Process characteristics of plastic-lined steel pipe

In the past two years, the production of plastic-lined steel pipes in my country has developed rapidly, especially in the field of water supply. At present, more than 90% of the water supply pipes of high-rise buildings in Shanghai use plastic-lined steel pipes.

Plastic-lined steel pipe not only has the high strength, toughness, fire resistance, and temperature resistance of steel pipes but also has the hygienic and environmental protection and non-scaling performance of plastic pipes. Composite piping.

The plastic-lined steel pipe is extruded the plastic pipe and coat it with an adhesive layer, then put into the steel pipe, heat it, pressurize, cool, and shaped together with the steel pipe, and combine the plastic pipe and the steel pipe firmly together, which can be used for cold water transportation or hot water delivery.

1.Lining plastic equipment and process flow

(1) Plastic pipe extrusion molding equipment

Plastic pipes are produced by screw extruders, including hot extruders, crawler tractors, vacuum cooling, shaping tanks, cut-to-length machines, electrical and temperature control systems, etc.

(2) Lining plastic equipment

①The feeding table is used to place steel pipes and insert plastic pipes into steel pipes;

②The chain transmission system drives the steel pipe to each station;

③The heating furnace is divided into five zones to heat the steel pipe, so that the temperature of the middle section of the steel pipe is higher than that of the two sides, and decreases in a gradient to ensure that the gas in the gap between the plastic pipe and the steel pipe can flow from the middle area to the steel pipe during the pressurization process. Discharge at both ends;

④The electrical control system automatically controls each action of the whole set of equipment, and controls the temperature according to the process parameter setting;

⑤ The pressurization system uses high-pressure gas to pressurize the inner wall of the plastic pipe so that the plastic pipe expands and fully contacts the inner wall of the steel pipe;

⑥ The spray cooling system sprays and cools the pressurized plastic-lined steel pipe so that the plastic pipe is shaped and firmly combined with the steel pipe.

2. Process principle and process of plastic-lined steel pipe

(1) Principle

By heating the steel pipe inserted into the plastic pipe, the heat is provided for thermoforming and bonding of the lined plastic pipe, and then the plastic pipe is pressurized to make the plastic pipe expand and bond with the steel pipe through the adhesive layer. Finally, it is formed by cooling and setting.

(2) Process flow

Deburring of steel pipes, sandblasting, inserting into lined plastic pipes, upper pressurization mold sets, furnace heating and heat preservation, pressurization expansion heat preservation, furnace discharge, spray cooling and shaping, pressure relief, lower pressurization mold sets, trimming pipes Terminal, inspection, packaging, weighing, storage.

3. Process characteristics of plastic-lined steel pipe

The plastic pipe and the adhesive layer are produced by co-extrusion, and the hot-melt adhesive layer is compounded on the surface of the plastic pipe. When the plastic pipe is extruded, the thickness of the surface adhesive layer should be uniform. The uniformity of the thickness of the adhesive layer can be judged by observing the difference in the reflectivity of the two layers of plastic on the end surface of the plastic pipe. The produced plastic pipes are required to have a smooth surface and no agglomeration inside the pipe wall. The limit deviation of the wall thickness on the same section shall not exceed 14%, and the thickness of the adhesive layer shall be controlled between 0.2-0.28mm.

Plastic-lined steel pipe combines the excellent performance of steel pipe and plastic pipe, and the cost is slightly higher than that of hot-dip galvanized pipe, which is only one-third of the cost of stainless steel pipe. It has obvious advantages in cost performance among many water supply pipes. Moreover, it is convenient and reliable to install and has become the main small and medium-caliber water supply pipe. Because it can be used for hot water transportation, it has a wider application range than plastic-coated pipes under the current technical conditions.

Post time: Nov-16-2022