How to make double-layer composite pipe electric fusion connection? Key operating points for oxide layer, socket depth, and cooling solidification
Release time: October 29, 2026
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Electric fusion connection is the most numerous process in double-layer composite pipe engineering, with hundreds of joints per station, each of which is related to the tightness of the entire pipeline. Standardize the three stages of oxide layer treatment, socket depth, and cooling solidification to ensure the quality of the joint.
Treatment of the oxide layer at the pipe end
During storage, a layer of oxide will form on the outer wall of the composite pipe, which is separated between the heating coil and the pipe during electric melting. No matter how high the current is, it cannot be welded through. Before connecting, use a scraper to evenly scrape the outer wall of the inserted section, with the scraping depth based on the exposure of new material. Do not touch the scraped surface with your hands or touch it with dust on the ground. The shorter the time from scraping to insertion, the better. Scrape and weld on the same day.
Socket depth and marking line
The insertion depth should be executed according to the requirements corresponding to the pipe diameter. If the insertion is shallow, the fusion of the pipe wall in the heating area may not be complete, and if it is inserted from the top to the bottom of the socket, it may cause nowhere for the melted material to flow. On site method: Measure the insertion depth, draw a circle of marking line at the end of the pipe, and after inserting it in place, the marking line just exposes the edge of the cuff. When inserting, slowly push in towards the positive axis to avoid tilting and hitting hard, scratching the coil or bringing in debris.
Why can't cooling and solidification save
After the electric melting is completed, the interior of the joint is still in a softened state, and any external force at this time - moving, backfilling, stepping - will cause the newly established fusion surface to be misaligned. According to the cooling time required by the process, do not move the pipe during the cooling period. The feeling of rushing to meet the deadline is understandable, but the strength of the joint grows in the cooling section, and early disturbance is equivalent to white welding.
On site inspection of connection quality
A qualified electric fusion joint will have the indicator post of the observation hole lifted evenly, and a small amount of melted material will overflow evenly at both ends of the sleeve to form two small loops of flanging. Uneven flanging, no movement in the observation hole, and deformation of the cuff should be noted and rechecked. Record the numbering of the joints and ensure that their positions are consistent with the corresponding drawings. In the future, when checking for leaks during pressure testing, locate them according to their numbers, which will greatly improve efficiency.
| link | Key points | Common mistakes |
|---|---|---|
| Oxidation layer treatment | Scrape to new material to avoid contamination | Leakage or dust accumulation after scraping |
| Socket depth | Draw marking lines and insert them correctly | Insufficient insertion or dead top |
| Cooling and solidification | Foot time cooling, free from external forces | Hurry up and disturb in advance |
| Visual inspection | Observe that the hole is raised and folded evenly | Abnormal connector not recorded |
Frequently Asked Questions
How to determine the parameters of electric fusion welding?
Execute according to the parameters given by the pipe manufacturer, adjust the voltage and time according to the pipe diameter and ambient temperature, and do not mix pipe parameters from different manufacturers.
What should I do if the scraped pipe end is left for too long?
Scrape again and weld again. The pipe end exposed to air for more than the specified time will regenerate the oxide layer.
What should be paid attention to during winter construction of electric fusion connections?
When the ambient temperature is low, the cooling time should be extended according to the process requirements. The pipes and electric melting fittings should be stored in a warm place in advance to avoid low-temperature embrittlement affecting the fusion quality.
What supporting services does WoHong offer?
Luoyang Wohong Petrochemical Equipment Co., Ltd. provides double-layer composite pipelines and connection matching for gas stations, including installation technical guidance. Contact number: 13526990215, email: lixiang@vohon.cn .
