Extruded high density polyethylene pipe is increasingly used as a replacement for traditional materials in infrastructure projects. But now even sewer structures, which traditionally would be built from precast concrete, are being made from extruded polymer.
England's Anglia Water is the water and sewerage company that supplies the East Anglia region in the United Kingdom. In August, Anglia Water installed a new sewer system, with an HDPE pumping station chamber rather than one produced from concrete.
The pipe — and pumping station — for the project was manufactured in Wales by Asset International Ltd., the UK licensee of the Weholite and WehoPanel systems, developed by Uponor Infra Ltd. of Vaasa, Finland.
The pumping station for the Cambridge Sewerage Treatment Works is 15 meters long, 4.5 meters wide and 5 meters high. It was delivered Aug. 12 in two sections, and was assembled and welded on site.
Simon Thomas, Asset International's managing director, explained the Weholite system: “The pipe is made from a hollow box section which we extrude using standard extrusion equipment. So, in effect, instead of making a round pipe, we're making a rectangular box. And then we spirally wind [the rectangular box profile] around a drum to make a pipe.”
The WehoPanel process takes away the winding stage. Thomas said.
“In this case, all we're doing is cutting lengths of profile, before they go to the drum. So we end up with straight lengths of profile. Then we have a machine that welds those together to form panels known as WehoPanels.
“We have a team of fabricators that erect the WehoPanels into all sorts of weird and wonderful shapes; in this case it's a big box that's going to be a pumping station.”
The box sections are about 250 millimeters wide and are welded together on a machine into pieces that are 2 meters wide.
“I liken it to putting up plasterboard,” he said. “We turn the profiles we weld on the machine into panels of 2 meters wide. And then the panels are erected in our prefabrication shop and welded by hand.”
The process used to join the extruded panels is heat extrusion welding. Thomas explained.
Asset started producing Weholite pipes in 1996, with two production lines making pipes up to 2.2 meters in diameter. In 2000 the company added a third production line to produce pipe of a 3 meter diameter.
“Then in 2008 we went one better,” said Thomas, “and put in a fourth line to take us up to 3.5 meter diameter which is, as you can imagine, a hell of a big pipe.