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IBG - SA Instrumentation & Control Buyers' Guide

March 2000 News

Futuristix -

Even in the electronic age many industrial sectors make effective use of diaphragm actuators with pneumatic or electro-pneumatic positioners as standard actuators.

Short floating speed and high control forces are criterions resulting in high efficiency, reliability and especially long duty lives.

ARCA diaphragm actuators have proven themselves in the industry for more than 50 years. Anywhere where robust design, functional safety and a specially favourable ratio of costs and performance are required.

The function

Air power moves the spindle via the diaphragm against the spring tension. In the case of decreasing air pressure the spring acts in the opposite direction. The initial spring tension can be adapted to the process data by means of the spring tensioning screw. The support is connecting the actuator with the control valve. At the same time the stroke indicator is the connection to the valve spindle.

The proven ARCA modular system enables the user to combine all valve types with the UMA-types.

Important advantages

*niversal – The same type is applicable for both control and regulation functions.

*Reversible – For reversing the control action, all that is needed is to loosen four screws, flip the actuator through 180° and tighten the screws again. Planning errors can still be corrected on the spot without any problems. (Swapping normally open for normally closed).

*Strong forces – The strong springs in a solid casing made of high quality aluminium alloy are providing these actuators with control forces of up to 4 t.

*Long duty life – All parts are designed for approximately one million strokes. A special diaphragm allows a maximum operating pressure of 600 kPa.

*Mounting facilities – Provision is made for the optional inclusion of a support (NAMUR) provided for positioner, limit switches, stroke limitations or field controller. Several instruments can be mounted directly.

*Low-priced hand adjustment – For emergency operation of valves, hand adjustment devices can also be mounted subsequently.

p Few spare parts, little maintenance – The restriction to four sizes only means that only a few spare parts need to be stored for emergency cases.

Valve & Automation

(031) 579 2593

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Wonderware's South African User Group conference attracts leading executives from the US and Europe

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