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HOW TO CALCULATE FUSION PRESSURE AND TIME OF BUTT FUSION MACHINES
To properly fuse the PE-HD pipes, fittings and sheets and ensure the weld quality, the operator is always obliged to find the right fusion pressure and time under the welding standard requested by the project. This page will indicate how to calculate the fusion pressure and time manually, based on standards **ISO21307:2017** and **DVS2207-1**. All recommended values apply to an outside temperature of approx. 20 °C and moderate air flow (interim values have to be interpolated). ---
Step 1 Check the butt fusion jointing cycle diagram
Butt Fusion Jointing Calculation
The figure shows the full pressure-time cycle of butt fusion jointing, with all phase parameters marked.
- X: time
- Y: pressure
- t1: bead-up time
- t2: heat soak time
- t3: heater plate removal time
- t4: time to achieve fusion jointing pressure
- t5: cooling time in the machine under pressure
- P1: bead-up pressure
- P2: drag pressure
- P3: fusion jointing pressure
Step 2 Check the formula of the gauge pressure calculation
Butt Fusion Jointing Calculation
The bead-up pressure (P1) and fusion jointing pressure (P3) can be calculated from the following formula:
> P1, P3= [IP × (dn - en) × en / S × 10] + P2
Key
- P2: Drag Pressure (bar)
- IP: Interfacial pressure (MPa), it is generally considered to be 0.15
- dn: nominal outside diameter of the pipe (mm)
- en: nominal wall thickness of the pipe (mm)
- S: Total piston area (mm²)
Note: The interfacial pressure is the amount of force per unit of pipe area required to butt fuse the pipe or fitting ends.
Step 3 Refer to standard parameters and value tables
Single low‑pressure fusion jointing
- Table 1 — Phases, parameters and values
- Table 2 Maximum time for removing the heating plate
- Calculation Demonstration
- Pipe: OD315mm SDR11
- Machine model: Welping 315
- Total piston area: 2002mm2
- Drag pressure: 10bar (just as an example)
- dn: 315mm
- en: 315/11≈28 .64mm
- P1 = P3: [0 . 15 × 3 . 14 × (315_28 .64) ×28 .64/2002 × 10]+10≈29bar
- Bead_up size: 0 . 15+0 . 1 ×28 .64≈ 3 .4mm
- t2: (13 .5±1 .5) ×28 .64≈ 344s~430s
- t3: 16s
- t4: 3+0 .03 × dn≈12s
- t5: 0 .015 ×28 .642_0 .47 ×28 .64+20≈ 19min
- Table 1 Recommended values for the heated tool butt welding of pipes, fittings and sheets made of PE‑ HD at an outside temperature of approx. 20 ° C and moderate air flow (interim values have to be interpolated).
- Pipe: OD315mm SDR11
- Machine model: Welping 315
- Total piston area: 2002mm2
- Drag pressure: 10bar (just as an example)
- dn: 315mm
- en: 315/11≈28 .64mm
- P1 = P3: [0 . 15 × 3 . 14 × (315_28 .64) ×28 .64/2002 × 10]+10≈29bar Bead_up size: 3mm
- t2: 260s~370s
- t3: 12~ 16s
- t4: 14~ 19s
- t5: 32~45min
Calculation Demonstration
Final Notes
All butt fusion parameters for PE-HD pipes shall strictly follow ISO21307:2017 and DVS2207-1 standards. Fusion pressure is determined by pipe outer diameter, wall thickness and machine piston area, while all time parameters are calculated based on wall thickness and pipe diameter. For non-standard pipe specifications, please perform reasonable interpolation to guarantee the strength and sealing performance of fusion joints. ---
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