ARO R37121-100 Air Regulator | 1/4 in. NPT, 0-140 PSI Pressure Range

Reliable Pressure Control for Pneumatic Equipment

The ARO R37121-100 Air Regulator is a relieving pressure regulator designed to provide controlled downstream air pressure for compatible pneumatic systems and industrial equipment. It features 1/4-inch NPT inlet and outlet ports and provides an adjustable pressure range of 0 to 140 psi.

This model belongs to ARO's air preparation product family and can be used where equipment requires stable, adjustable compressed-air pressure before the air reaches pumps, air motors, valves or other pneumatic components.

0-140 PSI Adjustable Outlet Pressure

The R37121-100 allows operators to set downstream working pressure according to equipment requirements. Its specified maximum inlet pressure is 250 psi, while the adjustable regulated pressure range is 0-140 psi.

The 250 psi value represents the regulator's maximum allowable inlet pressure and should not be confused with the regulated outlet-pressure range.

ARO specifies a published airflow capacity of approximately 59 SCFM for the 1/4-inch configuration under the manufacturer's stated test conditions.

Relieving Regulator Design

R37121-100 uses a relieving regulator design. When downstream pressure rises above the selected setting, the regulator can relieve excess downstream pressure through its relieving mechanism.

This feature is useful in pneumatic systems where controlled pressure reduction may be required after the set pressure has been lowered.

Easy Pressure Adjustment

The regulator uses a convenient pull-to-adjust control knob. Pull the knob upward to make a pressure adjustment, rotate it clockwise to increase pressure or counterclockwise to decrease pressure, and push the knob back down to secure the selected setting.

This arrangement helps operators make controlled pressure adjustments while reducing the chance of accidental changes during normal operation.

1/4-Inch NPT Connections

The 1/4-inch NPT inlet and outlet connections allow the R37121-100 to integrate into compatible compressed-air piping and pneumatic equipment.

Always verify the existing connection size and thread type before ordering. The connection size alone should not be used to determine compatibility; pressure requirements, airflow demand and system configuration should also be checked.

Gauge Not Included

The ARO R37121-100 is supplied without a pressure gauge. The regulator includes a 1/8-inch gauge port, allowing a suitable pressure gauge to be installed separately when visual downstream-pressure monitoring is required.

If your installation requires a gauge, include it as a separate item when preparing the order rather than assuming it is supplied with the regulator.

Industrial Construction and Serviceability

ARO documentation identifies an aluminum regulator body along with internal components including a brass-and-nitrile valve assembly and nitrile/acetal diaphragm construction.

The regulator is serviceable rather than being treated only as a disposable air-line component. ARO identifies service kit 104302 for servicing the R37121-100 regulator in documented applications.

Suitable for ARO Equipment Air-Supply Systems

R37121-100 is also documented by ARO as the regulator used in certain complete pump-system assemblies. For example, ARO's 650820 pump-system documentation specifically references R37121-100 and identifies 104302 as its regulator repair kit.

When installing a regulator ahead of an ARO pump or another pneumatic device, verify that the available inlet pressure, required outlet pressure and airflow capacity meet the equipment manufacturer's requirements.

Installation Considerations

Install the regulator according to the airflow direction marked on the body and position it where pressure adjustment and maintenance access are practical.

Where the compressed-air supply may contain moisture, dirt or other contaminants, using suitable upstream filtration can help protect both the regulator and downstream pneumatic equipment.

Before servicing any compressed-air component, isolate the air supply and relieve trapped system pressure.

Ordering ARO R37121-100

When ordering, specify ARO R37121-100 and confirm:

• 1/4-inch NPT connection requirement
• 0-140 psi regulated pressure requirement
• Maximum available inlet pressure
• Required pneumatic airflow
• Whether a separate pressure gauge is needed
• Any mounting or air-preparation accessories required

Matching these details to the application helps ensure the regulator is correctly selected for the pneumatic system.