1. Field of the Invention
The present invention relates to slide valves for fluid catalytic cracking (FCC) units, and more particularly to an actuator for FCC slide valves.
2. Background and Related Art
The actuator is a key component for a fluid catalytic cracking unit's (FCCU) slide valve's proper operation and performance. Currently, most slide valves in the FCCU are hydraulically driven due to the actuation speed requirements and the requirement of a 100% redundant source of power for emergency shut down (ESD) operation, such as secondary ESD hydraulic accumulators. The actuator's requirements are clearly defined in the FCC licensor's and client's specifications and are common in the industry.
Existing actuators continue to have certain deficiencies. In many instances, instrumentation for the actuator is disposed external to the actuator, where it is subject to strikes that can damage the instrumentation. Typically, each actuator is custom designed and manufactured for each project, with the frame elements (side and end plates) welded together. Accordingly, design and manufacture of current actuators is more expensive, time-consuming, and involves significant machining. When such actuators are to be serviced, they are often subject to significant downtime since any replacement actuator/parts needs to be custom manufactured to match the specifications of the prior actuator.
Some existing actuators include a manual actuation element, such as a hand-operated wheel, that permit control of the actuator even when a powered component (e.g. hydraulic piston rod) is not functioning (such as when hydraulic seals need to be replaced). Existing designs utilize a clamshell-type jaw block to selectively transmit force from the hand-operated wheel to a traveling block. Unfortunately, the clamshell-type jaw block tends not to engage as well as might be desired. Accordingly, due to problems such as these, existing actuators fail to fully address all needs within the FCCU valve actuator industry.