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.
Operating Principles
The 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 variation.
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 Model 85D is PO=PS+K where PO is output pressure, PS is signal pressure and K is the spring constant.
Features
Model 85D Multi-Stage Biasing Relay Features
- 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
- Two stage pilot operation allows precise control of set points
- 14 SCFM flow capacity in a small size unit allows use in applications requiring high flow and/or fast response
- Low air consumption preserves air and other costly gases
- Compact size permits installation where space is limited
- Available in 1/8", 1/4" and 3/8" standard port sizes - versatility makes it easy to design into new and existing applications
Specifications
Model 85D Multi-Stage Biasing Relay Specifications
| Parameter | Value |
|---|---|
| Maximum supply pressure | 250 psig (≈ 17.5 bar / 1750 kPa) |
| Recommended supply pressure | 150 psig (≈ 10 bar / 1000 kPa) |
| Maximum signal/output pressure | 150 psig (≈ 10 bar / 1000 kPa) |
| Flow capacity | 14 SCFM (≈ 23.8 m³/hr) @ 100 psig supply, 20 psig set-point |
| Exhaust capacity | 2.5 SCFM (≈ 4.25 m³/hr) when downstream pressure is 5 psig above setpoint |
| Supply pressure effect | Less than 0.2 psig (≈ 0.014 bar / 1.4 kPa) for a 100 psig (≈ 7 bar) change in supply pressure |
| Pressure change under flow conditions | Less than 0.1 psig (≈ 0.007 bar / 0.7 kPa) from dead-end service to 10 SCFM flow (≈ 17 m³/hr), at 10 psig set-point and 100 psig supply |
| Air consumption during operation | < 0.1 SCFM (≈ 0.17 m³/hr) |
| Ambient temperature range | –40 °F to +200 °F (–40 °C to +93.3 °C) |
| Materials of construction | Body: Aluminum; Trim: Aluminum, Stainless Steel, Brass; Diaphragms: Buna-N on Dacron |
| Available port sizes | 1/8", 1/4", 3/8" |
Q & A
Model 85D Multi-Stage Biasing Relay Q & A
Downloads
Download Rotork Fairchild Model 85D Multi-Stage Biasing Relay Datasheet
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