Mechanical fail-safe solutions exist for electric driven valves, but mainly for on-off applications.
The Mokveld axial flow valves require very low forces, since they are fully pressure balanced.
This inherent design feature makes electric fail-safe control valves possible - even for large or high pressure valves.
Two options exist for a fail-safe action in case the power supply is lost, either using spring action or a power pack such as a capacitor.
Mokveld supplied two 10 inch ASME 1500 Lbs subsea anti-surge control valves equipped with spring opening fail-safe electric actuators to a client.
These Mokveld anti-surge valves protected the subsea compressor by opening in less than two seconds.
The second solution for another client was by using a power pack.
In this case by using capacitors, these valves were installed on a metering and pressure reducing station and were operating satisfactorily for more than 12 months.
Two 12 inch ASME 600 Lbs control valves in an active/monitor configuration regulate the downstream pressure.
The latest generation capacitors are highly reliable and can be constantly monitored to further improve reliability and availability.
A power pack solution can also be used to improve plant availability, production and/or control can continue in case the power in the plant is lost. The low force and thus low power consumption of the Mokveld axial control valves makes it the optimum solution for electric actuation with fail-safe position or high availability requirements.
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