{"operation":"document","citation":"PI-74-013","title":"Virginia State Corporation Commission — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1974-02-20","effective_on":null,"summary":"PI-74-013 response to Virginia State Corporation Commission concerning 192.625.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-74-013.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-74-013.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-74-013","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1974/PI74013.pdf","body":"<<<PAGE 1>>>\n\nFebruary 20, 1974\nMr. James H. Gray\nvirginia State Corporation Commission\nDivision of Public Utilities\nP.O. Box 1197\nRichmond, VA 23209\nDear Mr. Gray:\nYour letter to the Office of Pipeline Safety, dated January 23, 1974, asked:\n\"Paragraph 192.625(f) requires the sampling of gas to assure proper concentrations of\nodorant which is prescribed in subparagraph (b). These requirements indicate a necessity\nfor determining the concentration as well as the detectability. There has been considerable\nargument that using the number of odorant complaints, injecting a specific amount of\nodorant into the gas, checking only that the odor is present in the lines by sniffing the raw\ngas, etc., is sufficient for determining the concentration requirement. Would you please\nforward your opinion as to the sufficiency of the above methods and if these methods are\ninsufficient a practical means of satisfying the requirements of this paragraph.\"\nA regular check of the injection rate of the odorant into the gas is a good indicator that the\ndesired level of injection is being maintained at the odorizer. This does not determine that there is\na sufficient odor level throughout the system. Odorant, under certain conditions, will drop out of\nthe gas within a piping system; thus, there can be excessive odorant in some areas and not enough\nin other areas at the same time. This could cause \"odorant complaints\" in one part of the gas\nsystem while some areas would be receiving insufficient odorant in the gas.\nThe language of Section 192.625, Odorization of gas, is purposely in performance terms.\nParagraph 192.625(b) defines the required strength of odor, that is, detectable at a gas\nconcentration in air of 1/5 of the lower explosive limit. Paragraph 192.625(f) requires periodic\nsampling of combustible gases to assure the proper concentration of odorant any where in the gas\nsystem.\nOdorant is often lost from the gas due to the effect of dirt in the system, velocity of flow,\nprecipitation of odorant on the walls of new pipe installed and low humidity of the gas stream, to\nlist a few influences. The various odorants used in gas distribution also vary widely in their\nstrength; therefore, the amount of odorant that should be injected in a given volume of gas cannot\nbe given as one number for all odorants.\n2\ndal\\192\\625\\74-02-20\n1\n\n<<<PAGE 2>>>\n\nThe most common method of checking the detectability of the gas is to create a control mixture\nthat gives a concentration of gas in air at 1/5 of the lower explosive limit and then have various\npersons see if they can detect the odor. This has in the past been done using a room of known\nvolume and releasing the correct amount of odoroized gas into the space and then determine if the\nodor is detectable. There are also some instruments that produce a mixture of the correct\nconcentration when connected to a gas line and actuated. The gas is then test with the nose to see\nif it is detectable. Recently a new instrument has been developed that will test the concentration\nof the various materials in a gas sample that is used to impart an odor to gas. This is then\ncompared with the effectiveness that was experienced in tests run with groups of people who\nwere considered to have a normal sense of smell. If this comparison indicates sufficient strength\nof odor then the test is satisfactory. Other means could also be used, such as several individuals\nat different locations in a gas system conducting sniff tests. Any of these methods of determining\ndetectability of the gas would be considered as acceptable if done correctly.\nWe trust this has answered your question. If we may assist you further, please let us know.\nSincerely,\nJoseph C. Caldwell\nDirector\nOffice of Pipeline Safety\ndal\\192\\625\\74-02-20\n2","truncated":false,"body_characters":3771}