Master Flo was the first to introduce the cage-with-external-sleeve trim design. It consists of a ported cage (nozzle) with an external sliding sleeve (flow ring). This arrangement results in flow that impinges in the center of the nozzle thereby dissipating the throttling energy within the process media. The external flow ring also tends to direct the impinging flow upward into the trim and away from the outlet; this further dissipates the throttling energy and contains the residual throttling wear within the hardened trim components. The body outlet is protected from wear because the throttling energy is dissipated before the flow enters the outlet bore.

Such control and containment of wear makes the Master Flo choke valve ideal for high pressures, large pressure drops, and severe-service applications for both liquids and gases.

Our trim is designed for an exceptional shutoff throughout its service life. The tapered seat faces are positioned upstream from the throttling components so that they are not subjected to throttling wear. Incoming flow is diverted away from the sliding seat face by a flow-deflection lip on the leading edge of the flow ring. An intentional dead band between the stationary seat face and the lower nozzle ports ensures that flow is minimal during seating or unseating, which further protects the seat faces from wear.

This trim achieves Class V shutoff per FCI 70-2-1998. Class VI shutoff is also available with suitable actuation.

The stationary trim components are held in place by a retaining sleeve that allows these parts to be easily aligned with the flow ring during valve assembly. Because the trim is mechanically retained rather than threaded into the valve body, all of the valve internals can be removed from the body as a unit without the need for special tools. Once the bonnet has been released from the valve body, the entire choke cylinder (including all internals as well as the actuator, if applicable) is free to be removed. This ensures ease of service and inspection.

The retaining sleeve also functions to control flow in the annular space around the trim by isolating the body bore and directing the flow to the nozzle ports. Through extensive erosion testing, the design of the retaining sleeve has been optimized to extend valve life.

Manually operated valves are supplied with a linear position indicator called a calibration head. This indicator has a square cross section, and it may have a different scale on each of its four faces. This ensures that the valve position can be monitored in the desired units including Cv, bean size, stem travel, or number of turns (micrometer scale).

Our standard scale is the "micrometer" scale, which indicates position by the number of turns of the handwheel. It is read similar to a micrometer caliper by using graduations on the stem nut to achieve a resolution of 1/10 of a turn. This provides exceptional repeatability in trim positioning.