(a) Vessels using vapor balancing while conducting a vessel-to-vessel transfer operation, directly or through a shore loop, must meet the requirements of this subpart in addition to the requirements of 46 CFR part 39, subparts 39.1000, 39.2000, and 39.3000. Arrangements other than vapor balancing used to control vapor emissions during a vessel-to-vessel transfer operation must receive approval from the Commandant.

(b) A vapor balancing operation must receive approval from the Commandant to use a compressor or blower to assist vapor transfer.

(c) Vapor balancing is prohibited when the cargo tanks on a vessel discharging cargo are inerted and the cargo tanks on a vessel receiving cargo are not inerted.

(d) A vessel that intends to collect vapors (during a vessel-to-vessel transfer operation) from cargoes not previously approved must receive specific approval from the Commandant before beginning transfer operations.

(a) During transfer operations, if the cargo tanks are inerted on a vessel discharging cargo to a receiving vessel with inerted cargo tanks, the service vessel must—

(1) Inert the vapor transfer hose prior to transferring cargo vapor; and

(2) Have an oxygen analyzer with a sensor or sampling connection fitted within 3 meters (9.74 feet) of the vessel vapor connection that—

(i) Activates a visible and an audible alarm on the service vessel where cargo transfer is controlled when the oxygen content in the vapor collection system exceeds 60 percent by volume of the cargo's minimum oxygen concentration for combustion (MOCC), or 8 percent by volume for vapor of crude oil, gasoline blends, or benzene;

(ii) Has an oxygen concentration indicator located on the service vessel where the cargo transfer is controlled; and

(iii) Has a connection for injecting a span gas of known concentration for calibration and testing of the oxygen analyzer.

(b) If the cargo tanks are not inerted on a vessel discharging cargo during transfer operations, and the cargo is flammable or combustible, the vapor collection line on the service vessel must be fitted with a detonation arrester that meets the requirements of 33 CFR 154.2106, and be located within 3 meters (9.74 feet) of the vessel vapor connection.

(c) An electrical insulating flange or one length of non-conductive hose must be provided between the vessel vapor connection on each vessel operating a vessel-to-vessel cargo transfer.

(a) During a vessel-to-vessel transfer operation, each cargo tank being loaded must be connected by the vapor collection system to a cargo tank that is being discharged.

(b) If the cargo tanks on both the vessel discharging cargo and the vessel receiving cargo are inerted, the following requirements must be met:

(1) Each tank on a vessel receiving cargo, which is connected to the vapor collection system, must be tested prior to cargo transfer to ensure that the oxygen content in the vapor space does not exceed 60 percent by volume of the cargo's minimum oxygen concentration for combustion (MOCC), or 8 percent by volume for vapor of crude oil, gasoline blends, or benzene. The oxygen content of each tank, or each area of a tank formed by each partial bulkhead, must be measured at a point 1 meter (3.28 feet) below the tank top and at a point equal to one-half of the ullage;

(2) Prior to starting transfer operations, the oxygen analyzer required by 46 CFR 39.4003(a) must be tested for proper operation;

(3) During transfer operations the oxygen content of vapors being transferred must be continuously monitored;

(4) Cargo transfer must be terminated if the oxygen content exceeds 60 percent by volume of the cargo's MOCC, or 8 percent by volume for vapor of crude oil, gasoline blends, or benzene;

(5) Transfer operations may resume once the oxygen content in the tanks of the vessel receiving cargo is reduced to 60 percent by volume or less of the cargo's MOCC, or 8 percent by volume or less for vapor of crude oil, gasoline blends, or benzene; and

(6) Prior to starting vapor transfer operations, the vapor transfer hose must be purged of air and inerted.

(c) The isolation valve located on the service vessel required by 46 CFR 39.2001(g) must not be opened until the pressure in the vapor collection system on the vessel receiving cargo exceeds the pressure in the vapor collection system on the vessel discharging cargo.

(d) The vessel discharging cargo must control the cargo transfer rate so that the transfer rate does not exceed—

(1) The authorized maximum discharge rate of the vessel discharging cargo;

(2) The authorized maximum loading rate of the vessel receiving cargo; or

(3) The processing rate of the approved vessel vapor processing system, if one is used to process the vapor collected during the transfer operations.

(e) The pressure in the vapor space of any cargo tank connected to the vapor collection line on either the vessel receiving cargo or the vessel discharging cargo must not exceed 80 percent of the lowest setting of any pressure relief valve during ballasting or cargo transfer.

(f) Impressed current cathodic protection systems must be de-energized during cargo transfer operations.

(g) Tank washing is prohibited unless the cargo tanks on both the vessel discharging cargo and the vessel receiving cargo are inerted, or the tank is isolated from the vapor collection line.