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


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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

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