Fisher 249 Series Instruction Manual

Instruction Manual

Form 1803
September 2004

Cageless 249 Series Sensors

Cageless 249 Series Displacer Sensors

Contents

Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scope of Manual 1. . . . . . . . . . . . . . . . . . . . . . . . . .

Description 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Type Number Description 2. . . . . . . . . . . . . . . . . .

Educational Services 2. . . . . . . . . . . . . . . . . . . . . . .

Maintenance 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Removing the Displacer and Stem 3. . . . . . . . . . .

Replacing the Displacer, Cotter Spring,

Stem End Piece, and Displacer Spud 5. . . . . .

Replacing the Displacer Rod/Driver Assembly 5.

Replacing the Torque Tube 6. . . . . . . . . . . . . . . . .

Replacing the Torque Tube Arm and

Changing the Mounting 7. . . . . . . . . . . . . . . . . .

Parts Ordering 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts Kits 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts List 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sensor Common Parts 8. . . . . . . . . . . . . . . . . . . .

Indicating Gauge 12. . . . . . . . . . . . . . . . . . . . . . . . .

W3120-3 / IL

Figure 1. Type 249V Sensor with DLC3000 Series

Digital Level Controller

Introduction

Scope of Manual

This instruction manual includes maintenance and
parts ordering information for the cageless 249
Series sensors.

Although a Type 249 sensor is usually shipped with
attached controller or transmitter, this manual does
not include operation, installation, calibration,
maintenance, and parts ordering information for the
controller/transmitter or for the complete unit. For
this information, refer to the appropriate controller/
transmitter instruction manual.

No person may install, operate or maintain a
cageless Type 249 Series sensor without first D
being fully trained and qualified in valve, actuator
and accessory installation, operation and
maintenance, and D carefully reading and
understanding the contents of this manual. If you
have any questions about these instructions, contact
your Fisher sales office.

Description

The 249 Series sensors are designed to measure
liquid level, interface level, or density/specific gravity
inside a process vessel.

A torque tube assembly (figure 2) and displacer
provide an indication of liquid level, interface level, or
density/specific gravity. The torque tube assembly
consists of a hollow torque tube with a shaft welded
inside it at one end and protruding from it at the
other end.

The unconnected end of the tube is sealed by a
gasket and clamped rigidly to the torque tube arm,
permitting the protruding end of the shaft to twist and
therefore transmit rotary motion. This allows the
interior of the torque tube to remain at atmospheric
pressure, thus eliminating packing and the
disadvantages of packing friction.

The displacer always exerts a downward force on
one end of the displacer rod. The other end of the
displacer rod rests on the knife-edge of the driver
bearing. A keyed shaft on the bearing end of the

www.Fisher.com

D200100X012

Cageless 249 Series Sensors

TRAVEL STOP
ASSEMBLY

W1800-1*/IL

DISPLACER ROD

DISPLACER

TORQUE TUBE

W0172-1*/IL

Figure 2. Typical Side-Mounted Cageless Displacer

displacer fits into a socket on the outside of the
welded end of the torque tube assembly.

A change in liquid level, interface level, or
density/specific gravity buoys up the displacer by a
force equal to the weight of the liquid displaced.
Corresponding vertical movement of the displacer
results in angular movement of the displacer rod
around the knife edge. Since the torque tube
assembly is a torsional spring which supports the
displacer and determines the amount of movement
of the displacer rod for a given displacement
change, it will twist a specific amount for each
increment of buoyancy change. This rotation is
brought through the torque tube arm by the
protruding rotary shaft. A controller or transmitter
attached to the end of the rotary shaft converts the
rotary motion into varying pneumatic or electric
signals.

Type Number Description

D Type 249BP—Class 150, 300, 600 steel

top-mounted sensor.

D Type 249CP—Class 150, 300, 600 stainless

steel top-mounted sensor.

D Type 249P—Class 900 and 1500 steel

top-mounted sensor

KNIFE EDGE
BEARING

Instruction Manual

Form 1803

September 2004

D Type 249V—Class 125 or 250 cast iron or
Class 150, 300, 600, 900, or 1500 steel
side-mounted sensor.

All cageless 249 Series sensors have flanged
connections.

The Parts List section shows some Type 249 sizes
by construction, standard displacer lengths, and
standard materials. However, Type 249 parts are
available in a wide variety of materials of
construction, part dimensions, and other
specifications. Contact your Fisher sales office for
assistance in selection of specific materials,
dimensions, and specifications.

Educational Services

For information on available courses for 249 Series
displacer sensors, as well as a variety of other
products, contact:

Emerson Process Management
Educational Services, Registration
P.O. Box 190; 301 S. 1st Ave.
Marshalltown, IA 50158-2823
Phone: [phone] or
Phone: [phone]
FAX: [phone]
e-mail: [e-mail]

Note

Fisher does not assume responsibility
for the selection, use, or maintenance
of any product. Responsibility for the
selection, use, or maintenance of any
Fisher product remains solely with the
purchaser and end-user.

Maintenance

Sensor parts are subject to normal wear and must
be inspected regularly and replaced as necessary.
The frequency of inspection and replacement
depends upon the severity of service conditions.

WARNING

Always wear protective clothing and
eyewear when performing any
maintenance operations to avoid
personal injury.

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Instruction Manual

Form 1803
September 2004

Cageless 249 Series Sensors

Avoid personal injury or property
damage resulting from the sudden
release of pressure. Before performing
any maintenance procedure:

D Relieve any process pressure in
the process vessel where the Type 249
sensor is installed.

D Drain the process liquid from the
process vessel.

D Shut off any electrical or
pneumatic input to the controller or
transmitter attached to the Type 249
sensor and vent any pneumatic supply
pressure.

D Use caution when loosening
flange bolting or pipe plugs (key 26).

D Remove the controller or
transmitter from the torque tube arm
(key 3).

Before performing any maintenance
procedure requiring the handling of
the displacer, inspect the displacer
(key 10) to make sure process
pressure or liquids have not
penetrated the displacer.

Check with your process or safety
engineer for any additional measures
that must be taken to protect against
process media.

Note

Except for gaskets (keys 13, 14),
trouble symptoms peculiar to specific
parts are discussed in the following
sections. Each section is specific to
these parts. Regardless of location,
gasket failure is indicated by leakage
in the gasket area. Every time a gasket
is removed, replace it with a new one
upon reassembly.

The procedures below apply to all sensor types
except where indicated. Key numbers used are
shown in the following illustrations:

D Type 249BP—figure 5
D Type 249CP—figure 6
D Type 249P—figure 7
D Type 249V—figure 8

The displacer in this unit is a sealed
container. If penetrated by process
pressure or liquid, the displacer may
hold pressure or hazardous liquid for
an extended period. A displacer that
has been penetrated by process
pressure or liquid may contain:

D pressure as a result of being in a
pressurized vessel.

D liquid that becomes pressurized
due to a change in temperature.

D liquid that is flammable,
corrosive, or hazardous.

Sudden release of pressure, contact
with hazardous liquid, fire, or
explosion, which might result in
personal injury or property damage,
can occur if a displacer that is
retaining pressure or process liquid is
punctured, subjected to heat, or
repaired.

Handle the displacer with care.
Consider the characteristics of the
specific process liquid in use.

Removing the Displacer and Stem

The displacer (key 10) is a sealed container. If the
displacer has been penetrated by process pressure
or liquid, it may hold pressure or hazardous liquid for
an extended period.

Process residue buildup on the displacer and stem
(key 24) may change displacer weight or
displacement. A bent stem or a dented or corroded
displacer can impair performance.

If the displacer rests against the travel stop, appears
to be overweight, or causes output drift or other
output inaccuracies, it may have been penetrated by
process pressure or liquid. Such a displacer may
contain pressure because it was in a pressurized
vessel, may contain process liquid that becomes
pressurized due to a change in temperature, and
may contain process liquid that is flammable,
hazardous or corrosive.

WARNING

Sudden release of pressure, contact
with hazardous liquid, fire, or

3

Cageless 249 Series Sensors

explosion, which may result in
personal injury or property damage,
can occur if a displacer that is
retaining pressure or process liquid is
punctured, subjected to heat, or
repaired.

Handle the displacer with care.

Note

On the Types 249V, 249P, and 249BP
with travel stop, the displacer must
come out with the sensor head (key 2)
or torque tube arm (key 3) before being
completely disconnected from the
displacer rod (key 7). If separating the
displacer and displacer rod, remove
the cotter spring (key 11).

Instruction Manual

Form 1803

September 2004

CAUTION

Be careful not to let the displacer slip
and drop into the bottom of the
process vessel, as displacer damage
could result.

1. Before starting any maintenance procedure, be
sure the following safety actions are completed.

D Relieve process pressure in the process vessel

where the Type 249 sensor is installed.

D Drain the process liquid from the process

vessel.

D Shut off any electrical or pneumatic input to the
controller or transmitter attached to the Type 249
sensor and vent any pneumatic supply pressure.
Remove the controller or transmitter from the torque
tube arm.

D Use caution when loosening flange bolting or
pipe plugs.

D Be sure process pressure or liquids have not
penetrated the displacer.

2. Support the sensor head (key 2) and the torque
tube arm (key 3). Remove the bolting that holds the
sensor head to the process vessel.

BJ8646-A/DOC

Figure 3. Type 249V Travel Stop Plate Positions

CAUTION

When removing a sensor from a
process vessel, the displacer may
remain attached to the displacer rod
and be lifted out with the sensor head
(key 2) when the sensor head is
removed. If separating the displacer
and displacer rod before removing the
sensor head, remove the cotter spring
(key 11).

Be careful not to let the displacer slip
and drop into the bottom of the
process vessel, as displacer damage
could result.

3. Carefully remove the sensor head or torque tube
arm. If the displacer comes out with the head or
torque tube arm, be careful not to damage the
displacer or bend the stem when setting the head or
arm down.

4. On the Type 249V, the travel stop plate can be
located in one of four positions as shown in figure 3.
With a standard or thin-walled displacer hanging free

4