Innovative technology brings mains to the Ice Age
22 April 2009
A pioneering experiment using ice could prove to be the way forward for removing iron from water mains.
Wessex Water said a trial by Bristol University researchers along a small stretch of main was so successful it may have been just the "tip of the iceberg" for things to come.
Traditionally polyurethane foam swabs known as solid plugs or pigs were propelled through the main with water, scouring the pipe clean as they went. But early indications show “ice pigs”, the new product that underwent testing in the Wessex Water region, have broken down several problems caused by the conventional process.
Ice pigging involves cleaning by injecting ice slush into a rising main before forcing it through the pipe with water. The trial, which took place over a 1.6 km stretch of a 150 mm diameter potable raw main in West Lavington, Wiltshire, produced results deemed ideal for pipe cleaning.
Although solid plugs have been used successfully for a number of years to clear and clean pipes in various industries using common methods such as foam swabbing and air scouring, the process has several drawbacks apparent when used in complex pipes.
Matthew Maggs, a production manager for Wessex Water, said: “Traditional foam swabbing involves installing several access points along a main which can be both costly and time consuming. While extensive flushing can be carried out, it’s sometimes to no avail due to the thickness of iron coating, which builds up in the main over time.
“Problems also arise in the complicated internal workings of a pipe which could cause the solid pigs to become intransigent, due to the potential build up of sediment ahead of the foam.”
A viable solution to the problem was needed and it was Professor Joe Quarini in Bristol University’s Department of Mechanical Engineering, who invented ice pigging, which initial tests suggest might just fly.
Researchers in partnership with Wessex Water and Bristol Water were able to develop this pioneering method using nine tones of slush during a two-day trial.
During the experiment in the Wessex Water region ice was treated with a freezing suppressant, which allowed it to retain its slush consistency without sticking to itself.
From this, a soft plug was formed and pushed along, scouring the main effectively and adapting its shape to navigate through complex pipe work with ease.
Samples of slush were taken at the exit point and initial analysis proved promising.
“The first pass created a large volume of sludge which was flushed away through the extraction hydrant and removed by tankers,” said Mr Maggs.
“Over the next series of passes we saw a dramatic drop in the amount of sludge being ejected and by the final pass the ice plug was clean at extraction point.”
Bristol University staff and students were monitoring and sampling the resultant waste and will provide a report which will quantify the amount of iron sediment which has been removed.
Mr Maggs added: “In this instance by using ice pigs we did not need to install multiple chambers and pigging points thus saving time and money.
“I’m convinced this technique could be used in other areas of our water supply network which spans more than 11,000 km.”
Joe Quarini, Professor of Process Engineering, said: "We are delighted that the technology is being adopted by the water industry. We all believe that it represents a paradigm shift in pipe cleaning, making difficult, time consuming and expensive tasks easy and fast to undertake as well as making some previously impossible jobs doable."