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fitting pipe selection method


At present, the water supply pipes used for residential decoration are mainly PPR pipes and copper pipes.

PPR pipe: The official name of PPR is random copolymer polypropylene, which is a random copolymer of propylene and other olefin monomers. There is no other functional group in the olefin monomer.

As a new type of water pipe, PPR pipe has the following characteristics:

1. Sanitary, non-toxic, can be directly used for pure water, drinking water piping system.

2. Corrosion resistance, not easy to scale, eliminate the secondary pollution caused by rusted scale of galvanized steel pipe.

3. Heat-resistant, can be long-term delivery of hot water below 70 °C, can withstand transient high temperature of 95 °C.

4. The thermal insulation performance is good, and the thermal conductivity at 20°C is only about 1/200 of the steel pipe and 1/1400 of the copper pipe.

5. Light weight, high strength, PPR density of 0.89 ~ 0.91g/cm3, only 1/9 of the steel pipe, 1/10 of the copper pipe.

6. The fluid resistance in the pipeline is small, the inner wall of the pipe is smooth, and it is not easy to foul. The fluid resistance is much lower than the metal pipeline.

7. The use of hot melt socket connection, simple and reliable installation, long service life.

In recent years, the development of domestic PPR tubes has been rapid, but the quality of products on the market has been mixed, and there is a phenomenon of confusion. Regardless of cold water pipes or hot water pipes, the material of the pipes should be the same, and the cold and hot water pipes only have different wall thicknesses. However, in the current market, pipes and hot water pipes are better used as raw materials, and cold water pipes use PPB (PPB is block polypropylene) as PPR. In this case, due to different materials, the welding place is prone to breakage. , desoldering, leaking, etc.

Consumers should pay attention to identify the marking on the pipe, the product name should be 'cold and hot water with random copolymer polypropylene pipe' or 'hot and cold water with PP-R pipe', and have expressly implemented the national standard 'GB /T18742-2002'. It should be noted when the product is found under other names or other standards.

In general, the hot water pipe should use the pipe series S of 2.5 or less, that is, the wall thickness of the outer diameter 20 pipe should be 3.4mm or more, and the wall thickness of the 25 pipe should be 4.2mm or more. In addition, the coefficient of linear expansion of the PP-R pipe is approximately 10 times that of the copper pipe, and attention should be paid to leaving room for expansion and contraction during construction and installation.

Copper tubes: The chemical properties of copper are fairly stable and not easily corroded. The strength of the copper tube is much higher than that of the plastic tube and can withstand considerable pressure. Compared with the steel tube, the copper tube has good toughness, and does not crack nor break under strong frost heave and impact. Copper has a high melting point, and it can work safely for a long period of time even if the medium temperature is as high as 200°C. The copper tube has good resistance to permeation. During its use, its surface can form a layer of dense, protective film that is not dissolved by the medium. No matter whether it is grease, carbohydrates, bacteria and viruses, harmful liquids, oxygen, or ultraviolet rays, it cannot Through it and then eroded the wall.

Copper pipe connection is mainly divided into mechanical connection and brazing connection. Mechanical connection is divided into card-type, plug-in and pressure-type connection.

Card sleeve type connection is a relatively simple construction method, and the operation is simple and easy to grasp. It is a common connection method in construction. When connecting, as long as the end face of the pipe incision can be kept perpendicular to the axis of the pipe, and the burr at the incision is cleaned, the position of the snap ring is correctly placed when the Pipe Fitting is assembled, and the tightening of the nut can achieve tight connection of the copper pipe.

Plug-in connection is also a simple construction method, as long as the vertical end of the incision and remove the burr tube, forcefully insert the pipe to the end, this connection method is mainly rely on the stainless steel clamp in the special pipe to fasten the steel wall In the pipe fittings, the 'O' rubber ring that is tightly fitted with the outer wall of the copper pipe inside the pipe fitting is used for sealing.

Press-fit connection is a more advanced construction method, and the operation is also relatively simple, but it needs to be equipped with a special and fully-compressed crimping machine to press the copper pipe and the pipe piece into one. This connection method uses a rubber ring in the Flange of the tube to seal it.

The method of brazing connection in copper pipe construction is the most widely used. Brazing is to heat the copper pipe and copper pipe fittings together with the copper phosphor solder or copper solder material whose melting point is lower than that of copper. The copper pipe and copper pipe fittings do not melt. In this case, it is heated to melt the solder, then the molten solder is filled into the slot of the socket, and the crystal is cooled and crystallized to form a brazing joint, which becomes a firm joint.

The current national standard for copper pipes is GB/T 18033-2000. The copper pipes for water supply are generally T2 or TP2 alloys, and the copper content should be above 99.9%. The disadvantage of copper tubes is their high thermal conductivity. To avoid this disadvantage, it is best to cover the copper pipe outside the hot water supply with a heat insulation layer to reduce heat loss.

Although plastic coated copper pipes are currently on the market, their thermal insulation effect is limited. It is better to put a foam rubber tube shell on the outer surface to improve the thermal insulation performance of hot water pipes.