Process Equipment Update
Fast-acting failsafe actuator T
he design and manufacture of customised valve actuators is one of the main areas of activity for
Rotork-Hiller, writes Mike Baker. Among recent examples, an enquiry to
build a fast-acting failsafe stop valve actuator for a plant fire-fighting system demanded an exceptionally innovative design solution. The specification called for a very
compact pneumatically operated actuator, with no springs for the failsafe function, necessitating the provision of a stored energy accumulator. The addition of a conventional
accumulator would have exceeded the dimensional constraints of the specification, so Rotork-Hiller engineers conceived a radical new design which incorporated the accumulator within the pneumatic actuator. The design not only eliminated the size problem but also freed-up additional space for mounting the controls to the actuator. These controls include filters, regulators, solenoid valves and pressure switches, contained within overall actuator dimensions of 470 x 584 x 680mm (18½ x 23 x 26¾ inches).
Fig. 1. Rotork-Hiller’s compact design is the company’s first to incorporate a failsafe stored energy accumulator within the dimensions of a fast-acting pneumatic actuator.
The controls reduce the customer’s
supply pressure of 45Barg (652psig) to 31Barg (450psig), which is pumped into the accumulator to provide approximately 4.4 litres (1 US gallon) of storage capacity. The actuator delivers a maximum thrust of 27,617N (6,209lbs).
When asked about the challenges presented by this project, Rotork-Hiller’s Engineering Manager replied: “Our biggest challenge was the ability to meet the customer’s expectations with a unique actuator design, built to stringent specifications and regulatory requirements and supplied within an expedited schedule. With the innovation applied to the design, our lead engineer on the project has confirmed that all expectations have been met or exceeded. “One of the best features of this design is
the pneumatic system redundancy with the ability to support the failsafe function of the valve in a simplified stand-alone package. The integration of the nitrogen storage accumulator within the actuator body itself can be further developed and potentially applied to all existing Rotork-Hiller failsafe pneumatic designs.” n
For more information ✔ at
www.engineerlive.com/epe
Mike Baker is with Rotork-Hiller, part of the Rotork Group, Bath, England, UK.
www.rotork.com
Removing solids in the 4 to 100+ micron range S
WECO’s latest in fine particle separation for wet processing is SWECO Hydrocyclone Systems.
These systems provide a method for removing solid particles in the 4 to 100+ micron range from various slurries.
Hydrocyclones typically
make finer separations than are practical with screening separators and at significantly higher capacities. In many applications cyclones can be used in place of decanting centrifuges, providing the desired result at lower cost. Hydrocyclones are supplied in either an open-manifold or a
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Packed-Vessel configuration. Manifolds (radial or linear orientation) utilise 2-, 4-, 5-, or 10-inch diameter cyclones while Packed Vessels contain either 1- or 2-inch diameter cyclones. Both configurations can process feed rates from 10 to 3,000 gallons per minute, depending on the size and number of hydrocyclones installed in the system. The use of SWECO Hydrocyclones can lower
the capital, operating, and maintenance costs of a solids- separation system. Installation is straightforward, as the
hydrocyclone system is shipped
assembled. Reliable operation of the system only requires a consistent
feed at a steady pressure. The only moving parts are the feed pump and the slurry itself. Energy costs are much lower than those of a large centrifuge and the maintenance, when needed, is much simpler and easier to accomplish. For demanding applications, SWECO can provide a hydrocyclone system integrated with a SWECO Centrifuge, Rectangular Separator, or Round Separator. The hydrocyclone system will concentrate the solids, reducing the volume to be handled by the centrifuge or screener. A smaller centrifuge or screener can then be selected at a considerable reduction in cost. n
For more information ✔ at
www.engineerlive.com/epe
SWECO is based in Florence, KY, USA.
www.sweco.com
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