I. Verification through Calculation of "Drag Pressure" + "Process Pressure"
1. Measuring Drag Pressure (P_drag)
Depressurize the hydraulic system and then slowly pressurize it. Record the pressure value when the pipe/workpiece just begins to move; this is the drag pressure.
This value reflects the internal frictional resistance of the equipment and is the basic reference for pressure setting.
2. Superimposing the Specified Welding Pressure (P_1)
Obtain the standard welding pressure from a table based on the material and wall thickness (e.g., PE pipe is typically 0.15–0.3 MPa/mm wall thickness).
Total pressure = P_drag + P_1. If the actual set pressure is not lower than this value, it is considered sufficient.
II. Observing Physical Characteristics During the Welding Process
1. Flange Uniformity
During the heating stage, both ends should form symmetrical, continuous, and rounded flanges, with a height of approximately 1–3 mm.
If the flanges are too small or asymmetrical, it indicates insufficient or uneven pressure.
2. Fitting Status During Butt Joint
After removing the heating plate, the two tube ends should fit together quickly and tightly without gaps.
If "not fitting" or "springing back" occurs, it indicates that the system pressure is insufficient.
3. Joint Quality After Cooling
After welding, cut the joint for inspection: Ideally, the weld depth should be uniform, without incomplete welding, porosity, or uneven melting.
If the weld zone is too narrow or not fully fused, it indicates insufficient pressure.
III. Using Instruments and Timers for Assisted Judgment
1. The pressure gauge reading should be stable within the set range (e.g., 5–6 MPa) without significant fluctuations.
2. Use a dual-channel timer to record the heat absorption and cooling times to ensure the entire process is completed under the specified pressure.
