Fisher 2500 Pneumatic Level Controller
Overview
The Fisher 2500 is a pneumatic level controller and transmitter series used with Fisher 249 displacer sensors to control or transmit liquid level, liquid-to-liquid interface level and liquid density. The family includes the 2500, 2500R, 2500S, 2500T, 2502, 2502F and 2503 instruments, covering proportional, proportional-plus-reset, on-off and transmitter duties. Emerson describes them as rugged, dependable and simply constructed displacer-style pneumatic instruments that are proven in power, chemical process, oil and gas production and petrochemical service, with sensors rated up to CL2500.
Seven Star LLC supplies the Fisher 2500 to oil and gas producers, gas plants and utilities in Oman and across the GCC. Pneumatic level control is still widely used on separators, scrubbers and remote production facilities in the region, and our engineers in Muscat help select the correct Fisher 2500 type, action and 249 sensor from the official Fisher 2500 datasheet for new and replacement installations.
Operating Principle
A change in liquid level, interface or density changes the buoyant force on the displacer hanging in the cage or vessel. The displacer rod transfers this force through a knife-edge driver bearing to the torque tube, which twists by an amount proportional to the change. The torque tube rotary shaft turns inside the controller, where a pneumatic relay with a 3:1 diaphragm area ratio converts the motion into an output pressure. This output either drives a control valve actuator directly or is transmitted to a remote controller or indicator.
In the Fisher 2500 proportional controller, the output changes in proportion to the level deviation over a proportional band of 0 to 100 percent of displacer length. The 2502 adds reset that is adjustable from 0.005 to over 0.9 minutes per repeat to remove steady-state offset, and the 2502F adds anti-reset differential relief of 0.14 to 0.48 bar to prevent reset windup. On-off 2500S and 2503 versions switch the output between two values over an adjustable differential gap, while the 2500T transmitter produces a proportional 0.2 to 1.0 or 0.4 to 2.0 bar signal over an adjustable span.
Engineering Design of the Fisher 2500
The design uses few moving parts, with a knife-edged driver bearing in the sensor and a plated brass ball bearing in the instrument case for the torque tube shaft, which keeps friction low. Set point, proportional valve opening and reset are adjusted with simple dial knobs, and the action can be reversed in the field from direct to reverse without extra parts. A spring-out cleaning wire allows the relay orifice to be cleaned in service, the torque tube can be replaced without removing the torque tube arm, and the relay exhaust opens only when output pressure is being reduced, conserving supply air or gas.
The Fisher 2500 mounts on 249 caged sensors with rotatable heads, which provide stable operation in vessels with internal obstructions or turbulence, and on cageless sensors that mount on the side or top of the vessel with flange connections up to NPS 8. Caged sensors include a liquid damping orifice in the lower equalizing connection to aid stability on small vessels. Standard displacers are 304 stainless steel with lengths of 356 mm or 813 mm, the standard torque tube is N05500, and sensor bodies in steel or stainless steel are rated for process temperatures up to 427 °C with appropriate materials.
Key Features
The Fisher 2500 product bulletin lists the following benefits.
- Set point, proportional band and reset changes are made with simple dial-knob controls.
- Few moving parts and low-friction bearings give simple, durable construction.
- Caged sensors are available in many orientations and connection styles, with right- or left-hand mounting.
- Displacer response to small specific gravity changes allows density applications.
- Action is field reversible from direct to reverse without additional parts.
- A spring-out wire cleans the relay orifice in service, reducing maintenance cost.
- Relay exhaust opens only when output pressure is being reduced, saving supply pressure.
- A damping orifice on caged sensors permits stable control on smaller vessels with narrower proportional settings.
Industrial Applications
The Fisher 2500 is a common choice for self-contained pneumatic level loops. Typical applications include level and oil-water interface control on two-phase and three-phase production separators, dump control on scrubbers and knock-out drums with on-off 2503 controllers, level control in condensate and produced water tanks, and density monitoring where fluid composition changes. Because it needs no electrical supply, it suits remote wellsites, gathering stations and skid packages that run on instrument gas. In the Sultanate of Oman these duties are found across onshore oil and gas fields, gas processing plants, and refining and petrochemical units in Sohar and Duqm.
Seven Star LLC supports pneumatic level control projects across Oman and the GCC with selection review and regional delivery. The Fisher 2500 is supplied with a Fisher 67C series supply regulator as standard, often drives a Fisher 667 diaphragm actuator on the level control valve, and can be compared with the Rosemount 5300 guided wave radar level transmitter where electronic measurement is preferred.
For a HART digital upgrade on the same 249 sensor, see the Fisher DLC3100 digital level controller.
Technical Specifications
The values below summarize Fisher 2500 specifications from Emerson bulletin D200037X012.
| Parameter | Specification |
|---|---|
| Model | Fisher 2500 series (2500, 2500R, 2500S, 2500T, 2502, 2502F, 2503) with 249 sensors |
| Measurement | Liquid level, interface level or density |
| Output (proportional, transmitter) | 0.2 to 1.0 bar (3 to 15 psig) or 0.4 to 2.0 bar (6 to 30 psig) |
| Output (on-off) | 0 and 1.4 bar or 0 and 2.4 bar (2500S); 0 and full supply (2503) |
| Normal supply pressure | 1.4 bar (20 psig) or 2.4 bar (35 psig); maximum 3 bar (45 psig) |
| Specific gravity range | 0.20 to 1.10 (2500); 0.25 to 1.10 (2503) |
| Hysteresis | 0.6% of output pressure change |
| Repeatability | 0.2% of displacer length or displacement force change |
| Independent linearity (transmitter) | 1% of output pressure change |
| Reset (2502) | 0.005 to over 0.9 minutes per repeat |
| Ambient temperature (controller) | –40 to 71 °C standard; –18 to 104 °C high temperature |
| Displacer | 304 SST standard; 356 mm or 813 mm length |
| Torque tube | N05500 standard; 316 SST, N06600, N10276 optional |
| Tubing connections | 1/4 NPT internal |
| Hazardous area | ATEX Group II Category 2 gas and dust (Ex h IIC / IIIC) |
How to Order
For a formal RFQ on the Fisher 2500, send Seven Star LLC the controller type and action, output range, supply medium and pressure, existing or required 249 sensor model, connection style and rating, displacer length, process specific gravity, pressure and temperature. Our instrumentation division will confirm the selection against the manufacturer’s Fisher 2500 datasheet, check availability and lead time, provide the bulletin for download and give engineering support from Muscat for level control projects across Oman and the GCC.
- Datasheet Fisher 2500-249 Pneumatic Controllers and Transmitters Product Bulletin (D200037X012), March 2026 Download
Fisher control valve and actuator families
Fisher groups its valves by body style. On this page you will find sliding-stem globe valves such as the easy-e ET, the high-pressure HPT and HPAT, and the GX valve and actuator system. Rotary designs include the Vee-Ball V150, V200 and V300 segmented ball valves, the V250 Hi-Ball and the CV500 eccentric plug valve. Actuators include the 1052 spring-and-diaphragm rotary actuator and the easy-Drive electric actuator. Instruments complete the loop: FIELDVUE digital valve controllers, pneumatic positioners, the 2500 pneumatic level controller with displacer sensor and the DLC3100 digital level controller. Fisher regulators such as the 627 reduce pressure on fuel gas and instrument supply lines.Where Fisher valves are used
Fisher control valves handle throttling duty on separators, compressors, steam systems, gas dehydration, refining units and power plant feedwater across the GCC. Vee-Ball valves suit fibrous or erosive fluids and high capacity, easy-e globe valves are the general-purpose choice, and HP series bodies cover high pressure classes.Ordering Fisher valves and parts: what we need
Every Fisher assembly carries a serial number on the actuator and body nameplates, and the manufacturer's records link that number to the original build: body size and rating, trim, materials, actuator size and bench set. For spare parts, send the serial number or a nameplate photo and the part needed, such as trim set, packing kit, diaphragm or positioner. For a new valve, send the process data sheet with fluid, flow, inlet and outlet pressure, temperature, line size, rating, end connections, fail action and material or sour service requirements.Browse Fisher products by category: Control Valves, Valve Positioner, Valve Actuator, Regulators.
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