitor regulators as mentioned in\n§192.197(c)(2), you ask three specific questions. Following are the questions and the answers to\nthose questions:\nQuestion 1 What is the official definition of a monitor system?\nAnswer A monitor regulator system consists of two pressure regulators set in series in a pipeline\nin a manner that will limit the downstream to its MAOP or less if one of the regulators should fail.\nThere are three modes of operation that are normally used with monitor regulator systems; these\nare:\n(1) The upstream regulator controlling the pressure delivered, with the downstream\nregulator set for a slightly higher pressure than the normal delivered pressure (still below the\nMAOP). If the upstream regulator fails, the downstream regulator then takes control of the\ndelivered pressure at a slightly higher than normal delivery pressure.\n(2) The downstream regulator controlling the pressure delivered, with the upstream\nregulators set for a slightly higher than normal pressure and the system pressure being monitored\nfrom the upstream regulator by a sensing line connecting the control of the upstream regulator to\nthe downstream piping. If the downstream regulator fails, the upstream regulator then takes over\ncontrol of the delivered pressure at a higher than normal pressure.\n(3) A third method would be to set the upstream regulator at the MAOP or less of the\npipeline being controlled and set the downstream regulator at an even lower pressure that would\nnormally be delivered to the downstream pipeline. If the downstream regulator should fail, the\nupstream regulator then takes control of the delivered pressure at its higher pressure setting.\nQuestion 2 When are regulators in series considered to be monitoring?\ndal\\192\\197\\79-12-24\n1\n\n<<<PAGE 2>>>\n\nAnswer regulator.\nThe regulator that is not normally controlling the delivery pressure is the monitoring\nQuestion 3 At what pressure should the monitor be set with respect to the operating regulator?\nAnswer This is explained in response to Question 1 above.\nCesar DeLeon\ndal\\192\\197\\79-12-24\n2","truncated":false,"body_characters":2272}