Rotork Fairchild Model M11 Low Pressure Pneumatic Regulator

The Rotork Fairchild Model M11 is a low pressure pneumatic regulator for circuits that run below about 12 psig. Its datasheet gives a sensitivity of 0.05 inch water column, the finest figure among the Fairchild regulators in this group, so it suits loads that respond to very small pressure changes: low pressure instrument signals, bubblers, purge systems, test fixtures and similar duties. Output ranges start at 0-0.5 psi, which is below the lowest range of the general-purpose Fairchild regulators.

Large diaphragm, relief valve and aspirator tube

The M11 has a wide control diaphragm, which is why its body looks flatter and broader than the Model 10. When the range screw is adjusted, the range spring pushes down on the diaphragm and opens the supply valve; output pressure reaches the control chamber through the aspirator tube and balances the spring at the setpoint. If the outlet pressure rises above the setpoint, the diaphragm lifts, the supply valve closes and the exhaust valve opens so the extra pressure leaves through the side vent. The relief valve gives high exhaust flow, an optional low bleed seat reduces air consumption, and the aspirator tube compensates downstream pressure droop.

Technical specifications

Catalog number options

The M11 catalog number combines the model code 111 with a range digit (1 for 0-0.5 psi through 5 for 0-12 psi), a port size digit (2, 3 or 4 for 1/4, 3/8 or 1/2 inch) and the following letters:

• Port thread: N NPTF, U BSPT, H BSPP
• Elastomer: N nitrile, J fluorocarbon
• Actuator: K knob, S screw adjust, T tamper proof
• Relief: B low bleed, N non-relieving, R relieving with normal bleed, S relieving with no bleed
• Vent: S straight or E tapped (1/4 inch NPT, BSPT)
• Mounting: B bonnet (two 1/4-20 UNC) or P panel (1/2-20 UNF)

The outline drawing shows gauge ports on the body, and an optional mounting bracket, part 21955-1, is listed.

What to confirm before ordering

Because the exhaust capacity is rated at only 0.1 psig above a 1.0 psig setpoint, it is worth checking the relief arrangement against the volume you need to vent. State the actual setpoint, the supply pressure and the flow in your enquiry, since the 20 SCFM figure applies to a 1.0 psig setpoint, not to the top of the 0-12 psi range. Confirm thread type and whether tamper proofing or panel mounting is required.

How the Fairchild Model M11 works

The Fairchild Model M11 is a pressure regulator with a large diaphragm. The range screw loads a spring that pushes the diaphragm down and opens the supply valve. The output pressure reaches the underside of the diaphragm through an aspirator tube and balances the spring at the set pressure. If the outlet pressure goes above the setting, the diaphragm lifts, the supply valve closes and the exhaust valve opens, so the excess leaves through the side vent. The large diaphragm makes it sensitive to very small changes.

Where the Fairchild Model M11 is used

• Low pressure instrument signals
• Bubbler level systems
• Purge air systems
• Test fixtures
• Loads that react to small pressure changes

Selection checklist for the Fairchild Model M11

• Output range: 0-0.5, 0-2, 0-4, 0-6 or 0-12 psi
• Port size: 1/4, 3/8 or 1/2 inch
• Thread: NPTF, BSPT or BSPP
• Diaphragm: nitrile or fluorocarbon
• Supply pressure up to 150 psig
• Flow capacity in SCFM
• Low bleed seat to cut air use
• Ambient temperature

Installation, commissioning and maintenance notes for Fairchild Model M11

Mount the regulator in a clean, dry air line with the arrow in the flow direction and the vent free. Fit a filter upstream. Turn the range screw slowly while watching a gauge on the outlet. Do not exceed the supply limit of 150 psig. The body is aluminum, with an ambient range of minus 40 to plus 200 degrees F. Check the vent for blockage in dusty areas.

Requesting a quotation for the Fairchild Model M11

Please send the range, the port size and thread, the elastomer and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Fairchild Model M11 sensitivity

The sensitivity is 0.05 inch of water column. The supply pressure effect is below 0.01 psig for a 100 psig change in supply.

Fairchild Model M11 flow capacity

The flow is 20 SCFM at 100 psig supply and a 1.0 psig setpoint. The exhaust capacity is 0.5 SCFM.

Fairchild Model M11 materials

The body and housing are aluminum. The trim is zinc plated steel and stainless steel.

Fairchild Model M11 catalog number

The number combines the model code 111, a range digit, a port size digit and letters for the thread, elastomer and actuator.

Regulator records for Fairchild Model M11

Note the set pressure and the date of each adjustment in the instrument file.

Choosing the right Fairchild Model M11 range

Choose the lowest range that covers the working pressure, because the setting is then finer.

Documents and quotation

The Rotork datasheet is attached. Send Seven Star LLC the catalog number or your range, port and options and we will quote from our regulators range. For higher pressures with no-bleed operation, see the Rotork Fairchild Model 1000.