Model AGVC
LogoManufactured in Australia

DELATITE STEP TRIM
DEL-ST

The Delatite Step Trim minimises cavitation damage in fluids that could contain
some solid particles, or low flow situations where small CV values are required.
The trim has a series of steps on either the plug or the seat which force the fluid
to take a torturous path between the plug and the seat.

This is most evident when the valve is opening or when the valve is operating
close to the seat, at this point cavitation is generally at it's most aggressive.
The trim has been designed to allow solids to flow through the valve without
blockage of the trim.
THE CAVITATION PROBLEM
Cavitation damage is one of the major causes of control valve failure

Cavitation occurs when the pressure of a fluid flowing through the restriction
of the seat in a control valve drops below the vapour pressure of the fluid, and
then the fluid pressure recovers to above the vapour pressure as the fluid leaves
the valve.
The first stage of cavitation occurs when the fluid pressure drops below the vapour pressure and bubbles form in and around the vena contracta of the valve (seat area) As the fluid continues it's path through the valve but after the vena contracta the pressure of the fluid begins to recover.
When the fluid pressure recovers to the point where it is just over the fluid vapour pressure the bubbles suddenly implode. The implosion forces are very high and the bubbles implode near a metal surface a small amount of metal will be removed every time a bubble implodes near the valve body or valve trim. This is know as cavitation damage.
THE DELATITE SOLUTION
The aim of the Delatite Step Trim is to keep the fluid pressure above the fluid
vapour pressure so that cavitation does not occur.
At no stage does the fluid pressure drop below the fluid vapour pressure.

The DEL-ST fits into all Delatite standard control valve bodies.

The trim is available in
Flow Under Fail Open
Flow Over Fail Closed