I. Electrical Parameter Matching: Ensuring Accurate Energy Supply
1. Voltage and Current Matching
The welding machine's output voltage must meet the rated requirements of the electrofusion fittings (commonly 39.5V), and the power cord must be able to carry the required current.
If using a generator, ensure stable voltage to avoid welding failure due to undervoltage.
2. Welding Parameter Consistency
Different brands of fittings have different heating times and current curves. Use the manufacturer's provided parameter table for input.
For example, Sichuan Huangsheng Pipe Industry's D110 fitting requires 37A current for 150 seconds, while D250 requires 30A for 200 seconds.
Using mismatched parameters may result in over-welding (molten adhesive overflow) or incomplete welding (incomplete fusion).
3. Plug and Terminal Compatibility
The electrofusion plug size (e.g., 4.7mm) must be perfectly aligned with the fitting's terminals to avoid loose connections and arcing.
If the welding machine output is incompatible with the pipe fitting, a dedicated adapter plug should be used; forced insertion is prohibited.
II. Mechanical Dimension Matching: Ensuring Connection Accuracy and Sealing
1. Pipe and Fitting Specifications Must Match
The outer diameter of the pipe (e.g., DN63) must correspond to the nominal size of the electrofusion fitting, and the wall thickness grade (SDR value) must match.
During installation, the fitting should be centered on the scribed mark, with a deviation not exceeding ±5mm, ensuring a uniform fusion zone.
2. Scraping Depth and Cleaning Range
The welding surface of the pipe needs to be scraped by 0.1–0.2mm to remove the oxide layer. The scraping length should cover the entire socket area.
After scraping, there should be no obvious scratches or oil stains; otherwise, the fusion strength will be affected.
3. Coaxiality Control
After the pipe and fitting are socketed, the misalignment should be less than 2%. This can be corrected using clamps or a straightener to prevent eccentric welding.
III. Process Verification: Confirming Compatibility Through Operation and Testing
1. Welding Process Observation
Fusion Indicator Rise: Some electrofusion fittings have observation holes. The molten adhesive pushing the ejector pin upwards signals welding completion.
No Molten Adhesion Overflow: Normal welding should not have a large amount of molten material flowing out. If this occurs, it indicates that the parameters are too high or the fitting is damaged.
2. Cooling and Fixing Requirements
After welding, the pipe must cool naturally. During this period, the pipe should not be moved or the clamps removed to prevent stress cracking.
Cooling time depends on the pipe diameter and ambient temperature, typically 30–120 minutes.
3. Post-Weld Quality Inspection
Visual Inspection: The fitting should be free from deformation and discoloration, be straight with the pipe, and have good alignment of the socket.
Pressure Test: A pressure test should be performed on the piping system. No leakage or rupture indicates acceptance.
Destructive Testing (Sampling):
Cross-Section Inspection: The resistance wires should be neatly arranged, without exposed or misaligned sections, and there should be no visible boundary lines on the weld surface.
Peel test: A brittle fracture rate of ≤33.3% is considered acceptable and is suitable for quality acceptance scenarios.
