MD4 Precision Series Port Sizes 3/8" thru 3/4"; Flow to 170 scfm (4814 L/min)

Product Overview

The ROSS Controls is a family of precision pressure regulators built on the MD4 modular platform, combining the tight pressure accuracy of a diaphragm precision regulator with the compact footprint and direct manifold connectivity of the MD4 FRL system. Available in 3/8", 1/2", and 3/4" port sizes, the series delivers flow up to 170 scfm (4814 L/min) while holding regulated pressure within 3 psig (0.2 bar) across varying demand conditions.

The MD4 platform is ROSS Controls' medium-duty modular FRL architecture, designed to provide higher flow capacity than the standard full-size modular series while maintaining a compact overall assembly footprint. The Series precision regulator integrates directly into MD4 manifold assemblies with upstream filters and downstream lubricators, creating compact FRL stations without intervening pipe fittings or adapter blocks. This direct connection minimizes pressure drop across the assembly and simplifies maintenance through module-by-module replacement.

Like all ROSS precision regulators, the series employs a small valve seat with a large diaphragm sensing area. This geometric relationship provides the fine sensitivity needed to correct downstream pressure deviations before they reach levels perceptible to pneumatic torque tools, precision actuators, or process control equipment. Pressure settings are held within 3 psig (0.2 bar), providing improved torque repeatability compared to standard industrial regulators.

Three pressure range options accommodate different application requirements: 15-100 psig (1.0-6.9 bar) for low-pressure tool and instrument circuits, 15-200 psig (1.0-13.8 bar) for standard industrial applications, and 15-250 psig (1.0-17.2 bar) for high-pressure tool and process applications. The self-relieving design is standard, with optional non-relieving configurations available.

Key Engineering Features

• MD4 Modular Platform Compatibility - Designed for direct integration into ROSS MD4 FRL manifold assemblies, enabling compact filter-regulator-lubricator combinations without pipe fittings and with reduced total pressure drop compared to pipe-connected individual components.
• High Flow Capacity at Compact Size - Delivers up to 170 scfm (4814 L/min) through 3/4" port, exceeding the 121 Series full-size modular capacity by approximately 10% in a similar body envelope, providing higher throughput in compact MD4 manifold configurations.
• Three Pressure Range Options - Factory-configured in three adjustment ranges - 15-100 psig (1.0-6.9 bar), 15-200 psig (1.0-13.8 bar), and 15-250 psig (1.0-17.2 bar) - ensuring optimum spring sensitivity at the target operating pressure for each application.
• Precision Diaphragm Design - Small valve seat combined with a large diaphragm sensing area achieves pressure accuracy within 3 psig (0.2 bar), providing improved torque control and consistent process conditions.
• Self-Relieving Standard Configuration - Standard self-relieving design allows downstream pressure to vent through the regulator body on set point reduction; non-relieving option available for circuits requiring held downstream pressure.
• Removable Adjusting Knob - The adjusting knob can be withdrawn after setting the desired pressure, providing tamper resistance in production environments. Yellow knob option available for visual identification of precision regulator stations.
• Panel Mount Capability - Accepts panel mounting through a 2-1/16" (52 mm) cutout with an optional panel mount nut for fixed, accessible installation in control panels and operator stations.
• Dual Gauge Port Orientation - Front and rear 1/4" NPT gauge ports allow pressure gauge installation in either direction to accommodate different panel and installation orientations.
• NPTF and G Thread Options - Available in both NPTF and G (BSPP) thread standards for compatibility with North American and international pneumatic systems.
• Zinc Body and Dome Construction - Zinc body and zinc dome provide strength and durability in industrial environments. Acetal bonnet and knob resist corrosion from oil-mist atmospheres common near FRL stations.

Technical Specifications

General Specifications

Temperature Ratings

Temperature limits apply to both ambient environment and compressed air media. Standard Nitrile seals provide the following operating window.

Flow Performance Data

Flow performance measured at 91 psig (6.3 bar) inlet. Maximum rated flow is 170 scfm (4814 L/min) at 3/4" port.

Certifications & Compliance

Typical Applications & Industries

Automotive Assembly and Torque Control

• Precision supply regulation for nutrunners and torque pulse tools at multi-spindle assembly stations, where the MD4 manifold configuration allows grouping several Series units into a compact service panel serving an entire assembly cell.
• Engine assembly line air supply conditioning for pneumatic torque tools during cylinder head, intake manifold, and accessory drive fastening operations requiring joint-to-joint torque repeatability.
• Transmission assembly precision air supply where multiple regulated circuits at different set pressures serve different torque tools in the same assembly cell from a single MD4 manifold station.
• Robot end-of-arm tooling supply regulation for pneumatically actuated grippers and press tools on automated assembly robots, where compact MD4 platform size reduces robot arm payload.
• Final assembly audit tool supply regulation for quality verification torque tools requiring certified, documented air pressure for traceability of assembly records.

Machine Tool and Workholding

• CNC machining center workholding air supply regulation for pneumatic chuck, vise, and fixture actuators, where consistent clamping pressure ensures part position repeatability and machined dimension quality.
• Air bearing and hydrostatic spindle supply conditioning on precision grinding and turning centers, where regulated air pressure maintains bearing film thickness and spindle alignment.
• Tool changer and automatic pallet changer actuation supply for horizontal machining centers, where consistent pressure ensures complete actuator stroke and reliable tool seating.
• Chip conveyor and coolant system pneumatic actuator supply regulation on large machining centers with MD4 manifold FRL systems integrated into the machine control enclosure.
• Multi-axis coordinate measuring machine (CMM) probe air supply regulation for air-bearing CMM systems requiring extremely stable, contamination-free air at precise pressures.

MD4 Integrated FRL Applications

• MD4 FRL station construction combining Series precision regulator with ROSS MD4 filters and lubricators in a single manifold, serving multi-tool pneumatic supply points in automotive, aerospace, and general manufacturing facilities.
• Zone air preparation systems where multiple MD4 FRL stations handle different pressure zones in a facility, with each Series unit independently regulated to the zone's required tool supply pressure.
• Lockout valve integration with ROSS MD4 L-O-X lockout valves immediately upstream of the series in the manifold, enabling lockout/tagout compliant energy isolation for maintenance.
• Compressed natural gas and nitrogen service (consult ROSS for compatibility) where gas-compatible components in the MD4 system require precise pressure reduction from high-pressure storage to process working pressure.

Process and Instrumentation Applications

• Pilot supply conditioning for pneumatically actuated process valves and positioners in chemical, petrochemical, and water treatment facilities where the MD4 manifold configuration allows combining multiple pilot supply regulators in a single compact assembly.
• Laboratory and R&D bench supply air regulation for test fixtures, pneumatic actuated mechanisms, and precision motion systems requiring reproducible, documented air pressure.
• Spray coating and material application system supply regulation in paint finishing lines where precise atomization pressure maintains coating thickness uniformity.
• Pharmaceutical and food processing pneumatic actuator supply where clean compressed air at regulated, verifiable pressure drives actuators in packaging, filling, and sealing equipment.

Ordering and Model Number Configuration

The ROSS uses the MD4 modular platform model number structure. Configuration codes specify pressure range, port size, gauge option, and knob color. Both NPTF and G thread options are available.

Specify adjustment range code (E, F, or G) to select the correct internal spring for optimum sensitivity at the target operating pressure.

Yellow knob option (code Y) is available for visual identification of precision regulator stations in multi-regulator FRL panels.

Panel mount nut is included with gauge codes D and E. Order code A or B if panel mounting is not required.

G (BSPP) thread port codes are C, D, and E (for 3/8", 1/2", and 3/4" respectively). NPTF port codes are 3, 4, and 5.

Non-relieving option available; contact ROSS Controls for configuration. Non-relieving models maintain downstream pressure when inlet pressure drops below set point.

Pressure Range Selection

Port Size Codes

Accessories

Pressure Gauges

0 to 200 psig (0 to 14 bar) pressure gauges available for 1/4" NPT gauge ports. Specify gauge code B in model number to include gauge with the regulator.

Panel Mount Nut

Panel mount nut for 2-1/16" (52 mm) cutout installation. Included with gauge codes D and E in the model number configuration.

MD4 Modular FRL Components

ROSS Controls MD4 platform filters, lubricators, and MD4 L-O-X lockout valves connect directly to the series in modular manifold configurations. Contact ROSS Controls for complete MD4 assembly configuration.

Related Products & Accessories

• 121 Series Full-Size Precision Regulator - Full-size modular precision regulator for 1/4" to 3/4" ports on the standard FRL platform, flow to 155 scfm. https://www.rosscontrols.com/en/series/121-full-size-precision-series
• 123 Series High-Capacity Precision Regulator - Inline high-capacity precision regulator for 3/4" to 1-1/2" ports, flow to 800 scfm. https://www.rosscontrols.com/en/series/123-high-capacity-precision-series
• 125 Series MD4 Remote Pilot Regulator - MD4 platform remote pilot regulator adding remote set point capability to the same MD4 manifold system. https://www.rosscontrols.com/en/series/125-md4-series-remote-pilot-reg
• ROSS MD4 FRL Filters - MD4 platform modular filters for direct manifold connection upstream of the series. https://www.rosscontrols.com/en/categories/filters
• ROSS MD4 Lubricators - MD4 platform lubricators for downstream oil-mist addition in tool supply circuits. https://www.rosscontrols.com/en/categories/lubricators
• ROSS MD4 L-O-X Lockout Valves - MD4 compatible lockout valves for energy isolation upstream of MD4 FRL assemblies. https://www.rosscontrols.com/en/categories/lockout-valves

Frequently Asked Questions (FAQ)

Q: What is the MD4 platform and how does the series fit into it?

A: The MD4 is ROSS Controls' medium-duty modular FRL architecture providing higher flow capacity than the standard full-size modular system in a compact footprint. The Series is the precision regulator module designed for MD4 manifold assemblies, connecting directly to MD4 filters and lubricators without pipe fittings between modules. This reduces pressure drop and allows compact FRL station construction.

Q: How does the series compare to the 121 Series Full-Size Precision Regulator?

A: Both are modular precision regulators using diaphragm construction and holding pressure within 3 psig. The MD4 Series provides higher maximum flow (170 vs. 155 scfm at 3/4"), operates on the MD4 manifold platform rather than the standard full-size platform, and is slightly larger in the H and W dimensions. The 121 Series uses the standard full-size modular port spacing; these two series are not interchangeable in the same manifold without adapter blocks.

Q: What pressure ranges are available?

A: Three ranges: 15-100 psig (1.0-6.9 bar) code G for low-pressure applications, 15-200 psig (1.0-13.8 bar) code E for standard industrial use, and 15-250 psig (1.0-17.2 bar) code F for high-pressure requirements. Select the range closest to the target operating pressure to ensure optimum diaphragm spring sensitivity and regulation accuracy.

Q: What is the maximum inlet pressure the series can accept?

A: The Series maximum inlet pressure is 250 psig (17 bar). This is slightly lower than the 121 and 123 Series (which accept 300 psig). Verify that the supply system pressure does not exceed 250 psig for Series applications.

Q: Is a non-relieving configuration available?

A: Yes. While the standard Series is self-relieving, a non-relieving configuration is available for circuits where downstream pressure must be maintained when inlet pressure temporarily drops below set point. Contact ROSS Controls to specify the non-relieving option.

Q: What does the yellow knob option provide?

A: The yellow adjusting knob (code Y) provides a visual identification marker for precision regulator stations in multi-regulator FRL panels, making it easy to distinguish precision regulators from standard regulators in complex pneumatic distribution systems.

Q: What filtration is required upstream?

A: 5-micron minimum particulate filtration is recommended. ROSS Controls MD4 platform filters connect directly to the series in a modular manifold, providing integrated filtration without additional fittings or piping.

Q: Can the series be used as an inline regulator (non-modular)?

A: Yes. While designed primarily for MD4 modular manifold use, the series can be used in conventional inline piped configurations using NPTF or G threaded port connections.

Q: What is the operating temperature range?

A: Standard Nitrile seals allow operation from 40 F to 125 F (4 C to 52 C) for both ambient and compressed air media temperature. For environments above 125 F, consult ROSS Controls for alternative seal options.

Q: How is the set pressure adjusted and locked?

A: Turn the adjusting knob clockwise to increase outlet pressure and counterclockwise to decrease. The knob is removable after setting: once removed, the set point cannot be changed without the knob. This provides tamper resistance in production environments where unintended pressure changes could affect product quality.

Q: Can the series regulate nitrogen or other inert gases?

A: The Series is rated for compressed air service. For nitrogen or other inert gas applications, the wetted materials (Zinc body, Brass valve, Nitrile seals) must be evaluated for compatibility. Consult ROSS Controls for gas service applications.

Q: What is the pressure droop characteristic of the series?

A: Pressure droop (the reduction in regulated pressure as flow increases from zero demand to maximum demand) is held within 3 psig (0.2 bar) for the series. This tight droop specification is what defines it as a precision regulator and distinguishes it from standard industrial regulators, which typically exhibit 5 to 15 psig of droop at equivalent conditions.

Installation & Maintenance Guidelines

• Install a ROSS MD4 5-micron filter or equivalent upstream filter to protect the series valve seat from particulate damage.
• For modular manifold installation, follow ROSS Controls MD4 assembly guidelines for proper module alignment, port seating, and tie-rod torque specifications.
• Ensure inlet supply pressure does not exceed 250 psig (17 bar). The Series maximum inlet rating is lower than the 121 and 123 Series at 250 psig.
• Set the adjusting knob to the target outlet pressure and verify with a calibrated gauge at the front or rear 1/4" NPT gauge port. Remove the knob for tamper resistance after setting.
• For panel mounting, use a 2-1/16" (52 mm) diameter cutout with the optional panel mount nut. Verify adequate depth behind the panel for the 2.9" (73 mm) body.
• Plug unused gauge ports with 1/4" NPT plugs to prevent air release and contamination ingress.
• Maintain ambient temperature within 40 to 125 F (4 to 52 C). Temperatures outside this range affect diaphragm flexibility and regulation accuracy.
• In MD4 manifold assemblies, ensure all module connections and tie-rods are tightened to ROSS Controls specifications before applying supply pressure.
• After installation and set point adjustment, cycle supply pressure from minimum to maximum and verify regulated outlet pressure remains within 3 psig of set point at both no-flow and maximum flow conditions.
• Replace filter elements in the upstream MD4 filter per ROSS Controls maintenance intervals to prevent pressure drop buildup that could reduce available inlet pressure to the series.

Warranty & Global Support

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

Technical support for the series and MD4 FRL system is available through ROSS Controls USA at (800) 438-7677 and through global ROSS offices.

Replacement parts, seal kits, and MD4 manifold components are available through ROSS Controls and its authorized distributor network.

Visit rosscontrols.com for Series product configuration assistance, technical data downloads, MD4 manifold assembly guides, and distributor locator services.

Download Catalog: https://www.rosscontrols.com/en/documents