Butt fusion is a thermo-fusion process which involves the simultaneous heating of the ends of two pipes which are to be joined, until a molten state is attained on each contact surface. The two surfaces are then brought together under controlled pressure for a specific cooling time and a homogeneous fusion joint is formed. The resulting joint is fully resistant to end loads and has comparable performance under pressure to the pipe itself.

An electrical heater plate is used to raise the temperature of the pipe ends to the required fusion temperature. Butt-fusion can be used to join both MDPE and HPPE (polyethylene) pipe sizes of 63mm and above of the same SDR.


To enable accurate record keeping we program our butt fusion machine with the following data prior to welding:

  • Location or site name

  • Project name or number

  • Our company name

  • Lead engineers name

  • Further to the above the machine will also record every weld number, whether the weld pass or failed, date and time and much more. All this information can be down loaded and form part of our completion report.

    Our butt fusion machines used to butt weld PE pipes have controls to ensure the welding parameters are strictly adhered to and impossible to bypass. The following parameters are controlled:

  • heater plate temperature

  • ovality and alignment

  • interface pressure

  • bead width

  • heat soak time

  • cooling time in clamps

  • Control of these is necessary to ensure premature failure of the weld does not occur. The field conditions under which PE pipe is welded have a considerable effect on the strength of the joint. In order to achieve an acceptable weld three elements are essential:

  • Cleanliness: Welding should always be performed on a dry level surface free from mud etc. Pipe ends are thoroughly cleaned and checked prior to welding in clamps as contamination will ruin joints

  • Weather: Adverse weather can affect weld quality so during wet, windy or cold weather our engineers would erect a tent around the equipment

  • Technique: Our engineers have many years’ experience in pipe welding, hold Water industry approved, TWI or City and Guilds qualifications and always follow the manufactures guidelines

  • Correctly designed equipment with proper maintenance: Enviroseal only use market leading Fusion Gator and McElroy butt fusion machines which are regularly serviced and calibrated

  • The resulting joint, if it has been properly made, is as strong as the original pipe and can withstand all the loads applied during routine installation and operation.

    During the fusion process internal and external ‘weld beads' are formed. Techniques have been developed to minimise the size of the beads, however as they do not add anything to the overall strength they may be safely removed if required. The removed weld beads can be inspected as part of a quality control programme.

    Our engineers are trained to the highest industry standards and we have a strictly adhered to code of practice and procedure for butt fusion welding which we have developed through years of experience in conjunction with manufacturer’s instructions to ensure all welds are performed correctly and with traceability as we mark each weld with weld number, date and our name etc and our butt fusion machines can be easily downloaded and the information included in our completion report.