Section 10 Container ships fitted with refrigerating plant to supply cooled air to insulated containers in holds

10.1.1 Classed installations designed to supply refrigerated air to insulated `porthole' containers in holds aboard container ships are to comply with the requirements of Pt 6, Ch 3, 1 General requirements to Pt 6, Ch 3, 9 Refrigerated cargo spaces and Pt 6, Ch 3, 11 Acceptance trials, so far as they are applicable, and the special requirements of this Section.

10.1.2 The classed refrigerating installation is to include the refrigerating machinery, air coolers, supply and return air ducting, and the flexible couplings between containers and the duct system. Where the arrangements are such that cell air conditioning is essential to the carriage of the containers, the air conditioning equipment and (if fitted) the insulation of the hold, deckheads, sides and tank tops are to be included in the classification.

10.2.1 In addition to those requirements detailed in Pt 6, Ch 3, 1 General requirements which are also applicable to refrigerated container ships, the following information is to be submitted before the work commences:

• Details of air coolers.
• Details of the design of ducting proposed, including joints, connections, insulation, vapour sealing and linings.
• Details of cell air conditioning arrangements and components.
• Details of couplings between ducting and containers, including operating arrangements.

10.3.1 Air ducts supplying more than ten standard 20 ft containers or five standard 40 ft containers are to have a single air cooler with multiple circuits or two independent coolers. The individual circuits or coolers are to be provided with stop valves so that each circuit or cooler may be readily isolated.

10.3.2 The refrigeration capacity of the air cooler arrangement is to be such that the temperature conditions can be maintained with any one circuit or independent cooler out of action.

10.3.3 For air ducts supplying ten standard 20 ft containers or five standard 40 ft containers or less, a single cooler with one circuit will be acceptable.

10.4.1 The air ducts, together with all branches and couplings, supplying refrigerated air to insulated containers in holds, are to be made airtight. For design purposes, however, an air leakage rate of 0,5 per cent of total volume flow at the design pressure for each duct is to be taken.

10.4.2 Where air ducting is insulated on the internal surfaces, provision is to be made to prevent retention of odour which may taint subsequent cargo.

10.4.3 Couplings are to be of a type that has been approved by LR. Prototypes are to be tested under all operating conditions, witnessed by the Surveyors, to demonstrate that they extend, retract and separate satisfactorily from a `container end wall' at the minimum temperature condition. When operated by means of air pressure they are to be supplied with air sufficiently dry to avoid ice formation. The air supply lines are to be strength pressure tested to 1,5 × design pressure.

10.5.1 Air leakage tests on at least 10 per cent of ducting, selected at random, are to be carried out to the satisfaction of the Surveyors before the insulation is applied. The Surveyors may require further testing to demonstrate airtightness of ducting. The air leakage from each duct will depend on several factors and, while complete airtightness should be the objective, the air leakage rate for design purposes is not to exceed 0,5 per cent of total volume flow at the design pressure of 250 Pa.

10.5.2 In the case of prefabricated ducts, the prototype is to be subjected to air distribution, heat leakage and air leakage tests. Each production duct is to be tested for air leakage and is not to exceed the prototype test results by more than five per cent. Additionally, one duct in 50 or part thereof is to be tested for heat leakage and the results are not to exceed the prototype test results by more than 10 per cent.

10.5.3 In all cases when prefabricated sections are assembled on board, the tests as detailed in Pt 6, Ch 3, 10.5 Duct air leakage and distribution tests 10.5.2, are to be carried out aboard the ship.

10.5.4 On application from the Owner, the air leakage tests on air ducts installed aboard the ship, as detailed in Pt 6, Ch 3, 10.5 Duct air leakage and distribution tests 10.5.1, may be omitted provided that:

• the installation is designed with at least 20 per cent surplus refrigerating capacity, or
• assignment of a temperature notation for the installation be deferred until verified by a thermal balance test to the Surveyor's satisfaction.

10.5.5 All ducts are to be tested for air distribution to the containers, at the manufacturer's works, by measuring the flow of air from the supply couplings while the fan is operated at full speed against the designed pressure. The air flow at each coupling is to meet the specified figure within ±5 per cent.

10.5.6 Systems comprising rigid prefabricated ducts complete with coolers and fans are to be tested for air distribution at the place of manufacture. The remaining tests are to be carried out aboard the ship.

10.6.1 The cell air-conditioning equipment and ducting, and/or insulation of the holds, deckheads, sides and tank tops, is to be such as to maintain a uniform temperature throughout the cell and to ensure the ship's steelwork is maintained above the minimum temperature acceptable for the steel grade, see also Pt 3, Ch 2, 2.2 Refrigerated spaces.