Fisher™ 249 Caged Displacer Sensors

Introduction

Scope of Manual

This instruction manual provides maintenance and parts ordering information for 249 caged sensors. It does not cover the operation, installation, calibration, or maintenance of attached controllers or transmitters.

Note: Caged sensors are shipped with a rod and block shipping lock on each end of the displacer to protect it during transit. These locks must be removed before installation to ensure proper displacer function.

Description

249 sensors are designed to measure liquid level, interface level, or density/specific gravity within a vessel. The sensor utilizes a torque tube assembly and a displacer to indicate these parameters. The torque tube assembly comprises a hollow torque tube with a shaft welded inside, protruding from one end.

Figure 2: Rod and Block Shipping Lock depicts the shipping lock mechanism.

Figure 3: Typical Caged Displacer illustrates the general construction of the sensor, showing components like the cage, displacer, torque tube, and knife edge bearing.

The torque tube assembly allows for rotary motion transmission without packing, maintaining atmospheric pressure within the tube. Changes in liquid level or density cause the displacer to move vertically, which in turn causes the displacer rod to pivot on a knife-edge bearing. This movement is transmitted via the torque tube arm to a rotary shaft, which a connected controller or transmitter converts into pneumatic or electric signals.

Figure 4: Torque Tube Arm Exploded View Showing Controller or Transmitter Mounting details how a controller or transmitter attaches to the torque tube arm.

Type Number Description

The 249 series offers various constructions based on cage material and connection type:

• 249: Cast iron cage with screwed or flanged connections (CL125 or 250).
• 249B: WCC (steel) cage with screwed or flanged connections (CL150, 300, or 600).
• 249BF: Cast steel or stainless steel cage with flanged connections only (CL150, 300, or 600). Available from Emerson in Europe.
• 249C: Stainless steel cage with screwed or flanged connections (CL150, 300, or 600).
• 249K: Steel cage with flanged connections only (CL900 or 1500).
• 249L: Steel cage with flanged connections only (CL2500).

The cage head can be rotated to eight alternate positions. Connection sizes are typically NPS 1-1/2 or 2.

Displacer and Torque Tube Materials

⁽¹⁾ N05500 is not recommended for spring applications above 232°C (450°F). Contact Emerson for higher temperature requirements.

Hazardous Area Classification

Complies with ATEX group II Category 2 Gas and Dust requirements:

• Ex h IIC Tx Gb
• Ex h IIIC Tx Db

Maximum surface temperature (Tx) varies with operating conditions: Gas: T6...T2, Dust: T85...T232.

Educational Services

For information on courses for 249 displacer sensors and other products, contact Emerson Automation Solutions Educational Services:

• Phone: +1-641-754-3771 or +1800-338-8158
• Email: education@emerson.com
• Website: emerson.com/fishervalvetraining

Maintenance

Sensor parts are subject to normal wear and require inspection and replacement as needed, depending on service conditions.

⚠ WARNING: Always wear appropriate protective clothing, gloves, and eyewear during installation and maintenance to prevent personal injury. Ensure all safety precautions are followed to avoid injury or property damage from sudden pressure release.

Pre-Maintenance Safety Actions:

• Relieve process pressure in the vessel.
• Drain the process liquid from the vessel.
• Shut off electrical or pneumatic input to the controller/transmitter and vent any pneumatic supply pressure.
• Remove the controller or transmitter from the torque tube arm.
• Ensure the cage is free of process pressure and liquid.
• Use caution when loosening flange bolting or pipe plugs.
• Inspect the displacer for signs of penetration by process pressure or liquid, as it may contain hazardous contents.

Note: Gasket failure typically results in leakage. Replace gaskets whenever removed.

Procedures described apply to all sensor types unless otherwise noted. Key numbers refer to illustrations in the manual.

Cleaning the Cage

Process residue buildup in the cage can restrict flow or interfere with displacer motion. The cage must be removed for cleaning.

Steps for Cleaning the Cage:

1. Complete pre-maintenance safety actions.
2. Support the cage head and torque tube arm. Remove cap screws/stud bolts and hex nuts holding the cage head to the cage.
3. Carefully remove the cage head and lift out the displacer.
4. For style 1 or 4 cages, disconnect the lower connection and remove the liquid damper.
5. For style 2 or 3 cages, remove the bottom pipe plug and liquid damper for drainage and cleaning. Complete cage removal from the vessel may be necessary.
6. Use appropriate cleaning methods. Reinstall the liquid damper, reconnect the cage, install the cage head and controller/transmitter, and calibrate as per the controller/transmitter manual.

Figure 5: Cage Connection Styles illustrates different connection types (Style 1-4) for screwed and flanged connections.

Removing the Displacer and Stem

The displacer is a sealed container. If penetrated, it may retain pressure or hazardous liquid. Handle with care.

⚠ WARNING: Sudden release of pressure, contact with hazardous liquid, fire, or explosion can occur if a displacer retaining pressure or liquid is punctured, heated, or repaired.

Steps for Removing the Displacer:

1. Complete pre-maintenance safety actions.
2. Support the cage head/sensor head and torque tube arm. Remove fasteners holding the cage head to the cage.
3. When removing the sensor, the displacer may stay attached to the rod. If separating them before cage head removal, remove the cotter spring (key 11). Avoid dropping the displacer.
4. Carefully remove the cage head and lift out the displacer.
5. Follow procedures for replacing the displacer, rod assembly, cotter spring, stem end piece, and displacer spud as needed.

Replacing the Displacer, Cotter Spring, Stem End Piece, and Displacer Spud

These parts may wear or become clogged, affecting displacer pivot function. Replace as necessary.

Steps for Replacement:

1. After removing the cage head and displacer, move the assembly to a maintenance area and support it.
2. Access the cotter spring, displacer spud, etc., through the appropriate connection (top connection, pipe plug, or by removing nuts/flange/ring depending on sensor style).
3. Remove the cotter spring to detach the displacer or stem end piece from the rod/driver assembly.
4. Replace worn parts and reassemble, installing the cotter spring.
5. Clean the cage if necessary, then reinstall the cage head and controller/transmitter. Calibrate the unit.

Replacing the Displacer Rod/Driver Assembly

The ball on the displacer rod/driver assembly may be worn or corroded, preventing proper pivoting. Replace the assembly if needed.

NOTICE: If disconnecting the displacer from the rod before cage removal, support the displacer to prevent damage.

Steps for Replacement:

1. Move the sensor assembly to a maintenance area and support it.
2. Remove the controller/transmitter and displacer. Remove hex nuts holding the torque tube arm to the cage head and separate them.
3. Remove nuts and retaining flange at the end of the torque tube arm.
4. Remove the positioning plate by freeing its lugs.
5. Use a screwdriver to release the positioning plate's lug from the torque tube arm, then carefully turn it back to rest the displacer and slip the other lug from its slot.
6. Pull the torque tube assembly out, removing and discarding the tube end gasket. Clean mating surfaces.
7. Loosen and remove the upper bearing driver bolt. Lift the displacer rod/driver assembly from the driver bearing.
8. Inspect the driver bearing for wear or corrosion; replace if necessary.
9. Install the new displacer rod/driver assembly onto the driver bearing. Install the upper bearing driver bolt (do not tighten yet).
10. Insert a new tube end gasket.
11. Insert the torque tube assembly, aligning its socket with the displacer rod assembly and ensuring the outer tube flange rests against the gasket. Use the positioning plate to preload the torque tube.
12. Install the retaining flange and secure with nuts, tightening evenly.
13. Tighten the upper bearing driver bolt, applying slight pressure to the assembly.
14. Clean the cage if needed, reinstall the cage head and controller/transmitter, and calibrate.

Figure 6: Torque Tube and Displacer Rod Assemblies shows the components and their exploded view.

Replacing the Torque Tube

Corrosion or leakage in the torque tube assembly or end gasket can cause issues. Improper engagement of the torque tube socket with the displacer rod assembly can lead to erratic output.

Steps for Replacement:

1. After removing the cage head and displacer, move the assembly to a maintenance area and support it.
2. Remove the controller/transmitter and displacer. Remove hex nuts holding the torque tube arm to the cage head and separate them.
3. Remove nuts and retaining flange holding the positioning plate.
4. Remove the positioning plate by freeing its lugs.
5. Pull the torque tube assembly and tube end gasket out. Discard the old gasket and clean mating surfaces.
6. Insert a new tube end gasket.
7. Insert the torque tube assembly into the torque tube arm, aligning its socket with the displacer rod assembly and ensuring the outer tube flange rests against the gasket. Use the positioning plate to preload the torque tube.
8. Install the retaining flange and secure with nuts.
9. Clean the cage if necessary, reinstall the cage head and controller/transmitter, and calibrate.

Changing Cage Head Position

The cage head can be mounted in eight alternate positions relative to the torque tube arm. This can be done without removing the displacer or torque tube arm.

Figure 7: Cage Head Mounting Positions illustrates the different mounting orientations (Right-hand and Left-hand).

Steps for Changing Head Position:

1. Complete pre-maintenance safety actions.
2. Remove hex nuts from the bolting and reposition the head as desired.

Replacing the Torque Tube Arm and Changing the Mounting

Issues with the driver bearing, knife-edge surface, or displacer rod assembly can affect performance. Check the ball on the displacer rod.

NOTICE: Support the sensor assembly during these procedures to prevent damage.

Steps for Replacement/Change:

1. After removing the cage head and displacer, move the assembly to a maintenance area.
2. Remove the controller/transmitter and displacer. Remove hex nuts holding the torque tube arm to the cage head and separate them.
3. Follow the procedure to remove the torque tube assembly.
4. Remove bearing bolts, displacer rod assembly, and driver bearing.
5. Determine the new mounting orientation.

Note: Ensure the driver bearing's knife edge points upwards. Changing the torque tube arm orientation by 180° reverses controller/transmitter action (direct to reverse or vice versa).

7. Install the driver bearing, displacer rod assembly, and bearing bolts into the torque tube arm. Install a new arm gasket. Mount the torque tube arm in the desired position on the cage head and secure it.
8. Install the torque tube assembly and the displacer.
9. Clean the cage if necessary, reinstall the cage head and controller/transmitter, and calibrate.

Simulation of Process Conditions for Calibration

Contact your Emerson sales office for information on the "Supplement to 249 Sensor Instruction Manuals—Simulation of Process Conditions for Calibration of Fisher Level Controllers and Transmitters" (D103066X012).

Related Documents

Additional information on the 249 level sensor is available in these documents:

• Bulletin 34.2:2500—2500-249 Pneumatic Controllers and Transmitters (D200037X012)
• Bulletin 34.2:249—Fisher 249 Sensor, Level Controller, and Transmitter Dimensions (D200039X012)
• Simulation of Process Conditions for Calibration of Fisher Level Controllers and Transmitters— Supplement to 249 Sensor Instruction Manuals (D103066X012)
• Bolt Torque Information— Supplement to 249 Sensor Instruction Manuals (D103220X012)
• Torque Tube Identification— Supplement to 249 Sensor Instruction Manuals (D103283X012)

All documents are available from your Emerson sales office or at Fisher.com.

Parts Ordering

When contacting Emerson sales for parts, always provide the sensor serial number, which is found on the nameplate attached to the torque tube arm. This number is also on the controller/transmitter nameplate for complete units.

⚠ WARNING: Use only genuine Fisher replacement parts. Using non-Emerson components may void the warranty, affect performance, and cause injury or damage.

Parts Kits

Parts List

Contact your Emerson sales office for Part Ordering information.

Sensor Common Parts

• 1 Cage
• 2 Cage Head
• 3 Torque Tube Arm
• 4 Driver Bearing⁽¹⁾
• 5 Driver Bearing Bolt⁽¹⁾ (2 required)
• 6 Retaining Flange

Parts Details by Model:

• 7 Rod/Driver Assy⁽¹⁾: 249 and 249B, 249C (Standard/Heavy wall torque tube), 249K, 249L
• 8 Positioning Plate
• 9 Torque Tube Assy⁽¹⁾: 249 and 249B (Standard, Thin, Heavy wall), 249C (Standard, Heavy wall), 249K and 249L (Standard, Thin wall)
• 10 Displacer⁽¹⁾: Various sizes and pressure ratings for 249, 249B, 249C, 249K, 249L models.
• 11 Cotter Spring⁽¹⁾ (2 required)
• 12 Cage Gasket⁽¹⁾: For 249 (CL125, CL250), 249B, 249C, 249K.

⁽¹⁾ Parts available in various materials, dimensions, and specifications. Contact Emerson sales for details.

Figure 8: Fisher 249 Sensor Construction shows the assembly details.

Figure 9: Fisher 249B Sensor Construction shows assembly details.

Figure 10: Fisher 249C Sensor Construction shows assembly details.

Figure 11: Fisher 249K Sensor Construction shows assembly details.

Figure 12: Fisher 249L Sensor Construction shows assembly details.

Additional keys and descriptions for various parts (Pipe Plugs, Hex Nuts, Stud Bolts, Liquid Damper, etc.) are provided in the manual, referencing figures 5, 6, and specific sensor construction diagrams.