MD3 Series Port Sizes 1/4" to 1/2"; Flow to 120 scfm (3398 l/min)

Product Overview

The ROSS Controls MD3 Series is a family of modular diaphragm pressure regulators covering port sizes from 1/4" to 1/2" with a maximum flow capacity of 120 scfm (3398 l/min). The MD3 designation reflects the series position within the ROSS modular FRL platform, providing a higher-flow and higher-pressure alternative to the 114 Mid-Size Series in the same port size range.

The MD3 Series uses diaphragm construction throughout, delivering precise downstream pressure response and high sensitivity to load changes. The maximum inlet pressure of 300 psig (21 bar) and outlet adjustable up to 200 psig (14 bar) exceed the capabilities of the 114 Mid-Size Series, making the MD3 suitable for higher-pressure compressed air systems.

Adjustment options include a knob (52K), T-Handle (52T), and locking knob (52L) for maximum flexibility in operator interface and tamper resistance. A reverse flow option is available for weld gun and downstream pressure release applications. Multiple pressure gauge options cover ranges from 0 to 60 psig (0 to 4.1 bar) to 0 to 200 psig (0 to 13.8 bar) with panel mounting nut versions for through-panel installation.

The zinc body, nylon dome, and acetal knob construction is rated for ambient temperatures from 40 to 175 degrees F (4 to 79 degrees C), a wider thermal envelope than the 112 Bantam and 113 Miniature Series, enabling use in warmer industrial environments such as those near process heating equipment.

Key Engineering Features

• Diaphragm Construction - Provides precise downstream pressure response and greater sensitivity to load changes versus piston designs, optimized for applications requiring stable regulated pressure under variable flow demand.
• Maximum Inlet Pressure 300 psig (21 bar) - Rated for higher-pressure supply systems than the standard 114 Mid-Size Series, extending MD3 applicability to higher-pressure compressed air and gas systems.
• Outlet Adjustable to 200 psig (14 bar) - Highest outlet pressure among the modular port-size regulators in the ROSS FRL line, supporting applications requiring downstream pressures above 150 psig.
• Three Adjustment Types - Knob (52K), T-Handle (52T), and Locking Knob (52L) options accommodate diverse installation requirements from standard to glove-friendly to permanently locked set points.
• Modular Mounting - Connects directly to MD3 Series FRL filters and lubricators without additional fittings, forming compact integrated air preparation assemblies.
• Reverse Flow Option - Standard flow (52S) or reverse flow (52R) options available, with reverse flow providing quick exhaust for weld gun and downstream pressure release applications.
• Wide Ambient Temperature Range - Rated for 40 to 175 degrees F (4 to 79 degrees C), suitable for warmer industrial environments including process areas near heat-generating equipment.
• Multiple Gauge Options - Available without gauge, with 0 to 200 psig (0 to 13.8 bar) gauge, or with 0 to 60 psig (0 to 4.1 bar) gauge, in standard and panel mount nut configurations.
• Removable Locking Key - Optional locking key is removable after set point confirmation to prevent unauthorized adjustment, with the locking knob version providing the most secure tamper resistance.

Technical Specifications

General Specifications

Certifications & Compliance

Typical Applications & Industries

Welding and Metal Fabrication

• Resistance spot weld gun circuits requiring regulated pressure with quick exhaust capability. The MD3 reverse flow option provides both functions in a single compact regulator.
• High-cycle robotic welding cells where the 300 psig inlet rating accommodates boosted air supply used to improve cycle response time.
• Pneumatic weld positioner and fixture controls requiring stable regulated pressure at moderate flow rates to maintain consistent electrode force.
• Projection welding and seam welding systems where diaphragm construction provides more consistent pressure regulation across the weld force cycle.

Automotive Manufacturing

• Body shop pneumatic clamp circuits requiring regulated pressure up to 150 psig for high-force workholding applications during welding.
• Assembly line air tool supply at individual stations where the 120 scfm capacity handles multiple simultaneous tool operations.
• Paint booth actuator supply circuits where the wider temperature rating (to 175 degrees F) accommodates elevated ambient temperatures near ovens.
• Vehicle test equipment requiring precisely regulated air at mid-range port sizes with the MD3's higher outlet pressure capability.

Pneumatic Actuator Systems

• High-force pneumatic cylinder supply circuits requiring regulated pressures above the 100 psig limit of standard modular regulators.
• Pneumatic intensifier feed circuits where regulated supply pressure at 100 to 200 psig provides the appropriate inlet condition for pressure multiplication.
• Rodless cylinder and guided actuator supply in automated assembly equipment requiring 1/4" to 1/2" regulated air supply.
• Pneumatic clamping and workholding circuits on machining centers requiring stable pressure over extended machining cycles.

Industrial Processes

• Plastics blow molding auxiliary air circuits where regulated pressure at 100 to 200 psig provides pre-blow or final blow pressure.
• Food and beverage processing equipment circuits using modular MD3 assemblies for combined filtration and regulation in food-grade environments.
• Textile and converting machine pneumatics where the 40 to 175 degrees F temperature rating accommodates process heating environments.
• Chemical processing instrumentation air supply at higher pressures than standard FRL regulators, using the MD3 300 psig inlet capability.

Ordering and Model Number Configuration

Related Products & Accessories

• 114 Mid-Size Series Pressure Regulators - Modular piston or diaphragm regulators, port sizes 1/4" to 1/2", flow to 100 scfm, inlet to 250 psig. https://www.rosscontrols.com/en/series/114-mid-size-series
• 116 Full-Size Series Pressure Regulators - Modular diaphragm regulators with port sizes 1/4" to 3/4", flow to 155 scfm, for larger port requirements. https://www.rosscontrols.com/en/series/116-full-size-series
• MD4 Series Pressure Regulators - Modular diaphragm regulators, port sizes 3/8" to 3/4", flow to 220 scfm, highest flow modular regulator. https://www.rosscontrols.com/en/series/117-md4-series
• ROSS FRL Filters MD3 Series - MD3 Series particulate and coalescing filters for modular assembly with MD3 regulators. https://www.rosscontrols.com/en/categories/36-air-preparation-frls

Frequently Asked Questions (FAQ)

Q: What port sizes are available for the MD3 Series?

A: The MD3 Series is available in 1/4", 3/8", and 1/2" port sizes in both NPTF and G (BSPP) thread forms. Modular port block assemblies are also available.

Q: What is the maximum flow capacity?

A: The MD3 Series has a maximum flow capacity of 120 scfm (3398 l/min), which is 20% higher than the 114 Mid-Size Series in the same port size range.

Q: What is the maximum inlet pressure?

A: The maximum inlet pressure is 300 psig (21 bar), significantly higher than the 250 psig (17 bar) rating of the 114 Mid-Size Series, extending MD3 applicability to higher-pressure systems.

Q: What outlet pressures can the MD3 regulate to?

A: The MD3 Series is adjustable up to 200 psig (14 bar) with the appropriate spring option. Four adjustment ranges are available: 0 to 200 psig, 0 to 150 psig, 0 to 100 psig, and 0 to 50 psig.

Q: Why is the MD3 a diaphragm-only design?

A: The MD3 Series uses diaphragm construction to provide precise downstream pressure response and greater sensitivity to load fluctuations. This makes it the preferred choice over piston designs in applications where regulated pressure must remain stable under variable flow demand, including weld gun and precision control applications.

Q: What is the reverse flow option?

A: The reverse flow option (code R in the model number) provides regulated inlet-to-outlet pressure control plus quick exhaust capability in the outlet-to-inlet direction. This is purpose-designed for weld gun applications where rapid downstream pressure release between welds reduces cycle time.

Q: What adjustment types are available?

A: Three adjustment types are offered: Knob (52K) for standard applications, T-Handle (52T) for increased adjustment torque and glove-friendly operation, and Locking Knob (52L) for maximum tamper resistance. All types include a removable locking key.

Q: What gauge options are available?

A: Six gauge configurations are offered: without gauge, with 0 to 200 psig (0 to 13.8 bar) gauge, and with 0 to 60 psig (0 to 4.1 bar) gauge, each available with or without panel mount nut.

Q: How does the MD3 differ from the 114 Mid-Size Series?

A: The MD3 has higher maximum flow (120 vs. 100 scfm), higher inlet pressure rating (300 vs. 250 psig), higher maximum outlet pressure (200 vs. 150 psig), a wider temperature range (175 vs. 125 degrees F max), and a configurable model number with more adjustment and gauge options. The MD3 is the appropriate choice when any of these expanded ratings are required.

Q: What panel mounting hole size is required?

A: The MD3 Series requires a 2-1/16 inch (52 mm) panel mounting hole, which is larger than the 1-9/16 inch hole required by the 114 Mid-Size Series.

Q: What is the ambient temperature range?

A: The MD3 Series is rated for 40 to 175 degrees F (4 to 79 degrees C), accommodating warmer industrial environments compared to the 40 to 125 degrees F rating of the Bantam and Miniature Series.

Q: Are non-relieving configurations available?

A: Non-relieving configurations are available by consulting ROSS Controls. Specify the non-relieving requirement when ordering.

Installation & Maintenance Guidelines

• Install the MD3 Series with the inlet port connected to the supply side and the outlet connected to the downstream circuit. Reversing flow through a standard (non-reverse flow) model will damage the internal valve.
• For modular assemblies, confirm that all MD3 Series interface connections are properly aligned and sealed before pressurizing the assembly.
• Apply thread sealant only to male port thread connections. Keep sealant away from the first two threads to prevent contamination of internal valve passages.
• For dome removal during maintenance, allow additional clearance above the dome: add 0.575 inches (14.6 mm) above dimension B. For cap removal, add 0.750 inches (19.1 mm).
• Set the outlet pressure with no downstream load by rotating the adjustment knob, T-Handle, or locking knob clockwise to increase and counterclockwise to decrease pressure.
• Monitor the selected gauge during adjustment to confirm the outlet pressure matches the desired set point.
• Remove or secure the locking key after final set point confirmation to prevent unauthorized adjustment during machine operation.
• For reverse flow models, test both the forward regulation function and the reverse exhaust function before placing the machine in service.
• Do not exceed 300 psig (21 bar) inlet pressure. Exceeding this limit risks body damage and uncontrolled downstream pressure increase.
• For panel mounting, use a 2-1/16 inch (52 mm) hole and confirm the panel thickness is compatible with the panel mount nut option if selected.
• In environments approaching the 175 degrees F (79 degrees C) maximum ambient temperature, confirm that the gauge and seals are specified for the operating temperature.
• Inspect all connections for leaks after initial pressurization using an appropriate leak detection solution. Address all leaks before returning the system to service.

Warranty & Global Support

ROSS Controls provides a one-year warranty on all products, covering defects in material and workmanship from date of purchase.

Technical support is available through ROSS Controls USA at (800) 438-7677 or by visiting rosscontrols.com.

For product configuration, dimensional drawings, modular assembly documentation, and catalog downloads, visit the ROSS Controls MD3 Series product page at rosscontrols.com or contact ROSS Controls directly.

Download Catalog: https://www.rosscontrols.com/en/series/115-md3-series