Electrofusion-welded PE piping: when to choose it for industrial water and effluent

Technical corner · Piping · 7 min read

For industrial water, effluent or treatment installations, the choice of piping determines the life of the installation and the installation time. High-density polyethylene (HDPE) joined by electrofusion, offered in particular by GF Piping Systems, has become the standard in many applications. Here is how to choose it, size it and get the welds right.

PE, PVC or stainless steel: which material?

Each material has its place. The table gives general guidelines; the final choice always depends on the fluid, pressure, temperature and environment.

PE stands out for its resistance to corrosion and impact, and for its flexibility, which tolerates small movements and vibrations. For wastewater or effluent at ambient temperature, it is often the most durable solution.

HDPE pipes: drinking water, pressure mains, gas

HDPE pipes today are almost all PE100, stronger than the older PE80. Their use is identified by colour: blue stripes for drinking water, yellow or orange for gas, brown for sewerage and pressurised wastewater, black for other uses. A pipe for drinking water must also be approved for contact with water intended for human consumption.

For pressure, we work in SDR (Standard Dimension Ratio): the ratio between outside diameter and wall thickness. An SDR 11 pipe in Ø63 therefore has a 63 ÷ 11 ≈ 5.8 mm wall. The lower the SDR, the thicker the wall and the higher the allowable pressure. For water at 20 °C, a PE100 SDR 11 pipe corresponds to PN 16 and an SDR 17 to PN 10. For gas, allowable pressures are lower, because the safety factor is higher.

Remember: for the same outside diameter, the inside diameter decreases as the wall gets thicker. For a given flow, check velocity and pressure losses with the actual inside diameter.

DN, inches or outside diameter: finding your way

This is the most common source of error on site. Steel pipes and threads are designated in DN or inches, whereas PE pipes are designated by their outside diameter in mm (d20, d63, d110…). A PE pipe “50” therefore has nothing to do with a DN50.

Example: you have a valve or pump with a 2″ threaded connection. In the table, 2″ corresponds to DN50, and the equivalent PE pipe is d63. So you need a d63 PE pipe and a d63 × 2″ PE transition fitting (BSP thread). Then choose the SDR according to pressure: in PE100 SDR 11, the d63 pipe has a 5.8 mm wall, an inside diameter of about 51 mm, and is rated 16 bar for water at 20 °C.

Electrofusion: a homogeneous joint

The electrofusion fitting contains a resistance wire. The welding unit passes a controlled current through it: the PE of the fitting and of the pipe melt and blend. Once cooled, the joint forms a single piece, with no glue or seal. Welding parameters are read from the fitting’s barcode, which limits errors.

Pitfalls to avoid

• Skipping the scraping. The pipe surface oxidises: without scraping, fusion is poor, even if the weld looks fine.
• Touching the cleaned zone. Fingers, dust or moisture are enough to weaken the joint.
• Forgetting the clamps. A pipe that moves during welding or cooling gives a defective joint.
• Pressurising too early. The manufacturer’s cooling times must be respected before any load or pressure test.
• Confusing DN and outside diameter when ordering: always check with the conversion table.

A real example

At Filao, ITS connected a DAF to an activated carbon silo to test additional wastewater treatment: submersible pump, electrofusion-welded GF PE piping, return to the sewer with the flow meter kept.

A piping project for water or effluent? Let’s talk.