Product Bulletin EZ-OVT Trim

EZ-OVT Trim			Figures Print Version Collapse Expand

Fisher ® EZ-Overtravel (EZ-OVT) Valve Trim

EZ-OVT Trim Description Fisher EZ-OVT valve trim is a patented, dual seat valve trim, designed to maintain long term tight shutoff in on-off services that contain particulates in the flow stream such as catalyst fines. An example of this type of service is the valves used to control and purge the hydrogen and nitrogen transfer gases used on the UOP continuous catalytic regeneration (CCR) refining process.
Control valves for this application must provide bubble tight shutoff to stop the transfer gas flow and be able to maintain this performance, even in the presence of catalyst and their fines. Ordinary single soft seated trim cannot achieve this function due to premature failure.

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Trim Features

Dual seat design—EZ-OVT trim features a dual seat design that includes a primary soft seat and a secondary metal seat. This dual seat design provides for long term ANSI and IEC Class VI shutoff.
Off-the-seat deadband—A double deadband area is built into the trim to inhibit erosive flow across the seating surfaces as the trim starts to open.
Flow deflector—A special flow deflector directs the flow stream away from the seating surfaces once the valve has traveled off the seat.
Simple design—The trim has no moving parts (other than standard sliding-stem plug action) that can become inoperative due to the buildup of flow stream particulate such as catalyst fines.

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Principle of Operation The EZ-OVT valve trim is shown seated in figure 1. When on the seat, the primary shutoff is provided by the soft seat insert. The metal seat provides a secondary seat.
In figure 2 the trim is shown just off the seat. At this point in travel, the deadband areas are fully engaged to inhibit flow across the trim seating surfaces.
In figure 3, the trim is shown at 20% travel. At this travel the trim is just starting to move out of the deadband areas to allow for flow.
With the seating surfaces significantly out of the flow path, the tight tolerances between the valve plug and the seat ring open enough to allow flow (see
figure 4). The flow deflector directs the flow stream away from the valve plug seats.
The seating surface is completely removed from the flow path, enabling full flow through the trim (see figure 5). The flow deflector is continually directing the flow stream away from the valve plug seats.

Note
Neither Emerson, Emerson Process Management, nor any of their affiliated entities assumes responsibility for the selection, use, or maintenance of any product. Responsibility for the selection, use, and maintenance of any product remains with the purchaser and end-user.

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