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.

§ 151.50-31 Chlorine. ( a ) *Chlorine barges.* Subparts 98.03 and 98.20 of Part 98 of this chapter have been revoked. However, chlorine barges that were certified in accordance with the requirements of subpart 98.20 of part 98 of this chapter and having hulls modified, if necessary, to comply with §§ 98.03-5(c) and 98.03-25(c) of this chapter, shall be considered as complying with this part.
( b ) *Design and construction of cargo tanks.* ( 1 ) The cargo tanks shall meet the requirements of Class I pressure vessels.
( 2 ) Tanks shall be designed for a pressure of not less than 300 pounds per square inch gauge. For the maximum allowable working pressure of tanks in service, see paragraph (q) of this section.
( 3 ) Each tank shall be provided with one or more 24-inch inside diameter manhole, fitted with a cover located above the maximum liquid level and as close as possible to the top of the tank. There shall be no other openings in the tank.
( c ) Tanks may be installed “on deck” or “under deck” with the tank protruding above deck. If a portion of the tank extends above the weatherdeck, provision shall be made to maintain the weathertightness on the deck. All tanks shall be installed with the manhole opening located above the weatherdeck. Hopper type barges operating on protected inland waters may have tanks located in the hopper space.
( d ) All valves, flanges, fittings and accessory equipment shall be of a type suitable for use with chlorine and shall be made of metal, corrosion-resistant to chlorine in either the gas or liquid phase. Cast or malleable iron shall not be used. Valves, flanges, and flanged joints shall be 300 pounds A.N.S.I. standard minimum with tongue and groove or raised face. Joints shall be fitted with sheet lead or other suitable gasket material. Welded fittings shall be used wherever possible and the number of pipe joints held to a minimum. Threaded joints in cargo lines and vapor lines shall not be used in sizes above 1 inch internal diameter. Welded “hammerlock” unions or other unions approved by the Commandant may be used at terminal points of fixed barge piping.
( e ) Each tank shall be provided with liquid and vapor connections fitted with manually operated shutoff valves and with safety relief valves. All valves shall be bolted to the cover or covers specified in paragraph (b)(3) of this section and shall be protected against mechanical damage by a suitable protective metal housing. A drain connection shall be provided from the protective housing.
( f ) All liquid and vapor connections, except safety relief valves, shall be fitted with automatic excess flow valves, which shall be located on the inside of the tank. Bypass openings are not permitted in excess flow valves.
( g ) Chlorine barge cargo piping shall not be fitted with the nonreturn valves specified by § 151.20-20(b).
( h ) Liquid level gauging devices of any type are prohibited on chlorine tanks.
( i ) A pressure gauge shall be attached to the vapor shutoff valve or vapor line so as to indicate the pressure in the tank at all times during loading and unloading.
( j ) Piping including connections between tank valves and fixed barge piping, shall be of a thickness of not less than Schedule 80.
( k ) In multiple tank installations the tanks shall not be interconnected by piping or manifolds which may contain liquid chlorine. Manifolding of vapor lines of individual tanks into a common header for connection to shore is permitted. More than one cargo tank may be filled or discharged at a time, provided each tank is filled from or discharged to shore tanks through separate lines.
( l ) Connections between fixed barge piping and shore piping shall be fabricated from one of the following: ( 1 ) Schedule 80 seamless pipe, having flexible metallic joints.
( 2 ) Corrosion-resistant metallic pipe (equivalent to Schedule 80) not subject to deterioration by chlorine, having flexible metallic joints.
( 3 ) Flexible metallic hose acceptable to the Commandant. If paragraphs (k)(1) or (2) of this section are used, the flexible metallic joints shall meet the requirements for cargo hose. See § 151.04-5(h).
( m ) Safety relief valves shall discharge into the protective housing surrounding the valves. Suitable provisions shall be made to vent the housing. The arrangement shall be such as to minimize the hazard of escaping vapors.
( n ) *Cargo transfer operations.* ( 1 ) The amount of chlorine loaded into each cargo tank shall be determined by weight. Draft marks shall not be used as a means of weighing. Any chlorine vapors vented during the filling operation shall be disregarded when calculating the maximum amount of chlorine to be loaded into the cargo tanks.
( 2 ) Prior to the start of filling operations, care shall be exercised to insure that the cargo tanks are empty, dry, and free from foreign matter.
( 3 ) After the filling operation is completed, the vapor in each cargo tank shall be analyzed to determine the percentage of gaseous chlorine in the vapor space. If it should contain less than 80 percent chlorine by volume, vapors shall be withdrawn through the vent or vapor line until the vapor in the cargo tanks contains at least 80 percent chlorine by volume.
( 4 ) After filling connections are removed, upon completion of the loading of a cargo tank, all connections at the tank shall be tested for leakage of chlorine by the aqua ammonia method.
( 5 ) The chlorine in the cargo tanks shall be discharged by the pressure differential method. If the vapor pressure of the chlorine is not sufficient to force the liquid out of the tank, compressed air, or other nonreactive gas, may be used to secure the desired rate of discharge, provided the air or gas is oil-free and thoroughly dried by passing it over activated aluminum oxide, silica gel, or other acceptable drying agent, and provided the supply pressure is limited to 75 percent of maximum allowable pressure of chlorine tanks.
( 6 ) After completion of cargo transfer, any liquid chlorine in the cargo piping shall be removed and cargo transfer piping shall be disconnected at the cargo tanks. After disconnecting the cargo piping, both ends of the line shall be closed and all inlet and outlet valves on the tank shall be plugged or fitted with blind flanges.
( o ) During cargo transfer, every person on the barge shall carry on his person a respiratory protective device which will protect the wearer against chlorine vapors and will provide respiratory protection for emergency escape from a contaminated area resulting from cargo leakage. This respiratory protective equipment shall be of such size and weight that the person wearing it will not be restricted in movement or in the wearing of a lifesaving device.
( p ) During each internal inspection, each cargo tank must be tested hydrostatically to 11 ⁄ 2 times the maximum allowable pressure as determined by the safety relief valve setting.
( q ) During each internal inspection, each cargo tank excess flow valve and safety relief valve must be inspected and tested in accordance with paragraphs (g) and (i) of § 151.04-5 of this chapter.
( r ) When periodic inspection indicates that a cargo tank has deteriorated in service, the maximum allowable pressure shall be recalculated, using the minimum thickness found by actual measurement. The recalculated maximum allowable pressure shall be not less than 275 pounds per square inch gauge. If the recalculated maximum allowable pressure is less than 275 pounds per square inch gauge, the cargo tanks shall be withdrawn from service.
( s ) The following substances shall not be carried as stores on board barges transporting chlorine in bulk: hydrogen, methane, liquefied petroleum gases, coal gas, acetylene, ammonia, turpentine, compounds containing metallic powders, finely divided metals or finely divided organic materials.
( t ) The requirements of § 151.50-30 for compressed gases are also applicable to the shipment of chlorine.
[CGFR 70-10, 35 FR 3714, Feb. 25, 1970, as amended by CGD 85-061, 54 FR 50966, Dec. 11, 1989; CGD 85-061, 55 FR 41918, Oct. 16, 1990; USCG-2014-0688, 79 FR 58284, Sept. 29, 2014]