Production process of steel-plastic pipe

Production process of steel-plastic pipe

The main method for the composite process of steel-plastic pipe base pipe and coating is to preheat the base pipe so that the surface temperature meets the temperature range required by plastic powder, and control the highest temperature, then coat the plastic powder, which is also called dispersion method.

Spraying: Plastic powder is sprayed by compressed air through a spray gun.

Suction coating: vacuum pump is used to form negative pressure in the pipe, and plastic powder is sucked in.

Impregnation: The plastic powder is stored in the container, and the preheated base pipe is immersed in the powder.

Rotary plastics: The plastic powder is stored on the wall of the tube, and the powder is evenly distributed by rotating the tube.

Because the surface of the base pipe has reached a certain temperature, the plastic powder is melted and coated on the wall of the pipe, forming a coating and forming an anticorrosive layer.

The bonding degree between inner coating and pipe is related to many factors, such as heating equipment type, heating mode, fuel type, heating temperature, the fineness of plastic powder, additive composition, etc. But the most critical factor is surface pretreatment. On the premise that the surface pretreatment meets the standard, the comprehensive index is assessed by adhesion. The original standard of adhesion in our country is low and has been improved (polyethylene coating (>30N/10mm) and epoxy resin coating (>1-3 grade). This standard is close to that of developed countries. But these measures can not completely eliminate the problem of coating shedding. One of the reasons is that galvanized steel pipes and steel-plastic pipes are heated in the heating furnace. Because galvanized steel pipes have an additional layer of galvanized layer on their surface, and galvanized layer reflects heat. In addition, galvanized layer improves the surface smoothness of steel pipes and reduces the heat absorption. Therefore, galvanized steel pipes are used as the base pipes for the coating efficiency of plastic-coated steel pipes. It is better to use the welded steel pipe as the base pipe of the coated steel pipe. The second reason is that there are bad ways to add adhesives in additives. According to experts in the industry, the plastic powder is mixed with some adhesives, which can firmly adhere the coating to the steel pipe wall after the composite process. When tested, the adhesion index can be fully qualified, but the adhesives have a validity period. Once the validity period is over (usually three months), the coating will fall off and clog the water passage. Accidents, serious consequences, the result is that the reputation of plastic-coated steel pipe is declining, gradually replaced by plastic-lined steel pipe. Therefore, in order to truly solve the quality problem of plastic-coated steel pipe, we need to rely on brand, eliminate fake and inferior products, so that users can rest assured that the plastic-coated steel pipe can remain invincible, and eventually replace the position of galvanized steel pipe.