Brand: Rosemount

Rosemount 2521 Enhanced Vibrating Fork Solids Level Switch

Name: Rosemount 2521 High-Sensitivity Solids Level Switch
Brand: Rosemount
SKU: 2521

Description

Rosemount 2521 enhanced vibrating fork for very light powders

The Rosemount 2521 is the high-sensitivity member of the Rosemount vibrating-fork family for bulk solids. Where a standard fork loses the signal on fluffy, aerated or pneumatically filled powders, the 2521 offers fork profiles and sensitivity options that work down to below 5 g/l. Seven Star LLC supplies the Rosemount 2521 in Oman and the GCC as an independent supplier in Muscat.

The 2521 model code has more building blocks than its sibling the 2511, for example 2521 S M D 1 5 NN B E A 0000 NA Q4: fork profile, thermal profile, material, conduit entry, connection, electronics, fork length and approvals. The sections below explain the choices that matter.

Rosemount 2521 technical specifications

Parameter	Specification
Manufacturer / part number	Rosemount (Emerson) / 2521 Solids Level Switch, Enhanced Vibrating Fork
Fork vibration frequency	2521S: 350 Hz; 2521H: 125 Hz (standard) or 90 Hz (V2 and V3)
Minimum density, setting B	2521S: 3 lb/ft³ (50 g/l); 2521H: 1.2 lb/ft³ (20 g/l); V1 option 0.3 lb/ft³ (5 g/l); V2/V3 below 5 g/l
Minimum density, setting A	2521S: 9 lb/ft³ (150 g/l); 2521H: 4.5 lb/ft³ (75 g/l)
Process temperature	-40 to +302 °F (-40 to +150 °C); cable-extended: -13 to +176 °F (-25 to +80 °C)
Process pressure	-1 to +16 bar; cable-extended versions -1 to +6 bar
Fork length	2521S 165 mm; 2521H 235 mm (260 mm for V2/V3); tube or cable extended on request
Fork material and finish	316L (1.4404) stainless steel, polished Ra below 0.75 µm; PTFE on request
Housing and ingress	Powder-coated aluminum, IP66 / NEMA Type 4X; remote housing available
Electronics	SPDT or DPDT relay, PNP, 2-wire AC switch, NAMUR
Maximum lateral load	600 N on the fork; 300 Nm torque (tube-extended); 2 kN pull (cable-extended)
Maximum grain size	10 mm (0.39 in.)

How the Rosemount 2521 reaches its sensitivity

The principle is the same tuning fork and piezo crystal as the 2511, but the fork geometry and drive frequency are changed. The standard-sensitivity S profile runs at 350 Hz and suits both dry and wet material at 50 g/l and above. The H profile is longer and runs at 125 Hz, giving 20 g/l on setting B.

Option codes V1, V2 and V3 push this further. V2 adds an aluminum fork with a larger vibrating surface and is more sensitive than V3. A separate option, V4, gives adjustable sensitivity for interface applications on the S profile, tuned with a potentiometer on the board.

Choosing between the 2521, 2511 and related Rosemount switches

Use the Rosemount 2511 when material is heavier than about 30 g/l and cost is the priority. Pick the 2521 when you handle fly ash, silica fume, powdered milk, talc, carbon black or similar lightweight powders, or when the vessel is filled pneumatically. For strongly caking product, the 2535 vibrating rod avoids bridging between tines, and for very hot service the 2555 capacitance probe reaches 500 °C.

Electronics modules are stocked as spares with part numbers such as 02500-1000-0073 (PNP), 02500-1000-0075 (2-wire without contact) and 02500-1000-0098 (NAMUR, intrinsically safe). Match the module to the fork sensitivity code, because several modules are labelled for 5 g/l or 20 g/l operation.

Ordering the Rosemount 2521 step by step

Fork profile: S for standard sensitivity or H for high sensitivity.
Thermal profile: M, E (extension tube), R (1500 mm remote cable), S (4000 mm remote cable) or C (cable extension for up to 80 °C process).
Material: D for 304/321 or S for 316L stainless steel.
Electronics: T (2-wire AC), G (PNP), V (DPDT relay), E (SPDT relay) or K (NAMUR, not with profile S).
Fork length: A (165 mm, profile S), B (235 mm, profile H), E/M tube-extended, F/N cable-extended.
Approvals: dust, flameproof, increased safety and intrinsically safe codes for ATEX, IECEx, China and North America, each tied to the conduit entry you select.
Options: Q4 test certificate, P2 weather cover, S2 sliding sleeve, WR5 warranty, WT tag plate.

Rosemount 2521 installation and maintenance notes

Fit the switch where light powder can reach the fork but away from the direct fall of product. If lateral loads are high, protect the fork with an angled shield above it. In cable-extended versions the tractive force is limited to 2 kN, so check the silo geometry before specifying long cables.

The remote-housing versions use a silicone triaxial cable with a 50 mm minimum bend radius; keep it away from hot surfaces. After commissioning, the status LED confirms output state, and the unit needs no recalibration in normal service. Inspect polished forks occasionally for heavy build-up and replace electronics modules as plug-in spares.

Rosemount 2521 applications in Oman and the GCC

Typical uses include cement and lime silos, fly ash handling at power plants, plastics and polymer powder storage in petrochemical sites, flour and food powders, and dust collector hoppers. Polished stainless forks help in hygienic applications, while the hot ambient conditions of the region are handled by the extension tube or remote housing options.

2521 option summary

Group	Codes	Notes
Fork profile	S, H	350 Hz standard or 125 Hz high sensitivity
Sensitivity options	V1, V2, V3, V4	V1 to V3 on profile H; V4 on profile S, no approvals
Housing arrangement	M, E, R, S, C	Direct, tube, 1.5 m remote, 4 m remote or cable
Outputs	T, G, V, E, K	AC switch, PNP, DPDT, SPDT, NAMUR

Information to send with a Rosemount 2521 RFQ

Model code or powder name and bulk density in g/l
Whether filling is pneumatic or aerated
Process temperature, ambient maximum and pressure
Required fork length or vessel wall thickness
Output type and supply voltage
Hazardous area zone and approval
Quantity and spare electronics modules

Documents and quotation

The official 2521 datasheet is attached on this page for reference, so you can check model codes, materials and approvals against your specification before ordering.

Send us the full model code or the process data, and Seven Star LLC will prepare a quotation for the Rosemount 2521 as an independent supplier in Muscat, with delivery to Oman and the GCC.

Other Models in the Rosemount Solids Level Switch Range

Seven Star LLC supplies models from the Rosemount Solids Level Switch range in Oman and the GCC. Compare the related models below and request a quote for the one that matches your application.

Model	Category
Rosemount 2511 Vibrating Fork Solids Level Switch	Level Instrumentation	View details
Rosemount 2521 Enhanced Vibrating Fork Solids Level Switch	Level Instrumentation	You are viewing this model
Rosemount 2535 Vibrating Rod Solids Level Switch	Level Instrumentation	View details
Rosemount 2555 Capacitance Probe Solids Level Switch	Level Instrumentation	View details

Datasheets & Documents

Datasheet Rosemount 2521 Datasheet Download

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About brand

Rosemount is Emerson's brand for pressure, temperature, level and flow measurement, best known for the 3051 pressure transmitter. Frank Werner, Robert Keppel and Vernon Heath founded it in Minnesota in 1956 as Rosemount Engineering Company, first making temperature sensors for aerospace. It moved into the process industries, took the name Rosemount Inc. in 1966, and has been part of Emerson since 1976.

Seven Star LLC is an independent supplier in Muscat. We list Rosemount transmitters, level instruments, flowmeters and analytical sensors, and supply them and their spares to oil and gas, power, water and process plants in Oman and the GCC by model code.

Rosemount company profile

Established	1956, Minnesota, USA, as Rosemount Engineering Company
Founders	Frank D. Werner, Robert E. Keppel and Vernon H. Heath
Ownership	Acquired by Emerson in 1976; now an Emerson brand
Product families	Pressure, DP flow and level transmitters, temperature sensors and transmitters, radar and guided wave radar level, vibrating fork switches, tank gauging, magnetic, vortex and ultrasonic flowmeters, liquid analysis sensors and wireless instruments

Milestones

1956: Robert Keppel, Vernon Heath and Frank Werner incorporate Rosemount Engineering Company in Minnesota; early work is aerospace sensors.
1969: The Rosemount 1151 analog pressure transmitter is introduced.
1976: Emerson acquires Rosemount.
1989: The Rosemount 3051 pressure transmitter, built on digital technology, is launched.
2001: The 3051S generation follows.

Rosemount products we list

Family	Models	Typical use
Pressure transmitters	3051, 3051C coplanar, 3051T in-line, 3051S, 3051S series, 3051SMV multivariable, 2051, 2088, 1199 diaphragm seals	Pressure, differential pressure and remote seal measurement
DP flow and DP level	3051CF flowmeter, 3051L, 3051SAL	Flow through primary elements, and level in pressurised vessels
Temperature	644, 248, 3144P, 848T, 648 wireless, 214C RTD sensor, 2240S multi-input	Process temperature, high-density multipoint and tank temperature
Radar and level	5408, 5400, 5300 GWR, 3300 GWR, 3308A wireless, 5900S, 5900C tank gauges	Level in tanks, separators and custody transfer tank gauging
Level switches	2120, 2140, 2160 wireless, 702 discrete transmitter	High and low level alarms, overfill protection and pump protection
Flowmeters	8700 magnetic, 8800D vortex, SeniorSonic 3414, 3415/3416, 3417, JuniorSonic 3411/3412, 3814 liquid	Water, steam and gas flow, and fiscal gas and liquid metering
Liquid analysis	396P TUpH, 396PVP, 499ACL chlorine sensor	pH, ORP and free chlorine in water and process streams

Many Rosemount transmitters share one platform, so the model code tells you what you have. On a 3051, the letter after the number sets the type: C for coplanar (differential or gauge), T for in-line, L for liquid level and CF for a complete flowmeter. The next characters set the measurement type, the range code, the output (4-20 mA HART, FOUNDATION Fieldbus or WirelessHART) and the wetted materials. A transmitter with the wrong range code may work, but with poor accuracy at the point that matters.

Where Rosemount instruments are used

In Oman and the GCC, Rosemount instruments are used across upstream oil and gas, gas plants and LNG, refineries, tank farms and terminals, power and desalination stations, and water networks. Ultrasonic gas meters and tank gauges are used for fiscal and custody transfer measurement.

Ordering Rosemount instruments: what we need

Send the full model code from the nameplate (for example 3051CD2A22A1AM5B4) and the tag if it is a replacement. For a new instrument, send the measuring range, process connection, wetted materials, output protocol and hazardous area approval.

Facts checked against Emerson's Rosemount history and published company histories, October 2026.

Browse Rosemount products by category: Pressure Instrumentation, Temperature Instrumentation, Level Transmitter, Liquid Analysis Sensors, Flowmeters.

FAQ

Questions about the Rosemount 2521 Enhanced Vibrating Fork Solids Level

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

01What density can the Rosemount 2521 detect?

With high-sensitivity profile H and options V2 or V3 it handles material below 0.3 lb/ft³ (5 g/l). The standard S profile works from 3 lb/ft³ (50 g/l) on setting B.

02What is the difference between 2521S and 2521H?

The S profile has a 165 mm fork running at 350 Hz. The H profile has a longer 235 mm fork (260 mm for V2/V3) running at 125 Hz or 90 Hz for lighter powders.

03Which output types does the 2521 offer?

2-wire AC direct load switching, PNP, DPDT relay, SPDT relay and NAMUR. NAMUR is not available with the S profile and is linked to intrinsically safe approvals.

04Can the electronics be separated from the fork?

Yes. Remote housing versions with a 1500 mm or 4000 mm cable are available for heat or space reasons, and a cable-extended fork is also offered for process temperatures up to 80 °C.

05What are the pressure limits?

Standard and tube-extended versions work from -1 to +16 bar. Cable-extended versions are limited to -1 to +6 bar, and flange ratings may reduce the limit further.