FRP pipe connection method, under what circumstances will FRP pipe leak, maintenance method
1、Common connection methods of FRP pipes
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1.Flange connection: Principle: Prefabricate or bond flanges (usually FRP flanges, sometimes metal flanges lined with FRP or all-metal flanges) at both ends of the pipeline, place sealing gaskets between the two flanges, and tighten with bolts to achieve sealing. Advantages: Reliable connection, good sealing, easy to disassemble and repair, suitable for various pressures and pipe diameters, especially suitable for large-diameter pipelines and connections with valves, equipment, etc. Disadvantages: Relatively high cost, flanges occupy a large space, and bolts need to be checked and tightened regularly. Key points: Flange surface flatness, gasket selection, bolt material, bolt tightening sequence and torque uniformity are crucial. |
When the flange of the FRP pipe is damaged, a flange pipe repair clamp is usually used for repair. The entire flange is wrapped to form a sealed environment to achieve the effect of repairing the pipeline. The body of the pipe repair clamp is made of carbon steel. Q235 carbon steel has strong flexibility and tensile strength (σb/MPa): ranges from 370-500
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2.Socket-and-spigot joint: Principle: The end of a pipe (socket end) is processed into a bell mouth (socket), and the other pipe (spigot end) is inserted into it. Apply special epoxy resin or polyester resin adhesive on the inner wall of the socket and the outer wall of the spigot, and solidify after insertion to form a firm bonding seal. Advantages: High connection strength (close to the strength of the pipe body), good sealing, low cost, low fluid resistance, suitable for small and medium diameter pipes. Disadvantages: It is a permanent connection and difficult to disassemble. It has extremely high requirements for construction technology (surface treatment, glue ratio, coating uniformity, insertion depth, curing conditions). It has high requirements for pipe end processing accuracy. Key points: This is the most commonly used but also the most prone to leakage due to improper construction. Cleaning, grinding, glue quality, curing time/temperature must be strictly operated according to specifications. |
Socket pipe repair clamp is usually used for repair of leaking FRP pipe socket connection, which wraps the entire socket to form a sealed environment and achieve the effect of repairing the pipeline. The pipe repair clamp body is made of carbon steel, Q235 carbon steel, and you can also choose 304, 36, 316L stainless steel pipe repair clamp. The length and size of the pipe mouth of the pipe repair clamp can be customized.
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3. Clamp connection: Principle: Put a rubber sealing ring on the butt end of the two pipes, tighten the outside with two half metal or reinforced plastic clamps, and press the sealing ring to achieve sealing. Advantages: Quick and easy installation, allowing a certain angle deviation and axial displacement, easy to maintain. Disadvantages: Limited pressure resistance (usually medium and low pressure), long-term reliability is affected by the aging of the sealing ring, and the outer diameter tolerance of the pipe is relatively high. Key points: The sealing ring material must be resistant to media and temperature; the clamp must have sufficient strength and corrosion resistance; it must be installed correctly. |
The FRP pipe clamp connection leaks, usually using a socket pipe repair clamp for repair, wrapping the entire clamp to form a sealed environment to achieve the effect of repairing the pipeline. The pipe repair clamp body is made of carbon steel, Q235 carbon steel, and you can also choose 304, 36, 316L stainless steel pipe repair clamp, the length of the pipe repair clamp and the size of the pipe mouth can be customized.
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4.Butt bonding: Principle: The end faces of the two pipes are processed flat, directly butted, and then the glass fiber reinforced material impregnated with resin is wound inside and outside the butt joint to form a whole after curing. Advantages: High connection strength, continuous and smooth inner wall. Disadvantages: Complex construction process, high technical requirements for operators, difficult quality control, less on-site application, mostly used for pipe fittings production or repair. Key points: End face treatment, number of winding layers, resin content, and curing process must be strictly controlled. |
When the FRP pipe is leaking, a straight pipe repair clamp is usually used for repair. The entire clamp is wrapped to form a sealed environment to achieve the effect of repairing the pipeline. The pipe repair clamp body is made of carbon steel, Q235 carbon steel, and you can also choose 304, 36, 316L stainless steel pipe repair clamp. The length and size of the pipe mouth of the pipe repair clamp can be customized.
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2、Common situations of glass fiber reinforced plastic pipe leakage
Leakage mainly occurs at the connection, and secondly in the pipe itself. The reasons can be summarized as follows:
- Installation and construction quality issues:
Gluing problems: When spigot or butt bonding, the surface treatment is not clean (there is oil, dust, moisture), the grinding is not thorough (no fresh rough surface is formed), the adhesive ratio is wrong, it is expired and invalid, the application is uneven, the insertion depth is insufficient, it is put into use before it is fully cured, and the curing temperature/time does not meet the requirements.
Flange connection problems: The flange sealing surface is damaged, contaminated or uneven; the gasket is selected incorrectly (not resistant to the medium or temperature), the gasket is damaged or aged; the bolts are not tightened evenly in the correct order and with the specified torque (too loose causes leakage, and too tight may cause damage to the flange or bolts); the bolts are corroded and broken.
Threaded connection problems: Poor thread processing, insufficient or excessive tightening torque, insufficient or invalid sealing packing.
Clamp connection problems: The sealing ring is not placed correctly, damaged or aged; the clamp is not tightened or unevenly stressed; the outer diameter of the pipe does not meet the requirements.
Improper pipe cutting/processing: The cut is uneven and cracked, which damages the pipe wall structure.
- Improper design or selection:
Wrong connection method selection: For example, threaded connection or socket joint is used in high-pressure occasions without considering sufficient safety factor.
Insufficient pipe grade/wall thickness: Design pressure or temperature exceeds the rated capacity of the pipe.
Not considering thermal expansion and contraction: Long straight pipes are not equipped with expansion joints or flexible connections, and temperature changes produce huge stress and crack the connection or pipe body.
Wrong chemical compatibility: Pipe material, adhesive, and seal cannot withstand the medium being transported, resulting in corrosion, swelling, degradation and leakage.
3. External mechanical damage or stress:
Construction damage: Cracking of pipes or joints due to collision or squeezing during lifting, handling, and backfilling.
Foundation settlement/external load: Improper pipe support or uneven foundation settlement causes excessive bending or shear stress on the pipe, resulting in connection failure or pipe rupture.
Water hammer/pressure shock: The water hammer pressure generated by the system's rapid start-stop valve or pump exceeds the design value and impacts weak parts.
Third-party damage: Accidental damage to the pipeline due to excavation operations, etc.
- Operating conditions outside the design range:
The system pressure, temperature or flow exceeds the design value for a long time or instantaneously.
The composition, concentration and temperature of the transported medium change and exceed the tolerance range of the material.
