🧿Let's first look at the material structure.

RPM pipe (reinforced plastic mortar pipe) is a composite of pure glass fiber and unsaturated polyester resin. Its structure is relatively simple, relying entirely on the glass fiber content for strength. It lacks a sand layer. RPMP pipe, on the other hand, is an upgraded RPM pipe with an additional core layer of quartz sand and resin, resulting in a three-layer structure. The inner layer is a corrosion-resistant resin layer that ensures the cleanliness of the conveyed medium; the middle layer is a glass fiber reinforcement layer that provides primary strength. Most importantly, the added sand layer significantly increases the pipe's hoop stiffness.

🧿Let's discuss its performance characteristics.

Because it lacks a sand layer, RPM pipe is lighter overall. Its stiffness, primarily due to fiber reinforcement, is relatively low, making its pressure-bearing capacity more suitable for low-pressure applications, such as cable protection. However, it offers excellent corrosion resistance, insulation, and non-magnetic properties, all of which are advantages. The addition of a sand layer to RPMP pipe enhances its ability to withstand soil pressure, resulting in high stiffness and a pressure resistance of up to 6.4 MPa, making it suitable for high-pressure applications. Although slightly heavier than RPM pipe, it's only about a quarter the weight of steel pipe. Both have smooth interiors and excellent hydraulic performance. RPMP pipe, however, offers a significant flow advantage due to its ability to accommodate larger diameters, and its corrosion resistance is not affected by sand inclusions.

🧿Applications

Each pipe has its own niche. RPM pipe is primarily used to protect power and communications cables, as seen in DBJ and DBS conduit models. It's well-suited for applications requiring lightweight and easy installation, such as cable crossings across rivers and on bridges, where it prevents eddy current heating in the cables. RPMP pipe is more suited to municipal engineering projects, such as large-diameter (up to DN4000) water and drainage pipelines buried deep and subject to high soil pressure. It's a reliable alternative to PCCP pipe in high-pressure water transmission projects, and is suitable for installation in corrosive soils or on the seabed, as demonstrated in the Pearl River Crossing Project.

Production processes and specifications also vary.

RPM pipe is mostly produced using a winding process (either mechanically or manually). Its diameter is generally small, typically under DN200, and single pipe lengths are typically 4 meters. RPMP pipe offers greater flexibility, allowing for centrifugal casting (using chopped fiber, with diameters up to 2400mm) or winding (using long fiber, with diameters up to 4000mm). Single pipe lengths can reach 12 meters, and with fewer joints, installation is more convenient.

Cost

RPM pipe has a lower unit price, but its application is limited, primarily for tasks like cable protection. While RPMP pipe is slightly more expensive (for example, DN1000 is approximately 930 yuan/meter, slightly more expensive than PCCP pipe at 860 yuan/meter), it offers a more cost-effective solution overall: transportation costs are only one-tenth of those of cement pipe, installation is quick, joints are well-sealed, and the smooth interior reduces water flow resistance, reducing pumping energy consumption by approximately 10%, resulting in significant long-term savings.

In general, RPM pipe is a basic fiberglass reinforced plastic pipe suitable for lightweight, low-pressure applications; RPMP pipe is a reinforced version, enhanced by a sand inclusion layer for increased rigidity, suitable for high-pressure, large-diameter applications. The choice depends on your needs: for cable protection and lightweight applications, choose RPM pipe; for municipal water supply and drainage applications requiring high pressure and high flow, choose RPMP pipe. Each has its own uses; one is not superior to the other; the applications differ.

🧿Repair Methods After a Leak:

Baoshuo socket repair clamps are customizable for pipe repairs of any diameter and length, including DN2600. Made of high-strength carbon steel, with custom stainless steel (304, 316, 316L) available. The sealing rubber is EPDM, and customizable with fluororubber, silicone rubber, and NBR. They can be repaired under water and pressure without shutting off the flow.

2. Flange Connection (for frequent disassembly or connection)

   - Steps:

   Flange Treatment: Install EPDM gaskets on both sides of the flange. Tighten the bolts three times in diagonal order (the final torque value must be within ±5% of the design value).

   Corrosion Protection: Apply molybdenum disulfide anti-corrosion grease to the bolts. Wrap the flange outer edge with fluororubber sealing tape to isolate moisture.

   Wrapping Butt Joint (Suitable for on-site repairs or special-shaped pipes)

   - Steps: Grind the joint to a 45° groove → Apply epoxy resin adhesive → Alternately wrap with glass fiber mat/cloth (≥ 3 layers) → After curing, apply UV protective adhesive to the exterior.

   Repair Methods After a Leak:

   Baoshuo tee repair clamp, a pipe repair clamp, is customizable in any diameter and length, and can wrap around flanges of any size. Made of high-strength carbon steel, stainless steel (304, 316, 316L) is also available. The sealing rubber is EPDM, fluororubber, silicone rubber, and NBR. Repairs can be performed under water and pressure without shutting off the water supply.

🧿II. Special Leakage Prevention Measures

Structural Leakage Prevention Design

- Double Seal System:

- First: Water-swelling rubber ring (self-expands to fill gaps in the event of leakage);

- Second: A water-absorbing and swelling layer (such as bentonite tape) embedded in the connecting sleeve expands 20 times its volume upon absorbing water, sealing micro-gaps.

- Leakage Sensing Unit:

- A pressure-sensing curved plate is installed inside the tee socket. Leaking liquid pushes against the curved plate, triggering a sensor alarm. The liquid is also temporarily stored in a recess (capacity ≥ 5L).

Thermal Deformation Compensation

- Flexible Constraint:

- The clamping assembly (e.g., connecting claw + return spring) allows for ±10mm axial displacement of the pipe to prevent thermal stress cracking.

- The fixed bracket is ≥ 2 pipe diameters away from the tee, using a sliding support.

Interface Strengthening

- End Face Treatment: Sandblasting roughening (Ra ≥ 50μm) before socketing to improve adhesive adhesion;

- Low-Temperature Protection: When ambient temperature is <5°C, preheat the stop bar to above 20°C to restore flexibility.

🧿 III. Key Quality Control Points

Alignment Check: Laser alignment test, axis deviation ≤ 1mm/m;

Pressure Test:

- Pressurize in stages to 1.5 times the working pressure, maintain pressure for 30 minutes, and a pressure drop of ≤1% is considered acceptable;

Leak Scanning:

- Infrared thermal imaging detects abnormal temperature patterns at the interface (temperature differences > 0.5°C indicate potential leaks).

🧿 IV. Conclusions and Recommendations

For DN2800 tee connections, the preferred solution is a socket-and-socket + double seal + stop bar locking solution, equipped with a leak detection unit. In areas at risk of subsidence, a return spring clamp assembly should be added to compensate for displacement. During construction, the rubber ring installation accuracy (no distortion) and pressure test holding time are strictly controlled.