Editorial Note on Part 151
Editorial Note: Nomenclature changes to part 151 appear by USCG-2009-0702, 74 FR 49236, Sept. 25, 2009, and USCG-2012-0832, 77 FR 59784, Oct. 1, 2012.

Editorial Note on Subpart 151.50 of Part 151
Editorial Note: Nomenclature changes to subpart 151.50 of part 151 appear by CGD-95-072, 60 FR 50465, Sept. 29, 1995, and CGD-96-041, 61 FR 50732, Sept. 27, 1996.

§ 151.50-34 Vinyl chloride (vinyl chloride monomer). ( a ) Copper, aluminum, magnesium, mercury, silver, and their alloys shall not be used as materials of construction for tanks, pipelines, valves, fittings, and other items of equipment that may come in contact with vinyl chloride liquid or vapor.
( b ) Valves, flanges, and pipe fittings shall be of the tongue and groove or raised-face type, fitted with suitable gasket material. Welded fittings shall be used wherever possible and the number of pipe joints shall be held to a minimum. Threaded joints are not permitted for pipe diameters exceeding 2 inches. Brazed joints are prohibited.
( c ) Each cargo tank shall be electrically grounded to the hull.
( d ) The vessel shall be electrically bonded to the shore piping prior to connecting the cargo hose. This electrical bonding shall be maintained until after the cargo hose has been disconnected and any spillage has been removed.
( e ) To the extent he deems it necessary, the Officer in Charge, Marine Inspection, may require that sufficient insulation shall be removed from insulated tanks at least once in each 8 calendar years to permit spot external examination of the tanks and insulation in accordance with § 151.04-5(c).
( f ) The requirements of § 151.50-30 for compressed gases are also applicable to the shipment of vinyl chloride.
( g ) The person in charge of cargo transfer shall ensure that: ( 1 ) Cargo vapors are returned to the cargo tank or shore disposition for reclamation or destruction during cargo transfer operations;
( 2 ) Continuous monitoring for vinyl chloride vapor leaks is conducted aboard a tank barge undergoing vinyl chloride transfer operations. Fixed or portable instrumentation may be utilized to ensure that personnel are not exposed to vinyl chloride vapor concentrations in excess of 1 ppm averaged over any eight hour period of 5 ppm averaged over any period not exceeding 15 minutes. The method of monitoring and measurement shall have an accuracy (with a confidence level of 95 percent) of not less than plus or minus 50 percent from 0.25 through 0.5 ppm, plus or minus 35 percent from over 0.5 ppm through 1.0 ppm, and plus or minus 25 percent over 1.0 ppm;
( 3 ) Cargo transfer operation is discontinued or corrective action is initiated by the person in charge to minimize exposure to personnel whenever a vinyl chloride vapor concentration in excess of 1 ppm is detected. If the vinyl chloride vapor concentration exceeds 5 ppm for over 15 minutes, action to reduce the leak can be continued only if the respiratory protection requirements of 29 CFR 1910.1017 are met by all personnel in the area of the leak;
( 4 ) Those portions of cargo lines which will be open to the atmosphere after piping is disconnected are free of vinyl chloride liquid and that the vinyl chloride vapor concentration in the area of the cargo piping disconnect points is not greater than 5 ppm;
( 5 ) Any restricted gauge fitted on a tank containing vinyl chloride is effectively out of service by locking or sealing the device so that it cannot be used; and
( 6 ) A restricted gauge is not to be used as a “check” on the required closed gauge, nor as a means or sampling.
( h ) The words “CANCER—SUSPECT AGENT” must be added to the warning signs required by 46 CFR 151.45-2(e).
( i ) Signs bearing the legend: cancer—suspect agent in this area protective equipment required authorized personnel only must be posted whenever hazardous operations, such as tank cleaning, are in progress.
( j ) A tank barge undergoing cargo transfer operations must be designated a “regulated area” having access limited to authorized persons and requiring a daily roster of authorized persons who may board the barge.
( k ) Employees engaged in hazardous operations, such as tank cleaning, must be provided, and be required to wear and use respiratory protection in accordance with the provisions of 29 CFR 1910.1017 and protective garments, provided clean and dry for each use, to prevent skin contact with liquid vinyl chloride.
[CGFR 70-10, 35 FR 3714, Feb. 25, 1970, as amended by CGD 74-167R, 40 FR 17026, Apr. 16, 1975; CGD 88-100, 54 FR 40040, Sept. 29, 1989]