The Swedish company Somas Instrument AB has designed a new pneumatic actuator(type A) in which the play between the valve and the actuator has been eliminated. This is achieved via a clamping joint that in combination with a commercial bushing leads to high friction between the actuator's drive shaft and the valve's spindle. According to the company, this will considerably increase the possibilities for process optimisation and safer operation.

"Development within electronic equipment has progressed extremely rapidly in recent years. Computerised control and regulation techniques have provided the industry with sophisticated instruments for reading different measurements. However, development on the mechanical side has not moved along as quickly. This is a step towards catching up," says Göran Andersson, head of technology at Somas Instrument AB in Säffle, Sweden.
"In order to be able to mount the actuator on a valve, there must be a certain amount of play between the actuator's hollow shaft and the valve's spindle. With new processing equipment, we've been able to successively reduce the tolerances, but there is always a small amount of play, which can be identified.

When a actuator receives a small control signal, it can happen that the valve doesn't move because of this play."

Varies Too Much
"The risk is that the regulator discrepancy becomes too large," explains Andersson. "The 'should be value' and the 'is value' don't agree, which can lead to disruptions in the process. This is where our new technology comes in."
The company's solution, for which a patent application has been submitted, is based on a clamping joint that increases the friction between the actuator's drive shaft and the valve spindle in order to eliminate the play. The slightest movement in the actuator affects the valve's spindle.
"One can, for example, regulate the temperature to within a tenth of a degree instead of a whole degree, simply because the valve moves more exactly," Andersson points out.
The new concept, with the designation actuator type A, includes different sized, double-action and single-action units from 55 up to 20,000 Nm. The actuators are said to have good corrosion resistance against exterior environments. This also includes a solution for eliminating the play in the transfer between the actuator and the positioner.

For more than 50 years, Somas instrument has developed and manufactured regulator and shutdown valves using acid-proof stainless steel and other alloys. The company's head office is located in Säffle, Sweden and subsidiaries are found in Norway and France.

Image text:
Somas has developed a new pneumatic actuator (type A) in which the play between the actuator and the valve has been eliminated with the aid of a clamping joint. This solution, for which a patent application has been submitted, shall increase the opportunities for process optimisation.

For further information, please contact:
Young & Cunningham Ltd.
42 Methil Street, Scotstoun, GLASGOW, G14 0AN
Telephone: 141 954 50 11
Fax 141 954 11 72
E-mail: sales@yandc.co.uk
Website: www.somas.co.uk

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