Actuators are up to scratch

Louise Smyth

Electric control valve actuation passes the glass-making test, says Katie Wilson

Following extensive testing, leading glass container manufacturers are specifying electric actuators for a critical valve control function in the glass making process.

The valves are used to control the temperature and pressure in the furnaces by regulating the air and gas mixture with extreme precision. Maintaining a constant temperature and pressure is essential for energy efficient glass making. Traditionally, the industry uses various pneumatic and electric actuators for the modulating and isolating valves involved, but has recognised the need for a more reliable and energy efficient universal solution for this application.

Tests have demonstrated that the Rotork CMA electric actuator out-performs existing equipment. Its makers says that it provides improved precision, reliability and energy savings in a compact and easy to set product that is available in a range of sizes that suit all the various valve types encountered. In addition, the CMA’s versatile ability to interface with industry-standard 4-20mA or RIRO (Remote In Remote Out) control signals enables plants in different countries to standardise on the same product.

Suitable for a variety of applications

The actuators are designed for quarter-turn, multi-turn or linear process valve applications demanding precise positional 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 provide manual operation at the valve, combined with an LCD display of valve position that 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.

The maintenance-free CMA drivetrain, 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 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.

Ideal solution for revamps

Glass-making furnace revamps, usually taking place after a period of 10 years operation, provide the opportunity to introduce the upgrade, which typically involves up to 40 valves on each furnace. Following the success of the tests, several hundred ATEX certified explosion-proof CMA actuators have been installed during revamps around the world.

Katie Wilson is with Rotork Controls USA.

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