5
ANDERSON GREENWOOD
SERIES 93T PILOT OPERATED SAFETY RELIEF VALVES
INSTALLATION AND MAINTENANCE INSTRUCTIONS
4.5 Adjustment tolerances
Pilot action
[1]
Set pressure
Set pressure
tolerance
Minimum crack pressure as %
of nameplate set
Supply pressure as % of set for
dome pressure recovery
[2]
Snap
2”WC to 1.0 psi
±3%
90
90 ± 1
1 psi to 15 psi
±3%
92½
92½ ± ½
-2”WC to 1.0 psi
±3%
90
90 ± 1
-1.0 psi to -14.7 psi
±3%
92½
92½ ± ½
Modulating
2”WC to 1.0 psi
±3%
90
100
1.0 psi to 15 psi
±3%
92½
100
-2”WC to 1.0 psi
±3%
90
100
-1.0 psi to -14.7 psi
±3%
92½
100
NOTES
1.
Snap action
- dome pressure decreases rapidly with a “snap” to 15% ± 10% of set pressure at set pressure.
Modulating action
- dome pressure decreases slowly to 30% ± 5% of set pressure and recovers to 60% ± 10%
of set pressure at set pressure.
2. Pilot seat should be bubble tight at dome recovery for “snap” pilot action and at 90% of set pressure for
“modulating” pilot action non-marine.
Pressure adjustment
Pressure adjustment
Pilot valve to be set
Blowdown adjustment
Adjustable
pressure
regulator
(relieving type)
Supply
pressure gage
Supply
pressure
Vent
Supply port
Supply
½" FNPT
ports
½" pipe
Blowdown adjustment
Dome pressure gage
Dome pressure
FIGURE 4 - Optional test set-up
4.6 Definitions
Set pressure
is defined as that pressure where the dome pressure is 15% of the supply pressure.
Crack pressure
is defined as the supply pressure where gas flow begins at the pilot exhaust.
Accumulator
