What is Die Drawing
The Die Draw process involves drawing a thermoplastic liner (usually PE 100) through a die at ambient temperature to elastically reduce the diameter of the liner. The diameter will be reduced sufficiently so the liner can be pulled through the host pipe. Once the liner has been pulled through, the tension is released and the stored energy in the liner causes it to revert naturally in an axial direction. As the liner reverts it expands diametrically which creates a tight fit on the bore of the host. This reversion is an essential part of the process and is entirely caused by the viscoelastic properties of the thermoplastic liner returning it to its natural state – no additional processes or materials are required.
The Die Draw process has been utilised since the late 1980’s and provides a reliable, industry proven method to rapidly install Polyethylene (PE 100) tight fit lining solutions. The materials used for the liners are fully qualified, extensively tested and dominate low pressure water and gas pipelines throughout the UK and Europe.
When correctly engineered these solutions offer a highly controllable installation process that only uses the natural properties of the materials themselves without any need for difficult to control post curing, spraying or post-pressurisation to establish the finished product. Polyethylene liners, when implemented correctly, offer a robust, reliable, environmentally friendly, and cost-effective method of rehabilitating pipelines with greater than 100 years design & life expectancy.