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BEIHAI YUEDA FRP PRODUCTS
Installation Methods for FRP Pipes and FRP Sand-Embedded Pipes
Release time:
2018/12/27
1. Installation methods for fiberglass reinforced plastic (FRP) pipes and fiberglass reinforced plastic sand-coated pipes: ① Before construction, the appearance and dimensions of the FRP pipes should be inspected and accepted according to the factory quality certificate. ② The pipeline installation drawings serve as the basis for the pipeline installation project. The laying of FRP/PVC pipes (including connection forms, coordinates, elevation, slope, direction, etc.), the connection between FRP/PVC pipes and equipment, and the installation positions and supports of pipeline accessories must all comply with the design drawings. Any changes must be resolved in consultation with the design unit. ③ Pipeline installation can be carried out sequentially from one end of the pipeline according to the sections defined in the pipeline installation drawings, installing pipeline accessories in order.
1. Installation methods for fiberglass reinforced plastic (FRP) pipes and FRP sand-coated pipes
1. Before construction, the appearance and dimensions of the FRP pipes should be checked and accepted according to the factory qualification certificate.
2. The pipeline installation diagram is the basis for the pipeline installation project. The laying of FRP/PVC pipes (including connection forms, coordinates, elevation, slope, direction, etc.), the connection between FRP/PVC pipes and equipment, and the installation positions and supports of pipeline accessories must comply with the design drawings. Any changes must be negotiated with the design unit.
3. Pipeline installation can be carried out according to the sections defined in the pipeline installation diagram. Install the pipeline accessories sequentially from one end of the pipeline to the other, and then set supports or brackets (temporary supports may be required during the installation process). During the lifting of the pipeline, protective measures must be taken for the outer wall surface, and direct contact with steel wire ropes is prohibited to avoid localized stress.
4. Connection points of FRP pipes are only allowed in the straight pipe sections. The distance from the welded connection point to the edge of the pipe support should be greater than the outer diameter of the pipe and not less than 100mm; the distance from the socket connection to the edge of the pipe support should be greater than 150mm.
5. The connection structures of the pipeline include socket connections, flange connections (welded ring loose flange connections and composite flat welded flange connections), and butt welding connections. The installation method will be determined based on the specific requirements of the design documents.
6. Welders engaged in welding must hold a welding qualification certificate and be familiar with the adhesive properties and installation methods of FRP/PVC pipes, as well as possess skilled PVC welding operation capabilities.
7. Before socket connections of the pipeline, the inner wall of the PVC pipe at the connection should be cleaned, and then the socket head should be inserted into the socket. The socket joint must not have defects such as misalignment or cracks. PVC welding can only be performed after reaching the required socket depth.
8. The socket area should be reinforced with FRP, applying a uniform layer of R glue on the reinforcement area, ensuring the thickness is even without missing spots or dripping. Then wrap a layer of glass cloth, apply unsaturated resin, wrap the glass cloth, and repeat until the thickness meets the requirements.
9. If the socket installation is unqualified and needs to be repaired, the socket head and socket must be remade, and previously used socket parts must not be used.
10. When connecting flanges to the pipeline, both the inner and outer surfaces must be welded to the pipe. The inclination of the flange surface to the pipe axis should be less than or equal to 1/100 of the pipe's outer diameter. Flange connections must be strictly centered, with a maximum allowable axial deviation of no more than 2mm, and misalignment must not be corrected by using excessively tight bolts. Bolts should be tightened in two stages: first, evenly and symmetrically tighten once, and then tighten the bolts again.
3. Installation of steel-lined rubber pipes
1. When handling and stacking rubber-lined pipes and fittings, strong vibrations or collisions should be avoided.
2. Before installation, check that the rubber lining is intact and keep the inside of the pipe clean.
3. During the installation of rubber-lined pipes, welding, local heating, twisting, or striking is not allowed.
4. For finished pipe fittings with DN≤500, each pipe section should be numbered according to the single line diagram before installation. During installation, follow the single line diagram and numbered sections for assembly. If the active part needs to be corrected, the corrected pipe section should be lined with rubber on-site.
5. Rubber-lined pipes should use soft or semi-rigid gaskets. During installation, the gaskets should be placed correctly, and if necessary, slanted gaskets can be used for alignment.
6. For pipes with DN≥500, fittings should be prefabricated and pre-installed on-site according to the single line diagram, using flange connections. A thickness of about 7mm should be reserved for the rubber lining and gasket between the flange surfaces. After passing the on-site pressure test, disassemble for on-site lining processing. The pre-installed pipeline should be marked on the pipe wall and numbered according to the drawing, so that the lining can still be installed according to the original drawings.
7. The flanges of the prefabricated pipes on-site should be welded on both the inner and outer surfaces. After welding, the inner and outer surfaces of the flanges must be polished smooth with an angle grinder to avoid unevenness, air holes, etc., to prevent air from being trapped in the gaps, which could cause the rubber lining to age.
8. If the rubber lining inside the pipe protrudes into the flange, the fittings must reach the inner mouth of the flange during production, and the corner should have a radius of r=5mm. If general flange welding is used, the weld seam at the flange inner mouth must be processed into a rounded corner of r=5mm.
9. For on-site processed bends, the bending angle should not exceed 90°, and the bending radius should not be less than four times the pipe diameter.
10. When opening a tee on a steel-lined rubber pipe, the small radius r=5mm at the inner wall corner should be smooth, using the heating and pulling method to meet the rubber lining requirements.
4. Pipe coiling processing
1. The longitudinal welds on the same section of the coiled pipe should not exceed two; the distance between two longitudinal seams should not be less than 200mm.
2. During the assembly of the coiled pipe, the distance between the two longitudinal seams should be greater than 100mm. The outer wall of the branch pipe should be at least 50mm away from the weld.
3. The coiled pipe should be checked for arc degree, end face deviation, straightness, etc., as specified.
4. For coiled pipes that cannot form double-sided welds, when the nominal diameter is greater than or equal to 600mm, it is advisable to perform bottom sealing welding inside the pipe.
5. During the processing of coiled pipes, care should be taken to prevent damage to the surface of the plate. Areas with serious scars must be ground to ensure a smooth transition, and the wall thickness at the ground area must not be less than the design wall thickness.
6. All welds on the coiled pipe should pass the kerosene penetration test.
5. Fabrication and installation of pipe supports and hangers
1. The pipe racks made on-site must strictly follow the specifications and drawings, and be painted for protection. The supports for the tie rod hangers and spring hangers should be welded according to the steel structure manufacturing standards and undergo 100% penetration or magnetic particle testing.
2. The positions of all pipe racks should be indicated in the single line diagram.
③ During pipeline installation, supports should be fixed and adjusted in a timely manner, the position of the supports should be accurate, the installation should be flat and firm, and the contact with the pipe should be tight.
④ Fixed supports should be installed according to the requirements of the design documents and should be fixed before the compensator is pre-stretched.
⑤ The sliding surfaces of guiding supports or sliding supports should be clean and flat, without any skew or jamming. The installation position should be offset from the center of the supporting surface in the opposite direction, with an offset amount of 1/2 of the displacement value or in accordance with the design documents, and the insulation layer should not hinder its displacement.
⑥ When using temporary supports for pipeline installation, they must not conflict with the position of the formal supports and should be clearly marked. They should be removed after the pipeline installation is completed.
⑦ FRP/PVC pipes must not be directly bonded or welded to the pipe rack (including supports). Between the pipe fittings (pipe clamps, pipe supports, or pipe clips) that fix the FRP/PVC pipes and the outer wall of the pipes, rubber blocks or other soft pads with a thickness of no less than 3mm should be placed.
⑧ After the pipeline installation is completed, the form and position of each support should be checked one by one according to the design documents.
Storage of products
(1) The storage area for pipes should be flat, with wooden sleepers or grass bags laid on the bottom to prevent contamination of the pipes.
(2) Pipes should be stacked using a grid stacking method or a single-row sequential placement method. When the stacking height is below 1 meter, the single-row sequential placement method or grid stacking method can be used. When it exceeds 1 meter, the grid stacking method should be used, but the stacking height should not exceed 2 meters. Additionally, wedges, stakes, and ropes should be used for reinforcement to prevent the pipes from scattering.
VI. Pressure Testing and Flushing of FRP Pipes
① In order to reduce the temporary pipelines added during purging, save time for pressure testing and purging, and improve the pass rate of pressure testing and purging, the pressure testing and purging work should be carried out according to the system, area, and pressure level. A plan must be prepared to guide the construction before pressure testing and purging.
② Clean water should be used for pressure testing of the pipeline. When testing and flushing connected stainless steel pipes, the chloride ion content in the water must not exceed 25×10 (25ppm), and the pressure testing and flushing procedures must comply with the general contractor's regulations.
③ During the pressure test, unrelated personnel must not enter. After the pressure test is completed, no repairs should be made on the pipeline.
④ Before the pressure test, the following conditions must be met:
a. The pipeline installation work within the test scope has been fully completed according to the design drawings, except for painting and insulation, and the installation quality meets relevant regulations.
b. Welds and other areas to be inspected have not yet been painted and insulated.
c. Temporary restraint devices have been set for the expansion joints on the pipeline.
d. The pressure gauge for testing has been calibrated and is within the period, with an accuracy of no less than 1.5 grade, and the full scale value of the gauge should be 1.5-2 times the maximum pressure to be measured, with no less than two pressure gauges.
e. The liquid or gas that meets the pressure testing requirements has been prepared.
f. The pipeline has been reinforced according to the testing requirements.
g. The pipeline to be tested has been isolated from unrelated systems using blind plates or other measures.
h. Safety valves and instrument components on the pipeline to be tested have been removed or isolated.
i. The testing plan has been approved and technical disclosure has been conducted.
⑤ Hydraulic testing should comply with the following regulations:
a. Before the test, all air should be expelled when injecting liquid.
b. The ambient temperature during the test should not be lower than 5℃. When the ambient temperature is below 5℃, frost protection measures should be taken.
c. The test pressure of the pipeline should be 1.5 times the design pressure.
d. When the design temperature of the pipeline is higher than the test temperature, the test pressure should be calculated according to the following formula:
Ps=1.5P[σ]1[σ]2
Where Ps----test pressure (gauge pressure) (MPa);
P----design pressure (gauge pressure) (MPa);
[σ]1----allowable stress of the pipe material at the test temperature (MPa);
[σ]2----allowable stress of the pipe material at the design temperature (MPa).
When [σ]1[σ]2 is greater than 6.5, take 6.5.
e. When the pipeline and equipment are tested as a system, if the test pressure of the pipeline is equal to or less than the test pressure of the equipment, the test should be conducted according to the test pressure of the pipeline; if the test pressure of the pipeline is greater than the test pressure of the equipment, and the test pressure of the equipment is not less than 1.15 times the design pressure of the pipeline, it can be tested according to the test pressure of the equipment with the consent of the construction unit.
f. For pipelines with significant elevation differences, the static pressure of the test medium should be included in the test pressure. The test pressure for liquid pipelines is based on the highest point, but the pressure at the lowest point should not exceed the bearing capacity of the pipeline components.
g. The hydraulic test pressure should be increased slowly. After reaching the test pressure, maintain the pressure for 10 minutes, then reduce the test pressure to the design pressure. Maintain the pressure for 30 minutes, and it is considered qualified if the pressure does not drop and there are no leaks.
h. After the test is completed, blind plates and expansion joint limiting devices should be removed in a timely manner, and accumulated liquid should be drained. During drainage, care should be taken to prevent negative pressure and not to discharge it indiscriminately.
i. If a leak is found during the test, it must not be handled under pressure. After eliminating the defect, the test should be conducted again.
⑥ For pipelines transporting toxic fluids, a leak test must also be conducted, using air as the test medium (i.e., conducting an airtight test). The airtight test should be conducted according to the following regulations:
a. The airtight test pressure is the design pressure.
b. The key points of the air tightness test are to check the valve packing, flanges or threaded connections, vent valves, exhaust valves, drainage valves, etc.
c. The method of using soapy water or other foaming agents for inspection during the air tightness test is considered qualified if there is no leakage.
After the pipeline passes the pressure test, the flushing or cleaning work should be organized according to the flushing plan.
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