What is the Valve Failure Position?
Despite how it sounds, “valve failure” does not mean that the valve itself has failed. In the event of power loss, electric actuators will cause their control valves to “fail,” or stop, in one of three positions—open, closed, or in place. Today we will look at what these three options mean.
The term “power” here refers to the means by which the actuator is moved, be that air pressure, gas pressure, or electric power. Air or gas pressure may be lost due to freezing, and electricity may be lost during a seasonal thunderstorm. At some point your site will experience one of these power loss events, and it is important to carefully consider which fail action you select on your valves, as this will affect local equipment and production significantly.
Fails Open (FO) means that when there is a loss of signal, the valve opens. This is typically chosen to prevent overpressure in the event of a blocked line or in case of catastrophic failure. This may also be referred to as “spring to open” or “air to close.”
Fails Closed (FC) means that when the signal is lost, the valve will close. This may be chosen in the case of a steam injection well. Uncontrolled steam is extremely dangerous, so the valve closing automatically would be the best option to maintain control. This is also referred to as “spring to close” or “air to open.”
Fails In Place means that the valve does not change or react when power is lost. This is ideal for applications where the process cannot be shut down or it is undesired to do so.