46 C.F.R. Subpart 39.20—Design and Equipment
Title 46 - Shipping
(a) Each vapor collection system must meet the following requirements: (1) Except as allowed by paragraph (a)(3) of this section or the Commandant (G-MSO), vapor collection piping must be permanently installed, with the vessel's vapor connection located as close as practical to the loading manifold; (2) If the vessel collects vapors from incompatible cargoes simultaneously, it must keep the incompatible vapors separate throughout the entire vapor collection system; (3) A vessel certified to carry cargo listed in Table 151.05 of part 151 or Table 1 of part 153 of this chapter may have vapor connections located in the vicinity of each tank in order to preserve segregation of cargo systems, in lieu of common header piping; (4) A means must be provided to eliminate liquid condensate which may collect in the system, such as draining and collecting liquid from each low point in the line; (5) Vapor collection piping must be electrically bonded to the hull and must be electrically continuous; and (6) An inerted tankship must have a means to isolate the inert gas supply from the vapor collection system. The inert gas main isolation valve required by SOLAS 74, as amended, chapter II–2, Regulation 62.10.8 may be used to satisfy this requirement. (b) The vapor collection system must not interfere with the proper operation of the cargo tank venting system. (c) An isolation valve capable of manual operation must be provided at the vessel vapor connection. The valve must have an indicator to show clearly whether the valve is in the open or closed position, unless the valve position can be readily determined from the valve handle or valve stem. (d) The last 1.0 meter (3.3 feet) of vapor piping before the vessel vapor connection must be: (1) Painted red/yellow/red with: (i) The red bands 0.1 meter (0.33 feet) wide, and (ii) The middle yellow band 0.8 meter (2.64 feet) wide; and (2) Labeled “VAPOR” in black letters at least 50 millimeters (2 inches) high. (e) Each vessel vapor connection flange must have a permanently attached 0.5 inch diameter stud at least 1.0 inch long projecting outward from the flange face. The stud must be located at the top of the flange, midway between bolt holes, and in line with the bolt hole pattern. (f) Each hose used for transferring vapors must: (1) Have a design burst pressure of at least 25 psig; (2) Have a maximum allowable working pressure of at least 5 psig; (3) Be capable of withstanding at least 2.0 psi vacuum without collapsing or constricting; (4) Be electrically continuous with a maximum resistance of ten thousand (10,000) ohms; (5) Have flanges with: (i) A bolt hole arrangement complying with the requirements for 150 pound class ANSI B16.5 flanges, and (ii) One or more 0.625 inch diameter holes in the flange located midway between bolt holes and in line with the bolt hole pattern; (6) Be abrasion resistant and resistant to kinking; and (7) Have the last 1.0 meter (3.3 feet) of each end of the vapor hose marked in accordance with paragraph (d) of this section. (g) Vapor hose handling equipment must be provided with hose saddles which provide adequate support to prevent kinking or collapse of hoses. [CGD 88–102, 55 FR 25446, June 21, 1990, as amended by CGD 95–072, 60 FR 50462, Sept. 29, 1995; CGD 96–041, 61 FR 50727, Sept. 27, 1996] (a) Each cargo tank of a tank vessel that is connected to a vapor collection system must be equipped with a cargo gauging device which: (1) Provides a closed gauging arrangement as defined in §151.15.10 of this chapter that does not require opening the tank to the atmosphere during cargo transfer; (2) Allows the operator to determine the liquid level in the tank for the full range of liquid levels in the tank; (3) Indicates the liquid level in the tank at the location where cargo transfer is controlled; and (4) If portable, is installed on the tank during the entire transfer operation. (b) Except when a tank barge complies with §39.20–9(a) of this part, each cargo tank of a barge must have a high level indicating device that: (1) Provides a visual indication of the liquid level in the cargo tank when the cargo level is within 1.0 meter (3.28 feet) of the tank top; (2) Has the maximum liquid level permitted under §39.30–1(e) of this part at even keel conditions conspicuously and permanently marked on the indicating device; and (3) Is visible from all cargo control areas on the tank barge. (a) Each cargo tank of a tankship must be equipped with an intrinsically safe high level alarm and a tank overfill alarm. (b) The high level alarm and tank overfill alarm required by paragraph (a) of this section, if installed after July 23, 1990 must: (1) Be independent of each other; (2) Alarm in the event of loss of power to the alarm system or failure of electrical circuitry to the tank level sensor; and (3) Be able to be checked at the tank for proper operation prior to each transfer or contain an electronic self-testing feature which monitors the condition of the alarm circuitry and sensor. (c) The high level alarm required by paragraph (a) of this section must: (1) Alarm before the tank overfill alarm, but no lower than 95 percent of tank capacity; (2) Be identified with the legend “High Level Alarm” in black letters at least 50 millimeters (2 inches) high on a white background; and (3) Have audible and visible alarm indications that can be seen and heard on the vessel where cargo transfer is controlled. (d) The tank overfill alarm required by paragraph (a) of this section must: (1) Be independent of the cargo gauging system; (2) Have audible and visible alarm indications that can be seen and heard on the vessel where cargo transfer is controlled and in the cargo deck area; (3) Be identified with the legend “TANK OVERFILL ALARM” in black letters at least 50 millimeters (2 inches) high on a white background; and (4) Alarm early enough to allow the person in charge of transfer operations to stop the transfer operation before the cargo tank overflows. (e) If a spill valve is installed on a cargo tank fitted with a vapor collection system, it must meet the requirements of §39.20–9(c) of this part. (f) If a rupture disk is installed on a cargo tank fitted with a vapor collection system, it must meet the requirements of §39.20–9(d) of this part. Each cargo tank of a tank barge must have one of the following liquid overfill protection arrangements. (a) A system meeting the requirements of §39.20–7 of this part which: (1) Includes a self-contained power supply; (2) Is powered by generators installed on the barge; or (3) Receives power from a facility and is fitted with a shore tie cable and a 120 volt 20 amp explosion-proof plug which meets: (i) ANSI/NEMA WD6; (ii) NFPA 70, Articles 410–57 and 501–12; and (iii) §111.105–9 of this chapter. (b) An intrinsically safe overfill control system which: (1) Is independent of the cargo gauging device required by §39.20–3(a) of this part; (2) Actuates an alarm and automatic shutdown system at the facility overfill control panel, or on the vessel to be lightered if a lightering operation, 60 seconds before the tank becomes 100 percent liquid full; (3) Is able to be checked at the tank for proper operation prior to each loading; (4) Consists of components which, individually or in series, will not generate or store a total of more than 1.2 V, 0.1 A, 25 mW, or 20 microjoules; (5) Has at least one tank overfill sensor switch with normally closed contacts per cargo tank; (6) Has all tank overfill sensor switches connected in series; (7) Has interconnecting cabling that meets §111.105–15(b) of this chapter; and (8) Has a male plug with a 5 wire, 16 amp connector body meeting IEC 309–1/309–2 which is: (i) Configured with pins S2 and R1 for the tank overfill sensor circuit, pin G connected to the cabling shield, and pins N and T3 reserved for an optional high level alarm circuit meeting the requirements of this paragraph; and (ii) Labeled “Connector for Barge Overflow Control System” and with the total inductance and capacitance of the connected switches and cabling. (c) A spill valve which: (1) Meets ASTM F 1271 (incorporated by reference, see §39.10–5); (2) Relieves at a pressure higher than the pressure at which the pressure relief valves meeting the requirements of §39.20–11 operate; (3) Limits the maximum pressure at the cargo tank top during liquid overfill, at the maximum loading rate for the tank, to not more than the maximum design working pressure for the tank; and (4) If the vessel is in ocean or coastwise service, has provisions to prevent opening due to cargo sloshing. (d) A rupture disk arrangement which meets paragraphs (c)(2), (c)(3) and (c)(4) of this section and is approved by the Commandant (G-MSO). [CGD 88–102, 55 FR 25446, June 21, 1990, as amended by CGD 95–072, 60 FR 50462, Sept. 29, 1995; CGD 96–041, 61 FR 50727, Sept. 27, 1996; USCG-2000–7790, 65 FR 58459, Sept. 29, 2000] (a) The cargo tank venting system required by §32.55 of this chapter must: (1) Be capable of discharging cargo vapor at 1.25 times the maximum transfer rate such that the pressure in the vapor space of each tank connected to the vapor collection system does not exceed: (i) The maximum design working pressure for the tank, or (ii) If a spill valve or rupture disk is fitted, the pressure at which the device operates; (2) Not relieve at a pressure corresponding to a pressure in the cargo tank vapor space of less than 1.0 psig; (3) Prevent a vacuum in the cargo tank vapor space, whether generated by withdrawal of cargo or vapor at maximum rates, that exceeds the maximum design vacuum for any tank connected to the vapor collection system; and (4) Not relieve at a vacuum corresponding to a vacuum in the cargo tank vapor space of less than 0.5 psi below atmospheric pressure. (b) Each pressure-vacuum relief valve must: (1) Be tested for venting capacity in accordance with paragraph 1.5.1.3 of API 2000; and (2) Have a means to check that the device operates freely and does not remain in the open position, if installed after July 23, 1991. (c) The relieving capacity test required by paragraph (b)(1) of this section must be carried out with a flame screen fitted at the vacuum relief opening and at the discharge opening if the pressure-vacuum relief valve is not designed to ensure a minimum vapor discharge velocity of 30 meters (98.4 ft.) per second. Each tankship vapor collection system must be fitted with a pressure sensing device that senses the pressure in the main vapor collection line, which: (a) Has a pressure indicator located on the vessel where the cargo transfer is controlled; and (b) Has a high pressure and a low pressure alarm that: (1) Is audible and visible on the vessel where cargo transfer is controlled; (2) Alarms at a high pressure of not more than 90 percent of the lowest pressure relief valve setting in the cargo tank venting system; and (3) Alarms at a low pressure of not less than four inches water gauge (0.144 psig) for an inerted tankship, or the lowest vacuum relief valve setting in the cargo tank venting system for a non-inerted tankship.
Title 46: Shipping
PART 39—VAPOR CONTROL SYSTEMS
Subpart 39.20—Design and Equipment
§ 39.20-1 Vapor collection system—TB/ALL.
§ 39.20-3 Cargo gauging system—TB/ALL.
§ 39.20-7 Tankship liquid overfill protection—T/ALL.
§ 39.20-9 Tank barge liquid overfill protection—B/ALL.
§ 39.20-11 Vapor overpressure and vacuum protection—TB/ALL.
§ 39.20-13 High and low vapor pressure protection for tankships—T/ALL.
