I. Six Steps to Achieve High-Quality Welding
PPR pipe hot-melt connections must follow a standardized process: "Preparation → Cleaning → Marking → Heating → Socketing → Cooling," and none step can be omitted.
1. Equipment and Environmental Preparation
Check that the hot-melt machine's power cord and plug are intact, and confirm that the heating die has no coating peeling or carbon buildup. Place the machine on a stable, dry workbench, away from water and flammable materials. Select a matching die according to the pipe's outer diameter (e.g., 20mm, 25mm) to avoid poor welding due to dimensional deviations.
2. Thoroughly Clean the Welding Surface
Wipe the outer wall of the pipe and the inner wall of the fitting with an alcohol swab or a special cleaning brush to remove oil, dust, and moisture. After cutting, the pipe ends must be beveled at a 15° angle and burrs removed to prevent impurities from entering the system. Also, wipe the die surface with a dry cloth before and after each heating to avoid residue affecting the melting effect.
3. Precisely Mark the Weld Depth: After inserting the pipe fitting into the die to determine the insertion depth, draw a "lifeline" on the pipe with a marker. During welding, the pipe must be inserted to this line to ensure uniform melting and avoid incomplete insertion or over-insertion, which can cause inner diameter reduction.
4. Set the Temperature and Preheat Sufficiently: The standard welding temperature for PPR is 260℃±10℃. In winter, this can be appropriately increased to 270℃, but it is strictly forbidden to exceed 280℃, otherwise it will cause material carbonization and brittleness. When using a welding machine with red and green indicator lights, wait for the second green light to illuminate before starting operation to ensure a uniform and stable heating plate temperature. The preheating time should be no less than 10 minutes; higher-power models require a longer time to reach thermal equilibrium.
5. Synchronous Heating and Rapid Insertion: Insert the pipe and fitting simultaneously, vertically, and without rotation into the heating die, maintaining parallel force. Heating time should be adjusted according to pipe diameter: approximately 5 seconds for 20mm, 7 seconds for 25mm, 8 seconds for 32mm, and gradually increasing for diameters above 40mm. Immediately remove the pipe after the allotted time and quickly insert it into the fitting along the axis in a straight line. The movement should be steady and fast, without rotation or shaking. Insert until the marked line is reached, and hold for a few seconds to prevent rebound.
6. Natural Cooling and Shaping After socketing, the fitting must be allowed to cool naturally. During this period, movement, bending, or application of external force is prohibited. The cooling time must not be less than the heating time; at least 2 minutes for small diameters and 4-5 minutes or more for large diameters. After complete cooling, check if the joint has formed two evenly round, full "double eyelid" fusion edges, which is a visual indicator of successful welding.
II. Common Problems and Risk Avoidance
1. Incomplete or Fake Welding: Often caused by excessively low temperature (below 253℃), insufficient heating time, or uncleaned surface. The joint strength is low; it may pass pressure testing, but long-term use is prone to leakage.
2. Inner Diameter Reduction: Excessive temperature, excessive insertion depth, or excessive force can cause the inner wall of the pipe to melt and collapse, affecting water flow and even causing blockages.
3. Yellowing or Carbonization of Joints: Temperatures exceeding 274℃ can degrade PPR materials, making the joint brittle and prone to bursting under water pressure.
4. Mismatched Die: Different brands of pipes have dimensional deviations. A suitable "standard die" should be selected, especially when welding European standard products.
Special Reminder: It is strictly forbidden to increase the temperature or shorten the heating time in pursuit of speed. This "one step faster" operation may have "life-threatening" consequences.
III. Three Verifications That Must Be Completed After Welding
1. Visual Inspection: Inspect each weld joint to ensure it forms a symmetrical "double eyelid," without stringing, eccentricity, or impurities.
2. Water Pressure Test: The test pressure for cold water pipes should not be lower than 0.8 MPa, and the pressure should be stabilized for 30 minutes. The pressure drop should not exceed 0.05 MPa, and all joints should be leak-free. Pipes should be fixed before the pressure test, and joints should be exposed for easy observation.
3. Record Keeping: It is recommended to take photos of key points for record keeping, especially concealed parts inside walls and under floors, for future maintenance and accountability.
