Emerson Fisher 2625, Fisher 2625NS Data Sheet
Product Bulletin
2625 Volume Booster
D200071X012
62.3:2625
January 2015
Fisherr 2625 and 2625NS Volume Boosters
A Fisher 2625 or 2625NS volume booster is used in
conjunction with a positioner on a throttling control
valve to increase stroking speed. The 2625NS is a
nuclear‐service version and uses elastomeric
components that better withstand high temperature
and radiation environments.
The booster incorporates fixed deadband, soft seat
construction, and an integral bypass restriction to
eliminate positioner saturation problems that can
occur with volume boosters that do not have these
features. Adjustment of the integral bypass restriction
is necessary for system stability. This adjustment does
not affect the deadband of the volume booster, but
does permit the control valve to respond to small input
signal changes without sacrificing steady‐state
accuracy. It also allows the booster to deliver
high‐volume output for fast stroking when large, rapid
input signal changes occur.
W4727-1
The volume booster is used to improve stroking speed.
If precision valve control is required, the use of a
positioner is recommended. If the volume booster is to
be used only with an actuator, for on‐off control, the
integral bypass restriction on the booster must be
closed (turned fully clockwise).
Connectors and piping can be installed with either
2625 or 2625NS volume booster for diagnostic
testing.
The 2625 is certified for use in Safety Instrumented
System (SIS) applications. Certification is by exida
Consulting LLC, a global provider of functional safety
and control system security. SIS certification is
identified on the product by the EXIDA logo on the
2625 nameplate.
Features
n Fast Response—Booster delivers the volume needed
for rapid actuator stroking when large input
changes suddenly occur.
n Adjustable Response—Integral bypass restriction
tunes the booster response so that smooth actuator
motion follows the slow signal changes.
n Efficient Operation—Soft seats provide tight shutoff
to reduce unnecessary air consumption and
eliminate saturation of positioner relays.
n Maintains Accuracy—Booster permits high actuator
stroking speeds upon demand without degrading
the positioner steady‐state accuracy.
n SIL 3 Capable - Certified for use in Safety
Instrumented System (SIS) applications.
www.Fisher.com
Product Bulletin
62.3:2625
January 2015
Specifications
2625 Volume Booster
D200071X012
Supply Pressure Ranges
When used in conjunction with a positioner or other
pneumatic accessory, always pipe the positioner and
volume booster with one common supply through a
Fisher 67D, 67DR, or 95H regulator (see figure 2). A
high‐capacity filter, such as the Fisher 262K, should
be installed in the supply line to the regulator. Supply
pressure also must not exceed the maximum
pressure rating of the actuator. Constructions are
available in two maximum supply ranges.
When Normally Used With Diaphragm Actuators: Up
to 2.8 bar (40 psig)
When Normally Used With Piston Actuators: Up to
10.3 bar (150 psig)
Input Signal Pressure
Positioner output
Maximum Input Signal Pressure
10.3 bar (150 psig)
Fixed Input‐to‐Output Pressure Ratio
1 to 1
Nominal Deadband
Percent of Positioner Output Span
(1)
:
2.4 mm (0.094 inch) exhaust port: 2%
9.5 mm (0.375 inch) exhaust port: 3.5%
12.7 mm (0.5 inch) exhaust port: 5%
Upper and Lower Valves:
2625: Nitrile‐CSM rubber/aluminum/stainless steel
2625NS: EPDM/aluminum/stainless steel
O‐Rings:
2625: Nitrile
2625NS: EPDM
Connectors for Diagnostic Testing:
or
J brass
Operative Temperature Limits
J Stainless steel
(2)
2625: -40 to 71_C (-40 to 160_F)
2625NS: -40 to 93_C (-40 to 200_F)
Connections
Input Signal: 1/4 NPT
Supply and Output: 3/4 NPT
Port Diameters
(3)
Supply Port: J9.5 mm (0.375 inch) or
J 12.7 mm (0.5 inch)
Exhaust Port:
J9.5 mm (0.375 inch) or J12.7 mm (0.5 inch)
J2.4 mm (0.094 inch),
Maximum Flow Coefficients
See table 1
Hazardous Area Classification
Complies with the requirements of ATEX Group II
Category 2 Gas and Dust
Construction Materials
Body: Aluminum
Seat Ring: Brass
Diaphragms
2625: Nitrile/nylon
2625NS: EPDM/meta‐aramid
NOTE: Specialized instrument terms are defined in ANSI/ISA Standard 51.1 - Process Instrument Terminology.
1. Zero to maximum supply.
2. The pressure/temperature limits in this document and any applicable code or standard should not be exceeded.
3. May be used in any combination.
2
Safety Instrumented System Classification
SIL3 capable - certified by exida Consulting LLC
Approximate Weight
2.3 kg (5 lb)
2625 Volume Booster
D200071X012
Figure 1. Sectional View of Fisher 2625 Volume Booster
INPUT SIGNAL
DIAPHRAGMS
EXHAUST
PORT
EXHAUST
Product Bulletin
62.3:2625
January 2015
BYPASS RESTRICTION
ADJUSTING SCREW
BYPASS
RESTRICTION
SUPPLY
PORT
SUPPLY
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
OUTPUT TO
ACTUATOR
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.
3
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