Valves
DOE-HDBK-1018/2-93
TYPES OF VALVES
Some parallel disk gate valves used in high pressure systems are made with an integral
Figure 8 Parallel Disk Gate Valve
bonnet vent and bypass line. A three-way valve is used to position the line to bypass in
order to equalize pressure across the disks prior to opening. When the gate valve is
closed, the three-way valve is positioned to vent the bonnet to one side or the other.
This prevents moisture from accumulating in the bonnet. The three-way valve is
positioned to the high pressure side of the gate valve when closed to ensure that flow
does not bypass the isolation valve. The high pressure acts against spring compression
and forces one gate off of its seat. The three-way valve vents this flow back to the
pressure source.
Rev. 0
ME-04
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