Sentry VREL Control Valve 5
Overview
The Sentry® VREL® Control Valve is a valve specifically designed for high-pressure liquid
sampling. Typical applications are for the pressure reduction and flow control of samples
greater than 500 psig (34.5 bar).
The adjustable rod-in-tube design allows for variable pressure drop and flow control of
high-pressure liquid samples. The VREL valve is also cleanable in place.
The VREL valve is an adjustable rod-in-tube pressure reducing device. The pressure of
the incoming sample is reduced as the liquid is forced to travel through the narrow gap
between the tapered rod and the rod opening. Because the reduction in pressure is done
over the entire length of the rod, localized wear is held to a minimum. The result is a very
long service life compared with devices in which the pressure drop is taken over a very
short distance (fixed orifice, pressure regulator, etc.). Other devices erode frequently
causing friction loss and down time.
With a VREL valve, the flow or pressure drop can be changed while the sample is flowing
by adjusting the position of the rods. Turning the handle moves the rods in or out on
the lead screw. If sample flow is blocked, the rods can be fully retracted to allow sample
pressure to flush the dirt through. The sample line never needs to be shut off or the VREL
valve disassembled to accomplish this. This is very important as the operator tries to get
critical samples while boiler pressure is rising or falling during startup or shutdown.
Installation
To ensure the protection provided by this equipment is not impaired, this equipment must not
be installed or used in any manner other than that which is specified in this manual .
Ensure that the VREL valve is installed such that it will not be subject to steam or water sample
temperatures greater than 300˚F . Damage to the VREL valve or downstream equipment may
occur .
The physical dimensions of the VREL valve are shown on the drawing in Figure 4. The VREL
valve can be mounted in any position. The cutouts for panel mounting are shown in
Figure 4. The locating pin ensures correct orientation to connecting tubing. As an
alternative, a U-bolt can be used to hold the body to a panel face or post.