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Model 85D Multi-Stage Positive Bias Relay

Brand: Fairchild Industrial Products
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The Rotork Fairchild Model 85D Multi-Stage Biasing Relay is a precision control combining the sensitivity of a precision pressure regulator with positive biasing capability. 

This compact, pilot-operated device offers unusually high output capacity with minimal air consumption, while providing excellent protection against supply or output pressure variations.

The versatile Model 85D is recommended for use in systems requiring precision pressure maintenance and instrument biasing, in dead end service and instrument panel supply applications.

The basic mathematical expression for the Fairchild Model 85D is PO = PS + K where PO is output pressure, PS is signal pressure and K is the spring constant.
Features
  • Two Stage Pilot Operation
  • 14 SCFM flow capacity in a small size unit
  • Low air consumption
  • Compact size
  • Available in 1/8", 1/4" and 3/8" standard port sizes
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The Rotork Fairchild Model 85D Multi-Stage Biasing Relay is a precision control combining the sensitivity of a precision pressure regulator with positive biasing capability. 

This compact, pilot-operated device offers unusually high output capacity with minimal air consumption, while providing excellent protection against supply or output pressure variations.

The versatile Model 85D is recommended for use in systems requiring precision pressure maintenance and instrument biasing, in dead end service and instrument panel supply applications.

The basic mathematical expression for the Fairchild Model 85D is PO = PS + K where PO is output pressure, PS is signal pressure and K is the spring constant.
Features
  • Two Stage Pilot Operation
  • 14 SCFM flow capacity in a small size unit
  • Low air consumption
  • Compact size
  • Available in 1/8", 1/4" and 3/8" standard port sizes
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Specifications

Brand

Air Consumption

  • < 0.1 scfm (0.17 m³/hour)

Ambient Temperature Range

  • -40° to 93.3° C (-40° to 200° F)

BSP Connection

  • 1/4” BSPT Female
  • 1/8” BSPT Female
  • 3/8” BSPT Female

Diaphragm Material

  • Buna-N & Dacron

Enclosure, Body Material

  • Aluminum

Exhaust Capacity - Relieving Units Only

  • 2.5 scfm (4.25 m³/hour) where Downstream Pressure is 5 psig (bar: 0.35, kPa: 35) Above Set Point

Exhaust Port

  • Tapped Exhaust

Flow Capacity

  • 14 scfm (23.8 m³/hour)

Mounting

  • Bonnet Mounting

NPT Connection

  • 1/4” NPT Female
  • 1/8” NPT Female
  • 3/8” NPT Female

Pressure Range

  • bar: 0 to 7
  • kPa: 0 to 700
  • psig: 0 to 100

Signal or Output Pressure - Maximum

  • psig: 150 (kPa: 1,000, bar: 10)

Standard Features

  • Tamper-Proof

Supply Pressure

  • psig: 150 (kPa: 1,000, bar: 10) Recommended Operating Supply Pressure

Supply Pressure - Maximum

  • bar: 17.5
  • kPa: 1,750
  • psig: 250

Supply Pressure Effect

  • Less than psig: 0.2 (bar: 0.0014, kPa: 1.4) for psig: 100 (bar: 7, kPa: 700) Change in Supply Pressure

Trim Material

  • Aluminum
  • Brass
  • Stainless Steel
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