Jerguson V-Series Tubular Valves and Assemblies

The simplest and least costly method of liquid level indication is the tubular gage glass. Two slightly different designs are available.  Both are simply transparent vertical tubes with their lowest visible point connected to the tank or boiler at the lowest level of interest. The top of the glass may be open to the atmosphere if the tank is open or to the unfilled part of a closed vessel above or at the highest level permitted. Isolating valves are placed above and below the gage glass connections.

One choice is a gage glass with slow closing valves and the second choice are valves with quick closing type where a one quarter turn of the valve spindle will change the valve from the fully open to the fully closed position. The valve spindles are fitted with levers to which chains may be attached in order to operate the valves from ground level if the vessel is located at a higher position. Drain valves or cocks may also be installed below the gage glass to remove any solid material that may collect.

Since many tanks and pressurized vessels are not under continuous supervision, a broken gage glass may allow a large amount of fluids to escape. To prevent this, the lower valve on the gage glass is often equipped with a safety shutoff device consisting of a stainless steel ball which closes off the fluid passage when the glass breaks. One disadvantage of this type of safety device is that it requires more maintenance.

Under normal conditions, the steel ball remains in the recess in front of the valve seat. However, when the gage glass breaks, the sudden rush of fluid through the valve will force the ball against the valve opening. This shuts off the flow out of the broken glass.

The gage glass is usually surrounded by a number of metal rods or transparent shield to protect the glass from breakage and the operator from flying particles in case the gage glass shatters.

The use of tubular gage glasses is limited to lower pressures and temperatures, and restricted to non-toxic and non-hazardous material. Tubular gage glasses should not exceed 750 mm in length. If the level range to be observed exceeds this length, then two or more gage glasses should be installed so that they overlap.

Conforming to A.S.M.E. power-boiler code requirements, these gage valves feature stainless steel ball checks in both upper and lower units.  This provides automatic closure in the event of glass breakage and requires the ball check in the lower valve to rise vertically to its seat.  A safety handle is also provided for manual operation of the 5/16" diameter drain valve.  This valve is of the full-flow ball valve design.  The valve body is constructed of rugged, heavy pattern bronze.  Standard packing materials are wear-resistant Teflon-Asbestos.  Maximum working pressure is rated at 500 psi @ 500°F, or 250 psi @ 400°F.