{"operation":"document","citation":"04-0055","title":"Commonwealth of Virginia Department of State Police — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2004-04-07","effective_on":null,"summary":"04-0055 response to Commonwealth of Virginia Department of State Police concerning 178.345.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-04-0055.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-04-0055.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-04-0055","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2004/040055.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\n400 Seventh St., S.W.\nSpecial Programs\nResearch and\nAPR\n7 2004\nWashington, D.C. 2059(\nAdministration\nSergeant David P. Feather\nRef. No. 04-0055\nSafety Division, Motor Carrier Safety\nCommonwealth of Virginia\nDepartment of State Police\nP.O. Box 10900\nFairfax Station, Virginia 22039-0900\nDear Sergeant Feather:\nThis serves as a retraction of our September 25, 2003, response to your October 24, 2002 (Ref. No.\n02-0287) letter requesting clarification on venting for double bulkheads or void spaces for MC 300\nand DOT 400 series cargo tanks under the Hazardous Materials Regulations (HMR; 49 CFR Parts\n171-180). Specifically, you asked whether it was permissible to plug the vent on top of the cargo tank\nat the double bulkhead, provided that the bottom drain opening was left open. This follow-up letter is to\ninform you that our previous response was incorrect.\nSections 178.340-7(c), 178.345-1(i)(2) and 178.345-3 require any MC 300 and MC 400 cargo tank\nvoid or airspace to be vented and equipped with a drain, located on the bottom centerline, that is\naccessible and open at all times. In our previous response, we indicated that it was permissible to plug\nthe vent on top of the cargo tank, provided the bottom opening or drain is open and operational at all\ntimes. This is not correct.\nThe correct response to your question is that both the top vent and bottom drain must be kept open.\nVents are normally located in the top centerline of the tank and are required to communicate with the\nvapor space in order to allow any gases that have accumulated in the void area to escape through the\nvent located at the top of the tank. In the case of the void area, if the vent is plugged and there is a leak\nin the bulkhead, the gas will drain out of the drain located at the bottom centerline of the tank, but the\nvapors will have no means of escape if the vent is plugged. Further, if the bottom drain is closed or\nplugged vi sid or dorio any no euranterise fom the top ent kill be abrid and beating.\nan open vent and drain, thus allowing for vapors to escape, would be permissible.\nWe apologize for any inconvenience and hope this answers your inquiry.\nSincerely\nC\n/John A. Gate\nChief, Standards Development\n-\nOffice of Hazardous Materials Standards\n5178.345-1\n040055","truncated":false,"body_characters":2313}