Rosemount 2120 Vibrating Fork Level Switch
Overview
The Rosemount 2120 is a vibrating fork level switch for point level detection in liquids, including aerated liquids, coating liquids and slurries. It is used as a high or low level alarm, an overfill prevention layer, a pump control switch or a dry-run protection device in pipes and tanks. Emerson designed the switch for process temperatures from –40 to 150 °C, with electronic self-checking and condition monitoring, a SIL2 certificate to IEC 61508 as required by IEC 61511, and SIL3 capability. Because it has no moving parts and needs no calibration, the switch is practically install-and-forget once it is mounted.
Seven Star LLC supplies the Rosemount 2120 to oil and gas, refining, water, power and chemical customers in Oman and the GCC. Our engineering team in Muscat helps match the fork material, process connection, electronics cassette and hazardous area approval to each tank or line, using the Rosemount 2120 datasheet as the reference, and confirms lead time for maintenance and project orders.
Measurement Principle
The switch works on the tuning fork principle. A piezo-electric crystal oscillates the forks at their natural frequency, and the electronics monitor this frequency continuously. The frequency depends on the medium surrounding the fork: the denser the liquid, the lower the oscillation frequency. In a low level alarm, the liquid drains down past the fork and the frequency change switches the output from wet to dry. In a high level alarm, rising liquid contacts the fork and switches the output from dry to wet.
This principle makes the Rosemount 2120 virtually unaffected by flow, bubbles, turbulence, foam, vibration, solids content, coating products and changes in liquid properties. The fast drip fork shape draws liquid away from the tip quickly, giving a faster response with viscous or high-density liquids, while a user-selectable delay of 0.3, 1, 3, 10 or 30 seconds prevents false switching where liquid splashes in agitated or turbulent tanks. In water the hysteresis is 2.5 mm and the switching point is 13 mm from the fork tip when mounted vertically.
Engineering Design of the Rosemount 2120
Wetted parts are 316/316L stainless steel as standard, with alloy C and C-276 or ECTFE-coated stainless steel for corrosive service. Process connections include 3/4, 1 and 2 inch threads in BSPT, BSPP and NPT, Tri Clamp fittings, and ASME B16.5, EN 1092 and JIS flanges from 1 to 4 inches in pressure classes up to Class 600 and PN 100. The standard fork projects only about 44 mm on threaded versions, so it can be installed in small pipes at any angle, and extended lengths up to 4,000 mm let the fork reach a precise level from a top-mounted nozzle.
Housings are glass-filled nylon, aluminum alloy or 316 stainless steel, all rated IP66/67 with NEMA 4X on the metal versions, and M20, 1/2 inch NPT or 3/4 inch NPT conduit entries. A heartbeat LED flashes when the output is off and stays lit when it is on, giving a constant indication that the Rosemount 2120 is healthy. Holding a magnet to the test point on the side of the housing changes the output state, so the switch and the connected system can be function-tested without draining the vessel.
Key Features
The Rosemount 2120 datasheet highlights these features for safety and process duties.
- SIL2 certified to IEC 61508 as required by IEC 61511, and SIL3 capable for safety instrumented functions.
- Operates at process temperatures from –40 to 150 °C and threaded process pressures up to 100 barg.
- Detects liquids with a density of 600 kg/m3 or more and viscosities up to 10,000 cP.
- Offers plug-in direct load, PNP/PLC, DPCO relay, NAMUR and 8/16 mA electronics with selectable mode and delay.
- Uses a fast drip fork design for quicker response in viscous liquids.
- Provides a quick release kit that makes inspection, proof-testing and servicing easier.
- Includes general area, explosion-proof/flameproof and intrinsically safe certification options.
- Carries 3-A and EHEDG hygienic certification with polished fork options for sanitary service.
Industrial Applications
In Oman and the wider GCC, the Rosemount 2120 is used for independent high and high-high alarms on crude, condensate and product storage tanks, for overfill protection on chemical day tanks, for low level and dry-run protection on pump suction lines, and for level limits in drain vessels, sumps and lube oil reservoirs. Its compact fork suits small pipes and skid-mounted packages, and extended forks reach into deep tanks at terminals and depots. Desalination plants, district cooling stations and water utilities use it for chemical dosing tanks and reservoir limits, while food and beverage producers can use the hygienic versions with CIP and SIP routines.
Seven Star LLC supports level protection projects in Muscat, Sohar, Duqm and Salalah with application review and delivery planning. For a gas-tight, higher-specification alternative, compare the Rosemount 2120 with the Rosemount 2140 vibrating fork level detector. Where continuous measurement is required alongside the point alarm, the Rosemount 5300 guided wave radar level transmitter and the Rosemount 3051SAL liquid level transmitter are common pairings.
Technical Specifications
The following Rosemount 2120 values are taken from Emerson product data sheet 00813-0100-4030.
| Parameter | Specification |
|---|---|
| Model | Rosemount 2120 Level Switch, vibrating fork |
| Application | Point level detection in liquids, aerated and coating liquids and slurries |
| Process temperature | –40 to 150 °C |
| Process pressure (threaded) | Up to 100 barg, derated with temperature; Tri Clamp 30 barg |
| Flange ratings | ASME Class 150, 300, 600; EN 1092 PN 10/16 to PN 100; JIS 10K and 20K |
| Wetted materials | 316/316L SST; alloy C / C-276; ECTFE-coated 316/316L SST |
| Fork length | Standard 44 mm (threaded) or 102 mm (flanged); extended up to 4,000 mm |
| Minimum liquid density | 600 kg/m3 |
| Viscosity range | Up to 10,000 cP |
| Hysteresis / switching point (water) | 2.5 mm / 13 mm from fork tip (vertical) |
| Outputs | Direct load, PNP/PLC, DPCO relay, NAMUR, 8/16 mA |
| Switching delay | 0.3, 1, 3, 10 or 30 s, user selectable |
| Housing | Glass-filled nylon, aluminum alloy or 316 SST; IP66/67 |
| Safety | SIL2 certified to IEC 61508, SIL3 capable |
| Maximum altitude | 2,000 m |
How to Order
To receive a formal RFQ response for the Rosemount 2120, send Seven Star LLC the process connection and size, wetted material, required fork length, electronics type and supply voltage, housing and conduit entry, hazardous area approval and whether a SIL certificate or quick release kit is needed. Our instrumentation division will confirm the model code against the Rosemount 2120 datasheet, confirm availability and lead time, share the data sheet for download and provide engineering support from Muscat for level switching applications across Oman and the GCC.
- Datasheet Emerson Rosemount 2120 Level Switch Vibrating Fork Product Data Sheet 00813-0100-4030, Rev HG, September 2024 Download
Rosemount product families on this page
Pressure includes the 3051 in its variants (3051T in-line, 3051L for liquid level, 3051CF DP flowmeter and the 3051SMV MultiVariable transmitter), the 2051 and 1199 diaphragm seal systems. Level instruments are the 3300 guided wave radar, the 5408 non-contacting radar and the 2120 vibrating fork switch. Temperature is covered by the 248 and 644 head mount transmitters and the 848T high density transmitter for multiple sensor inputs. The 8800D vortex flowmeter and the 702 wireless discrete transmitter are also listed, along with liquid analysis sensors.Where Rosemount instruments are used
These are standard instruments in oil and gas production, refining, petrochemical, power and water plants. Typical duties are line and vessel pressure, differential pressure flow across orifice plates, tank and separator level and interface, and temperature measurement on pipes, reactors and rotating equipment.Ordering Rosemount transmitters: what we need
Send the complete model string and the serial number from the nameplate; a photo is ideal. Every character of the string selects something: range, output, materials of the isolating diaphragm and flange, process connection, housing, approval and options. If you are specifying a new point, give the measured variable and span, process fluid, pressure and temperature, connection, output (4-20 mA HART, FOUNDATION Fieldbus or wireless), display and hazardous area approval. For remote seals add flange size, rating and capillary length.Browse Rosemount products by category: Pressure Instrumentation, Temperature Instrumentation, Level Transmitter, Liquid Analysis Sensors, Flowmeters.
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