21312DU Fairchild Products Pneumatic Adjustable Ratio Bias Relay

$1,218.78 / Each
  • Product Type: Adjustable Ratio Relay

Fairchild Model 21 Pneumatic Adjustable Ratio Bias Relay, 1/4" BSPT Pipe, 3 PSIG Input, 9 PSIG Output, Aluminum, Buna-N and Dacron Diaphragm, Pneumatic Adjustable Ratio Bias Relay.

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Product Description

Pneumatic Adjustable Ratio Bias Relay; Item Adjustable Ratio Bias Relay; Overall Dimension 3-5/8 Inch Width; Pipe Size 1/4 Inch BSPT Threaded; Material Aluminum (Body/Housing); Mounting Hole Size (2) 2-29/32 Inch, 7-13/32 Inch; Panel Mounting Hole Size 11/32 Inch; Gauge Tap Size (2) 1/4 Inch Threaded; Maximum Bias Pressure 3 PSIG (Input), 9 PSIG (Output); Supply Pressure 250 PSIG (Maximum); Signal/Output Pressure 150 PSIG (Maximum); Supply Pressure Effect 0.1 PSIG; Flow Capacity 40 SCFM at 100 PSIG; Exhaust Capacity 5.5 SCFM; Sensitivity 0.5 Inch WC; Ambient Temperature -40 to 200 Deg F; Includes Stainless Steel/Brass/Zinc Plated Steel Trim, Buna-N and Dacron Diaphragm, Hardened Steel Lever and Fulcrum; Applicable Standard ISO 9001, FM


An Aspirator Tube Compensates Downstream Pressure Droop Under Flow Conditions; Adjustable from 30:1 Dividing Ratio to 1:30 Multiplying Ratio Assures Infinite Pressure Adjustments; Floating Seal Ring Isolates Control Chamber which Increases Stability by Reducing Effects of High Flows; Assures Infinite Pressure Adjustments; Compensates for Downstream Pressure Losses; Allows Versatility in Applications; Easy Installation and Service in the Field

Series/Model Info

The Model 21 Adjustable Ratio pneumatic relay has a signal chamber lever arm, whereby the ratio of output pressure to signal pressure is infinitely adjustable. The adjustment range permits signal amplification of 1:30 or signal reduction of 30:1 by rotation of the ratio adjustment knob which moves the fulcrum. . Output pressure is a function of signal pressure times the ratio of lever arm lengths on either side of the fulcrum. Bias may be introduced by means of the set screws. The Model 21D is available with both input and output adjustable bias.