The process flow of 3PE anti-corrosion steel pipe manual patching mainly includes two processes: surface pretreatment and coating processing.
1.3PE anti-corrosion steel pipe surface pretreatment
(1) Degreasing: Before the anti-corrosion layer is applied, the grease and dirt on the surface of the 3PE anti-corrosion steel pipe should be removed. Grease will inevitably adhere to the 3PE anti-corrosion steel pipe during the manufacturing and transportation process. The grease on the surface must be removed to ensure strong bonding between the coating and the 3PE anti-corrosion steel pipe. In this project, cotton yarn is used to wipe the grease. Since the surface of the 3PE anti-corrosion steel pipe is relatively clean and basically free of grease, the degreasing workload is very small.
(2) Inspection: The 3PE anti-corrosion steel pipe enters the pipe rack of the pipe entry platform, and the surface of the 3PE anti-corrosion steel pipe is inspected by the pipe entry quality inspection control area. The main inspection items include weld height, drop pits, corrosion pits, groove damage, pipe end ovality, pipe body curvature, etc.; the pipe number, pipe length, steel grade, wall thickness, furnace number, production date, quantity, etc. are recorded. 3PE anti-corrosion steel pipes that do not meet the coating requirements will be withdrawn from the pipe entry platform and handled separately.
(3) Preheating: After inspection, the qualified 3PE anti-corrosion steel pipe enters the medium frequency heating furnace through the rust removal transmission line. Usually, the pipe body temperature should be heated to 40-60℃. The 3PE anti-corrosion steel pipe preheating of this operation line adopts direct heating by a 100kW medium frequency heating furnace, and the temperature of the 3PE anti-corrosion steel pipe is controlled by the rust removal quality inspection control area.
(4) Shot blasting and rust removal: The heated 3PE anti-corrosion steel pipe enters the shot blasting and rust removal machine through the rust removal transmission line. A high-power shot blaster throws steel sand and steel balls to hit the surface of the 3PE anti-corrosion steel pipe for rust removal. After rust removal, the surface cleanliness of the 3PE anti-corrosion steel pipe can reach the standard requirement of Sa2.5.
(5) Surface inspection: After shot blasting and rust removal, the 3PE anti-corrosion steel pipe enters the middle platform through the rust removal transmission line and is monitored by the rust removal quality inspection control area. The quality, surface cleanliness, and anchor pattern depth of each 3PE anti-corrosion steel pipe are inspected. 3PE anti-corrosion steel pipes that do not meet the standard requirements will be returned through the feedback line for re-rust removal. 3PE anti-corrosion steel pipes with surface defects will exit the production line; qualified 3PE anti-corrosion steel pipes will enter the coating production line. The quality inspection personnel in this area record the pipe number, pipe length, steel grade, wall thickness, furnace number, production date, quantity, etc. of the 3PE anti-corrosion steel pipe after rust removal.
(6) Dust removal inside 3PE anti-corrosion steel pipe: Use a special industrial vacuum cleaner to sweep the steel shot and dust inside the pipe.
(7) 3PE anti-corrosion steel pipe end reservation: Since the steel pipes are coated one by one and a certain reserved section is required at both ends of the pipe body, stickers must be placed according to the width of the reserved section before coating. After coating, they are cut off manually to improve the efficiency of the end treatment.
2. Steel pipeline surface coating technology
(1) Dust removal: After rust removal, the qualified 3PE anti-corrosion steel pipe is sent to the dust treatment station through the coating transmission line. The suction and rolling brush cleaning methods are used to remove some tiny dust on the surface of the pipe after rust removal, so as to improve the adhesion of the epoxy powder coating.
(2) Medium frequency induction heating: After dust treatment, the 3PE anti-corrosion steel pipe is heated by the medium frequency coil before epoxy powder spraying. The pollution-free medium frequency induction electric heating method is adopted to quickly and evenly heat the pipe body to the required temperature. The medium frequency heating equipment can be adjusted steplessly according to the temperature requirements of the raw materials to meet the coating temperature requirements. The power of the medium frequency heating is 500 kW, and the frequency is 400-1000Hz. The device is equipped with an automatic temperature monitoring system, an automatic start frequency tracking system, and an automatic cooling water circulation heat exchange device.
(3) Epoxy powder spraying: The heated 3PE anti-corrosion steel pipe enters the epoxy powder spraying room through the coating transmission line. The epoxy powder with static electricity is evenly sprayed on the surface of the 3PE anti-corrosion steel pipe and gelled within the specified time to meet the coating requirements.
(4) Side-wrapped copolymer primer: According to customer requirements, multiple glue wrapping processes such as upper and lower winding and side winding of 3PE anti-corrosion steel pipe can be adopted. The copolymer glue extruded by the copolymer extruder is wound on the gelled and solidified powder layer through the filter and the head. The air trapped in the winding belt is extruded by the silicone roller, and the glue is combined with the 3PE anti-corrosion steel pipe powder layer to be densely combined.
(5) Side-wrapped polyethylene tape: The polyethylene tape extruded from the copolymer polyethylene outlet machine is formed into a strip-shaped body through the filter and the machine head and is wrapped around the powder and copolymer adhesive layer of the 3PE anti-corrosion steel pipe. The air sandwiched between the tapes is extruded by the silicone roller.
(6) Water cooling: After medium-frequency heating, electrostatic spraying, wrapping with copolymer primer, polyethylene tape, and other processes, the coated 3PE anti-corrosion steel pipe enters the water cooling transmission line. The cooling circulating water is evenly sprayed on the surface of the coated steel pipe to gradually cool and harden the coating so that the outlet pipe body temperature meets the standard requirements. The water-cooling section of the operation line is 22m long. Water spray pipes are installed on both sides and the bottom of the water-cooling inlet section to ensure that the cooling water is evenly sprayed to avoid water impact points and indentations and ensure the outlet of the pipe.
(7) Pipe end treatment: After the anti-corrosion coating is completed, the anti-corrosion layer of the reserved part of the pipe end should be removed. The reserved length of the pipe end shall comply with the corresponding standards or the requirements specified by the owner. This project uses a beveling trolley to grind the pipe end, forming a chamfer of less than or equal to 30° on the end face of the finished 3PE anti-corrosion steel pipe. The grinder is turned on at 120-150mm on both ends until the anti-corrosion bottom layer exposes 2-4mm of the epoxy coating, and there are no sticky paper marks on both ends for welding.
(8) Anti-corrosion steel pipe inspection: The surface coating quality of the anti-corrosion steel pipe is monitored by the finished steel pipe monitoring area, including the appearance, thickness, peeling strength, manual electric spark leak detection, and end length of the anti-corrosion steel pipe. The anti-corrosion steel pipes that pass the inspection are left at the end, and the unqualified pipes are placed in the waiting area for inspection and can be processed at any time. The quality inspection personnel in the monitoring area record the coated steel pipes, including the pipe length, pipe number, quantity, appearance, thickness, etc.
(9) Repair of the external anti-corrosion layer: Repair the anti-corrosion layer according to standard requirements. (10) Marking of finished external anti-corrosion steel pipes: Finished steel pipes will be sprayed with marks at both ends 2 to 3 meters away from the pipe ends, including the 3PE anti-corrosion steel pipe number, manufacturer, implementation standard, anti-corrosion level, steel pipe length, production date and anti-corrosion steel pipe number, etc. They will then be stacked on finished steel pipe stacks waiting for shipment.
Post time: Jul-11-2025