Model 25 Reversing Relay is designed for applications requiring an output that equals a manually preset spring load minus a variable signal pressure. This high-quality unit combines excellent sensitivity with unusually high flow capacity.
Operating Principles
The Model 25 Reversing Relay is designed for applications requiring an output that equals a manually preset spring load minus a variable signal pressure. This high-quality unit combines excellent sensitivity with unusually high flow capacity.
The Model 25 is ideally suited for a variety of precision control applications, including converting direct acting valves to reverse action, controlling opposite acting valves from a single transmitter, and cushioning cylinder loads.
The basic mathematical expression for the Model 25 is PO = K - PS where PO is output pressure, PS is signal pressure and K is the spring constant.
Features
Model 25 Reversing Relay Features
- The Model 25 is ideally suited for a variety of precision control applications, including converting direct acting valves to reverse action, controlling opposite acting valves from a single transmitter, and cushioning cylinder loads
- The basic mathematical expression for the Model 25 is PO = K - PS where PO is output pressure, PS is signal pressure and K is the spring constant
- Control sensitivity of 1/8" water column allows for use in high precision applications
- Balanced supply valve minimizes the effects of supply pressure variation
- Aspirator tube design compensates for output pressure droop under flow conditions
- Separate control chamber isolates the diaphragm from the main flow to eliminate hunting and buzzing
- Unit construction allows servicing without removal from air line
Specifications
Model 25 Reversing Relay Specifications
| Category | Specification |
|---|---|
| Maximum Supply Pressure | 250 psig (17.5 bar / 1750 kPa) |
| Flow Capacity | 40 SCFM (68 m³/hr) @ 100 psig supply, 20 psig setpoint |
| Exhaust Capacity | 11 SCFM (18.7 m³/hr) when downstream pressure is 5 psig above setpoint |
| Maximum Signal/Output Pressure | 150 psig (10 bar / 1000 kPa) |
| Supply Pressure Effect | < 0.1 psig (0.007 bar / 0.7 kPa) change per 100 psig supply change |
| Sensitivity | < 1/8" (0.32 cm) water column |
| Ambient Temperature Limits | –40 to +200 °F (–40 to 93.3 °C) |
| Mounting Options | Pipe or panel mounting |
| Body Material | Aluminum |
| Trim Materials | Aluminum, stainless steel, brass |
| Diaphragm Materials | Buna-N and Dacron |
| Pressure Range Options | • 0–10 psig • 0.5–30 psig • 1–60 psig • 2–150 psig |
| Pipe Size Options | 1/4" NPT, 3/8" NPT, 1/2" NPT |
| Gauge Port Options | Standard: 1/4-18 NPT Optional (U & H): 1/4-19 BSPT or BSPP |
| Available Options | Tapped exhaust (E), BSPP threads (H), fluorocarbon elastomers (J), BSPT threads (U) |
| Service Kit Availability | Service kit available (per Fairchild IOM IS-30000025) |
| Primary Function | Provides output that inversely follows input/ signal pressure (PO = K – PS) |
| Typical Applications | Reverse-acting valve control, converting direct-acting valves to reverse action, operating opposite-acting valves from a single transmitter, cushioning cylinder loads |
Q & A
Model 25 Reversing Relay Q & A
Downloads
Download Rotork Fairchild Model 25 Reversing Relay Datasheet
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