Differential Pressure Gauge Differential Pressure Gauge

Product Overview

The ROSS Controls provides differential pressure gauges for monitoring the condition of FRL filter elements. These gauges measure the pressure drop across the filter element - the difference between inlet and outlet pressure - and provide a visual indication of filter loading. As a filter element becomes saturated with particulate, pressure drop increases; the series gauge indicates when the element has reached the service threshold and requires replacement.

The Series includes two gauge types: the small slide gauge (models R-A60F-28 and R-K103-151) and the large dual-face gauge (models R-106-35, R-106-35E, R-106-35EC). The large dual-face gauge displays both inlet and outlet pressure simultaneously on color-coded graduated arcs, providing immediate visual comparison of inlet and outlet conditions. The R-106-35E and R-106-35EC models add a reed switch output for remote electrical indication of filter loading - normally open (NO) and normally closed (NC) configurations respectively.

Without a differential pressure gauge, filter element replacement is performed on a scheduled calendar basis regardless of actual loading condition. This can result in premature replacement of still-serviceable elements (increasing maintenance cost) or continued operation with an excessively loaded element (causing pressure drop losses and downstream flow starvation). The Series provides condition-based maintenance capability, ensuring filter elements are replaced based on actual condition rather than arbitrary time intervals.

Five model variants cover applications from compact visual monitoring (R-A60F-28) to large-scale visual monitoring with remote PLC alarm output (R-106-35E, R-106-35EC). Engineers specifying FRL systems for applications where compressed air pressure loss monitoring is critical will find the series an essential element of the complete air preparation package.

Key Engineering Features

• Condition-Based Filter Maintenance - Indicates actual filter element loading rather than calendar time, enabling replacement only when needed and preventing both premature replacements and operation with excessively loaded elements.
• Dual Inlet and Outlet Pressure Display - The large dual-face models (R-106-35 series) simultaneously display both inlet and outlet pressure on a single gauge face, allowing immediate visual assessment of pressure drop across the filter element.
• Reed Switch Output for Remote Alarming - R-106-35E (normally open) and R-106-35EC (normally closed) models provide an electrical reed switch output that activates at the filter loading threshold, enabling remote alarm indication via PLC or control system without physical inspection of the gauge.
• Color-Coded Gauge Zones - The large dual-face gauge features color-coded indicator zones (green, yellow, red arcs) for clear visual identification of filter element condition from a distance, reducing inspection time at FRL installations with multiple filter assemblies.
• Two Gauge Sizes - Small slide gauge formats (R-A60F-28, R-K103-151) for compact installations and large dual-face gauge format (R-106-35 series) for prominent visual monitoring, providing appropriate gauge sizing for each application.
• Compatible Across ROSS FRL Product Range - The Series differential pressure gauges are designed for use with ROSS FRL filter assemblies across the Bantam, Miniature, Mid-Size, Full-Size, MD3, MD4, and High-Capacity filter product families.

Technical Specifications

General Specifications

Temperature Ratings

The Series differential pressure gauges are designed for installation in the compressed air media stream at FRL filter assemblies within standard industrial temperature conditions.

Important: Verify gauge temperature compatibility with the specific FRL filter installation, particularly for metal bowl assemblies where media temperature can reach 175F (80C).

Electrical Data (Solenoid Pilot Valves)

The R-106-35E and R-106-35EC models include a reed switch electrical output. Reed switches are dry contact outputs with no internal power supply requirement.

Electrical Connection Options

Certifications & Compliance

Typical Applications & Industries

Condition-Based Maintenance Programs

• FRL filter assemblies throughout a large manufacturing facility equipped with R-106-35 large dual-face gauges, enabling maintenance technicians to assess filter loading during walkthrough inspections without removing filter elements for visual inspection.
• MD3 and MD4 filter installations in continuous process facilities with R-106-35E gauges providing reed switch output to a SCADA system for remote filter loading alarm indication, eliminating the need for physical gauge inspection at each filter location.
• High-capacity filter assemblies in compressor rooms where R-K103-151 slide gauges provide compact visual loading indication without requiring additional panel space at already-crowded compressor station installations.

Pharmaceutical and Food Processing

• FRL filter elements in pharmaceutical cleanroom air supply systems monitored with R-106-35EC (normally closed reed switch) gauges wired to building management systems to generate automatic maintenance work orders when filter loading reaches the service threshold.
• Food processing compressed air filters with R-106-35 large dual-face gauges providing immediate color-coded visual indication of filter status to operators during production line inspection rounds, supporting food safety air quality management programs.
• Multiple filter stations in beverage production facilities monitored with R-106-35E gauge outputs wired to a central PLC alarm panel for consolidated filter status monitoring across the facility.

Automotive and General Manufacturing

• FRL filter assemblies at robotic welding cells with R-A60F-28 small slide gauges for compact, cost-effective filter condition indication at multiple cell supply points.
• High-flow Full-Size and MD4 filter assemblies in paint line supply systems with R-106-35E gauges providing remote alarm output to paint line supervisory systems, ensuring consistent paint quality is not degraded by excessive filter loading causing pressure drops.
• Mid-Size filter assemblies at assembly cell supply drops with R-K103-151 slide gauges, enabling cell operators to identify filter condition at a glance without waiting for maintenance inspection.

Energy Management and Compressed Air Auditing

• Differential pressure gauges installed at all FRL filters in a compressed air audit program to quantify system-wide pressure losses from filter loading, identifying the highest-loaded filters for priority replacement and energy recovery.
• R-106-35 large dual-face gauges at main air preparation filter banks enabling facilities engineers to correlate filter loading patterns with compressor operating hours and air consumption trends for optimization of maintenance intervals.
• R-106-35E gauges with reed switch outputs connected to energy management systems to track filter replacement frequency and calculate compressed air energy costs attributable to elevated filter pressure drop.

Ordering and Model Number Configuration

The Series differential pressure gauge is selected based on gauge size and whether remote electrical output is required. Five models cover all application requirements from compact visual monitoring to remote electrical alarm integration.

Select R-A60F-28 or R-K103-151 for compact installations requiring visual-only indication at small filter assemblies.

Select R-106-35 for prominent visual indication at larger filter assemblies (Full-Size, MD3, MD4) where the large dual-face display is visible from a distance.

Select R-106-35E (normally open) when remote PLC alarm output is required and the PLC input is configured for a closing-contact alarm signal.

Select R-106-35EC (normally closed) when the PLC input is configured for an opening-contact (fail-safe) alarm signal, where loss of the reed switch circuit also triggers the alarm.

Verify reed switch contact ratings against control circuit specifications before wiring R-106-35E or R-106-35EC to control systems.

Consult the specific FRL filter model data sheet to identify the gauge port size and location for correct differential pressure gauge installation.

Accessories

Series Model Selection Summary

Select based on gauge size, display type, and remote output requirements.

Companion FRL Accessories

Complete filter condition management with additional accessories.

Related Products & Accessories

• 163 Series External Automatic Drains - Float-operated automatic drain for Full-Size, High-Capacity, MD3, and MD4 FRL filter bowls, used alongside differential pressure gauges for complete filter maintenance management. https://www.rosscontrols.com/en/series/163-full-size-high-capacity-md3-md4
• 164 Series Electronically Controlled Drains - Programmable electronic drain for FRL filter bowls, complementing differential pressure gauge condition monitoring. https://www.rosscontrols.com/en/series/164-electronically-controlled-drains
• 173 Series MD3 and MD4 Port Blocks - End ports for MD3 and MD4 FRL assemblies where extra port blocks between modules provide auxiliary connection points for differential pressure gauge installation. https://www.rosscontrols.com/en/series/173-md3-md4
• Full-Size Series FRL Filters - ROSS Full-Size Series filters where Series differential pressure gauges monitor filter element condition. https://www.rosscontrols.com/en/categories/59-frl-accessories
• 169 Series Connector and Bracket Kit - Modular assembly accessories for Mid-Size and Full-Size FRL systems that incorporate Series differential pressure gauges. https://www.rosscontrols.com/en/series/169-mid-size-full-size

Frequently Asked Questions (FAQ)

Q: How does a differential pressure gauge indicate filter condition?

A: A differential pressure gauge measures the pressure difference between the filter inlet and outlet. When the filter element is clean, pressure drop is minimal and the gauge reads low. As the element loads with particulate, flow restriction increases, and the pressure difference (differential pressure) increases. When the reading reaches the service threshold marked on the gauge, the element requires replacement. The gauge provides a direct, real-time indication of actual filter condition.

Q: What is the difference between R-106-35, R-106-35E, and R-106-35EC?

A: All three are large dual-face differential pressure gauges with the same visual display. The R-106-35 is visual only. The R-106-35E adds a reed switch with normally open (NO) contacts that close when the filter loading threshold is reached, providing an electrical alarm output to a PLC or relay. The R-106-35EC provides the same reed switch but with normally closed (NC) contacts that open at threshold - the preferred configuration for fail-safe alarm circuits.

Q: What is a reed switch and how does it work in the R-106-35E/EC?

A: A reed switch is a magnetically actuated dry contact switch enclosed in a sealed glass capsule. In the R-106-35E/EC, the gauge indicator mechanism activates the reed switch when the differential pressure reading reaches the service threshold. The reed switch provides a clean electrical contact that can be wired to a PLC digital input, relay coil, or alarm indicator without any electrical connection to the gauge body.

Q: At what pressure differential does the R-106-35E reed switch activate?

A: Contact ROSS Controls at (800) 438-7677 for the specific differential pressure activation setpoint for the reed switch models. The activation threshold is matched to the service interval recommendation for ROSS FRL filter elements.

Q: Can the series gauge be used with all ROSS FRL filter sizes?

A: Yes. The Series gauges are designed for use across the ROSS FRL filter range including Bantam, Miniature, Mid-Size, Full-Size, MD3, MD4, and High-Capacity Series filters. Verify gauge port size compatibility with the specific filter model data sheet.

Q: What is the advantage of the large dual-face R-106-35 gauge over the small slide gauge?

A: The large dual-face R-106-35 gauge simultaneously displays both inlet and outlet pressure on separate color-coded arcs, making the pressure differential immediately clear at a glance and visible from a greater distance. The small slide gauges (R-A60F-28, R-K103-151) are more compact but provide less visual prominence, appropriate for installations where gauge visibility is less critical or space is limited.

Q: Is the series gauge required on all FRL installations?

A: The Series gauge is optional but strongly recommended for any FRL installation where filter maintenance intervals cannot be reliably predicted from operating experience alone, or where filter loading affects production equipment performance. On installations where compressed air quality is critical (food processing, pharmaceuticals, paint finishing), the gauge provides a valuable condition monitoring layer.

Q: Can the R-106-35E reed switch output be connected directly to a 24 VDC PLC input?

A: Reed switches are typically rated for low currents compatible with PLC digital inputs. Verify the R-106-35E reed switch contact ratings with ROSS Controls before wiring to any control circuit. Do not exceed the contact current or voltage rating.

Q: Does the gauge reading change if the inlet pressure changes?

A: Yes. Differential pressure across the filter element depends on both flow rate and filter loading. Changes in inlet pressure that alter flow rate will change the differential pressure reading without any change in filter loading. Interpret gauge readings in the context of normal system operating pressure and flow conditions.

Q: Is there a gauge version with a 4 to 20 mA output for SCADA integration?

A: The Series catalog currently offers reed switch outputs on the R-106-35E and R-106-35EC models. For 4 to 20 mA analog output requirements, contact ROSS Controls at (800) 438-7677 to discuss available options.

Q: Can I install a Series gauge on an existing FRL assembly that does not currently have one?

A: Yes. ROSS FRL filter bodies include dedicated gauge ports (1/8 or 1/4 inch NPT) on both the inlet side and outlet side for differential pressure gauge connection. Consult the specific FRL filter data sheet for gauge port locations and sizes.

Q: What is the price of the large dual-face gauge with the normally open reed switch?

A: The R-106-35E (large dual-face gauge with normally open reed switch) is priced at $304.50. The R-106-35 (visual only, no reed switch) is $249.25. The R-A60F-28 small slide gauge is $45.25.

Installation & Maintenance Guidelines

• Identify the inlet gauge port and outlet gauge port on the FRL filter body (typically 1/8 or 1/4 inch NPT ports on front and rear of the filter housing).
• Ensure system is depressurized before installing gauge connections.
• Connect the high-pressure port of the differential pressure gauge to the filter inlet gauge port.
• Connect the low-pressure port of the differential pressure gauge to the filter outlet gauge port.
• Apply PTFE tape or appropriate thread sealant to all NPT gauge port fittings.
• Tighten gauge connections to standard pneumatic gauge port torque values. Do not overtighten.
• Pressurize the system and verify no leaks at gauge connections.
• Confirm the gauge reads near zero differential pressure with a clean, new filter element installed.
• For reed switch models (R-106-35E and R-106-35EC): connect the reed switch leads to the control circuit per the wiring diagram in the gauge documentation. Verify correct contact state (NO or NC) against PLC input configuration.
• Record the baseline differential pressure reading at startup for reference during monitoring.

Warranty & Global Support

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

Global technical support available through ROSS offices in the USA, Canada, Brazil, Germany, France, United Kingdom, India, China, and Japan.

Contact ROSS Controls USA at (800) 438-7677 or visit rosscontrols.com for product configuration, technical support, and distributor locator services.

For the complete FRL accessories catalog, gauge dimensional drawings, and installation instructions, visit rosscontrols.com or contact ROSS Controls at (800) 438-7677.

Download Catalog: https://www.rosscontrols.com/en/series/174-differential-pressure-gauge