Reg31 Approved PE 100 Liner Selection and Design Optimisation

The Die Draw technique is incredibly versatile in that it is possible to engineer any thickness of PE 100 liner to rehabilitate a host pipe. This has been made possible by the development of flexible extrusion by some pipe manufacturers. In addition to the possibilities of the full range of manufactured pipe sizes being produced according to BS EN ISO 12201, bespoke pipe sizes within and beyond the current specification limits can also be manufactured to the same quality levels.

Reduced Flow Capacity

Currently, PE 100 liner design is frequently restricted to loose-fitting slip lining defaulting to relatively thick SDR 17 and SDR 11 liners. Industry data shows extensive evidence of this practice, which leads to over-engineered, costlier liners with a higher carbon footprint than necessary.

Critically, these designs reduce the original flow capacity of the pipeline. There is no technical requirement to default to such thick liners, and doing so detrimentally impacts network performance, costs, and sustainability. By fully applying BS EN ISO 12201 to optimise liner selection based on operating pressure, engineers can specify SDR 41 liners using the Die Draw technique – or even thinner for larger pipes. Even where host conditions require thicker liners, SDR 21, SDR 26, or SDR 33 designs improve flow capacity through the smooth PE 100 bore.

Liner Optimisation

It is clear that liner selection is not being optimised. BS EN ISO 12201 provides a framework to ensure liners are tailored to operational needs, yet this standard’s potential remains underutilised. The difference in cost, flow capacity, and carbon footprint between default thick liners and optimised thin liners is substantial.

To address this, Die Draw is developing a liner sizing tool to aid designers and water companies in selecting the most efficient solution for potable water and wastewater rehabilitation. The tool calculates the final lined pipe’s internal diameter based on the host pipe’s dimensions and operating pressure, ensuring compliance with BS EN ISO 12201 .

To clarify the options available, liner designs can be categorised as follows:

  1. Die Draw Tight-Fit Semi-Structural Interactive Liners: Designed for collapse resistance, hole spanning, and gap bridging. These liners are used when the host pipe is in good condition and provides sufficient hoop strength.
  2. Die Draw Tight-Fit Fully Structural Liners: Provide full pressure rating, acting as a “pipe within a pipe” with additional security from the host.
  3. Die Draw Close-Fit Fully Structural Liners: Use standard-sized pipes where a tight fit is not fully achievable, leaving a small gap between the liner and host.
  4. Slip Liners (Loose-Fit Fully Structural Liners): Feature a large gap between liner and host, often requiring grouting for support.

The tool will initially focus on Categories 1 and 2 (tight-fit liners), with close-fit and slip-lining options added later.