The pressure is reduced smoothly under laminar flow conditions, minimizing dissociation of any components through discontinuous pressure drops. The rod position is controlled externally by turning the knob, and can be adjusted while the sample is flowing. If blockage occurs, the rods can be retracted so that system pressure can blow the solid matter through. Since corrosion products, scale, and other foreign matter often find their way into sample lines, plugging of the pressure reduction valve is common. This is particularly true of Labyrinth type (Drag) valves, and diaphragm operated high-pressure regulators. If these valves plug, the sample line must be shut down while the valve is removed for cleaning or replacement. If the VREL plugs with solids, the rods can be fully retracted and the obstruction blown free without disconnecting any lines. The analyzer remains in service during this operation.
Sentry Equipment Corporation, 856 E. Armour Road, Oconomowoc, WI 53066-0127. Tel: 262-567-7256; Fax: 262-567-4523.