LR V.10 Heated cargoes

LR V.10.1.1 In order to facilitate assessment of the seagoing operating temperatures of cargo tank structure, a temperature distribution investigation is to be submitted when:

1. the cargo heating source is integral with the structure of cargo tank boundaries which are not in contact with the sea, or

2. heated cargoes are to be carried in longitudinally framed ships at temperatures exceeding 80°C in integral tanks. Consideration will be given to permissible temperatures for ships with partial transverse framing, taking account of the submitted structural arrangements.

LR V.10.1.2 If the steel temperature exceeds the values given above, calculations giving resultant stresses on the hull structure, based on a sea temperature of 0°C and an air temperature of 5°C, are to be submitted, together with proposals for necessary reinforcement of the hull structure and/or limitation of the still water bending moment for heated cargo conditions.

LR V.10.1.3 Submitted proposals are to take account of non-uniform loading patterns with resultant variations in temperature distribution, where appropriate.

LR V.10.1.4 Provided that the heat source is not adjacent to the hull structure, cargo temperatures of up to 80°C will be accepted without temperature and thermal stress calculations, in cases where transverse framing is adopted for longitudinal bulkhead and side shell, and the integral cargo tanks have common boundaries with the sea.

LR V.10.1.5 For bituminous cargoes which form a mastic layer on cargo tank boundaries, acceptance of higher temperatures in integral centre tanks of single bottom tankers without thermal stress investigation will be considered provided the appropriate requirements of MARPOL 73/78 Annex I of MARPOL 73/78Regulations for the Prevention of Pollution by Oil are complied with.

LR V.10.1.6 Where molten cargoes are to be carried at temperatures which may result in excessive condensation in spaces adjacent to cargo tanks, consideration will be given, in appraisal, to the possibility of increased corrosion and the need for additional protection.

LR V.10.2.1 Where integral stainless steel tanks are to be used for heated cargoes, and the conditions specified in LR V.10.1 General (a) or (b) apply, account is to be taken of the operating steel temperature. Where σ₂ is less than 235 N/mm² (24 kgf/mm²), scantlings are to be increased by substituting the corresponding value of k ₂ for k in the cargo tank boundary formulae for stiffener and plating thickness. The value of k ₂ is not, however, to be used to reduce Rule inertia or plate thickness requirements. Also, the hull section modulus is to be not less than Z _R k ₂ where stainless steel is incorporated in continuous longitudinal material in the vicinity of deck or bottom.

LR V.10.2.2 Where clad steel is fitted, k ₂ is to be calculated on the basis of the yield stress or 0,2 per cent proof stress of the stainless steel cladding at the operating temperature.

LR V.10.3.1 Where heating ducts are integral with the tank structure, they are to be designed to withstand a head equal to the maximum pressure in the heating system, but in no case less than that imposed by the highest cargo load for which the tanks have been designed.

LR V.10.3.2 For other aspects of cargo heating, see Pt 5, Ch 15, 6 Cargo heating arrangements*.