In recent years, China has always attached great importance to the development and application of new types of pipes, prohibiting or restricting the use of certain metal pipes, and the application of new types of pipes has become increasingly widespread. Among the pipes used for promotion, there are mainly various plastic pipes. However, due to the fact that some new types of pipes have no design and construction acceptance national standards, they are prone to various problems in use. According to the experience in construction supervision, the following issues should be noted in the construction supervision of plastic pipes for water supply:
Universal switch Wei Shuibao
1. Selection of water supply plastic pipe
The water supply plastic pipe has high chemical stability, corrosion resistance, smooth wall, and can effectively prevent corrosion and scaling of the pipe. At present, the commonly used plastic pipes for water supply mainly include UPVC, HDPE, PP-R, PP-C, PB, and propylene. Nitrile-butadiene-styrene (ABS), crosslinked polyethylene (PE-X), etc. Its common advantages are non-toxic, sanitary, long service life, smooth pipe wall, small head loss, corrosion resistance, non-fouling, environmental protection and energy saving, light weight, and easy installation. However, there are disadvantages and deficiencies, such as large linear expansion coefficient, poor resistance to ultraviolet radiation, small overhead spans of pipes, multiple supporting points, and some pipes with high light transmittance. The main advantages and disadvantages of various pipes are as follows:
1.1 Unplasticized PVC Pipe (UPVC)
Advantages: high impact resistance and chemical resistance, hard texture, corrosion-resistant, non-fouling, easy installation, and low cost;
Disadvantages: poor shock resistance, in the use of the process, there will be UPVC monomer and additives seepage, not suitable for hot water delivery, joint bonding technology requirements are higher, the curing time is longer.
1.2 High-density polyethylene pipe (HDPE)
Advantages: It is the best anti-seismic pipe, good toughness, good fatigue resistance, good temperature resistance, high impact strength, light weight, and service life up to 50a;
Disadvantages: Welding requires electrical power, mechanical connections, and large connections.
1.3 Modified Polypropylene Pipe (PP-R)
Advantages: Good impact resistance, temperature resistance and creep resistance;
Disadvantages: At the same pressure and temperature, the wall thickness is the thickest, the coefficient of linear expansion is large, and the UV resistance is poor.
1.4 Polybutylene Pipe (PB)
Advantages: good temperature resistance, can be used safely between 20-95 °C, can withstand high loads for a long time without deformation, strong creep resistance, high flexibility;
Disadvantages: At present, there is no PB resin material in China, and it is dependent on imports, so the price is higher;
1.5 Acrylonitrile Butadiene Styrene (ABS)
Advantages: high strength, impact resistance, corrosion resistance and soil corrosion;
Disadvantages: poor UV resistance, long curing time.
1.6 Cross-linked Polyethylene Pipe (PE-X):
Advantages: good temperature resistance, high hardness, good creep resistance;
Disadvantages: Can only be connected with metal parts, and can not be recycled.
2. Material approach and inspection
In order to ensure the quality of the project, each batch of materials requires the construction unit to fill in the application form before entering the site. According to the specifications (GB50242-2002), the supervisor shall check the variety, specification and appearance of the incoming materials. The packaging shall be in good condition and the surface shall not be marked. Traces and external force impact damage, the appearance of the entire root canal should be smooth, no color unevenness, check the wall thickness and roundness of the pipeline. Check the quality certification documents issued by the manufacturer, such as product certification, quality inspection report and the use permit issued by the competent government department, and sign it after meeting the requirements. After the material enters the site, the incoming materials and accessories shall be sampled and submitted for inspection according to the specified batch size and frequency. The contractor shall not be allowed to start operation until it has obtained the inspection certificate. When the supervisors witness sampling, they must pay special attention to the production lot number. Due to certain unpredictable factors in the production process, the same manufacturer, the same raw material, the same formula and process, the quality of products in different production batches will be different.
3. Supervision of the construction process
As many plastic pipes for water supply are still in the promotion stage, construction personnel are not familiar with the construction process, and these new pipes require high technical level of construction personnel and are difficult to construct. Therefore, pre-job training for construction workers is particularly important. Inspectors pay special attention to the connection of pipelines during on-site inspections. The places where the plastic pipes for water supply are most prone to leakage and pipe burst are the pipe joints. Water supply plastic pipe connection methods are mainly adhesive, hot melt or fused connection, special pipe fittings and flange connection, pay attention not to set the wire on the plastic pipe. Here are a few brief notes about the major connection methods:
3.1 Adhesive connection
UPVC pipes and ABS pipes are used for water supply plastic pipes with adhesive connections. The pipes, fittings and adhesives should be supplied by the same manufacturer. At this stage, the adhesives are generally not submitted for inspection. The supervisor must carefully inspect the adhesive quality certification documents and the conditions of use. Before applying the adhesive, sand the adhesive surface with sandpaper and clean it with a dry cloth so that the bonding surface is free from dust, water marks, oil stains, and when the surface is stained with oil, use cotton yarn to dip the acetone. Cleaner and other cleaners. When brushing the adhesive, pay attention to the amount, not too much or too little, otherwise it will affect the adhesive strength. After the socket is coated with adhesive, the pipe is gently inserted into the socket, and the insertion depth should meet the requirements. And ensure the straightness of the socket interface and the correct position of the interface. The key to ensure the quality of the adhesive interface is the interface surface according to the provisions of hair, glue brushing uniform, the amount required, the depth of the insertion port to meet the requirements.
3.2 hot melt or fused connection
The plastic pipes for water supply that are connected by hot melt or electrofusion are PE pipes, PP-R pipes, and PB pipes. The special welding tool provided by the manufacturer should be used. Before connection, the position of the pipe joint and the pipe fittings should be cleaned to ensure that it is clean, dry and free of oil. Marks are made on the pipe and pipe fittings. The fusion temperature should be checked regularly to ensure that it is at the correct value. When the pipe and pipe should be prevented from sliding outwards, they must not be rotated after heating. Strictly observe the holding time and cooling time.
3.3 Card sleeve (hoop) type special pipe connection
The water supply plastic pipe connected by a special pipe fitting (hoop) type pipe has a PE-X pipe. Cut the pipe to ensure that the incision is straight, straight, and free from burrs. When connecting, the two ports should be flat and seamless, and the grooves should be even. After the bolts are tightened, the pipes should be straight and the mounting direction of the clamps should be the same. After completion of the installation of the pipeline system, attention should be paid to finished product protection. Never step on the car. Handle the follow-up work types clearly. Handover procedures, especially for the pipes buried inside walls or floor coverings, must be marked to avoid Destroy pipelines and prevent any damage during subsequent work or secondary decoration. Pipeline pressure test should be strictly in accordance with the requirements of the specification, and only in this way can the system be operated normally and reliably.
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