Petroleum and natural gas industries - Glass-reinforced plastics (GRP) piping - Part 3: System design
1 Scope
This document gives guidelines for the design of GRP piping systems. The requirements and recommendations apply to layout dimensions, hydraulic design, structural design, detailing, fire endurance, spread of fire and emissions and control of electrostatic discharge.
This document is intended to be read in conjunction with GB/T 29165.1-2022.
Guidance on the use of this document can be found in Figure 1, which is a more detailed flowchart of steps 5 and 6 in GB/T 29165.1-2022, Figure 1.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 29165.1-2022 Petroleum and natural gas industries - Glass-reinforced plastics (GRP) piping - Part 1: Vocabulary, symbols, applications and materials
GB/T 29165.2-2022 Petroleum and natural gas industries - Glass-reinforced plastics (GRP) piping - Part 2: Qualification and manufacture
ASTM D2412 Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading
ASTM D2992 Standard Practice for Obtaining Hydrostatic or Pressure Design Basis for Fiberglass (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe and Fittings
AWWA Manual M45 Fiberglass pipe design
3 Terms and definitions
For the purposes of this document, the terms, definitions, symbols and abbreviated terms given in GB/T 29165.1-2022 apply.
4 Layout requirements
4.1 General
GRP products are proprietary and the choice of component sizes, fittings and material types can be limited depending on the supplier. Potential vendors should be identified early in design to determine possible limitations of component availability. The level of engineering support that can be provided by the supplier should also be a key consideration during vendor selection.
Where possible, piping systems should maximize the use of prefabricated spoolpieces to minimize the amount of site work. Overall spool dimensions should be sized taking into account the following considerations:
——limitations of site transport and handling equipment;
——installation and erection limitations;
——limitations caused by the necessity to allow a fitting tolerance for installation (“cut to fit” requirements).
The designer shall evaluate system layout requirements in relation to the properties of proprietary piping systems available from manufacturers, including but not limited to the following:
a) axial thermal expansion requirements;
b) ultraviolet radiation and weathering resistance requirements;
c) component dimensions;
d) jointing system requirements;
e) support requirements;
f) provision for isolation for maintenance purposes;
g) connections between modules and decks;
h) flexing during lifting of modules;
i) ease of possible future repair and tie-ins;
j) vulnerability to risk of damage during installation and service;
k) fire performance;
l) control of electrostatic charge.
The hydrotest provides the most reliable means of assessing system integrity. Whenever possible, the system should be designed to enable pressure testing to be performed on limited parts of the system as soon as installation of those parts is complete. This is to avoid a final pressure test late in the construction work of a large GRP piping system, when problems discovered at a late stage would have a negative effect on the overall project schedule.
4.2 Space requirements
The designer shall take account of the larger space envelope of some GRP components compared to steel. Some GRP fittings have longer lay lengths and are proportionally more bulky than the equivalent metal component and may be difficult to accommodate within confined spaces. If appropriate, the problem can be reduced by fabricating the pipework or piping as an integral spoolpiece in the factory rather than assembling it from the individual pipe fittings.
If space is limited, consideration should be given to designing the system to optimize the attributes of both GRP and metal components.
4.3 System supports
4.3.1 General
GRP piping systems can be supported using the same principles as those for metallic piping systems.
However, due to the proprietary nature of piping systems, standard-size supports will not necessarily match the pipe outside diameters.
The following requirements and recommendations apply to the use of system supports.
a) Supports shall be spaced to avoid sag (excessive displacement over time) and/or excessive vibration
for the design life of the piping system.
b) In all cases, support design shall be in accordance with the manufacturer’s guidelines.
c) Where there are long runs, it is possible to use the low modulus of the material to accommodate axial expansion and eliminate the need for expansion joints, provided the system is well anchored and guided. In this case, the designer shall recognize that the axial expansion due to internal pressure is now restrained and the corresponding thrust loads are partly transferred to the anchors.
d) Valves or other heavy attached equipment shall be adequately and, if necessary, independently supported. When evaluating valve weight, valve actuation torque shall also be considered.
Note: Some valves are equipped with heavy control mechanisms located far from the pipe centreline and can cause large bending and torsional loads.
e) GRP piping shall not be used to support other piping, unless agreed with the principal.
f) GRP piping shall be adequately supported to ensure that the attachment of hoses at locations such as utility or loading stations does not result in the pipework being pulled in a manner that can overstress the material.
Pipe supports can be categorized into those that permit movement and those that anchor the pipe.
