ABB RS85 Vibrating Fork Level Switch
Overview
The ABB RS85 is a vibrating fork level switch for point level detection of liquids and slurries in vessels, tanks and pipe systems. Its tuning-fork sensing element vibrates at its natural resonance frequency, and the electronics detect the frequency shift when the fork is covered by medium, triggering a switching output. The switch has no moving parts and is immune to flow, turbulence, bubbles, foam and changing product characteristics, which makes it a reliable choice for overflow protection, pump protection and low-level alarms.
Because detection relies on the physics of the fork’s own resonance rather than an optical or capacitive property of the medium, the RS85 works reliably across a very wide range of liquids and slurries – from clean water to viscous or coating-prone process fluids – without needing a medium-specific calibration. Seven Star LLC supplies the RS85 as an authorized ABB partner across Oman and the GCC, configuring the fail-safe mode, density set point, and process connection to the customer’s actual tank or pipeline conditions before shipment.
Engineering and Design
The fork assembly is manufactured in stainless steel with a robust sensing element that resists coating, buildup and mechanical damage. Field adjustment is possible without opening the housing: the fail-safe mode (high or low), density setting (0.52 to 2.0 g/cm3) and time delay (0.5 to 35 s) are selected with an external magnet or internal pushbuttons. Modular electronics with an alarm-status LED and built-in self-test diagnostics simplify commissioning and maintenance.
The RS85 operates at process temperatures from -40 to 250 F (-40 to 121 C) and pressures up to 2000 psig (137.8 bar), and handles media with viscosity up to 1000 cP. The electrical input accepts 18 to 36 VDC with a 1 x DPDT relay contact rated 8 A at 250 VAC or 30 VDC, and power consumption is only 1.5 W. Process connections include 3/4 in NPT threads, tri-clamp, and ASME flanges up to class 600, in 316 stainless steel as standard; the standard probe length is 85.8 mm (3-3/8 in).
Key Features
- Vibrating fork design with no moving parts – immune to flow, turbulence, bubbles and foam
- Field-selectable fail-safe (high/low), density (0.52-2.0) and time delay (0.5-35 s)
- Process pressure up to 2000 psig (137.8 bar) and temperature -40 to 250 F (-40 to 121 C)
- Stainless steel construction with 316SS process connection and robust coating-resistant fork
- Modular electronics with alarm-status LED and built-in self-test diagnostics
- ATEX/IECEx Ex d IIC T5/T6 Ga/Gb and II 1D Ex ta IIIC T150 C Da approvals
- FM approval: XP Class I, Division 1 Groups ABCD, Class III EFG
- Low power consumption of 1.5 W with 18-36 VDC supply and DPDT relay output
- Configurable with external magnet or internal pushbuttons without opening the housing
- High repeatability of 2.6 mm (0.1 in) for consistent switching performance
Applications
Overflow protection, pump dry-run protection and low-level alarm in storage tanks, process vessels, separators, pipe systems and sumps for liquids, slurries and media with changing dielectric properties. The ATEX/IECEx Ex d and FM Class I Division 1 certifications make the RS85 suitable for classified hazardous areas in upstream oil and gas facilities, while its 316 stainless steel wetted parts and tri-clamp connection option extend its use into hygienic food, beverage, and pharmaceutical processing lines across Muscat, Sohar, Salalah, and the wider GCC.
As an authorized ABB representative, Seven Star LLC helps customers select the correct probe length, connection type, and fail-safe logic (high or low) for the specific tank geometry and safety-instrumented function the switch is protecting, rather than supplying a generic off-the-shelf configuration that may not match the actual installation.
Specifications
| Measurement principle | Vibrating fork (tuning fork) point level switch |
| Process temperature | -40 to 250 F (-40 to 121 C) |
| Process pressure | Up to 2000 psig (137.8 bar) |
| Density set point | 0.52 to 2.0 g/cm3 (field selectable) |
| Viscosity | Up to 1000 cP |
| Input power | 18 to 36 VDC |
| Power consumption | 1.5 W |
| Output | 1 x DPDT relay, 8 A @ 250 VAC / 8 A @ 30 VDC resistive |
| Time delay | 0.5 to 35 s (adjustable) |
| Repeatability | 2.6 mm (0.1 in) |
| Probe length | 85.8 mm (3-3/8 in) standard |
| Process connection | 3/4 in NPT threaded, tri-clamp, ASME flanges to class 600 (316SS standard) |
| Cable entry | 2 x 3/4 in NPT (single compartment) |
| Approvals | ATEX/IECEx II 1/2G Ex d IIC T5/T6 Ga/Gb; II 1D Ex ta IIIC T150 C Da; FM XP Class I Div 1 |
Why Seven Star LLC
Seven Star LLC supplies ABB level instrumentation across Oman and the GCC with factory-verified specifications and certificates. Our engineers help you select the correct fork length, process connection and fail-safe configuration for your tank, vessel or pipeline application.
Request a Quote for ABB RS85 Vibrating Fork Level Switch
Send your tank dimensions, process medium and set-point requirements to our engineering team for a quotation. Use the Inquiry Form below and attach your datasheet or P&ID extract – we confirm availability and pricing for your project. | Inquiry Form
Related Products
ABB is one of the world’s leading technology companies in electrification and automation, recognized for its commitment to innovation, reliability, and energy efficiency. With a history spanning more than a century, ABB delivers high-performance products and systems that help industries operate more intelligently and sustainably.
The company’s expertise covers a wide range of fields including power distribution, process automation, robotics, motion control, and digital solutions for smart manufacturing. ABB’s products are designed to enhance productivity, safety, and operational efficiency while reducing energy consumption and environmental impact.
Seven Star LLC supplies a complete selection of genuine ABB products, including industrial drives, PLCs, contactors, sensors, relays, and automation components, serving clients across oil & gas, energy, marine, and manufacturing sectors.
By combining ABB’s advanced engineering with Seven Star LLC’s trusted sourcing and support, customers gain access to reliable, future-ready industrial solutions built to meet the most demanding standards of modern industries.
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