The skills to stay in the frame

Predictive maintenance, extending the use of open control systems and off-site repair - there is more to an actuation framework agreement than supply, as Rotork Controls reports

Rotork Controls was recently awarded a second term for its valve actuation framework agreement with Thames, renewing the original five-year agreement - one of the first of its kind with a UK water utility.

In fact, Rotork has experienced a dramatic development in its association with Thames during the course of the first five years, encompassing many areas and services that go beyond the scope of a simple supplier relationship.

The first development involves the actuation equipment itself and in particular the growth of monitoring and control system sophistication, both within the actuator itself and communications with plant supervisory systems. Rotork has pioneered the concept of built-in data loggers, enabling the history of an individual valve to be gathered, downloaded to a hand-held device and used to assist with predictive maintenance. Alternatively, some of this information can be communicated along the same route as the actuator's remote control system, which increasingly these days consists of one of the dominant open two-wire digital loop control protocols.

Rotork quickly introduced two-wire connectivity for its electric actuator products as new digital control architectures and strategies have become popular with end users. The company was the first actuator manufacturer to launch a proprietary digital control system, Pakscan, controlling actuators, pumps and associated plant instrumentation on the same loop. Pakscan has been developed further and provides an effective tool, although Rotork now offers connectivity with a number of open control systems favoured by the water industry including the Profibus and DeviceNet.

Mike Dale, Rotork's service and site projects manager takes up the story: "The German origins of Profibus possibly gave the initial impression that our European competitors had the edge when it came to digital control systems. In fact, we never took our eye off the ball and were always quick to offer connectivity on new products or as an on-site retro-fit on nearly all our ranges. We have also invested to ensure that we can fully support all our connectivity options. This has been an essential ingredient in the framework environment at Thames Water and elsewhere.

"Much of the recent work on both new plant and modernisations has included the introduction or extension of Profibus systems, whilst those planned for the near future will probably also include DeviceNet. If we were unable to respond, then our framework status would be affected, it's as simple as that."

Other aspects of Rotork's relationship with Thames Water are more specialised than simply supplying equipment of the right specification for new-builds and refurbishments. Thames places a high emphasis on asset care - increasing plant reliability, reducing maintenance requirements and lowering operating costs. With AMP3 this has become an even more important priority. Rotork has therefore become progressively more involved in these aspects, performing audits and 'health checks' on installed equipment, advising on the best course of action and carrying out maintenance and repair programmes, either on-site or in the workshop.

A recent example involves ten of Thames' key sewage pumping stations in east London, where Rotork has been working in collaboration with the water company's engineers to ensure the continued reliability of actuators and controls in order to maintain the integrity of the pumping stations, even in the event of a '20-year flood'.

Mike Dale explains: "We carried out a predictive maintenance audit, going through a checklist drawn-up in conjunction with Thames Water and Engenica engineers.

"Some of these actuators are over 20-years old, operating in really harsh environments and subjected to corrosive elements from day one. We were looking out for oil leaks, rusting and water ingress, most of which could be repaired on-site, but we also took the precaution of replacing O-ring seals and fasteners on all the actuators. Sometimes, they needed more than on-site maintenance in which case we took them back to the factory, replaced damaged components, put them on a test rig and returned them to site."

These programmes are proving to be popular not only with the end user, where health checks on existing plants are expected to increase, but also with contractors working on plant extensions and modernisation programmes. Often the contractor is calling in Rotork at an early stage for specialised advice on the actuated valve and control system aspects of the project. Consultation can result in an equally efficient and far more economical solution than simply fitting new actuators throughout the works.

For example, Rotork can recommend fitting brand new actuators only on those valves identified as critical, moving the existing actuators from those valves to other, less critical valves in the plant, and possibly using the actuators from those valves to motorise manually-operated valves or replace obsolete actuation equipment from any manufacturer. At each stage, unless they cannot be supported with spares, actuators can be refurbished and re-installed with the benefit of the same warranty as a new unit. In this way, throwing an old actuator away only becomes an option when no possible future duty can be identified for it or the cost of repair makes it uneconomic. Cost savings are therefore significant.

In some cases, the retrofitting of actuators on previously hand-operated valves can make a dramatic difference. One such site, known as The Catacombs, is at Walton-on-Thames, where water is abstracted from the river and stored in the adjacent Queen Elizabeth II and Knight & Bessborough reservoirs. Up to 100M gallons of water per day pass through the pump station's 48 inch pipework and valves, most of which date back to the 1920s


Communications | consultation


Waste & resource management

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