At a time when modern agriculture and water conservancy projects are booming, building an efficient irrigation system has become a key measure to improve the efficiency of water resource utilization and promote sustainable agricultural development. The efficient irrigation system is like the "lifeline" of farmland water conservancy. Its stable and efficient operation is directly related to the healthy growth of crops and the optimal allocation of water resources. In the entire efficient irrigation construction system, pipeline installation technology occupies a core position. It is like the core component of precision instruments. Its scientificity and standardization not only affect the stability of system operation, but also determine the length of system service life. Based on rich engineering practice experience, this article deeply analyzes the unique performance characteristics of different pipes, and meticulously explains the key technical points and quality control measures in the pipeline installation process, striving to provide a comprehensive and valuable reference for related engineering operations.
1. Classification of commonly used pipeline materials for efficient irrigation systems
Selecting pipeline materials for efficient irrigation systems is like building a cornerstone for complex projects, and many factors need to be weighed comprehensively. The scale of the project determines the amount of water that the pipeline needs to carry, the complexity of the terrain affects the flexibility and adaptability of the pipe, the specific characteristics of the water quality are related to the corrosion resistance of the pipe, and the expected service life is an important indicator for measuring the long-term stability of the material. Taking these factors into consideration, the widely used pipe materials are mainly divided into the following categories:
(I) Polyvinyl chloride pipe (UPVC)
Polyvinyl chloride pipe occupies an important position in the pressure irrigation system due to its outstanding performance advantages. Its high hardness enables it to withstand a certain pressure and is not easy to deform; its strong chemical corrosion resistance is not afraid of the erosion of various chemical substances, ensuring long-term stable operation in complex water quality environments; its small fluid resistance, like a wide and flat highway, allows water to flow smoothly, effectively reducing energy consumption. This type of pipe is mostly presented in the form of a hard pipe, and the common connection method depends on the size of the pipe diameter. When the pipe diameter DN≥110mm, the socket rubber ring connection becomes the first choice. The rubber ring is like a tightly fitting sealing guard to ensure that the connection is leak-proof; when the pipe diameter DN<110mm, the special glue adhesive connection achieves the rapid sealing of small-diameter pipes with its convenience and efficiency. This kind of pipe can give full play to its advantages in areas with relatively flat terrain and high requirements for pipe rigidity to ensure the stable operation of the irrigation system.
UPVC (rigid polyvinyl chloride)
1. Characteristics: high compressive strength (design pressure can reach 1.6MPa), acid and alkali corrosion resistance, UV aging resistance, suitable for long-term buried environment.
2. Limitations: It is brittle and easy to break in low temperature environment, and mechanical impact should be avoided.
3. Application scenario: agricultural water distribution main pipes and branch pipes, with a nominal diameter of usually ≤DN315.
(II) Polyethylene pipe (PE)
Polyethylene pipe combines the two characteristics of flexibility and low temperature resistance, like a warrior who can bend and stretch and is not afraid of the cold. According to the actual use scenario, it can be divided into two types: hard pipe and soft pipe. Hard pipe is suitable for fixed irrigation lines, providing reliable support for long-term and stable irrigation operations; soft pipe is very useful in mobile irrigation scenes and areas with complex and changeable terrain. Its flexible body can easily adapt to various terrains, such as winding mountain trails or undulating hilly areas. The connection methods are mainly electric fusion connection and hot melt connection. These two methods are like magic, which make the molecules at the interface of the pipe fuse with each other to form a high-strength sealing effect. For this reason, polyethylene pipes are widely used in project areas with large terrain fluctuations such as hills and mountains, providing more possibilities for the laying of efficient irrigation systems.
PE (Polyethylene)
Classification
1. HDPE (High-density Polyethylene): Strong rigidity and wear resistance, suitable for pressure pipes (design pressure 0.6-1.6MPa).
2. LDPE (Low-density Polyethylene): Good flexibility and anti-freezing cracking, mostly used for micro-irrigation capillary pipes and temporary pipes.
2. Advantages: Chemical corrosion resistance, strong resistance to geological settlement, can be hot-melt connection to achieve leak-free sealing.
3. Application scenarios: water pipelines, drip irrigation systems, and temporary drought relief facilities in hilly areas.
(III) Other pipes
Steel pipes, with their excellent compressive resistance, have become the only choice for high-pressure irrigation systems and trunk pipes of large-scale water conservancy projects. Under high-pressure conditions, steel pipes are like solid fortresses that can withstand huge pressures and ensure stable water flow. Concrete pipes play an irreplaceable role in irrigation channel reconstruction projects and gravity flow irrigation projects. They are low in cost and suitable for large-scale laying. At the same time, they are durable and can withstand the test of time and the natural environment, laying the foundation for the long-term stable operation of water conservancy projects.
Steel pipes
1. Characteristics: high pressure bearing capacity (up to 10MPa or more), high mechanical strength, suitable for high-pressure water delivery or crossing obstacles.
2. Disadvantages: easy to rust, requiring regular anti-corrosion treatment (such as internal and external plastic coating).
3. Application scenarios: trunk pipes of large irrigation areas, water inlet and outlet pipes of pump stations, and casings crossing rivers/roads.
Concrete pipe
Classification
1. Prestressed concrete cylinder pipe (PCCP): high sealing and impermeability, suitable for long-distance water supply.
2. Reinforced concrete pipe: low cost, wear resistance, mostly used for gravity flow drainage.
2. Limitations: heavy weight, complex installation, and need supporting lifting equipment.
Application scenarios: channel lining transformation, fixed water supply main canal.
2. Key points of polyvinyl chloride pipe (UPVC) installation technology
(I) Pipe connection and pipe fitting selection
In the construction of the irrigation system in the project area, the UPVC socket rubber ring connection process has become a key link to ensure the quality of pipe connection. For branch pipes below DN110mm, special glue adhesive connection is like a quick adhesive, which quickly realizes the sealing of small-diameter pipes and improves construction efficiency. In terms of pipe fitting connection, the flexible joint has become a powerful assistant for later maintenance and local adjustment due to its unique adjustability. When using socket connection, it is very important to strictly control the insertion depth, which is directly related to the uniformity of the force of the rubber ring. Once the insertion depth is improper and bias pressure is caused, the sealing performance of the rubber ring will be greatly reduced, which is very likely to cause leakage risk and affect the normal operation of the entire irrigation system.
(II) Trench excavation and backfill construction specifications
Trench size control
UPVC pipes are light in weight, about one-fifth of the weight of steel pipes, which makes manual loading and unloading and laying possible, reducing the construction's dependence on large equipment. However, trench excavation work must strictly follow the specifications. Taking DN200mm pipes as an example, the standard trench width should be greater than or equal to 0.6m, and the depth should be determined by comprehensive factors such as frozen soil thickness and road load, generally not less than 1.2m. When cross-construction is carried out simultaneously with road engineering, the segmented excavation method becomes an effective means to avoid trenches that are too narrow. In actual construction, narrow trenches of 0.4-0.5m have appeared, which not only brings great difficulties to backfill compaction work, making it difficult to meet the compaction standard, but also may cause the pipeline to be subjected to excessive shear force during road rolling, causing pipeline damage, seriously affecting the quality of irrigation systems and road engineering.
Foundation treatment technology
If the bottom of the trench encounters a rock layer or a gravel foundation, the surface hard debris must be completely removed. This is a key step to create a good foundation for pipeline laying. The excavation depth should be increased by more than 200mm, and then a 100mm thick medium-coarse sand cushion layer should be backfilled to form a flexible support foundation. The sand cushion layer is like a soft mattress for the pipeline. It needs to be compacted layer by layer, and the compaction degree should reach more than 90% to ensure that the pipeline is evenly stressed during operation, avoid cracking of the pipe due to local stress concentration, and provide a solid guarantee for the long-term stable operation of the pipeline.
(III) Installation details and quality control
Port marking and groove treatment
Before installation, a striking red paint is used to draw the top depth mark line on the pipe port. This small mark line plays an important role in construction. Especially during night construction, construction workers can quickly locate the mark line with the help of the light of the flashlight and accurately control the insertion depth error within 5mm. When cutting pipes, a special cutting machine is an essential tool to ensure the quality of the cut. The cut end face needs to be beveled at 45°, and the bevel width should be kept at 3-5mm. This operation may seem simple, but it is crucial to prevent the rubber ring from being misaligned or flipped during installation. Especially at complex node locations such as where the pipe crosses the trench, a bevel gauge is used to strictly inspect each pipe to ensure the straightness of the interface and provide a guarantee for high-quality pipe connections.
Pressure test and backfill requirements
Pipeline pressure testing is a comprehensive inspection of installation quality and must be strictly carried out in accordance with the "Construction Code for Irrigation and Drainage Engineering" (GB 50288-2022). The test pressure is set to 1.5 times the design working pressure. Taking this project as an example, the design pressure is 0.9MPa, the test pressure is 1.35MPa, and the pressure stabilization time is extended to 1 hour. During this period, the pressure drop shall not exceed 0.05MPa. The electronic pressure recorder is used for real-time monitoring, which is like installing an "electronic eye" for the quality of pipeline installation. The focus is on checking whether there is bubble overflow or water seepage at the rubber ring interface. After the pressure test is qualified, the backfill work needs to be carried out in layers, and the thickness of each layer shall not exceed 300mm. Within 500mm of the top of the pipe, mechanical compaction is prohibited to ensure that the compaction degree reaches more than 95%, providing a stable surrounding support environment for the pipeline.
3. Key points of polyethylene pipe (PE) installation technology
(I) Material properties and connection process
PE pipe has excellent flexibility and a breaking elongation greater than or equal to 350%, which enables it to be directly bent and laid in terrain with a slope of less than or equal to 15°, with a minimum bending radius of 20D. This unique performance advantage reduces the use of elbows by more than 30%, which not only reduces material costs but also simplifies the construction process. The connection method is cleverly selected according to the pipe diameter: when DN≤110mm, the electric fusion connection uses a special electric fusion machine to accurately control the heating time and voltage, just like pressing the "start button" for the molecular fusion at the interface to ensure that the weld surface is completely fused; when DN>110mm, the hot melt connection uses a hot melt butt welding machine to control the heating temperature at 210±10℃, and the pressure holding time is adjusted accordingly according to the pipe wall thickness. After the interface is completed, both connection methods need to wait for 4 hours, and then conduct an appearance inspection after the interface cools down. Before the interface is completely cooled, it is strictly forbidden to apply external force to ensure the quality of the interface.
(II) Groove construction and pipeline protection
Flexible foundation construction
Compared with UPVC pipes, the trench excavation width of PE pipes can be appropriately narrowed, generally the pipe diameter plus 0.3m, but the trench bottom flatness requirements are extremely high, and the height difference needs to be controlled within 20mm. If the stratum is a pebble stratum, laying a 50mm thick fine soil cushion becomes a necessary measure to protect the pipe wall to prevent sharp particles from scratching the pipe wall. In the process of transporting pipes, it is strictly forbidden to drag the pipes. Special nylon slings become the "intimate partner" of pipe transportation. The spacing between slings does not exceed 2m to avoid excessive pipe ovality due to external force extrusion. The allowable deviation is controlled within 5% to ensure that the pipes are not damaged during transportation.
Environmental adaptability treatment
When PE pipes are stored in the open air, covering with sunshade cloth is an important means to prevent material aging, and the ultraviolet exposure time shall not exceed 7 days. During winter construction, the pipes must be placed on the construction site 24 hours in advance, and the ambient temperature of the construction site must be kept above 5℃ to avoid increased material brittleness due to low temperature. When the pipeline needs to cross the road, the installation of steel casing becomes a necessary measure to protect the pipeline. The inner diameter of the casing is greater than or equal to 1.5 times the pipe diameter, and flexible sealing materials are used at both ends of the casing to reduce the direct force of the vehicle load on the pipeline and extend the service life of the pipeline.
(III) System pressure test and operation commissioning
Before the pressure test, the air in the pipeline is completely exhausted by the exhaust valve in sections. This is an important prerequisite for ensuring the accuracy of the pressure test results. The test pressure is set to 1.25 times the design pressure and shall not be less than 0.8MPa. The pressure stabilization time is 60 minutes. Due to the creep characteristics of PE pipes, the pressure drop is allowed to be within 0.1MPa, but it is necessary to continue to closely observe whether there is slow leakage at the interface. After the pressure test is passed, a water test run is carried out. By adjusting the head valve, the pressure of each water outlet is checked to see if it is balanced. The pressure deviation must be controlled within 10%, and the longitudinal displacement of the pipeline in the water-filled state is recorded in detail. The normal displacement should be controlled within 20mm to ensure stable operation of the system and provide reliable guarantee for efficient irrigation.
4. Other key points for pipe installation
(I) Steel pipe installation
Steel pipe installation mainly adopts welding or flange connection. Before welding, the pipe interface is beveled and polished at an angle of 60±5°. This operation is like laying the foundation for welding quality. After welding, the weld needs to be inspected by radiographic flaw detection. The test results must reach level Ⅲ or above to be qualified to ensure the quality of the weld is impeccable. In terms of anti-corrosion treatment, "two cloths and three oils" epoxy coal tar coating is used, and the coating thickness is greater than or equal to 0.6mm, which puts on a solid "anti-corrosion armor" for the steel pipe. For buried steel pipes, cathodic protection devices are installed to further extend their service life and enable them to operate stably underground for a long time.
(II) Concrete pipe installation
Concrete pipes use a socket-type interface. During installation, the rubber sealing ring must be accurately embedded in the groove, which is the key to ensuring the sealing performance of the interface. Use a chain pulley to slowly push in to ensure that the interface gap does not exceed 3mm. The foundation needs to be poured with a C15 concrete cushion layer with a thickness of 150mm or more to provide stable support for the pipeline. When backfilling soil on both sides of the pipeline, symmetrical compaction is an important measure to prevent interface dislocation and ensure that the quality of pipeline installation meets the requirements.
5. Quality Control and Safety Measures
Material On-site Acceptance
Each batch of pipes must provide a complete factory certificate and a professional test report, which is the "identity card" of the pipe quality. At the same time, at a sampling rate of not less than 5%, the pipes are tested for tensile strength, Vicat softening temperature and other tests, just like a "physical examination" for the quality of the pipes to ensure that the quality of the pipes meets the requirements and provide reliable material guarantees for subsequent construction.
Process Acceptance System
Key construction processes such as trench excavation, pipeline connection, and pressure test backfilling must be signed and confirmed by the supervision engineer, which is an important checkpoint to ensure construction quality. In addition, during the construction process, a detailed construction log and a complete image data archive should be formed, just like leaving a "growth record" for the construction process for subsequent review and tracing, to ensure that every construction link has a traceable trace.
Safety operation specifications
For hot melt equipment, an overload protection device is installed, just like a "safety guard" is installed for the operation of the equipment to ensure the safety of the equipment. Welding operators must wear insulating gloves when working, take personal protection measures, and ensure personal safety. When the depth of the trench exceeds 1.5m, set up edge guardrails and ladders to provide protection for the construction workers' work safety and avoid safety accidents.
The pipeline installation project of the efficient irrigation system has high technical requirements and strong systematization. It is like a precise symphony performance, which requires close cooperation in all links. According to the characteristics of different pipes, a targeted construction plan is formulated to match them. From the initial material selection, to the trench construction, the implementation of the connection process, and the final pressure test acceptance, each link is like an important note in the symphony and must be strictly controlled. Only in this way can we ensure that the pipeline system has good sealing, pressure resistance and environmental adaptability. Through standardized construction operations and refined management models, the operating efficiency of high-efficiency irrigation systems can be effectively improved, providing solid and reliable guarantees for modern agricultural water-saving projects and water conservancy infrastructure construction, and playing a beautiful melody of efficient agricultural development.
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