Procedure: Construction and Laying of Polyethylene Mains

Purpose. This procedure describes how crews establish the worksite, excavate, lay, fuse, test and commission polyethylene distribution mains to the network standard.

1.Scope

This procedure applies to new polyethylene mains and to mains replacement by open trench or insertion. It applies to Gasline crews and to contractors working under Gasline supervision.

2.Step 1: Establish the worksite

The crew leader must review the construction plan and the traffic management plan, must obtain the road opening consent and must locate, prove and protect every utility asset by potholing before any mechanical excavation. The worksite must be fenced and signed before excavation starts.

3.Step 2: Excavate

Excavation must follow the general excavation rules for benching, battering and shoring. Mechanical excavation is not permitted within the hand dig zone of any located asset. Spoil must be placed clear of the trench edge and sediment controls installed.

• Pothole every crossing and parallel asset
• Hand dig within the no-go zone of located assets
• Shore or batter any trench deeper than 1.5 metres
• Keep spoil at least 600 millimetres from the trench edge

4.Step 3: Lay and fuse

Pipe must be inspected for damage and stored out of sunlight. Butt fusion and electrofusion must be performed by an authorised operator using a calibrated machine, with each joint recorded by joint number, operator and machine log. The main must be laid on a bed of sand with marker tape above it.

5.Step 4: Test

The completed section must be pressure tested to the network standard with a calibrated recording gauge for the specified duration. The test record must be attached to the work order. A failed test must be investigated and the section retested after repair.

6.Step 5: Commission

Commissioning must be done under a permit to work with the control centre notified. Air must be purged to a safe location until the detector reads full gas, and the new section must be leak surveyed before backfill of joints.

7.Step 6: Restore and record

Backfill and compaction must meet the road authority requirements. The crew leader must complete the as laid drawing, update the asset register and close the work order within five days.