Apparatus and method for controlling fluid flow

摘要

A choke system or valve assembly includes a valve having an orifice through which fluid flow can be choked or controlled. An actuator is adapted to position the valve at one or more incremental positions between an open position and a closed position. The valve, orifice, and actuator may be adapted to provide a substantially consistent (or otherwise predetermined) change in pressure drop and flow rate between different valve positions. This is accomplished by varying the flow area of the valve orifice non-linearly as the valve is shifted or stepped through the several valve positions. Another feature is the ability of the actuator in conjunction with an indexing mechanism to provide substantially precise control of the valve orifice through the several valve positions. The indexing mechanism is separated into two portions: an indexer device to index the actuator through the several valve positions; and a positioner device to maintain the valve at a fixed position after the actuator has shifted the valve to the next incremental position.