Coast Guard, Dept. of Homeland Security § 56.50–85

(i) Steam driven propulsion machin- at least Schedule 40 in wall thickness. ery must be provided with an emer- Except for barges in inland service and gency supply of lubricating oil that for Great Lakes vessels, the height must operate automatically upon fail- from the deck to any point where ure of the lubricating oil system. The water may gain access through the emergency oil supply must be adequate vent to below deck must be at least 30 to provide lubrication until the equip- inches (760mm) on the freeboard deck ment comes to rest during automatic and 171⁄2 inches (450mm) on the super- shutdown. structure deck. On Great Lakes ves- sels, the height from the deck to any [CGFR 68–82, 33 FR 18843, Dec. 18, 1968, as amended by CGFR 69–127, 35 FR 9979, June 17, point where water may gain access 1970; CGD 81–030, 53 FR 17837, May 18, 1988; through the vent to below deck must CGD 83–043, 60 FR 24774, May 10, 1995] be at least 30 inches (760mm) on the freeboard deck, 24 inches (610mm) on § 56.50–85 Tank-vent piping. the raised quarterdeck, and 12 inches (a) This section applies to vents for (305mm) on other superstructure decks. all independent, fixed, non-pressure Where the height of vents on Great tanks or containers or for spaces in Lakes vessels may interfere with the which liquids, such as fuel, ship’s working of the vessel, a lower height stores, cargo, or ballast, are carried. may be approved by the Marine Safety (1) The structural arrangement in Center provided the vent cap is prop- double bottom and other tanks shall be erly protected from mechanical dam- such as to permit the free passage of age. For barges in inland service, the air and gases from all parts of the vents must extend at least six inches tanks to vent pipes. above the deck. A lesser amount may (2) Tanks having a comparatively be approved by the Marine Safety Cen- small surface, such as fuel oil settling ter if evidence is provided that a par- tanks, need be fitted with only one ticular vent has proven satisfactory in vent pipe, but tanks having a compara- service. tively large surface shall be fitted with (7) Satisfactory means, permanently at least two vent pipes. The vents shall attached, shall be provided for closing be located so as to provide venting of the openings of all vents, except that the tanks under any service condition. barges in inland service may be ex- (3) Vent pipes for fuel oil tanks shall, empted. Acceptable means of closure wherever possible, have a slope of no are: less than 30°. Header lines, where both (i) A ball check valve where the ball ends are adequately drained to a tank, float, normally in the open position, are excluded from this requirement. will float up and close under the action (4) Tank vents must extend above the of a submerging wave. The valve shall weather deck, except vents from fresh be designed so that the effective clear water tanks, bilge oily-water holding discharge area through the valve with tanks, bilge slop tanks, and tanks con- the float in the open position is not taining Grade E combustible liquids, less than the inlet area of the vent pipe such as lubricating oil, may terminate to which the valve is connected. in the machinery space, provided— (ii) A hinged closure normally open (i) The vents are arranged to prevent on the outlet of the return bend, which overflow on machinery, electrical must close automatically by the force equipment, and hot surfaces; of a submerging wave; or (ii) Tanks containing combustible (iii) Another suitable device accept- liquids are not heated; and able to the Commanding Officer, Ma- (iii) The vents terminate above the rine Safety Center. deep load waterline if the tanks have (8) Vent outlets from all tanks which boundaries in common with the hull. may emit flammable or combustible (5) Vents from oil tanks must termi- vapors, such as bilge slop tanks and nate not less than three feet from any contaminated drain tanks, must be opening into living quarters. fitted with a single screen of corrosion- (6) Vents extending above the resistant wire of at least 30 by 30 mesh, freeboard deck or superstructure deck or two screens of at least 20 by 20 mesh from fuel oil and other tanks must be spaced not less than one-half inch

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(13mm) nor more than 11⁄2 inches must terminate above the weather (38mm) apart. The clear area through deck. the mesh must not be less than the in- [CGFR 68–82, 33 FR 18843, Dec. 18, 1968, as ternal unobstructed area of the re- amended by CGD 77–140, 54 FR 40610, Oct. 2, quired pipe. 1989; CGD 83–043, 60 FR 24774, May 10, 1995; (9) Where vents are provided with CGD 95–012, 60 FR 48050, Sept. 18, 1995] flame screens, the closure device shall be situated so as not to damage these § 56.50–90 Sounding devices. screens. (a) Each tank must be provided with (10) The diameter of each vent pipe a suitable means of determining liquid must not be less than 11⁄2 inches nomi- level. Except for a main cargo tank on nal pipe size for fresh water tanks, 2 a tank vessel, each integral hull tank inches nominal pipe size for water bal- and compartment, unless at all times last tanks, and 21⁄2 inches nominal pipe accessible while the vessel is operating, size for fuel oil tanks, except that must be fitted with a sounding pipe. small independent tanks need not have (b) Where sounding pipes terminate a vent more than 25% greater in cross- below the freeboard deck on cargo ves- sectional area than the fill line. sels, they shall be fitted with gate (11)(i) If a tank may be filled by a valves. On passenger vessels, where pressure head exceeding that for which sounding pipes terminate below the the tank is designed, the aggregate bulkhead deck, they shall be fitted cross-sectional area of the vents in with self-closing gate valves. each tank must be not less than the (c) Except as allowed by this para- cross-sectional area of the filling line graph, on each vessel constructed on or unless the tank is protected by over- after June 9, 1995, no sounding pipe flows, in which case the aggregate used in a fuel-oil tank may terminate cross-sectional area of the overflows in any space where the risk of ignition must be not less than the cross-sec- of spillage from the pipe might arise. tional area of the filling line. None may terminate in a space for pas- (ii) Provision must be made to guard sengers or crew. When practicable, against liquids rising in the venting none may terminate in a machinery system to a height that would exceed space. When the Commanding Officer, the design head of a cargo tank or fuel- Marine Safety Center, determines it oil tank. It may be made by high-level impracticable to avoid terminating a alarms or overflow-control systems or pipe in a machinery space, a sounding other, equivalent means, together with pipe may terminate in a machinery gauging devices and procedures for fill- space if all the following requirements ing cargo tanks. are met: (12) Where deep tanks are intended (1) In addition to the sounding pipe, for the occasional carriage of dry or the fuel-oil tank has an oil-level gauge liquid cargo, a ‘‘spectacle’’ or ring and complying with paragraph (d) of this blank flange may be fitted in the over- section. flow pipe so arranged as not to inter- (2) The pipe terminates in a place re- fere with venting when the tanks con- mote from ignition hazards unless pre- tain oil. cautions are taken such as fitting an (13) Vents from fresh water or water effective screen (shield) to prevent the ballast tanks shall not be connected to fuel oil, in case of spillage through the a common header with vents from oil end of the pipe, from coming into con- or oily ballast tanks. tact with a source of ignition. (b) Tank vents must remain within (3) The end of the pipe is fitted with the watertight subdivision boundaries a self-closing blanking device and a in which the tanks they vent are lo- small-diameter, self-closing control cated. Where the structural configura- cock located below the blanking device tion of a vessel makes meeting this re- for the purpose of ascertaining before quirement impracticable, the Marine the blanking device is opened that no Safety Center may permit a tank vent fuel oil is present. Provision must be to penetrate a watertight subdivision made to ensure that no spillage of fuel bulkhead. All tank vents which pene- oil through the control cock involves trate watertight subdivision bulkheads an ignition hazard.

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