TJ Hayes and Son Specialise in Butt Fusion Welding

Butt Fusion Welding of Polythene Pipe

Introduction

Using the very latest equipment T J Hayes & Son also provides a nationwide specialist contracting service in butt and electro fusion jointing of polyethylene (PE) pipe. All our on site service personnel have many years experience working in the pipeline utility sectors and as a minimum our site teams are trained to CSCS accreditation, Confined Space operations and of course Butt and Electro fusion certification.

As part of our Quality assurance and in addition to industry specification T J Hayes and Son also undertakes additional quality checks at the start of each shift.

Pre-Welding Checks

Before commencing a welding operation check that:

		There is sufficient fuel for the generator (if not direct power) to complete the joint and that it is functioning correctly before it is connected to the machine.
		The trimming tool and hydraulic pump are in working order.
		The heater plate is clean and residues from previous welds have been removed.
		A tent is available to provide shelter during welding.
		The machine is complete and undamaged.
		The correct welding parameters for the machine and pipe being welded.
		The heater plate is at the correct temperature. (Connect the heater plate to the power supply and retain for at least 20 minutes inside the thermally insulated guard). To remove dirt deposits the heater plate may be washed, when cold

Butt Fusion

Butt-fusion jointing is a thermofusion process which involving the simultaneous heating of the ends of two components which are to be joined until a melt state is attained on each contact surface. The two surfaces are then brought together under controlled pressure for a specific cooling time and homogeneous fusion is formed upon cooling. The resultant joint is resistant to end thrust and has comparable performance under pressure to the pipe.

These checks are traceable with data analysed and confirmed at the end of each day supported with a report if requested to our clients, either printed out or data transferred via CD \ DVD \ USB or email. ( Note all security measures are taken and data is encrypted whilst in transfer).

Equipment Requirement

		Generator to supply the heater plate, trimmer and hydraulic pump
		Butt-fusion machine fitted with the correct size clamp shells, trimmer, heater
		Plate, hydraulic pump and timer
		Pipe support rollers
		Welding tent
		Cleaning material, lint free cotton cloth or paper towel
		External/Internal debeading tool
		Bead gauge
		Digital thermometer with surface probe to check heater plate.
		Pipe end covers
		Baseboard
		Pipe cutters
		Air temperature thermometer
		Indelible marker pen
		Timer

The Process

The heating phase, sometimes referred to as 'bead up', is where the pipe ends are pressed against a heated plate for a period of time. This is followed by the 'heat soak' phase where the pressure is reduced to just hold the pipe ends on the hot plate. This allows time for the heat to soak into the material at the pipe ends.

After the heat soak phase, the hot plate is removed and the pipe ends brought together. The time taken to do this is called 'dwell time' and needs to be as short as possible. The final phase is the welding/cooling time, predetermined subject to pipe diameter and wall thickness. T J Hayes and Son Ltd provide Butt Fusion from 63mmØ up to 900mmØ if requested larger diameter is required.

Dummy Welds

T J Hayes and Son Ltd take every precaution although its possible very fine particles of dust may still remain on the heater plate. To remove such dust it is necessary to make a dummy joint at the start of each jointing session, whenever the plate has been allowed to cool below 180°C, or at a change of pipe size. Two dummy joints will be made if the pipe size is greater than 180mm.

A dummy joint can be made using pipe off cuts of the same size, SDR and material as the pipe being installed, It is not necessary to actually make a joint. The procedure can be discontinued after the full heat cycle.

Rules for Butt Fusion

Always Remember - NEVER:

		Attempt to weld together pipes of different SDR (wall thickness).
		Touch trimmed pipe ends.
		Leave trimming swarf inside pipe or on welding machine
		Allow equipment to get wet or dusty.
		Use non-approved machinery.
		Remove a weld from the machine before cooling time has elapsed.
		Allow untrained personnel to use welding equipment.
		Cut corners in any part of the welding procedure
		Weld pipes of different material on site (In factory controlled conditions it may be possible to do this).
		Use a generator of inadequate capacity.

For Electro Fusion welding please click here

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TJ Hayes & Son

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