Emerson Fisher 644, Fisher 645 Data Sheet

Product Bulletin

644 and 645 Pump Governors

D100185X012

December 2012

Fisherr 644 and 645 Differential Pressure
Pump Governor Actuators

Fisher 644 and 645 actuators are used in combination
with any of several sliding-stem valves to automatically
control steam-driven boiler feedwater pumps
(reciprocating or turbine). The 644 or 645 actuator
(see figure 2), when used in combination with one of
several push-down-to-close sliding-stem valves, forms
a pump governor.

644 and 645 actuators may also be combined with
push-down-to-open valves to be used as relief
governors. Relief governors are used to divert excess
pump discharge back to the suction side of the pump.

61.9:644

Features

 Rugged Construction–Steel and cast iron

construction provides long service life.

 Ease of Maintenance–Few moving parts and easy

access reduce maintenance and downtime.

 Ease of Adjustment–Spring adjustment is readily

accessible without removing any parts.

 Fast Acting–Direct-operated configuration provides

fast speed of response.

Determining Buildup or
Droop

To determine the buildup (for relief applications) or
droop (for pressure reducing applications):

1. Find a pressure setting limit range that includes the
required pressure setting from table 1.

W2265-1

Fisher 644 ActuatorMounted on easy-et Valve Body

2. Find the sensitivity factor for the desired spring and
actuator casing combination from table 1.

3. Use the formula below to determine the buildup or
droop required for normal actuator travel.

Y

P=

X

where,

P = Buildup (for pressure relief) or Droop (for pressure
reduction), bar (psig)
Y = Normal actuator travel, mm (inches)
X = Sensitivity factor from table 1 mm/newtons
(inches/psig)

www.Fisher.com

Product Bulletin

61.9:644
December 2012

Specifications

644 and 645 Pump Governors

D100185X012

Actuator Sizes

See table 1

Actuator Travel

Chloroprene Diaphragm: 11 mm (0.4375 inch)
maximum
Stainless Steel Diaphragm: 3 mm (0.125 inch)
maximum

Operating Principle

J Direct-acting with push-down-to-close valve
J Reverse-acting with push-down-to-open valve

Differential Pressure Ranges

See table 1

Maximum Casing Pressure

644 Actuator:

Cast-Iron Casing: 20.7 bar (300 psig)
Steel Casing: 41.4 bar (600 psig)

645 Actuator:

Cast-Iron Casing: 34.5 bar (500 psig)
Steel Casing: 69.0 bar (1000 psig)

Maximum nP Across Diaphragm

13.8 bar (200 psi)

Effective Diaphragm Area

644:

Size 1: 146 cm
Size 2: 243 cm
Size 3: 364 cm

645: 338 cm

Material Temperature Capabilities

644:
Chloroprene Diaphragm:-40 to 82_C
(-40 to 180_F)

Stainless Steel Diaphragm:

Cast-iron casing: -40 to 232_C(-40to450_F); Steel
casing: -40 to +399_C(-40to750_F)

645: -37 to 82_C(-35_ to 180_F)

Casing Pressure Connections

1/4 NPT internal

Spring Ranges and Sensitivity

See table 1

2

(8.9 inch2)

2

(14.8 inch2)

2

(22.2 inch2)

2

(20.6 inch2)

Construction Materials

Diaphragm:
644:

J Chloroprene or J Stainless steel

645: Chloroprene
Diaphragm Casing:
Diaphragm Head:
Diaphragm Rod: Stainless Steel
Packing:

J Graphite or J PTFE

J Cast iron or J Steel

J Cast iron or J Steel

Installation

Theseactuatorsmaybeinstalledinanyposition.
Typical installations are shown in figure 1. Dimensions
are shown in figure 3.

Ordering Information

Application

1. Differential pressure

2. Temperature (normal operating and maximum)

Stem Size

644: 9.5mm(3/8inch)
645: 12.7 mm (1/2 inch)

Yoke Boss Diameters

644:

J 54 mm (2-1/8 inch) or

J 71 mm (2-13/16 inch)

645: 71 mm (2-13/16 inch)

3. Required spring

Actuator

Refer to the specifications table. Review the
description to the right of each specification and in the
referenced table. Specify a choice wherever there is a
selection to be made.

Valve Body and Accessories

Refer to separate valve bulletin and bulletins covering
accessories for ordering information.

2