These Limitorque SBD actuators are operating the main steam stop valves in a power station in Queensland Australia.
Due to high temperature, the valves undergo large thermal transients, this condition is due to the expansion and contraction of the stem, disc, and or valve seat.
The Limitorque SBD utilizes a Belleville spring assembly to allow the drive sleeve and stem nut to float upward or downward while ensuring tight closure or tight backseating of the valve, more importantly, it is also able to compensate for expansion or contraction without valve and or actuator damage.
In addition to high temperature operation, the SBD is the best choice for high speed operation, typically the “lag” of the motor controller and inertia of the motor in high speed operation can provide an over-torque in torque seated applications, furthermore having this type of protection built into the actuator outperforms VSD type of control which is subject to failure and or incorrect setup or configuration.
