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X. Operating Principles (Cont.)
B. PV Valve Open (Relieving Position)
As inlet pressure increases, the pilot piston strokes and seals off the main valve inlet pressure from the dome
pressure. The pilot simultaneously opens the vent seal to relieve the dome pressure to atmospheric pressure.
The main valve disc is allowed to lift off the seat as the fluid force overcomes the now removed pressure load
above the main valve piston. The valve discharges to relieve system pressure.
When the discharging main valve reduces the inlet pressure to the pre-set blowdown pressure of the pilot,
the pilot piston closes the vent seal. Simultaneously, the inlet seal is reopened in the pilot. The main valve inlet
pressure is again allowed to enter the dome above the main valve piston. As the dome pressure equalizes with
the inlet pressure, the downward force created by the differential areas of the piston and disc closes the main
valve.
Figure 5: Pilot Valve (Opened)
20 | BHGE
© 2019 Baker Hughes, a GE company. All Rights Reserved.
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