Sentry Equipment - Sampling Systems - Sampling Equipment

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VREL - High Pressure Sample Flow Control Valve

Variable Pressure Reducing Element

Sentry VREL - Patented Design

The VREL® is an adjustable sample pressure reducer for sample pressures above 500 psig (35 barg). A precisely machined tapered rod assembly moves inside precision holes within the barrel of the VREL®. Pressure drop is a function of the length of the rods inserted into the barrel.


The Sentry VREL adjustable rod-in-tube design allows for variable pressure drop and flow control. Plus, unlike other valves, the VREL is cleanable in place without shutdown of the sample line. Since corrosion products, scale and other foreign matter often fi nd their way into sample lines, plugging of the pressure reduction valve is common, and the sample line must be shut down while the valve is removed for cleaning or replacement. However, if the Sentry VREL plugs with solids, the rods can be fully retracted and the obstruction blown free without disconnecting any lines. The analyzer can be returned to service in minutes.

Both of these design advantages provide consistent sample conditioning.

And, when source pressures change, such as at startup and shutdown, the Sentry VREL can be easily adjusted to allow continuous monitoring under all pressure conditions.


  • Adjustable rod-in-tube type design allows for variable pressure drop and flow control
  • The VREL allows precise control of flow and pressure without valve erosion or fluid dissociation
  • All wetted parts are fabricated from 316 stainless steel
  • Rated to 5000 psig at 300ºF (345 barg at 149ºC), and 7803 psig (538 bar) for supercritical power plant applications
  • The VREL is cleanable in place, "in situ", by retracting the rods without disconnecting or isolating the sample line

The standard VREL is recommended for standard fossil power plant applications. For nuclear applications, we offer a different packing design that is specifically designed to eliminate boric acid from leaching out from the steam and packing. Please contact us for nuclear application information.

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Sentry VREL   

U.S. Pat. No. RE37,153

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