| Applicable Process | Joint method | Heated-tool butt fusion of thermoplastic pipes and fittings | Use a machine designed for butt fusion, with controlled alignment, heating, joining, and cooling stages. | The procedure is intended for thermoplastic materials suitable for butt welding; the approved material procedure remains controlling. |
| Pipe Compatibility | Material and dimensions | Material grade, outside diameter, wall thickness, SDR, and fitting geometry must be entered before welding. | Select a machine whose clamping range covers the complete project diameter range and wall-thickness range without overloading the carriage. | Heat, pressure, and time values are dependent on the material and pipe dimensions; they are not universal fixed settings. |
| Heating Temperature | Heated-tool surface temperature | Typically 200–220 °C for PE-HD applications; use the approved material-specific welding procedure for PP, PVDF, or other polymers. | The heating plate should provide closed-loop temperature control, distributed heating, over-temperature protection, and a calibrated display or data output. | The selected setpoint must follow the applicable DVS material table and the pipe manufacturer’s qualified procedure. |
| Temperature Uniformity | Heating plate across the working area | Specify a documented temperature verification across the active heating surface before production. | Choose a plate with stable heat distribution, low thermal recovery time, and a calibration record traceable to the project quality system. | Uniform heating is necessary to avoid incomplete melting, local overheating, or asymmetric bead formation. |
| Bead-Up Pressure | Initial contact and bead formation | Normally limited to approximately 0.02 N/mm² or less, subject to the approved welding procedure. | The hydraulic system must permit low, stable pressure control and prevent accidental application of joining pressure during the initial heating stage. | Excessive initial pressure can force molten material away from the joint interface and reduce the effective fusion area. |
| Heat-Soak Pressure | Maintaining contact during heating | Maintain the low heating pressure specified by the approved procedure; do not use the full joining pressure. | Select a machine with a pressure-relief or controlled hold function that remains stable while the pipe ends are heated. | The heating phase must produce adequate melt layers without excessive displacement of the softened polymer. |
| Joining Pressure | Fusion pressure after heater removal | Common PE planning value: about 0.15 N/mm²; confirm the exact value for material, SDR, diameter, and procedure. | The machine must calculate or display the required hydraulic pressure from the selected fusion pressure and effective piston area. | Do not compare hydraulic gauge pressure directly with interface pressure; the conversion depends on machine geometry and piston area. |
| Pressure Calculation | Machine pressure versus interface pressure | Use the machine-specific relationship: hydraulic pressure = required joining force ÷ effective piston area. | Require a calibrated pressure gauge or transducer, verified piston-area data, pressure compensation for drag, and a documented pressure chart. | Pipe-wall friction and carriage drag must be considered when converting the specified fusion pressure into machine settings. |
| Changeover Control | Removing the heater and closing the joint | Keep the changeover interval as short as practicable and within the approved procedure’s maximum limit. | Choose a machine with rapid, unobstructed heater withdrawal, clear operator access, and an adjustable changeover timer. | Long or uncontrolled changeover time can cool the melt surface and reduce joint quality. |
| Heating Time | Time at the heated tool | Set by material and wall thickness; for PE, a commonly used planning reference is approximately 10 seconds per millimetre of wall thickness, subject to the approved procedure. | The controller should support recipe-based timing, countdown indication, operator confirmation, and data logging. | The project procedure takes precedence over generic planning estimates. |
| Cooling Under Pressure | Cooling time and pressure hold | Maintain the specified joining pressure throughout the required cooling period; cooling time must be selected from the approved material and wall-thickness procedure. | Require a locked pressure-hold cycle, cooling timer, low-pressure alarm, and protection against premature clamp release. | The joint should not be moved, stressed, or removed from the clamps before the specified cooling period has elapsed. |
| Ambient Conditions | Wind, rain, dust, and temperature | Use a weather shelter where wind, precipitation, direct solar heating, or contamination could affect the joint. | Select equipment compatible with outdoor power supplies and provide a wind shield, protected controls, and stable operating support. | Environmental conditions may alter heat transfer and cooling behavior; the procedure should define acceptable limits and corrective actions. |
| Alignment and Drag | Mismatch, ovality, and carriage resistance | Verify alignment, clean pipe ends, measure drag pressure, and include drag compensation in the pressure setting. | Choose rigid clamps, an adjustable carriage, a facing tool with sufficient torque, and a method for recording drag pressure. | Poor alignment or unaccounted drag can produce uneven bead geometry and an incorrect actual fusion pressure. |
| Data Recording | Traceability and quality records | Record joint ID, date, operator, material, diameter, wall thickness, temperature, pressure, heating time, changeover time, joining time, and cooling time. | For international projects, prefer automatic cycle recording, exportable files, calibration reminders, and multilingual operating instructions. | Recorded parameters support verification that each joint followed the approved welding procedure. |
| Calibration and Verification | Temperature, pressure, and timer accuracy | Complete pre-project and periodic checks using calibrated reference instruments and retain the certificates. | Specify accessible calibration points, replaceable sensors, pressure-gauge verification, and service support for the project region. | Control settings are only reliable when the measuring and control systems are verified and maintained. |