Case study - Commissioning Test Identifies Leak in Newly Laid Mains

The challenge

When mains water pipes are first laid they are subjected to pressure tests, typically at levels considerably above normal working pressures to ensure they can withstand any surge that may occur. In the case of one newly laid 800mm diameter main that ran for 1500m, the contractor for the water services company tested the pipeline at a pressure of 13 bar. However, when the main repeatedly failed the pressure test, the contractor suspected a leak. Unable to find any obvious source, it was decided to call upon the expertise of WRc to conduct a survey that would hopefully resolve matters.

The solution

Using its Sahara® acoustic leak detection umbilical system and accompanying location device, a special combination of technology that is not available elsewhere, WRC performed a pull-through pipeline commission survey. The equipment was pulled to the end of the mains using a rope that had been pre-positioned by a submersible ROV (remotely operated vehicle). After a 2-3 hour process of filling the large main using a nearby 2” hydrant supply at 13 bar, WRc’s equipment was gradually pulled back along the pipeline. Throughout the test, the pipeline remained connected to the hydrant supply to maintain pressure.

The outcome

Despite staff from the contractor exclaiming “it can’t be there”, a leak was detected on a joint. This meant that either the joint had not been secured properly, or there was a manufacturer’s defect. The joint was replaced in March 2017 and the mains pipeline immediately passed its pressure test at 13 bar.

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