Located on South Quay, close to a gas holder, the 200 metre sections of two-way fed main were being abandoned so that governors could be installed in order to connect into a medium pressure system.
Two x two-way flow stop operations, using a total of eight bags, were carried out by a two-man team using the Foam Bag™ technique, developed by Steve Vick International. The Foam Bags were introduced into each of the live mains, either side of the cut-off points, via standpipes installed into 2” tappings through standard Wask bases.
The bags are constructed of semi-porous fabric and have an integral steel support bar to which a nylon fill tube is fitted. Through this an expanding resin foam is introduced using a mix and inject machine. Due to the large diameter of this main, the bags were of a double-skin construction. The inner bags were filled initially and allowed to cure before the outer bags were filled. On full expansion, some of the foam seeps through the bag to adhere to the surface of the main creating a more effective seal.
The flow stopping project took half a day to complete. Filling of the Foam Bags™ began at 09.00 and was completed by 10.30. By 14.30, the main had been cut and capped. Billy Hay, Distribution Manager for Manx Gas, reported that the job went perfectly. “Using conventional, mechanical flow stopping methods would have cost far more than the Foam Bag™ operation,” he said.
Date Published – 11th August 2005