BULLETIN 146APRIL 2002
Port Throttling GAD™ Trim - 34699 PORT THROTTLING GAD
™
TRIM
For Conventional or Custom Engineered Characteristics
Introduction
The Copes-Vulcan Port Throttling GAD
™ trimwas developed to meet the rigorous
requirements of applications such as
feedwater and feedwater startup control,
high pressure steam and gas letdown and
other high mass flow rate pressure reduc-
tions. Designed to give optimum flexibility
in electric, hydraulic and air operated
control valves, the trim is available in
Double Seat, Balanced Single Seat and
Tandem versions.The GAD trim is equally suitable for use with steam and many other fluids. It has been successfully used on high pressure water applications involving pressure of up to 5075 psi (34,970 kPa) and pressure
differential of up to 3625 psi (24,980 kPa).
Flow
Typical Features Operation
The GAD trim is a proven design utilizing a unique concept in flow management.• The control mechanism is situated in a zone of low turbulence which avoids flow induced instability or standing pressure waves. • External cage guiding results in low hydraulic unbalance requiring reduced
actuator force.• Custom engineering of the flow control areas optimizes the valve characteristic to system requirements.• The flow streams through the stationary cage result in energy dissipating jet impingement within the bore of the cage.• Three versions of the trim are available: Double Seat, Balanced Single Seat and Tandem. The GAD trim is quick change and consists
of a cylindrical cage spacer and cage which
are the boundary between the upstream
and downstream sections of the valve body.The control of the fluid through the valve is through ports provided around theperimeter of both the cage spacer and cage.The ports in the cage spacer are very large.
Therefore, no significant pressure drop is
created. The cage ports, which are either
from a standard range or designed to
provide a specific characteristic, create the
required valve pressure drop. Standard ports
are available in linear, modified parabolic or
equal percentage characteristics.The cage ports are arranged diametricallyopposite each other and effectively break
the mass flow of fluid down into a series of
jets which impinge upon each other in the
center of the cage. This jet impingement
also creates a back pressure within the bore
of the cage which reduces the pressure
drop across the ports thus minimizing trim
velocity, erosion and noise. Also, all flow
reaction is contained within the center of
the cage, preventing plug instability.
