2.1 Requirements Applicable to all Piping Systems

  2.1.1.1 The requirements of this section apply to all piping and piping systems independent of service location.

  2.1.1.2 The specification of the piping should be to a recognized standard acceptable to the Administration and should meet the additional performance guidelines that follow.

  2.1.1.3 The piping should have sufficient strength to take account of the most severe coincident conditions of pressure, temperature, the weight of the piping itself and any static and dynamic loads imposed by the design or environment.

  2.1.1.4 For the purpose of assuring adequate robustness for all piping including open-ended piping (e.g. overflows, vents and open-ended drains), all pipes should have a minimum wall thickness to ensure adequate strength for use on board ships, also to withstand loads due to transportation, handling, personnel traffic, etc. This may require the pipe to have additional thickness than otherwise required by service consideration (e.g. pipes for vacuum and pressure systems).

  2.1.1.5 The performance requirements for any component of a piping system such as fittings, joints, and method of joining are the same as those requirements for the piping system they are installed in.

  2.1.2.1 A piping system should be designed for an internal pressure not less than the maximum working pressure to be expected under operating conditions or the highest set of any safety valve or pressure relief device on the system, if fitted.

  2.1.2.2 The nominal internal pressure for a pipe should be determined by dividing the short-term hydrostatic test failure pressure by a safety factor of 4 or the long-term hydrostatic (>100,000 hours) test failure pressure by a safety factor of 2.5, whichever is the lesser. The hydrostatic test failure pressure should be verified experimentally or by a combination of testing and calculation methods to the satisfaction of the Administration.

  2.1.3.1 External pressure should be taken into account in the design of piping for any installation which may be subject to vacuum conditions inside the pipe or a head of liquid acting on the outside of the pipe.

  2.1.3.2 Piping should be designed for an external pressure not less than the sum of the maximum potential head of liquid outside the pipe, plus full vacuum (1 bar). The nominal external pressure for a pipe should be determined by dividing the collapse test pressure by a safety factor of 3. The collapse test pressure should be verified experimentally or by a combination of testing and calculation methods to the satisfaction of the Administration.

  2.1.4.1 The sum of the longitudinal stresses due to pressure, weight and other dynamic and sustained loads should not exceed the allowable stress in the longitudinal direction. Forces due to thermal expansion, contraction and external loads, where applicable, should be considered when determining longitudinal stresses in the system.

  2.1.4.2 In the case if fibre reinforced plastic pipes, the sum of the longitudinal stresses should not exceed the half of the nominal circumferential stress derived from the nominal internal pressure determined according to paragraph 2.1.2.2, unless the minimum allowable longitudinal stress is verified experimentally or by a combination of testing and calculation methods to the satisfaction of the Administration.

  2.1.5.1 Piping should meet the design requirements of these guidelines over the range of service temperatures it will experience.

  2.1.5.2 High temperature limits and pressure reductions relative to nominal pressures should be according to the recognized standard, but in each case the maximum working temperature should be at least 20°C lower than the minimum heat distortion temperature (determined according to ISO 75 method A, or equivalent) of the resin or plastic material. The minimum heat distortion temperature should not be less than 80°C.

  2.1.5.3 Where low temperature services are considered, special attention should be paid to material properties.

  2.1.6.1 Piping should have a minimum resistance to impact to the satisfaction of the Administration.

  2.1.7.1 Before selection of a piping material, the manufacturer should confirm that the environmental effects including but not limited to ultraviolet rays, saltwater exposure, oil and grease exposure, temperature, and humidity, will not degrade the mechanical and physical properties of the piping material below the values necessary to meet these guidelines. The manufacturer should establish material ageing characteristics by subjecting samples of piping to an ageing test acceptable to the Administration and then confirming its physical and mechanical properties by the performance criteria in these guidelines.

  2.1.8.1 In cases where design loading incorporate a significant cyclic or fluctuating component, fatigue should be considered in the material selection process and taken into account in the installation design.

  2.1.8.2 In addressing material fatigue, the designer may rely on experience with similar materials in similar service or on laboratory evaluation of mechanical test specimens. However, the designer is cautioned that small changes in the material composition may significantly affect fatigue behaviour. This may require additional support of the piping systems.

  2.1.9.1 In the cases where fluid in the system has high flow velocities, abrasive characteristics or where there are flow path discontinuities producing excessive turbulence the possible effect of erosion should be considered. If erosion cannot be avoided then adequate measures should be taken such as increased wall thickness, special lines, change of materials, etc.

  2.1.10.1 Absorption of fluid by the piping material should not cause a reduction of mechanical and physical properties of the material below that required by these guidelines.

  2.1.10.2 The fluid being carried or in which the pipe is immersed should not permeate through the wall of the pipe. Testing for fluid absorption characteristics of the pipe material should be to a recognized standard.

  2.1.11.1 The piping material should be compatible with the fluid being carried or in which it is immersed such that its design strength does not degenerate below that recognized by these guidelines. Where the reaction between the pipe material and the fluid is unknown, the compatibility should be demonstrated to the satisfaction of the Administration.