UPVC pipe construction technology in irrigation system

1. Core advantages and environmental adaptability of UPVC pipes in irrigation system

(I) Anti-aging and durability advantages of underground laying

UPVC pipes are based on polyvinyl chloride resin. By adding calcium-zinc composite heat stabilizer, a stable molecular structure is formed, which fundamentally eliminates the electrochemical corrosion problem of metal pipes that are prone to rust. When buried in the soil, the soil environment can effectively isolate ultraviolet rays and oxygen, slowing down the aging of the material. Its low temperature resistance can reach -15℃, and it can still maintain a certain flexibility in the frozen soil area in winter, while its high temperature resistance is limited to below 60℃. Long-term open-air environment is prone to molecular chain breakage due to ultraviolet radiation, so it is strictly forbidden to use it under unsheltered conditions to ensure a design life of more than 50 years.

(II) Technical parameters of physical properties and environmental tolerance

After testing, the linear expansion coefficient of buried UPVC pipe is 6×10⁻⁵/℃, which is only 1/3 of that of HDPE pipe, the heat deformation temperature (Vicat) is ≥90℃, and the ring stiffness is ≥10kPa, which meets the soil load requirements at a buried depth of 1.5m. Its inner wall roughness coefficient is as low as 0.009, which reduces the water flow resistance by 30% compared with cast iron pipes, and does not scale. The long-term water delivery capacity is stable, which solves the problem of reduced water delivery efficiency caused by rust and scaling of the inner wall of metal pipes from the essence of the material.

2. Pipeline connection technology system adapted to multiple scenarios

(I) Large-diameter pipe socket rubber ring connection process

For pipes above DN110, a socket rubber ring connection is adopted, and the compression elasticity of the rubber ring is used to form a sealing interface, combined with the geometric matching of the pipe socket, to achieve an axial pull-out resistance of ≥15kN/m. During construction, the chamfer of the socket must be strictly controlled (15°±5°), and V-type fatty acid salt lubricant must be applied to the socket groove to ensure that the insertion depth meets the design mark (error ≤±2mm). This connection method has good resistance to uneven foundation settlement, allowing axial displacement of ±5mm and angular deflection ≤3°, and is suitable for areas with undulating terrain or soft soil foundations in irrigation systems.

(II) Technical specifications for adhesive connection of small-diameter pipes

Pipes below DN110 are connected with solvent-based adhesives. Common brands include IPS 711, Huaya 770g, etc. The corresponding viscosity grade (2000-3000cps) must be selected according to the wall thickness of the pipe (≥2.8mm). The construction process includes: fracture milling (verticality deviation ≤0.5%), surface roughening (roughness Ra≥12.5μm), double-sided glue coating (glue layer thickness 0.3-0.5mm), quick plug-in (rotate 15° to ensure uniform glue layer) and curing and curing (stand for 24h at 23℃±2℃). Pay special attention to the need to preheat the pipe to above 15℃ in low temperature environment (<5℃) to avoid a sudden increase in the viscosity of the glue and cause bonding failure.

3. Selection logic and engineering application of pipe connection methods

(I) Dynamic compensation characteristics of flexible joint connection

The flexible joint (flexible joint) is composed of a rubber sealing ring and a metal flange, which allows the pipeline to axially expand and contract by ±10mm and radially deflect by ±8°, effectively absorbing the thermal expansion and contraction stress caused by water temperature changes (ΔT≤30℃), and avoiding the cracking problem caused by stress concentration in rigid connections. It is suitable for crossing roads, building foundations and other parts that may cause slight displacement. During installation, expansion gaps must be reserved, and the flange bolts must be tightened symmetrically (torque 8-10N·m) to ensure dynamic sealing performance.

(II) Key points of rigid fixing technology for socket connection

Socket-type pipe fittings (such as elbows and tees) use an injection molding structure that is the same as the pipe. When connecting, the insertion depth must be marked on the socket end (usually 3/4 of the socket depth), and a mechanical jacking tool must be used to ensure that the interface fits tightly. The tensile strength of this connection method is ≥12MPa, and the sealing test pressure can reach 1.5 times the working pressure (conventional 0.8MPa). It is suitable for straight pipe sections with stable pressure and no displacement risk. The key to construction lies in the tolerance matching of pipe fittings and pipes (the gap between the inner diameter of the socket and the outer diameter of the pipe is ≤0.3mm) to avoid interface leakage caused by dimensional deviation.

4. Key points of construction quality control and risk prevention and control

(I) Technical standards for trench excavation and backfilling

The trench width is controlled by the outer diameter of the pipe + 0.5m, and a 100mm medium-coarse sand cushion layer (compaction degree ≥90%) is laid at the bottom of the trench. Direct contact with sharp rocks is strictly prohibited. Backfilling is carried out in two times: the first backfilling is to 0.3m above the top of the pipe, and sand and soil are used for layered compaction (each layer thickness ≤0.2m, compaction degree ≥95%); the second backfilling is to the designed elevation, and stones with a particle size of >50mm are removed when backfilling the original soil to avoid mechanical damage to the pipeline. Pay special attention to the need to set up drainage ditches during construction in the rainy season to prevent water from accumulating in the ditches and soaking the pipes.

(II) Pressure test and leakage detection method

After the pipeline is installed, a water pressure test is carried out. The test pressure is 1.5 times the working pressure (and ≥0.8MPa). The pressure drop within 30 minutes of steady pressure is ≤0.05MPa to pass. Use an electronic leakage detector to scan the interface, focusing on checking the compression uniformity of the socket rubber ring and the continuity of the adhesive layer of the adhesive interface. If leakage is found, it needs to be disassembled and repaired immediately to ensure that there is no dripping when the irrigation system is running, and improve the efficiency of water resource utilization.

FAQ

Q1: What is the maximum working temperature for UPVC pipes in irrigation systems?

A: UPVC pipes are suitable for temperatures up to 60°C. Long-term exposure above this may cause material degradation.

Q2: Can UPVC pipes be used in cold regions?

A: Yes, UPVC pipes can tolerate temperatures down to -15°C when buried, but preheating may be necessary during installation in extreme cold.

Q3: What is the recommended connection method for large-diameter UPVC pipes?

A: Socket rubber ring connection is used for pipes above DN110, providing good flexibility and sealing in uneven terrains.

Q4: How long should UPVC adhesive joints cure before use?

A: After applying adhesive, joints should be left undisturbed for at least 24 hours at room temperature (~23℃) to ensure full bonding.

Q5: How is leakage tested after UPVC pipe installation?

A: A water pressure test is performed at 1.5 times the working pressure. Pressure drop must not exceed 0.05 MPa within 30 minutes.