Retrofit upgrade replaces actuators after 60 years

Paul Boughton

Kieran Hicks reports on how valve actuators have clocked up 60 years of service.

Some of the very first valve actuators to carry the Rotork name are being replaced with the latest intelligent IQ3 actuators after 60 years of unbroken service on a demanding and critical process control duty in the aerospace industry.

Dating from 1953, the Rotork Model 100A actuators were part of a contract to operate the valves on one of the world's first large scale supersonic wind tunnels.

Designed and built by the then newly formed Aircraft Research Association at Bedford, the Transonic Wind Tunnel was created to keep the British aviation industry at the cutting edge of technology by testing the effects of supersonic speeds on new aircraft designs. The facility is operated by a 25,000hp AC motor and a 13,000hp DC motor.

In addition, a 10,000hp compressor is used to provide extra power to enable testing at high transonic and supersonic speeds up to mach 1.4 (1065mph approx). Since the wind tunnel was first commissioned in 1956 it has been in virtually continuous daily operation, testing military and civil aircraft from around the world.

Although designed for isolating valves, the Rotork 100A actuators have been performing modulating duties throughout their years of service, constantly altering the position of large gate valves by small degrees to control the level of wind speeds and provide the data that is needed for the highly accurate measurement of test results. The automation of this process with a bespoke control system incorporating a Modbus control network has necessitated the replacement of these units with new IQ3M actuators that are specifically designed for modulating duties.

Because there is a constant demand to use the wind tunnel, careful and detailed planning has taken place to ensure that the retrofit operations can be successfully completed in the brief periods of time that are available between test programmes. The restricted access around the valves also demands particular attention. Detailed planning paid off when the first two actuators were removed and the replacement IQ3M actuators installed and commissioned in two days, half the allocated time allowed before the wind tunnel was due to re-start operations.

Richard Harvey, Senior Process Engineer at the Aircraft Research Association, explains: "The existing Rotork 100A actuators have functioned very well considering they are being used well outside of their rated specification, but at 60 years old they were due for retirement. The replacement valve drives needed to be very reliable and have an accurate positional indication as they are vital for the operation of the tunnel and the data we collect. Rotork pointed us in the direction of the new IQ3M35 actuator. I was delighted with the vast amount of information and precise control that I could achieve using the Modbus interface card. The installation was a success and the tunnel drivers have reported that the new actuators provide them with much better control."

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Kieran Hicks is with Rotork Controls Ltd, Bath, England, UK.

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