Data Sheet

2625 Volume Booster

D200071X012

Product Bulletin

62.3:2625

January 2015

Figure 1. Sectional View of Fisher 2625 Volume Booster

INPUT SIGNAL

BYPASS RESTRICTION

ADJUSTING SCREW

BYPASS

RESTRICTION

SUPPLY

PORT

OUTPUT TO

ACTUATOR

SUPPLY

EXHAUST

PORT

DIAPHRAGMS

W0679‐1

Principle of Operation

Refer to figures 1 and 2. Because of the bypass

restriction, large input signal changes register on the

booster input diaphragm sooner than in the actuator.

A large, sudden change in input signal causes a

pressure differential to exist between the input signal

and the output of the booster. When this occurs, he

diaphragms move to open either the supply port or the

exhaust port, whichever action is required to reduce

the differential. The port remains open until the

difference between the booster input and output

pressures returns to within the deadband limit of the

booster. With the bypass restriction adjusted for stable

operation, a signal with small magnitude and rate

changes passes through the bypass restriction and into

the actuator without initiating booster operation.

Both supply and exhaust ports remain closed,

preventing unnecessary air consumption and possible

saturation of positioner relays.