Principle Of Operation - Fisher 627F Instruction Manual

FILTER (FACTORY
INSTALLATION
OPTIONAL)
PILOT DIAPHRAGM
A6558
INLET PRESSURE INLET PRESSURE
OUTLET PRESSURE OUTLET PRESSURE
ATMOSPHERIC PRESSURE
ATMOSPHERIC PRESSURE
LOADING PRESSURE LOADING PRESSURE
INTERMEDIATE PRESSURE
PILOT SUPPLY PRESSURE
VACUUM PRESSURE
TANK PRESSURE
Figure 2. Type 627F Pilot-Operated Pressure Reducing Regulator Operational Schematic
VAPOR PRESSURE
ORIFICE SIZE
5 psig / 0.34 bar
inch mm psig
3/8 x 1/8 9.5 x 3.2 30 to 250
3/8 x 1/4 9.5 x 6.4 30 to 250
3/8 9.5 30 to 250
1/2 13 25 to 125
1. For best performance, outlet pressure setting should be made using an inlet pressure that is midway between the highest and lowest expected inlet pressure.
Description
The Type 627F pilot-operated (Type 6351F pilot)
pressure reducing regulator (Figure 1) provides
economical, accurate pressure control in a wide variety
of applications using pressure factor measurement
(fixed factor billing). The regulator can be used with
natural gas, air, or a variety of other gases.

Principle of Operation

The superior performance of a Type 627F regulator is
due to the amplifying effect of the pilot and the two-path
control system (Figure 2). Changes in outlet pressure
act quickly on the main regulator diaphragm which
RESTRICTION
(BLEED)
PILOT ADJUSTING
SCREW
TYPE 6351F PILOT
PILOT SUPPLY TUBING
(FACTORY INSTALLATION OPTIONAL)
Table 3. Additional Specifications
ALLOWABLE INLET PRESSURE RANGE FOR MAINTAINING OUTLET PRESSURE
WITHIN ±1% OF THE ABSOLUTE OUTLET PRESSURE SETTING
30 psig / 2.1 bar
bar psig bar
2.1 to 17.2 55 to 250 3.8 to 17.2
2.1 to 17.2 55 to 250 3.8 to 17.2
2.1 to 17.2 55 to 250 3.8 to 17.2
1.7 to 8.6 50 to 125 3.4 to 8.6
FIELD INSTALLED
DOWNSTREAM
CONTROL LINE
TYPE 627F REGULATOR
40 psig / 2.8 bar 60 psig / 4.1 bar
psig bar psig
65 to 250 4.5 to 17.2 85 to 250
65 to 250 4.5 to 17.2 85 to 250
65 to 250 4.5 to 17.2 85 to 250
60 to 125 4.1 to 8.6 80 to 125
repositions the valve disk to provide fast response to
system changes. Simultaneously, the pilot amplifies
system pressure changes to position the main
regulator valve disk for precise pressure control.
Inlet pressure is used for the pilot supply pressure.
If downstream flow increases, lowering the outlet
pressure below the regulator setpoint, pressure on
the pilot diaphragm and the lever side of the main
regulator diaphragm decreases. The pilot opens to
supply the required loading pressure increase. The
increased loading pressure from the pilot overcomes
the main regulator spring force, and the main
regulator valve disk moves farther open to supply the
required flow.
Type 627F
SPRING SEAT BOLT
(THIS IS NOT AN
ADJUSTING SCREW)
TENSION SPRING
MAIN REGULATOR
DIAPHRAGM
LEVER
VALVE DISK
(1)
100 psig / 6.9 bar
bar psig bar
5.9 to 17.2 125 to 250 8.6 to 17.2
5.9 to 17.2 125 to 250 8.6 to 17.2
5.9 to 17.2 125 to 250 8.6 to 17.2
5.9 to 8.6 120 to 125 8.3 to 8.6
3