I. Judging Incomplete Welding by the "Double Eyelid" Edge
The "double eyelid" is a double-ringed edge formed by the even overflow of molten material, a sign of sufficient welding.
✅ Normal Characteristics: The edge is continuous, symmetrical, and full, encircling the joint, with a noticeable bulge on both the inner and outer sides, and a consistent thickness.
❌ Incomplete Welding Characteristics: No edge or discontinuous edge (partial missing parts) Edge too narrow, bulging on one side (resembling a "single eyelid") White or brittle edge indicates insufficient heating and incomplete melting of the material.
Principle: When the heating temperature is insufficient or the time is too short, the PPR only reaches a plastic state, not a molten state. After insertion, the material cannot form a stack, naturally failing to produce the "double eyelid."
II. Judging Incomplete Welding by the Fusion Surface
The fusion surface should be a single, continuous piece, without delamination or gaps.
✅ Normal appearance: The joint has a uniform color, no obvious interface, and the transition between the pipe and fitting is natural. After cutting, the molecular layers are completely fused.
❌ Incorrect weld appearance: Small gaps or a broken feel at the joint root; delamination may occur when the joint is forcefully bent; after cutting, unfused gaps are visible on the inner wall, i.e., "inner layer incomplete weld."
Risk: This type of incomplete weld may not leak under pressure, but it is prone to cracking and leakage after long-term pressure or thermal expansion and contraction.
III. Judging Incomplete Welds by Porosity and Impurities
Porosity and impurities can damage the integrity of the weld and often accompany incomplete welds.
✅ Normal appearance: The weld surface is smooth and clean, without black spots, bubbles, or foreign matter.
❌ Symptoms of Incomplete Welding:
Porosity: Often caused by damp pipes or excessively rapid heating, preventing gas from escaping and forming micropores, weakening the bond.
Impurities: Dust and oil residue hinder molten contact, leading to localized incomplete fusion.
Slag: The use of inferior pipe fittings or excessively high temperatures produces carbides, affecting sealing.
Note: Even with a "double eyelid" weld, if accompanied by porosity or impurities, it is still considered an unqualified weld.
