PE pipe construction scheme

1, overview

As a new type of pipe, pe water supply pipe has the characteristics of corrosion resistance, non-toxicity, smooth inner wall, long service life (50 years), light weight (the density is only 1/8 of that of steel pipe), low installation labor intensity, low construction cost, strong seismic performance and good material flexibility. While HDPE pipe has high density.

Under normal circumstances, PE pipes are required to be laid underground, and the coverage depth is more than 0.7m If local ground laying is really necessary, black PE pipes with ultraviolet resistance should be adopted, and protective measures should be taken.

2, material approach and inspection

In order to ensure the engineering quality, the construction unit is required to fill in the entry declaration form before each batch of materials enters the site. The supervisor shall inspect the varieties, specifications and appearance of the incoming materials according to the specifications (GB50242-2002). The package shall be intact, and the surface shall be free of scratches and external impact damage. The appearance of the whole pipeline should be smooth without uneven color, and the wall thickness and roundness of the pipeline should be checked. Check the product certificate issued by the manufacturer, the quality acceptance report and the use license issued by the competent government department, and sign after meeting the requirements. After the materials enter the site, witness sampling and inspection shall be conducted on the materials and accessories entering the site according to the specified batch and frequency, and the contractor shall not start using the materials and accessories before obtaining the qualified inspection documents. When witnessing sampling, the supervisor should pay special attention to the production batch number. Due to some unforeseen factors in the production process, the product quality of the same manufacturer, the same raw material, the same formula and the same process will be different in different production batches.

3, the construction sequence:

Trenching → pipeline installation → partial backfilling → pressure test → laying marker piles → full backfilling.

4. Pipe trough section and pipeline foundation

The size of trench excavation section has great influence on construction progress and cost. Usually, long pipes are prefabricated on the ground to reduce the excavation width b of the pipe trench. Generally, the pipe trench width can be determined according to b = d+0.3m(d- pipe outside diameter) to meet the requirements.

The pipeline foundation should be flat and have sufficient strength, and the undisturbed soil of the basement should be prevented from being disturbed when excavating the trench. When the basement is in the soft soil layer below the groundwater level, gravel with a thickness of 15cm and a particle size less than 50mm can be laid first, and then a sand cushion with a thickness of 5cm can be laid, so that the pipeline can obtain long-term stable support. This project adopts the method of C 15 concrete fixed pier to stabilize.

When the pipe groove is excavated manually, the bottom of the groove should be flat and dense, without sharp objects. There may be ups and downs at the bottom of the ditch, but the pipe must be supported smoothly. If there is overbreak, it must be backfilled and compacted.

5. Pipe joint

(1), select the connection mode.

The connection of PE pipes mainly includes hot melt connection, mechanical connection and electric melt connection.

Hot-melt connection method is widely used because of its advantages of low cost, good quality of pipeline interface and no need of pipe fittings. Due to the disadvantages of welding equipment, long time-consuming interface hot-melt operation and high technical requirements,

The main steps of hot melt connection are as follows:

(1) material preparation: lay the pipe or pipe fitting flat and put it on the docking machine, leaving enough cutting allowance10-20 mm. ..

(2) Clamping: According to the welded pipes and fittings, select the appropriate sliding clamp to clamp the pipes and make good preparations for cutting.

(3) Cutting: cutting impurities and oxide layers on the end faces of welded pipe sections and pipe fittings to ensure that the two butt ends are smooth, flat and free of impurities.

④ Centering: The end faces of two welded pipes should be completely centered, and the staggered edges should be as small as possible, and the staggered edges should not exceed 10% of the wall thickness. Otherwise, the docking quality will be affected.

⑤ Heating: Generally, the butt joint temperature is between 2 10-230℃, the heating time of the heating plate is different in winter and summer, and the melting length of both ends is 1-2mm.

⑥ Switching: Take down the heating plate, and quickly make the two hot-melt end faces stick together and press tightly. In order to ensure the quality of fusion docking, the shorter the switching period, the better.

⑦. Fusion butt joint: This is the key to welding. The butt joint process should always be carried out under the melting pressure, and the appropriate hem width is 2-4 mm. ..

⑧ Cooling: Keep the docking pressure constant and let the interface cool slowly. The cooling time depends on whether the manual crimping is hard and whether the heat is felt.

Pet-name ruby, docking is complete: after cooling, loosen the slips, take down the docking machine, and re-prepare the next interface connection.

(2), hot melt connection quality control points

Hot-melt connection has high technical requirements for operators, so attention should be paid to the appearance inspection of interface quality, and a unified flange should be formed at the interface. Connection quality problems are often caused by the following reasons, and preventive measures should be taken during construction:

① Mixing pipes and fittings with different materials, brands and wall thicknesses;

(2), joint end face is not kept clean, sticky water or soil should be cleaned up in time;

③ The operator's skill is not high, and the process parameters (heating time, heating temperature, connection pressure and cooling time) of hot melt connection are not strictly controlled according to the specified requirements;

(4) moving the connector or applying external force to the connector without complete cooling;

(5) The ultrasonic welding machine should be maintained regularly to ensure the good use of the equipment.

In the application process of PE pipeline, the problem of opening the main pipe according to the actual needs is often encountered. The traditional pipeline must first cut off a section of the main pipe, and then install the tee to complete the opening.

Saddle-shaped tee can be connected by saddle butt welding, that is, a saddle-shaped tee is directly connected to the main pipe by saddle butt welding machine, and then the main pipe is cut by the equipped cutter, so that the opening of the main pipe is completed and the construction speed is very fast.

Steel pipe flange connection

Steel-plastic flanges should be adopted for the connection of pe pipes with steel pipes and valves: PE pipes and corresponding plastic support rings can be connected by hot-melt butt joint, and the connection between steel pipe ends and metal flanges should meet the corresponding steel pipe welding requirements; then the connection between PE pipes and steel pipes can be completed by flanges.

Flange connection is also suitable for interconnection between PE pipes. Generally speaking, there is no need for sealing rings between PE support rings and between PE support rings, but sealing rings are still needed under large-size and high-pressure working conditions. When the PE support ring is connected with flanges of pipes made of other materials (steel pipes, galvanized pipes, etc.). ), a sealing ring must be used.

(2) laying pipes in the trench

1, pipeline laying

When the pipeline changes direction, it can be bent and laid by using the good flexibility of the pipeline, and the bending radius must meet the requirements in the following table, otherwise an elbow must be used.

Nominal outside diameter D(mm) and allowable bending radius R(mm)

D≤50 30D

50