Brand: ABB

ABB RS85 Vibrating Fork Level Switch

Name: ABB RS85 Vibrating Fork Level Switch – Datasheet & Quote
Brand: ABB

Description

Overview

The ABB RS85 vibrating fork level switch is designed 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 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 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.

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.

Choosing the Switch Configuration

Point level switches are simple devices, but most field problems come from a configuration that does not match the duty. Before ordering the ABB RS85 vibrating fork level switch, confirm the following:

Switching function: high-level (overfill) or low-level (dry-run) protection, and the fail-safe mode that goes with it.
Medium density: whether the liquid falls inside the adjustable density range listed above, particularly for light hydrocarbons.
Mounting position: top, side or pipe installation, and whether an extension is needed to reach the switching point.
Process connection and electronics: the thread or flange on the vessel and the output type required by the control system.

Installation Best Practice

In side-mounted installations, orient the fork so that its tines are vertical, allowing liquid to drain away and solids to slide off. Avoid positions directly in the fill stream or where the tines can be struck by agitators or falling product. In pipes, mount the fork so the flow passes between the tines rather than across their flat faces.

Commissioning and Testing

After installation, check the switching state with the vessel both empty and covered, and confirm that the delay setting suits the level behaviour of the process. Many sites include a periodic functional test in their maintenance plan, especially where the switch forms part of an overfill or pump-protection function.

Troubleshooting

False switching is usually caused by heavy coating bridging the tines, a density setting that does not suit the product, or mechanical vibration transmitted from nearby pumps. Cleaning the fork and reviewing the density and delay settings resolves most cases.

Use in Oman and the GCC

Storage tanks, sumps, desalination chemical dosing tanks and pump suction vessels across the region use vibrating fork switches for reliable alarms in high ambient temperatures. Seven Star LLC supplies the RS85 vibrating fork level switch with the settings reviewed against your process data before dispatch.

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 lead time for your project. | Inquiry Form

Reviews

There are no reviews yet.

How would you rate this product?

About brand

ABB is the Swiss-Swedish engineering group for electrification and automation: low voltage drives, motors, circuit breakers and motor control, process instruments and analysers, control systems and robots. It was formed on 5 January 1988 by the merger of two older companies. ASEA was founded in Västerås, Sweden, in 1883 by Ludvig Fredholm to make electric lighting and generators. BBC Brown Boveri was founded in Baden near Zurich in 1891 by Charles E. L. Brown and Walter Boveri. ABB Ltd is incorporated in Switzerland, headquartered in Zurich and listed on the SIX Swiss Exchange and Nasdaq Stockholm.

ABB company profile

Formed	5 January 1988, by the merger of ASEA (Sweden) and BBC Brown Boveri (Switzerland), each holding 50%
ASEA	Founded 1883 in Västerås, Sweden, by Ludvig Fredholm; first products electric lighting and generators
Brown, Boveri & Cie	Founded 1891 in Baden, Switzerland, by Charles E. L. Brown and Walter Boveri
Headquarters	Zurich, Switzerland; ABB Ltd became the group holding company in 1999
Ownership	Public company listed on SIX Swiss Exchange and Nasdaq Stockholm
Brands in the group	Baldor (US motors, acquired 2011), B&R (machine automation, acquired 2017), K-TEK level instruments, Endura and Navigator analysers, SACE breakers
Product families	Low and medium voltage drives (ACS series), motors, SACE Tmax and Emax breakers, contactors and soft starters, flow, pressure, temperature and level instruments, liquid and gas analysers, Contrac actuators, AC500 PLCs, Ability System 800xA and S800 I/O, protection relays, robots

Milestones

1883: ASEA is founded in Västerås, Sweden.
1891: Brown, Boveri & Cie is founded in Baden, Switzerland.
1987–1988: The merger is announced on 10 August 1987; ABB Asea Brown Boveri starts operating on 5 January 1988.
1999: ABB Ltd, incorporated in Switzerland, becomes the single holding company of the group.
2011 and 2017: Baldor Electric and B&R join ABB.
2020: ABB sells its power grids business to Hitachi, focusing on electrification, motion, process and machine automation.

Choosing an ABB drive

ABB's ACS drive codes are easy to read once you know the pattern. In ACS580-01-046A-4, "ACS580" is the drive family, "01" means a wall-mounted single drive, "046A" is the rated output current (about 46 A) and "-4" means a 380–480 V supply. The family is chosen by application: ACS355 for compact machinery, ACS310 for simple pumps and fans, ACS580 as the general-purpose drive, ACQ580 for water and wastewater with pump functions such as pipe fill and dry-run protection, and ACS880 for heavy industrial duty with direct torque control. Size the drive on the motor's full-load current, not only its kW rating, and allow derating for the high ambient temperatures common in Gulf electrical rooms.

Where ABB products are used

In Oman and the GCC, ABB drives and motors run pumps, fans and compressors in water and wastewater plants, district cooling, oil and gas and industry. ABB flowmeters, level instruments and analysers are used in water utilities, power and desalination plants and refineries, and SACE breakers protect switchboards in buildings and plants.

ABB products we list

Family	Examples
AC drives	ACS580, ACS580-01-046A-4, ACQ580, ACS355, ACS310, ACS880-01, FEN-31 encoder module
Breakers, motor control and protection	SACE Tmax XT, XT3N 250, SACE Emax 2, AF09 contactor, PSR soft starter, REM615 relay
Flow measurement	ProcessMaster FEP300, AquaMaster4, CoriolisMaster FCB430, VortexMaster FSV430, SwirlMaster FSS430, OriMaster FPD500
Pressure, temperature and level	266DRH, 267CS multivariable, TTH300, K-TEK AT100, LMT200, MT5000 GWR, KM26 gauge
Analysers	Endura AZ20, AK100 hydrogen purity, Navigator AW641 silica, AW402 chlorine, AWT210
Control systems and actuators	AC500, AC500-S, S800 AI810, AC 800F SA 811F, Contrac RSD50, Contrac RHD4000

Ordering ABB products: what we need

Send the full type code from the nameplate (for example ACS580-01-046A-4 or 266DSH...) and, for spare parts, the ABB ID number (such as 3BSE008508R1 or 1SBL176001R3010). For drives, add the motor power and current and any option codes (+...). For instruments, send the complete order code, which sets range, materials and approvals. Baldor motors are listed on their own brand page.

Facts checked against ABB company filings and published histories of ASEA and Brown, Boveri & Cie, October 2026.

FAQ

Questions about the ABB RS85 Vibrating Fork Level Switch

Answers from our engineering team on installation, compatibility and integration.

01What is the ABB RS85 vibrating fork level switch used for?

The RS85 provides point level detection of liquids and slurries: overflow protection, pump dry-run protection and low-level alarms in tanks, vessels, separators, pipe systems and sumps.

02What process conditions can the RS85 handle?

The RS85 operates at temperatures from -40 to 250 F (-40 to 121 C) and pressures up to 2000 psig (137.8 bar), with media viscosity up to 1000 cP and density settings from 0.52 to 2.0 g/cm3.

03What approvals does the RS85 carry?

ATEX/IECEx II 1/2G Ex d IIC T5/T6 Ga/Gb and II 1D Ex ta IIIC T150 C Da, plus FM XP Class I Division 1 Groups ABCD and Class III EFG.

04How is the RS85 configured in the field?

Fail-safe mode (high or low), density and time delay (0.5 to 35 s) are selected with an external magnet or internal pushbuttons without opening the housing.

05What is the output of the RS85?

A 1 x DPDT relay contact rated 8 A at 250 VAC or 30 VDC, powered from 18 to 36 V DC with only 1.5 W power consumption.