Model 1500A Positive Bias Relay is designed for applications that require an output pressure that is the sum of a controlled input signal plus a fixed bias. This pneumatic relay provides high output flow at an output pressure that represents the input signal pressure plus a preset bias.
Operating Principles
The output of the relay is the sum of the spring bias, set with the range screw, plus a pneumatic input signal. (Po = Ps + K); where Po is output pressure, Ps is signal pressure, and K is the spring constant set by the range screw. The signal pressure exerts a force against the top of the signal diaphragm that creates a downward force on the diaphragm assembly and opens the supply valve. Output pressure flows through the outlet port and the aspirator tube to the control chamber where it creates an upward force on the bottom of the control diaphragm.
When the setpoint is reached, the forces of the signal pressure and the range spring that act on the top of the signal diaphragm, balance with the force of the output pressure that acts on the bottom of the control diaphragm to close the supply valve.
When the output pressure increases above the setpoint, the diaphragm assembly moves upward to close the supply valve and open the exhaust valve. Because the poppet valve is closed, pressure flows down the control tube to the bottom of the motor diaphragm. This pressure keeps the supply valve tightly closed while in the exhaust mode. The poppet valve opens and excess output pressure exhausts through the vent in the side of the unit until it reaches the setpoint.
Features
Model 1500A Positive Bias Relay Features
- The output of the relay is the sum of the spring bias, set with the Range Screw, plus a pneumatic input signal. (Po = Ps + K); where Po is output pressure, Ps is signal pressure, and K is the spring constant set by the Range Screw
- Control sensitivity of 1" water column allows use in precision applications
- Large supply and exhaust valves provide high forward and exhaust flows
- Soft supply and exhaust valve seats minimizes air consumption
- A balanced supply valve minimizes the effect of any supply pressure variation
- Aspirator tube design compensates downstream pressure droop under flow conditions
- A separate control chamber isolates the diaphragm from the main flow to eliminate hunting and buzzing
- Unit construction allows you to service the Model 1500A without removing it from the line
Specifications
Model 1500A Positive Bias Relay Specifications
| Specification | Value / Description |
|---|---|
| Model | Model 1500A Positive Bias Relay |
| Function | Pneumatic relay: Output pressure = input (signal) pressure + preset bias (Po = Ps + K) |
| Pressure range (setpoint input) | 0–10 psig / 0–0.7 bar (0–70 kPa) 0.5–30 psig / 0.03–2 bar (3–200 kPa) 1–60 psig / 0.1–4 bar (10–400 kPa) 2–150 psig / 0.15–10 bar (15–1000 kPa) |
| Max. Output (or Signal) Pressure | 150 psig / 10 bar / 1000 kPa |
| Max. Supply Pressure | 250 psig / 17.0 bar / 1700 kPa |
| Flow Capacity | 150 SCFM (≈ 255 m3/hr) — at 100 psig supply and 20 psig setpoint |
| Exhaust Capacity (relieving units) | 40 SCFM (≈ 65–68 m3/hr) at ~5 psig above 20 psig setpoint |
| Supply Pressure Effect (sensitivity to supply fluctuation) | Less than 0.1 psig (≈ 0.007 bar / 0.7 kPa) change in output per 100 psig change in supply. |
| Sensitivity (control) | 1” water column (≈ 2.54 cm W.C.) |
| Pipe / Port Size (available) | 3/8", 1/2", 3/4" |
| Pipe / Port Thread Type | NPT or BSPT (depending on config) |
| Body / Housing Material | Aluminum Alloy |
| Diaphragm Material | Nitrile on Dacron |
| Trim Material | Brass and Zinc-Plated Steel |
| Ambient Temperature Range | ?40 °F to +200 °F (?40 °C to +93.3 °C) |
Q & A
Model 1500A Positive Bias Relay Q & A
Downloads
Download Rotork Fairchild Model 1500A Positive Bias Relay Datasheet
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