How to Calculate the Welding Pressure and Time for HDPE Pipe Fusion?
Understanding Welding Standards
The HPDE Pipe Butt Fusion Welding Machine comes with a user manual containing welding data. You may also request a welding parameter table from our sales team.
The calculation involved in this article is based on ISO 21307:2017. If welding standards in your region differ from this standard, please refer to DVS 2207, ASTM F2620, etc.
Operator Responsibilities
The operator is always obliged to get the following skills.
Understand the fusion process
Pressure & parameter calculation ability
Machine operation skills
Observation & judgement
Timing awareness
Material & standards knowledge
Safety & discipline
Calculation of the gauge pressure
The gauge pressure can be calculated from the following formula:
GP=(IP×As/Ac×10) + DP
GP: Gauge pressure (bar)
IP: Interfacial pressure (MPa), usually 0.15
Ac: Total piston area, given by the manufacturer of the butt fusion welding machine (mm²)
As: Interfacial surface area (mm²), As=π × (dn − en) × en
dn: Nominal outside diameter of the pipe (mm),
en: nominal wall thickness of the pipe
DP: Drag pressure
Table I — Phases, parameters, and values for a single low-pressure fusion jointing procedure
| Phase | Parameters | Unit | Value |
| 1 & 2 | Heater plate temperature | °C | 225±10 |
| 1 | Bead-up pressure | MPa | 0.17±0.02 + drag pressure |
| Minimum bead-up size | mm | 0.5 + 0.1 × en | |
2 | Minimum heat soak time | s | (13.5±1.5) × en |
Heat soak pressure | MPa | 0 to drag pressure | |
3 | Maximum heater plate removal time | s | See table II |
4 | Maximum time to achieve fusion jointing pressure | s | 3 + 0.03 × dn |
Fusion jointing pressure | MPa | 0.17 ± 0.02
+ drag pressure | |
5 | Minimum cooling time in the machine under pressure, for wall thickness < 18 mm | min | en + 3 |
Minimum cooling time in the machine under pressure, for wall thickness ≥ 18 mm | min | 0.015 × en² − 0.47 × en + 20 | |
6 | Minimum cooling time out of the machine | min | Not specified |
Table II — Maximum heater plate removal time
| Nominal Wall Thickness
En, mm | Maximum time
T3, s |
| En≤4.5
4.5<En≤7
7< En≤12
12< En≤19
19< En≤26
26< En≤37
37< En≤50
50< En≤70
70< En≤90
90< En≤130 | ≤5
≤6
≤8
≤10
≤12
≤16
≤20
≤25
≤30
≤35 |
Example
Machine: Welping Butt Fusion Welding Machine FX315
Total piston area: 2002mm²
Pipe: OD315, SDR11
en: 315/11=28.6mm
Drag Pressure: 8bar
P1=P3: 0.15×(3.14×(315-28.6)×28.6)/2002×10+8=27.3bar
P2=Drag pressure: 8bar
Minimum bead-up size: 0.15+0.1×28.6=3.01mm
t2: 13.5×28.6=386.1s
t3: 16s
t4: 3+0.03×315=12.45s
t5 0.015×28.6²-0.47×28.6+20=18.8min
