Water & Wastewater Treatment

In the know Technically speaking: pipes and pipelines An example of the data produced by the SmartBall pipe wall assessment 44 | NOVEMBERW 2015 | WWT | www.wwtonline.co.uk technology transfer to water has been mooted, cost and logistical challenges created seemingly insurmountable barriers. That was until very recently. Now some of these techniques are being used in the UK and the advantages these techniques offer are being realised by the water industry. Pressurised pipes First, we'll look at systems for inspection of pressure pipes. One technique which has been extensively used in United States and Canada (over 10,000km of pipeline inspected in water, sewer, oil and gas networks) and is now being used in the UK is a technology called SmartBall. SmartBall is a low- resolution inspection technology. It's also free-swimming, which means that it can be released into a live water main and allowed to roll along, gathering data all day, until it is trapped and removed from the pipe up to 40km downstream. SmartBall has on-board military-grade gyroscopes, so it knows where it is at all times and can plot the course of the pipeline. There are two versions. One type uses acoustics to detect leaks down to the size of a pinhole, even at 1 bar (of pressure). The other type uses electromagnetic waves to carry out condition assessment by determining the level of stress in the pipe wall. Because damaged pipe is more stressed than undamaged pipe, this shows up where problems lie. SmartBall condition assessment also reveals the position of pipe joints. This means that each individual length of pipe can be compared to other lengths of pipe and any anomalies can be located. Where higher resolution is required, alternative tools are available, these again originating from the oil and gas industry. PipeDiver is a free-swimming inspection technology for condition assessment of pipes from 400–3000mm diameter. It carries an array of petals, on which a variety of sensors can be mounted. These provide high-resolution electromagnetic scanning capabilities. The PipeDiver can identify broken metal wires in reinforced concrete pipes, as well as cracking, corrosion, excessive stress, and other defects on a variety of pipe materials. It can autonomously negotiate butterfly valves and bends. As an alternative to free swimming techniques the WRc Sahara platform offers the potential to introduce tethered sensors into a live water main. In addition to the established acoustic sensors used for leak location Gross Metal Loss inspection offers an alternative low-resolution option. It plots the relative thickness of the walls of ferrous pipes. This allows it to detect internal and external corrosion and gives the information needed to determine whether a pipe is in need of further attention. For plastic pipes an alternative approach can be used based on Conductivity Assessment and the same Sahara platform giving a maximum range of 2000m from the point of insertion. The plastic pipe conductivity assessment technique can find and size leaks, identify old repairs, and find 'lost' fittings. It also plots the course of the pipeline, which is traditionally challenging for plastic pipes. Other techniques offer specific advantages. Sonar inspection on the Sahara platform gives an image of the cross-section of the pipe. It has the advantage that it can be used in turbid water. It is ošen used for quantifying the extent of sedimentation and build-up of zebra mussels in raw water mains and can be used in tanks as well as pipes. For some tasks the human eye is unbeatable. Identifying an obstruction, inspecting blocked connections and determining the extent of epoxy lining failure are some of the tasks the CCTV survey has been used for. The Sahara CCTV system is capable of sending back live images up to 2000m from the insertion point, and does not interrupt flow. Gravity sewers We'll now turn our attention to systems for inspecting gravity-flow pipes. WRc quite literally wrote the manual on benchmarking gravity sewer inspection. In that original manual, we identified that current CCTV procedures fall short. Limited field of view, inability to see below the water level, and – the elephant in the room – operator subjectivity all combine to make CCTV surveys somewhat unreliable. Electro Scan doesn't have any of those problems, because it simultaneously scans every point of the clock using electrical currents – which are completely objective. Electro Scan can 'see' defects because any defect that leaks water must also leak electrical current. It can assess their length, height, and infiltration rate – valuable information that cannot be reliably obtained by CCTV methods. As a recent example, in a UK sewer inspection in May 2015, a CCTV survey identified no defects at all. A 15-minute Electro Scan survey identified 11 defects and prioritised them by infiltration capacity – the

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