Mid-Size Series Port Sizes 1/4" to 1/2"; Flow to 100 scfm (2832 l/min)

Product Overview

The ROSS Controls Mid-Size Series is a family of modular pressure regulators covering port sizes of 1/4", 3/8", and 1/2" with a maximum flow capacity of 100 scfm (2832 l/min). The modular construction enables direct connection to other Mid-Size Series FRL components, forming integrated filter-regulator-lubricator assemblies without additional fittings.

Both piston and diaphragm construction options are available. Piston construction provides the highest air flow through the Mid-Size body. Diaphragm construction delivers faster downstream pressure response, making it the preferred choice for weld gun pressure control and other applications requiring rapid pressure recovery.

A reverse flow option is available on the Mid-Size Series, providing regulated pressure control in the normal (inlet-to-outlet) flow direction plus quick exhausting capability in the reverse (outlet-to-inlet) direction. This feature is particularly valuable for weld gun pneumatic circuits where rapid downstream pressure release between welds is required.

Adjustment is available via a knob or T-Handle. The T-Handle option provides increased adjustment torque, facilitating set point changes on high-spring-force models or in installations where gloves are worn. Both adjustment types include a removable locking key for tamper resistance after commissioning. All models are self-relieving as standard, and non-relieving configurations are available by special order.

Key Engineering Features

• Modular Mounting - Connects directly to Mid-Size Series FRL filters and lubricators without additional fittings, forming compact air preparation assemblies.
• Piston and Diaphragm Construction - Piston provides maximum flow; diaphragm provides faster downstream pressure response for weld gun and precision control applications.
• Reverse Flow Option - Provides regulated downstream pressure in normal flow plus quick exhaust capability in reverse flow direction, purpose-designed for weld gun and downstream pressure release applications.
• Knob and T-Handle Adjustment - Standard knob for most installations; T-Handle for increased adjustment torque in applications requiring high spring force or glove-friendly operation.
• Removable Locking Key - After setting the outlet pressure, the locking key can be removed to prevent unauthorized set point changes during machine operation.
• Self-Relieving Standard - Automatically exhausts excess downstream pressure when the set point is reduced. Non-relieving available by special order.
• Maximum Flow 100 scfm (2832 l/min) - More than four times the flow capacity of the 112 Bantam Series, suitable for larger actuators and higher air demand circuits.
• Pressure Gauge Included - Integrated gauge with 1/4" gauge ports on front and rear for bidirectional installation, providing continuous outlet pressure monitoring.
• Panel Mounting Option - 1-9/16 inch (40 mm) panel mounting hole allows direct panel installation without a separate bracket.

Technical Specifications

General Specifications

Certifications & Compliance

Typical Applications & Industries

Welding and Metal Fabrication

• Resistance spot weld gun air pressure circuits requiring both regulated downstream pressure for electrode force control and rapid exhaust between welds. The reverse flow option provides both functions in a single regulator body.
• Pneumatic weld positioner and fixture actuators where independently regulated pressure zones ensure consistent electrode contact force across multiple welding stations.
• MIG and TIG welding purge gas pressure regulation circuits where the Mid-Size piston regulator provides stable flow at moderate pressure.
• Robotic weld cell pneumatic air preparation using modular Mid-Size filter-regulator assemblies to maintain regulated supply pressure at each robot station.

Automotive Manufacturing

• Body shop pneumatic clamp and fixture circuits requiring regulated air at 1/4" to 1/2" port sizes for workholding during welding and assembly operations.
• Assembly line pneumatic torque tool supply circuits where regulated pressure at 0 to 100 psig ensures consistent fastener torque output.
• Trim and final assembly station pneumatic circuits using modular FRL assemblies with Mid-Size regulators to prepare air for multiple downstream tools.

Packaging and Food Processing

• Horizontal form-fill-seal machine actuators requiring regulated air at 1/4" or 3/8" port sizes within machine frames.
• Rotary and linear indexing table pneumatic circuits where regulated pressure ensures consistent cycle timing and actuator force.
• Beverage filling machine actuator supply using modular filter-regulator assemblies for air preparation at each filling head station.

General Industrial Automation

• Multi-zone pneumatic systems where each zone requires independently regulated and tamper-resistant pressure using modular Mid-Size assemblies.
• Pneumatic press and forming machine circuits where 100 scfm flow capacity supports rapid actuator cycling without excessive pressure drop.
• Material handling pneumatic circuits using the T-Handle adjustment option for convenient set point changes by operators wearing gloves.
• Modular FRL stations combining Mid-Size filters, regulators, and lubricators for centralized air preparation in machine tool enclosures.

Ordering and Model Number Configuration

Related Products & Accessories

• 112 Bantam Series Pressure Regulators - Compact modular-mount regulators with port sizes 1/8" to 3/8", piston or diaphragm construction, flow to 23 scfm. https://www.rosscontrols.com/en/series/112-bantam-series
• MD3 Series Pressure Regulators - Modular diaphragm regulators with port sizes 1/4" to 1/2", flow to 120 scfm, higher inlet pressure rating. https://www.rosscontrols.com/en/series/115-md3-series
• 116 Full-Size Series Pressure Regulators - Modular diaphragm regulators with port sizes 1/4" to 3/4", flow to 155 scfm. https://www.rosscontrols.com/en/series/116-full-size-series
• ROSS FRL Filters Mid-Size Series - Mid-Size Series particulate filters for modular assembly with Mid-Size Series regulators. https://www.rosscontrols.com/en/categories/36-air-preparation-frls

Frequently Asked Questions (FAQ)

Q: What port sizes are available for the Mid-Size Series?

A: The Mid-Size Series is available in 1/4", 3/8", and 1/2" port sizes in both NPTF and G (BSPP) thread forms.

Q: What is the maximum flow capacity?

A: The Mid-Size Series has a maximum flow capacity of 100 scfm (2832 l/min) at standard conditions.

Q: What is the maximum inlet pressure?

A: The maximum inlet pressure is 250 psig (17 bar).

Q: What regulated pressure ranges are available?

A: Three pressure ranges are offered: 0 to 50 psig (0 to 3.4 bar), 0 to 100 psig (0 to 6.9 bar), and 0 to 150 psig (0 to 10.3 bar). Select the range that covers the desired set point with adequate adjustment resolution.

Q: Should I choose piston or diaphragm construction?

A: Choose piston for maximum flow and standard pressure regulation. Choose diaphragm for faster downstream pressure response and greater sensitivity, particularly for weld gun applications where rapid pressure recovery between cycles is required.

Q: What is the reverse flow option and when should I use it?

A: The reverse flow option provides regulated pressure in the normal inlet-to-outlet direction plus quick exhaust capability in the outlet-to-inlet direction. This is the standard selection for weld gun pneumatic circuits, where rapid downstream pressure release between welds reduces cycle time.

Q: What adjustment options are available?

A: Knob and T-Handle adjustments are both available. The T-Handle provides higher adjustment torque for set point changes on high-spring-force models or when operators are wearing gloves. Both types include a removable locking key for tamper resistance.

Q: Is the Mid-Size Series self-relieving?

A: Yes. The standard Mid-Size Series is self-relieving, automatically exhausting excess downstream pressure when the set point is reduced. Non-relieving configurations are available by consulting ROSS Controls.

Q: What panel mounting hole size is required?

A: The Mid-Size Series requires a 1-9/16 inch (40 mm) panel mounting hole for direct panel installation.

Q: Does the series include a pressure gauge?

A: Yes. A pressure gauge rated 0 to 200 psig (0 to 14 bar) is included, with 1/4" gauge ports on both front and rear of the body.

Q: What body material is used?

A: The body is zinc. The dome is acetal. The knob is acetal. The cap is nylon. Seals are nitrile. This construction is appropriate for standard industrial compressed air service.

Q: Are G (BSPP) thread models available?

A: Yes. G thread models are available by prefixing the standard model number with 'C' (e.g., C5211B3015 for a 3/8" G thread regulator at 0 to 100 psig).

Q: How does modular mounting work with the series?

A: Mid-Size Series FRL components connect side-by-side using internal porting at the modular interface faces, eliminating the need for pipe nipples or fittings between components. Contact ROSS Controls for modular port block and assembly hardware.

Q: What is the ambient temperature range?

A: The Mid-Size Series is rated for ambient temperatures from 40 to 125 degrees F (4 to 52 degrees C), covering standard industrial indoor environments.

Installation & Maintenance Guidelines

• Install the Mid-Size Series with the inlet port connected to the supply side and the outlet port 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 Mid-Size Series interface connections are secure before pressurizing the assembly.
• Apply thread sealant only to male threaded connections. Keep sealant away from the first two threads to prevent contamination of internal passages and the downstream circuit.
• Set the outlet pressure with no load on the downstream system by rotating the adjustment knob or T-Handle clockwise to increase and counterclockwise to decrease.
• Monitor the integrated gauge during adjustment to confirm the outlet pressure matches the desired set point before locking the adjustment.
• Remove the locking key after reaching the final set point to prevent unauthorized adjustment during machine operation.
• Verify self-relieving operation by reducing the set point and confirming downstream pressure decreases without requiring separate exhaust actuation.
• For reverse flow models, verify both functions after installation: confirm regulated pressure in the forward direction and confirm quick exhaust operation in the reverse direction.
• Do not exceed 250 psig (17 bar) inlet pressure. Exceeding this limit risks body damage and uncontrolled downstream pressure increase.
• For panel-mounted installations, use a 1-9/16 inch (40 mm) hole. Ensure the gauge is accessible from the normal operator or maintenance position.
• Inspect all port connections for leaks after initial pressurization using soapy water or an approved leak detection solution.
• Ensure upstream filtration is installed. The Series requires clean compressed air to protect nitrile seals and internal seating surfaces from particulate damage.

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 product page at rosscontrols.com or contact ROSS Controls directly.

Download Catalog: https://www.rosscontrols.com/en/series/114-mid-size-series