Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | sepTember 2014 | 43 Digging deeper A new era of condition assessment methods The setting of challenging performance commit- ments to avoid interruptions to service by utilities in their latest price control review is also driving innovation in the development of sensing tech- niques to determine the condition and leak flow rates of pipelines in situ. Since WRc produced the guidance for the water sector on structural condi- tion assessment of water mains, water companies have relied on traditional methods of removing pipe samples and coupons for off-site measure- ment of remaining wall thickness and tubercula- tion and/or exposing the pipe and taking a series of wall thickness measurements using ultrasound from the outside. This can only ever give a snap- shot of pipeline condition and hence the sector has been looking for alternative methods to assess condition using in-pipe methods. The challenge is compounded by the fact that no single condition assessment technology or technique can meet the needs of all asset owners: each has its 'sphere of influence' which depends, for example, on pipeline diameter, material and pipeline access. WRc recently completed a review of alternative existing technologies available to deploy to allow us to define our investment into novel sensors for the water and wastewater sectors. A growing need for sensors which could determine the condition of plastic rising mains, large diameter cementations trunk mains, and smaller-diameter cast iron mains was identified. At the same time, a number of our clients have expressed a real need to tackle increasing numbers of trunk main failures and understand the condi- tion of critical assets such as pipe bridges, sewers crossing railways and strategic rising mains. The consequential costs of asset failure on any of the latter asset types runs into millions of pounds and hence a step change in failure prediction – and just-in-time intervention – is needed. New sensor development WRc's contribution to this field has been the recent development of a new sensor for non-ferrous pres- surised pipelines which has been tested in both water and wastewater systems and is now being developed to operate in medium-pressure gas pipelines. Using WRc's Sahara tethered pipeline inspection system to deploy the sensor into the pipeline through a small tapping point, the new sensor detects changes in electrical conductivity to determine the location of metallic fittings and leak pathways (each of which have different conductiv- ity 'signatures'). This has proved to be invaluable in sewerage rising mains for detecting previous repairs where metal repair clamps were used. This is particularly relevant where repair records were defective or absent, and where renovation or replacement techniques could have been compro- mised without the knowledge that metal fittings were present. Also exciting is the fact that this sen- sor can identify leaks with considerable sensitivity; weeping joints where seals were poorly made or had failed are clearly visible. Recognising that a sizeable proportion of water and gas distribution networks are constructed from ferrous materials, WRc has also been looking at magnetic sensing techniques to identify metallic wall thinning. There is a critical minimum wall thickness below which the pipeline integrity may be compromised through dynamic operation, and hence there is need to measure wall thick- ness accurately to estimate remaining asset life. Ultrasound has a place here, but is challenging to implement in larger pipelines and hence WRc is working on developing and trialling an alterna- tive method which can give a self-calibrated wall thickness measurement for both small and larger diameter mains. Initial tests are encouraging but more validation work is required. Both techniques have been developed in-house with a group of wa- ter companies and are being offered commercially through WRc's in-pipe inspection business. Greater cost efficiency = greater PE joint leakage? There is real concern (and a whole lot of finger- pointing) about the quality of polyethylene (PE) electrofusion (EF) jointing practice in the UK water sector. Manufacturers produce pipeline products which meet or exceed the existing product stand- ards. Water companies blame poor workmanship, and recent UKWIR research appears to confirm that on-site workmanship is an issue. However, contractors complain of difficult site conditions and pipeline ovality which, while not out of spec, increases the time taken to make a good PE joint and hence diminishes the profitability of their work. Utilities and their contractors are reaching a tipping point in terms of squeezing out further efficiencies. Is it fair to say that water companies are now reaping the 'rewards' of the rate card they have set their contractors? In this climate of claim and counter-claim (and insufficient hard evidence) it became obvious that no one party could move the debate on. WRc, with the agreement of a core set of manufactur- ers, contractors and utility companies, set up the Leakage and Excavations Innovation Action Group (LEIAG) to tackle the strategic issues of today and tomorrow to see if, together, we could deliver the necessary evidence, policy and actions that would allow the utilities sector to make a step change towards our goal of zero leakage, zero excavations. Our initial research suggests that the size of the prize is huge, but that we need to move forward on more than one front; better training, yes; higher product standards, possibly; better supervision, certainly. A methodical approach has been developed by Wrc which deploys a mixture of desk-top and in-pipe services to efficiently and effectively target interventions based on actual asset condition

• Cover