Enhanced functionality for Rotork CMA boosts electric process valve control
31 March 2015
Rotork has announced an extensive advancement of CMA electric actuation technology for the operation of process control and choke valves, introducing new options to meet evolving customer and market requirements.
With the latest developments, the innovative CMA design can now be specified with increased functionality encompassing local controls, LCD positional display and programmable fail-to-position performance.
Designed for quarter-turn, rotary or linear operation, robust Rotork CMA actuators perform numerous process control valve, metering pump and damper applications demanding precise position control and continuous modulation. Single-phase or DC electrical power is all that is required for simplified installation and control valve actuation. Explosion proof certification to international standards is available for hazardous area applications.
Local controls now offer manual operation at the valve, combined with a vivid LCD display of valve position which also incorporates critical and non-critical fault symbols. Control selection knobs enable selection of Local, Stop or Remote operation and Open or Close input commands in the Local control mode. Each mode can be locked in place to prevent unauthorised operation. The LCD display shows the valve position as a precise percentage of total valve travel.
For fail-to-position performance, a reserve power pack provides the actuator with the ability to perform a predetermined action on power failure. The power pack also preserves position indication on the LCD display during power failure. Upon restoration of mains power, the power pack is swiftly recharged to ensure continued fail-to-position functionality. Action on power loss is easily configured with the standard CMA HMI interface as part of the user-friendly actuator set-up menu, utilising a 6-segment LCD display and push button configuration.
The maintenance-free CMA drive train, environmentally protected to IP67 and permanently lubricated for operation in sub-zero temperatures as standard, can be mounted in any orientation. Accepting an industry-standard 4-20mA control signal, the CMA provides accurate, repeatable and backlash-free positional control. Resolution is 0.2% on linear and quarter-turn applications, 2 degrees on the multi-turn models. All CMA actuators have output speeds that are adjustable down to 50% of full speed in 10% increments and manual operation is provided as standard. Network compatibility encompasses Rotork Pakscan, HART®, Profibus®, Modbus®, DeviceNet® and Foundation Fieldbus®.
The latest CMA developments follow other recent refinements including upgraded electronics, HMI enhancements and a user selectable increased seating torque/thrust option, enabling a more tailored and cost-effective sizing regime to be applied to the combination of modulating and tight seating demands often found in control valve applications. A new rotary model size has also been introduced.
The combination of all these improvements represents a comprehensive advancement of CMA actuator technology and functionality, focussed on precise process valve control, system simplification and reduced maintenance. In addition to traditional control valves, successful CMA applications include choke valves on shale gas installations, stroke adjusters on metering pumps, precision metering on chemical dosing and the operation of dampers.
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