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On-site butt fusion

HDPE welding — quality guide

ISO 21307SANS 10268-1DVS 2207-1

Before you weld — site conditions

  • Shelter the joint from wind, rain and dust; fit end caps to stop draught-cooling through the bore.
  • Ambient generally −5 °C to 40 °C — outside this, tent/heat and run trial welds.
  • Pipe ends clean, dry and square; acclimatised, supported on rollers and aligned.
  • Heater plate clean (PTFE-coated, undamaged); temperature checked with a pyrometer.
  • Weld like-to-like only: same material (PE100↔PE100) and the same wall / SDR.

Butt-fusion cycle

1
Face & align
Trim both ends to a clean continuous ribbon; check high/low.
Misalignment ≤ 10% of wall
2
Heater temperature
PE100 heater-plate temperature, verified with a pyrometer.
200–230 °C (≈210 °C)
3
Bead-up
Press ends to the plate until the initial bead forms.
Interfacial ≈ 0.15 N/mm² + drag
4
Heat soak
Drop to near-zero pressure and hold to soak heat in.
Soak time ∝ wall thickness
5
Changeover
Remove the plate and bring the ends together — fast.
A few seconds (grows with wall)
6
Fuse & cool
Ramp to fusion pressure, hold under pressure until cool.
Cooling time ∝ wall thickness

Acceptance — inspect the bead

  • Uniform double bead all the way round, symmetrical, both rolls a similar size.
  • The valley (K) between the beads stays above the pipe surface — never undercut below it.
  • No contamination, cracks or flat spots.
  • Trial weld at shift start and at every material change.
  • Bead width consistent with wall thickness per the standard's table.

Quality assurance & traceability

  • Qualified operators; calibrated, serviced machine with a data logger.
  • Weld record per joint: joint no., operator, date/time, OD/SDR, heater temp, pressures, soak/cool times, ambient.
  • Number and mark each weld on the pipe for traceability.
  • Respect cooling time fully — no movement or load until cool.
  • Optional destructive checks (bend / tensile) on trial joints.

Guide values are indicative. Exact times, temperatures and gauge pressures MUST come from the fusion machine's WPS table for the specific OD/SDR (gauge pressure = interfacial pressure × pipe-wall area ÷ cylinder area + drag pressure). This is a reference, not a substitute for the machine tables or the governing standard.