Section 8 Plastic pipes

8.1.1 Proposals to use plastic pipes in shipboard piping systems will be considered in relation to the properties of the materials, the operating conditions, the intended service and location. Details are to be submitted for approval. Special consideration will be given to any proposed service for plastic pipes not mentioned in these Rules.

8.1.2 5Plastic pipes and fittings will, in general, be accepted in Class III piping systems. Proposals for the use of plastic in Class I and Class II piping systems will be specially considered.

8.1.3 For Class I, Class II and any Class III piping systems for which there are Rule requirements, the pipes are to be of a type which has been approved by LR.

8.1.4 For domestic and similar services where there are no Rule requirements, the pipes need not be of a type which has been approved by LR. However, the fire safety aspects, as referenced in Pt 4, Ch 4, 8.4 Fire performance criteria and Pt 4, Ch 4, 8.5 Additional fire performance criteria applicable to linkspans, are to be considered.

8.1.5 The use of plastic pipes may be restricted by statutory requirements of the National Authority of the country in which the vessel is to be registered.

8.2.1  Pipes and fittings are to be of robust construction and are to comply with an acceptable National or International Standard, consistent with the intended use. Particulars of pipes, fittings and joints are to be submitted for consideration.

8.2.2 The design and performance criteria of all piping systems, independent of service or location, are to meet the requirements of Pt 4, Ch 4, 8.3 Design strength.

8.2.3 Depending on the service and location, the fire safety aspects, such as fire endurance, flame spread, smoke generation, toxicity and fire protection coatings, are to meet the requirements of Pt 4, Ch 4, 8.4 Fire performance criteria and Pt 4, Ch 4, 8.5 Additional fire performance criteria applicable to linkspans.

8.2.4 Plastic piping, connections and fittings are to be electrically conductive when:

1. carrying fluids capable of generating electrostatic charges; or
2. passing through hazardous zones and spaces, regardless of the fluid being conveyed.

Suitable precautions against the build-up of electrostatic charges are to be provided in accordance with the requirements of Pt 4, Ch 4, 8.6 Electrical conductivity.

8.3.1 The strength of pipes is to be determined by hydrostatic pressure tests to failure on representative sizes of pipe. The strength of fittings is to be not less than the strength of the pipes.

8.3.2 The nominal internal pressure, p_Ni, (in MPa) of the pipe is to be determined by the lesser of the following:

Failure pressures obtained over a reduced period and extrapolated in accordance with a recognised National or International Standard will be specially considered.

8.3.3 In service, the pipe is not to be subjected to a pressure greater than p_Ni.

8.3.4 The nominal external pressure, p_Ne, (in MPa) of the pipe, defined as the maximum total of internal vacuum and external static pressure head to which the pipe may be subjected, is to be determined by the following:

8.3.5 p_col is not to be less than 0,3 MPa.

8.3.6 Piping is to meet the requirements of Pt 4, Ch 4, 8.3 Design strength over the range of service temperature which will be experienced in service.

8.3.7 High temperature limits and pressure reductions relative to nominal pressures are to be in accordance with a recognised standard, but in each case the maximum working temperature is to be at least 20°C lower than the minimum temperature for deflection under load of the resin or plastic material without reinforcement. The minimum heat distortion temperature is not to be less than 80°C. See also Ch 14, 4 Plastic pipes and fittings of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

8.3.8 Where it is proposed to use plastic piping in low temperature services, design strength testing is to be made at a temperature 10°C lower than the minimum working temperature.

8.3.9 The selection of plastic materials for piping is to take account of other factors such as impact resistance, ageing, fatigue, erosion resistance, fluid absorption and material compatibility such that the design strength of the piping is not reduced below that required by these Rules.

8.3.10 Design strength values may be verified experimentally or by a combination of testing and calculation methods.

8.4.1 Where a fire protective coating of pipes and fittings is necessary for achieving the fire endurance standards required, the coating is to be resistant to products likely to come into contact with the piping and be suitable for the intended application.

8.4.2 The materials used for plastic pipes, except those fitted on open decks and within tanks, cofferdams, void spaces, pipe tunnels and ducts are to have low flame spread characteristics.

8.4.3 The materials used for plastic pipes within accommodation, service and control spaces are not to be capable of producing excessive quantities of smoke and toxic products that may be a hazard to personnel within those spaces.

8.5.1 Where plastic pipes are used in systems essential for the safe operation of the linkspan or for containing combustible fluids or sea water where leakage or failure could result in fire or in the flooding of watertight compartments, the pipes and fittings are to be of a type which has been fire endurance tested.

8.6.1 Where a piping system is required to be electrically conductive for the control of static electricity, the resistance per unit length of the pipe, bends, elbows, fabricated branch pieces, etc. is not to exceed 0,1 MΩ/m.

8.6.2 Where a piping system is required to be electrically conductive for the control of static electricity, electrical continuity is to be maintained across the joints and fittings and the system is to be earthed. The resistance to earth from any point in the piping system is not to exceed 1 MΩ.

8.7.1 All materials for plastic pipes and fittings are to be approved by LR, and are in general to be tested in accordance with Ch 14, 4 Plastic pipes and fittings of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. For pipes and fittings not employing hand lay up techniques, the hydrostatic pressure test required by Ch 14, 4.9 Hydraulic test of the Rules for the Manufacture, Testing and Certification of Materials, July 2022 may be replaced by testing carried out in accordance with the requirements stipulated in a recognised National or International Standard, consistent with the intended use for which the pipe or fittings are manufactured, provided that there is an effective quality system in place complying with the requirements of Ch 14, 4.4 Quality assurance of the Rules for the Manufacture, Testing and Certification of Materials, July 2022 and the testing is completed to the satisfaction of the LR Surveyor.

8.7.2 The material manufacturer’s test certificate, based on actual tested data, is to be provided for each batch of material.

8.7.3 Plastic pipes and fittings are to be manufactured at a works approved by LR in accordance with agreed quality control procedures which shall be capable of detecting at any stage (e.g. incoming material, production, finished article, etc.) deviations in the material, product or process.

8.7.4 Plastic pipes are to be manufactured and tested in accordance with Ch 14, 4 Plastic pipes and fittings of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. For Class III piping systems the pipe manufacturer’s test certificate may be accepted in lieu of an LR Certificate and is to be provided for each consignment of pipe.

8.8.1 All pipes are to be adequately but freely supported. Suitable provision is to be made for expansion and contraction to take place without unduly straining the pipes.

8.8.2 Pipes may be joined by mechanical couplings or by bonding methods such as welding, laminating and adhesive bonding.

8.8.3 Where bonding systems are used, the manufacturer or installer shall provide a written procedure covering all aspects of installation, including temperature and humidity conditions. The bonding procedure is to be approved by LR.

8.8.4 The person carrying out the bonding is to be qualified. Records are to be available to the Surveyor for each qualified person showing the bonding procedure and performance qualification, together with dates and results of the qualification testing.

8.8.5 Conditions during installation, such as temperature and humidity, which may affect the strength of the finished joints, are to be in accordance with the agreed bonding procedure.

8.8.6 The required fire endurance level of the pipe is to be maintained in way of pipe supports, joints and fittings, including those between plastic and metallic pipes.

8.8.7 Where piping systems are arranged to pass through watertight bulkheads or decks, provision is to be made for maintaining the integrity of the bulkhead or deck by means of metallic bulkhead or deck pieces. The bulkhead or deck pieces are to be of substantial construction and suitably protected against corrosion and so constructed to be of a strength equivalent to the intact bulkhead; attention is drawn to Pt 4, Ch 4, 8.8 Construction and installation 8.8.1, details of the arrangements are to be submitted for approval.

8.8.8 Pipes or other fittings attached directly to the plating of tanks and to bulkheads, which are required to be of watertight construction, are to be secured by means of studs screwed through the plating or by tap bolts, and not by bolts passing through clearance holes. Alternatively, the studs or the bulkhead or tank pieces may be welded to the plating.

8.9.1 Where a piping system is required to be electrically conductive, tests are to be carried out in accordance with Pt 4, Ch 4, 8.6 Electrical conductivity

8.9.2 The hydraulic testing of pipes and fittings is to be in accordance with Pt 4, Ch 4, 12 Hydraulic tests on pipes and fittings

8.9.3 In the case of pipes intended for essential services each qualified person is, at the place of construction, to make at least one test joint, representative of each type of joint to be used. The joined pipe section is to be tested to an internal hydrostatic pressure of four times the design pressure of the pipe system and the pressure held for not less than one hour, with no leakage or separation of joints. The bonding procedure test is to be witnessed by the Surveyor.