AUMA Actuators Limited offers a range of high performance actuator solutions capable of accurately controlling the opening and closing speed of valves and penstocks, delivering significant benefits in terms of flow control, reduction of water hammer and calm network performance.
Water hammer can be a significant issue in many applications. Valve seats may suffer if they are driven hard to their end positions whenever the valve is closed. A variable speed actuator, gives the control engineer the opportunity to specify the speed of actuation at different points in the cycle. The valve moves quickly through the majority of its cycle, slowing down as it nears the close position, alleviating water hammer problems and extending the life of the valve seat. For emergency situations a ‘fast close’ speed can be specified.
AUMA variable speed multi-turn actuators bring together AUMA’s SAV/SARV actuators and ACV 01.2 actuator controls. Variable speed is achieved by the integral frequency converter within the actuator controls.
Operations from an end position start at zero speed. Speed is increased by a ramp function until the predefined value is reached. Soft stop is achieved by linearly decreasing speed prior to reaching the end position. The gentle operation benefits all valve and actuator components subject to wear.
Higher positioning accuracy is achieved by decreasing the operating speed when approaching the valve setpoint position. This ability is particularly important for the SARV modulating duty model.
Closing at excessive speed results in pressure surges and can cause overloads in both valves and pipeline systems depending on flow conditions. Tailored speed profiles within the AC controller are the ideal solution for controlling closing procedures and maintaining pressures within the permissible range. Speed values may be specified for up to ten sections of travel irrespective of the direction of operation. Thus, the operating speed profile can be tailored to the specific valve requirements.
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