First, Cutting Plastic-Coated Steel Pipes.
Plastic-coated steel pipes should be cut using a metal saw. For large-diameter pipes, a sawing machine is recommended. When using a disc cutter, the rotation speed should not exceed 800 r/min. The cut section of the steel pipe should be perpendicular to the pipe axis.
Second, Preparation Before Connecting Plastic-Coated Steel Pipes.
1. After cutting, the ends of the plastic-coated steel pipe should be smoothed with a fine file to remove any burrs.
2. A special reamer should be used to chamfer half the thickness of the plastic coating layer, with a chamfer angle of 10°-15°.
3. If the coating layer of the plastic-coated steel pipe is intact at the end, it should be chamfered inwards using a reamer. If the end is damaged, it must be repaired (using repair fluid) until the coating layer of the plastic-coated steel pipe is completely crack-free.
4. After grooving, the plastic coating on the protruding parts of the plastic-coated steel pipe will be damaged and must be repaired until the coating surface is smooth, without cracks or damage.
5. Cleaning should be done using cotton scraps and a brush to remove oil, water, and metal debris from the pipe ends and inside the pipe.
Third, Connection Methods of Plastic-Coated Steel Pipes
1. Threaded Connection: Threading should be done using an automatic threading machine, following current national standards.
2. Flange Connection:
Single Installation Method: On-site measurement and drawing of a single-line pipeline processing diagram are performed. After processing, coating, and lining are completed, the pipes are transported to the site for installation.
Two-Step Installation Method: On-site welding of non-coated/non-lined steel pipes and fittings with flanges is used to assemble the pipeline. Then, the pipes are disassembled for coating and lining before being transported to the site for installation.
3. Grooved Connection: Grooved plastic-coated steel pipe fittings made from pre-made plastic-coated steel pipes should be used preferentially. Grooving should be done using a dedicated grooving machine, ensuring the groove depth meets relevant standards.
Fourth, Specific Design Principles for Plastic-Coated Steel Pipes
Pipeline design should comprehensively consider practicality, safety, reliability, and economy when selecting a solution. Specific design and calculations should follow these principles:
1. Meet service life requirements. From the perspective of intended use, the service life of new steel pipes, especially plastic-coated pressure steel pipes, should be considered first, rather than the allowable load. This is because the pipeline itself is a permanent structure, and its service life should be consistent with that of the building.
2. The inner diameter of the steel pipe must meet flow rate requirements. The inner diameter, flow rate, and flow velocity of the steel pipe are closely related. Under the premise of meeting the flow rate requirements, the flow velocity should be selected to determine the inner diameter of the steel pipe.
3. The wall thickness of the steel pipe must meet pressure requirements. The rated pressure of a pipeline is closely related to the wall thickness of the steel pipe and the ring stress of the steel pipe itself. Once the steel pipe is selected, it means that the ring stress of the steel pipe is determined, and the rated pressure of the pipeline is only related to the pipe wall thickness. Therefore, the wall thickness of the steel pipe must meet the rated pressure requirements.
Post time: Jan-28-2026