Section 1 General

1.1.1 The requirements of this Chapter apply to the design and construction of piping systems, including pipe fittings forming parts of such systems.

1.1.2 The materials used for pipes, valves and fittings are to be suitable for the medium and the service for which the piping is intended.

1.1.3 The piping systems for LPG and LNG carriers, gas fuelled ships and classed refrigeration systems are to comply with the relevant Sections of this Chapter where applicable and the additional requirements in Pt 5, Ch 12, 9 Piping for LPG/LNG carriers, gas fuelled ships and classed refrigeration systems as well as the requirements contained in the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquefied Gases in Bulk, July 2022 (hereinafter referred to as the Rules for Ships for Liquefied Gases).

1.1.4 The cargo piping systems for chemical tankers are to comply with the relevant Sections of this Chapter where applicable, except where there are specific alternative or additional requirements provided in the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquid Chemicals in Bulk, July 2022.

1.2.1  Piping system includes pipes and fittings such as expansion joints, valves, pipe joints, support arrangements, flexible tube lengths, etc. and components in direct connection with the piping such as pumps, heat exchangers, air receivers, independent tanks, etc.

1.3.1 The symbols used in this Chapter are defined as follows:

1.3.2 The outside diameter, D, is subject to manufacturing tolerances, but these are not to be used in the evaluation of formulae.

1.3.3 The inside diameter, d, is not to be confused with nominal size, which is an accepted designation associated with outside diameters of standard rolling sizes.

1.3.4 The weld efficiency factor, e, is to be taken as 1 for seamless and electric resistance and induction welded steel pipes. Where other methods of pipe manufacture are proposed, the value of e will be specially considered.

1.4.1 The design pressure, p, is the maximum permissible working pressure and is to be not less than the highest set pressure of the safety valve or relief valve.

1.4.2 In water tube boiler installations, the design pressure for steam piping between the boiler and integral superheater outlet is to be taken as the design pressure of the boiler, i.e. not less than the highest set pressure of any safety valve on the boiler drum. For piping leading from the superheater outlet, the design pressure is to be taken as the highest set pressure of the superheater safety valves.

1.4.3 The design pressure of feed piping and other piping on the discharge from pumps is to be taken as the pump pressure at full rated speed against a shut valve. Where a safety valve or other protective device is fitted to restrict the pressure to a lower value than the shut valve load, the design pressure is to be the highest set pressure of the device.

1.4.4 For design pressure of steering gear components and piping, see Pt 5, Ch 19, 3.1 General 3.1.5.

1.5.1 The design temperature is to be taken as the maximum temperature of the internal fluid, but in no case is it to be less than 50°C.

1.5.2 In the case of pipes for superheated steam, the temperature is to be taken as the designed operating steam temperature for the pipeline, provided that the temperature at the superheater outlet is closely controlled. Where temperature fluctuations exceeding 15°C above the designed temperature are to be expected in normal service, the steam temperature to be used for determining the allowable stress is to be increased by the amount of this excess.

1.6.1 Pressure piping systems are divided into three classes for the purpose of assigning appropriate testing requirements, types of joints to be adopted, heat treatment and weld procedure.

1.6.2 Dependent on the service for which they are intended, Class II and III pipes are not to be used for design pressure or temperature conditions in excess of those shown in Table 12.1.1 Maximum pressure and temperature conditions for Class II and III piping systems. Where either the maximum design pressure or temperature exceeds that applicable to Class II pipes, Class I pipes are to be used. To illustrate this, see Figure 12.1.1 Classes of piping system.

1.6.3 In addition to the pressure piping systems in Table 12.1.1 Maximum pressure and temperature conditions for Class II and III piping systems, Class III pipes may be used for open ended piping, e.g. overflows, vents, boiler waste steam pipes, open ended drains, sounding pipes etc.

1.6.4 Class II and III pipes are not to be used for toxic media.

1.6.5 Class I pipes are generally required for corrosive media. Class II pipes may be used for corrosive media where special safeguards for reducing the potential for leakage and limiting its consequences are provided, e.g. the use of pipe ducts, shielding, screening, etc. in such a way that a leakage will not cause a potential hazard or damage to surrounding areas. Class III pipes are not to be used for corrosive media. Materials used for piping for corrosive media are to be specially considered.

1.6.6 For piping systems or components using cast iron, see Pt 5, Ch 12, 4 Cast iron.

1.7.1 Materials for metallic castings and forgings of Class I and Class II piping systems are to be produced at a works approved by Lloyd’s Register (commonly referred to as ‘LR’) and are to be tested in accordance with the Rules for the Manufacture, Testing and Certification of Materials, July 2022 (commonly referred to as the Rules for Materials).

1.7.2 The Manufacturer’s materials certificate will be accepted in lieu of an LR materials certificate for Class III piping systems and for all other classes of piping and associated components where the maximum design conditions are less than the values shown in Table 12.1.2 Maximum conditions for pipes, valves and fittings for which manufacturer's materials test certificate is acceptable. See Ch 1, 3.1 General 3.1.3.(c) of the Rules for Materials.

1.7.3 The manufacturer's certificate for materials for ship-side valves and fittings and valves on the collision bulkhead equal to or less than 500 mm nominal diameter will be accepted in lieu of LR's materials certificate where the valves and fittings are in accordance with a recognised National Standard applicable to the intended application and are manufactured and tested in accordance with the appropriate requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.