Section 18 Heat exchangers

18.1.1 The requirements in this Section are applicable to heat exchangers of the shell and tube type and plate type and which are necessary for the operation of Mobility and Ship Type engineering systems.

18.1.2 The requirements of this Section are with the goal of providing heat exchange capability whereby normal operation of Mobility and Ship Type engineering systems can be sustained or restored when the performance of the heat exchanger has become degraded due to operating in normal sea-going conditions.

18.1.3 The number, type and capability rating of heat exchangers installed for Mobility and Ship Type engineering systems are to be adequate for all envisaged operating conditions taking into account all relevant ambient environmental conditions that may affect the performance of a heat exchanger.

18.1.4 Heat exchangers are to be installed such that where sea water is used for cooling purposes, the suction pipes to the supply pumps are to be provided with strainers which can be cleaned without interruption to the cooling water supply to the heater exchanger.

18.1.5 The design of heat exchangers is to be in accordance with an applicable and recognised standard acceptable to LR.

18.1.6 Heat exchangers are to be capable of stable operation at their specified rating under all envisaged operating conditions, see Vol 2, Pt 1, Ch 3, 4 Operating conditions. Any degraded performance under extreme environmental operating conditions is to be stated by the manufacturer and included in the System Design Description required by Vol 2, Pt 7, Ch 1, 18.1 General 18.1.11.

18.1.7 The selection of heat exchangers is to recognise the required functional performance of their intended duty in terms of effective heat transfer capacity, fluid media, fluid design flow rates and pressures, and, also recognise the design coefficient of heat transfer in different fouled conditions. See also Vol 2, Pt 7, Ch 1, 15.1 General 15.1.1.

18.1.8 Heat exchangers are to be capable of being cleaned when installed onboard. They are to be installed such that there are adequate access arrangements to permit cleaning and maintenance in accordance with the manufacturer's instructions.

18.1.9 To provide for venting of entrapped air from heat exchangers, high points on each fluid side of the heat exchanger not otherwise vented by fluid branches are provided with an air vent connection. Each air vent is to include a valve attached to the heat exchanger.

18.1.10 Heat exchangers are to be type tested in accordance with a specification acceptable to LR.

18.1.11 A System Design Description for each size and type of heat exchanger used in Mobility and Ship Type engineering systems is to be submitted for information purposes. The System Design Description is to include details of margins for fouling and plugging of tubes where applicable.

18.2.1 Materials used in the construction of heat exchangers are to be manufactured and tested in accordance with the requirements of theRules for the Manufacture, Testing and Certification of Materials, July 2022. For requirements of copper and copper alloy tubes intended for use in heat exchangers, see Ch 9, 3 Tubes of the Rules for Materials.

18.2.2 Materials of heat exchangers are to be compatible with, and offer suitable erosion and corrosion resistance against, the intended fluid media. See also Vol 2, Pt 7, Ch 1, 17 Guidance notes on metal pipes for water service. Sea-water wetted surfaces are to be non-ferrous or coated with a suitable rubber or plastic material where they are not part of the heat exchange system.

18.2.3 Means are to be provided to enable non-ferrous materials to be protected against the effects of exposure to polluted cooling water.

18.2.4 Combinations of incompatible materials are to be avoided, including those of the system pipe work in which the heat exchanger is to be fitted.

18.3.1 The design of shell, end boxes and fluid openings in shell and tube type heat exchangers is to ensure:

1. Uniform distribution of fluids over and through the tubes.

2. A smooth flow of the fluids from the inlet pipes to the tubes and from the tubes to the outlet pipes. In particular end boxes are to have sufficient depth to allow fluid to travel freely to all tubes. The minimum end box depth is to be at least equivalent to the internal diameter of the inlet/outlet connecting pipes.

3. That pockets or obstructions which might interfere with fluid flow are avoided.

4. That the water velocity complies with Vol 2, Pt 7, Ch 1, 17.6 Water velocity 17.6.3.

5. That the form of hand holes and sight holes on end boxes preclude the formation of eddies.

6. That the inclusion of internal ribs to provide a means of strengthening is avoided. However, there is to be sufficient support to avoid vibration of tubes in the tube-bundle which may detrimentally affect their specified life.

7. That positive drainage of heat exchangers is provided. Drain valves, or for small heat exchangers drain plugs, are to be provided to ensure that tubes and shells are emptied and no large quantities of fluid are trapped in end boxes and shells.

18.3.2 Shell and tube type heat exchangers are to be arranged in the ship such that tube plates are readily accessible for cleaning/inspection and to allow for withdrawal of tubes for replacement without disturbing adjacent machinery.

18.3.3 Where ever practicable, viewing ports are to be provided on heat exchanger shell end boxes or covers to permit visual inspection of tubes, baffles and tube plates. In general, this will be limited to larger units of over 300 mm internal shell dimension.

18.4.1 The design of the fluid openings and plates of plate type heat exchangers is to ensure:

1. Uniform distribution of fluids through the plate passages.

2. That pockets or obstructions which might interfere with fluid flow are avoided.

3. Positive drainage of heat exchangers is provided. Drain valves, or for small heat exchangers drain plugs, are to be provided to ensure complete drainage.

18.4.2 Plate type heat exchangers are to be arranged in the ship such that plates are readily accessible for cleaning/inspection and to allow for withdrawal of plates for replacement with the minimum disturbance of adjacent pipe work.

18.5.1 In general, heat exchangers are to be tested hydraulically to 1,5 times their maximum working pressures on the tube and shell sides or on both sides of the heat transfer plates as appropriate.