What is Heat Fusion?
Heat fusion melts the pipe and fitting surfaces. They are joined under light pressure. The materials mix on a molecular level. This creates a monolithic piece. The joint is as strong as the pipe itself. It is a permanent connection.
Material Properties for Welding
PPR is a thermoplastic polymer. It softens at around 260°C (500°F). It does not burn immediately at this point. This allows a working window. The melted material becomes viscous. It flows to create a perfect seal.
Critical Temperature Control
The welding machine must be accurate. Temperature variation causes weak joints. Underheating leads to incomplete fusion. Overheting degrades the polypropylene. Always use a digital temperature reader. Calibrate your tool regularly.
The Importance of Heating Time
Heating time depends on pipe size. For 20mm pipe, heat for 5 seconds. For 25mm, heat for 7 seconds. Refer to the manufacturer's chart. Timing starts when pipe/fitting are fully on the mandrel. Use a stopwatch for precision.
Assembly and Holding Time
After heating, remove parts quickly. Join them in one smooth motion. Align them perfectly without twisting. Hold them steady under pressure. Hold for the specified time. This allows initial solidification.
Cooling Phase Chemistry
The polymer chains re-entangle during cooling. This process is called crystallization. It takes several minutes to complete. Do not disturb the joint. External force breaks the forming bonds. Full strength develops after cooling.
Inspecting a Good Weld Joint
A proper weld forms a uniform bead. The bead appears around the fitting collar. It should be even and continuous. No gaps or voids are acceptable. The bead size should match specifications. Cut and inspect a sample joint first.
Safety During the Process
Wear heat-resistant gloves. Work in a well-ventilated area. The heater plate is extremely hot. Keep it away from flammable materials. Focus on the task to avoid burns. Let all equipment cool before storage.
