Model 14 Relay from Rotork Fairchild

Rotork Fairchild Model 14 RelayDesigned for applications that require an output pressure that is the sum of a controlled input signal plus or minus a fixed bias, Rotork Fairchild Model 14 Biasing Pneumatic Relay provides versatility in its ability to provide either positive or negative biasing in a single unit.

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 combined spring constant. 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 force that acts on the bottom of the control diaphragm balances with the force that acts on the top and bottom of the signal diaphragm.
When the output pressure increases above the setpoint, the increase is transmitted through the aspirator tube to the control diaphragm. The increased pressure that acts on the control diaphragm moves the diaphragm assembly upward to seat the supply valve, move the relief seat away from the relief valve, and let downstream air exhaust through the port in the ring spacer.

Features

Model 14 Relay Features

  • The output of the Model 14 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 combined spring constant
  • Control sensitivity of 1/2" water column allows use in precision applications
  • Balanced supply valve minimizes the effects of supply pressure variation
  • Aspirator tube design minimizes downstream pressure droop under flow conditions
  • Separate control chamber isolates the diaphragm from the main flow to eliminate hunting and buzzing
  • Mounting bracket available - easy to install in the field
  • Certification for use in all Canadian territories and provinces

Specifications

Model 14 Relay Specifications

  • Supply Pressure: 250 psig, [17.0 BAR], (1700 kPa) maximum
  • Flow Capacity (SCFM): 40 SCFM (68 m3/HR) @ 100 psig, [7.0 BAR], (700 kPa) supply and 20 psig, [1.5 BAR], (150 kPa) setpoint
  • Exhaust Capacity (SCFM): 5.5 SCFM (9.35 m3/HR) where downstream pressure is 5 psig, [.35 BAR], (35 kPa) above 20 psig, [1.5 BAR], (150 kPa) setpoint
  • Signal or Output Pressure: 150 psig, [10.0 BAR], (1000 kPa) maximum
  • Supply Pressure Effect: Less than 0.1 psig, [.007 BAR], (.7 kPa) for 100 psig, [7.0 BAR], (700 kPa) change in supply pressure
  • Sensitivity: Less than 1/2" (1.27 cm) water column
  • Ambient Temperature: -40 to +200 oF (-40 to 93.3 oC)
  • Hazardous Locations: Acceptable for use in Zones 1 and 2 for gas atmosphere; Groups IIA and IIB and Zones 21 and 22 for dust atmospheres
  • Materials of Construction:
    • Body and Housing: Aluminum
    • Trim: Stainless Steel, Brass, Zinc Plated Steel Diaphragms: Nitrite on Dacron

Dimensions

Model 14 Relay Dimensions

Rotork Fairchild Model 14 Relay Dimensions

Q & A

Q&A Section with Expand/Collapse Icons

Model 14 Relay Q & A

+ What does the Fairchild M14 relay do?
The Rotork Fairchild M14 is a positive and negative bias pneumatic relay that adjusts output pressure by adding or subtracting a fixed spring bias from the input signal. This allows it to raise or lower the output pressure relative to the signal for precise control in industrial pneumatic systems. It is used to stabilize, shift, or fine-tune pressures in instrumentation applications where accuracy and responsiveness are important.
 
+ What are the operating pressure limits and flow capacity?
The M14 supports supply pressures up to 250 psig and output pressures up to 150 psig. It delivers approximately 40 SCFM of forward flow and several SCFM of exhaust capability, depending on system conditions. These specifications make it suitable for medium- to high-flow pneumatic control environments that require stable pressure management.
+ How precise and stable is the M14’s output?

The M14 is designed for high-precision pneumatic control, offering a sensitivity of roughly ? inch of water column. Its balanced supply valve minimizes the impact of supply pressure fluctuations, and its internal aspirator design helps reduce droop under flow. This combination provides reliable output stability for critical control loops.

 
+ What materials, mounting options, and environmental conditions does it support?
The relay is built with an aluminum housing and durable internal components such as stainless steel, brass, and nitrile diaphragms. It operates effectively in temperatures ranging from –40°F to about 200°F, making it suitable for harsh plant environments. A mounting bracket is available for easy installation in panels or field locations.  
 
+ Can the M14 be used for both positive and negative bias, and how is the bias set?
Yes — the M14 can function as either a positive or negative bias relay within a single unit. Bias is adjusted through a range screw that increases or decreases the internal spring preload, allowing you to shift output pressure above or below the incoming signal. Multiple pressure ranges and port sizes are available to fit different system requirements.
 


 

Downloads

Download Rotork Fairchild Model 14 Positive and Negative Bias Relay Datasheet

Download Rotork Fairchild Precision Control Product Overview Catalog

Call us today at (855) 737-4714 to learn more, or fill out our online form and someone will get back to you.

 
You were tireless in your support and it will not be forgotten!
 
When we needed technical assistance and application support, Valin was there for us. Their knowledgeable engineers saved us an invaluable amount of time, helping us get up and running quickly. We are very happy with their services.