Flow Safe F8000 Series - Pilot Valve Set Pressure Adjustment and Testing; Definition of Set Pressure; Pressure Adjustment and Verification Methods

INSTALLATION, OPERATION, &
MAINTENANCE MANUAL
TITLE: F7000 / 8000 Series Rev. V
Pilot-Operated Safety Relief Valve Page 26 of 41
5.0 PILOT VALVE SET PRESSURE ADJUSTMENT
5.1 Set pressure may be defined in terms of ASME Section VIII or US DOT regulations for natural gas
transmission and distribution, subject to the jurisdiction in effect at the particular valve installation. Contact
Flow Safe for confirmation of spring range or new spring part number before resetting any pilot to a
different set pressure.
5.1.1 ASME VIII: Set pressure is the inlet supply pressure at which the main piston opens or main valve
dome pressure is reduced so as to permit the piston to open (based differential between piston
seat and top seal). The ASME Sec. VIII tolerance on set pressure is + 2 psi for set pressures < 70
psig, and + 3% of set pressure for set pressures > 70 psig.
5.1.2 DOT: Set pressure is the point of first exhaust from the pilot. Tolerances are the same as in 5.1.1
above. Main piston lift should follow within 3 to 5% of set pressure value after pilot first exhaust.
This setting method normally applies to the Flow Safe F70PR valve series, but may apply to the
F7000/8000 series if ordered for a DOT application.
5.2 PRESSURE ADJUSTMENT / VERIFICATION
5.2.1 Testing of Pilot Only
Set pressure adjustments can be made with the pilot valve removed from the main valve and connected to
a test plate assembly (available from Flow Safe), as shown below. The adjustment is made by turning the
pressure adjusting screw clockwise (in) to increase set pressure and counterclockwise (out) to decrease
set pressure.
The F200 snap-acting pilot will suddenly exhaust dome to zero in a “pop” action.
F100, F300, and F500 modulating pilots gradually reduce dome pressure to the point where the piston can
lift, as follows:
F7000/8000 Dome Pressure % F7000/8000 Dome Pressure %
Valve Size at Set Point * Valve Size at Set Point *
1 x 2 50 % 6 x 8 80 %
1-1/2 x 3 63 8 x 10 84
2 x 3 68 10 x 12 78
3 x 4 76 12 x 16 73
4 x 6 76 * Dome pressure as a percentage of inlet pressure,
to achieve main valve piston lift (F100, F300, F500)
Example: For a 3x4 set at 150 psig to begin discharging through the outlet, a modulating pilot
must vent off dome pressure until it drops to approx. 114 psig (0.76 x 150).
Detailed pilot testing instructions are contained in Sections 5.3 through 5.6. Auxiliary setter adjustments
are detailed in 5.7.