Valves, Actuators & Pump Control


Efficient control volve actuation

February 2009 Valves, Actuators & Pump Control

For the first time in more than 20 years the standard Mitech globe control valve, now Spirax Mitech, is undergoing significant changes. These changes are centred on the actuator, and are aimed at making the valve more user-friendly and reducing long-term operating costs.

Visually, the most obvious change is the replacement of the traditional four or more mounting bars with a two-pillar cast yoke. This yoke has been designed in such a way that it is very easy to remove and re-fit without the need for any special tooling or any risk of it loosening due to vibration.

This change makes it easier to maintain the gland flange tension or to replace the packing, reduces the time required to fit or remove the actuator and simplifies affecting a trim change in the valve when a change in stroke length is required.

Further advantages brought about by the yoke-mounted actuator include: a split-block stem clamp; jam nuts that retain the gland flanges under conditions of severe vibration; better flexibility in positioner mounting (via the Namur mounting rib) and the use of composite cylinder tubes as standard.

According to the company the benefits of the re-design include the following:

* Significant reduction in the cost of the actuator.

* Easy replacement of the cylinder tube.

* Reduced friction improves the accuracy of control and reduces the dead-band.

* Reduced mass and sturdier mounting arrangement improve permissible earthquake loading.

* Improved ease of lifting and rigging are achieved due to lighter weight.

* Carbon steel and stainless steel cylinder barrels are available as options.

The standard composite cylinder is designed for operation at temperatures up to 180°C, making it suitable for outdoor use with the fail action of the actuator remaining field-reversible.

For more information contact Debbie Groenewald, Spirax Sarco, +27 (0)11 230 1300, [email protected], www.spiraxsarco.com



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