• 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.

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)

Application

1. Differential pressure
2. Temperature (normal operating and maximum)
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.

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

■Direct-acting with push-down-to-close valve
■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)

Construction Materials

Diaphragm:
644: ■Chloroprene or ■Stainless steel
645: Chloroprene
Diaphragm Casing: ■Cast iron or ■Steel
Diaphragm Head: ■Cast iron or ■Steel
Diaphragm Rod: Stainless Steel
Packing: ■Graphite or ■PTFE

Maximum ∆P Across Diaphragm

13.8 bar (200 psi)

Effective Diaphragm Area

644:
Size 1: 146 cm2 (8.9 inch2)
Size 2: 243 cm2 (14.8 inch2)
Size 3: 364 cm2 (22.2 inch2)
645: 338 cm2 (20.6 inch2)

Material Temperature Capabilities

644:
Chloroprene Diaphragm:-40 to 82°C
(-40 to 180°F)
Stainless Steel Diaphragm:
Cast-iron casing: -40 to 232°C (-40 to 450°F); Steel casing: -40 to +399°C (-40 to 750°F)
645: -37 to 82°C (-35° to 180°F)

Casing Pressure Connections

1/4 NPT internal

Spring Ranges and Sensitivity

See table 1

Stem Size

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

Yoke Boss Diameters

644: ■54 mm (2-1/8 inch) or
■71 mm (2-13/16 inch)
645: 71 mm (2-13/16 inch)

Note
Neither Emerson, Emerson Process Management, nor any of their affiliated entities assumes responsibility for the selection, use and maintenance of any product. Responsibility for the selection, use, and maintenance of any product remains with the purchaser and end-user.