Numbered Cascade Trim0 pages

BULLETIN 135APRIL 2002

Application

Copes-Vulcans Numbered Cascade Trim assemblyis used in control valves where low flow rates and
high turndown requirements prevail such as in
desuperheater cooling water control, fuel oil
control, blowdown and chemical feed.The cascade trim can be applied when differential pressures are as high as 5000 psi
(34,450 kPa) with service temperature as high as 1050ҰF (566C).Exceptional tight shutoff can easily be maintained. >

Function

A series of labyrinth grooves along the throttlingsurface of the plug provide a cascading effect so
that the pressure drop is equally divided among
the grooves, thereby reducing the seat wear that would normally be experienced if the entire
pressure drop is taken across the seat. The cage
guided tapered plug, in conjunction with the
tapered cage bore, provides for maximum trim rangeability. The plug and cage are designed so that metal-to-metal contact is made on beveled seating surfaces
and the clearance between plug and cage tapers
in the labyrinth groove section is held to .001"
(.0254mm) for proper cascading effect. For those applications where valve pressuredecreases with increased flow, Numbered
Cascade Trim is ideal. At light loads when pressure
drop is maximum, the plug is close to the seat
and the cascading has optimum effect. As load
increases and pressure drop decreases, the need
for cascading diminishes. Since the total pressure drop is broken down intostages, erosion is held to a minimum, assuring
that Numbered Cascade Trim will have a longservice life. >
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