Emerson Fisher L2 User manual

www.Fisher.com
FisherrL2 Liquid Level Controller
Contents
Introduction 1.................................
Scope of Manual 1.............................
Description 3.................................
Specifications 3...............................
Education Services 3...........................
Installation 4..................................
Attaching Vertical Displacer 4...................
Attaching Horizontal Displacer 4.................
Attaching the Sensor to the Vessel 5.............
Pressure Connections 5........................
Vent 6.......................................
Changing Controller Action or Mode 6.............
Throttling and On/Off Controllers 6..............
Snap‐Acting Controller 6.......................
Span Adjustment 8.............................
Preliminary Checks 8...........................
Direct‐Acting Throttling Controllers 9............
Reverse‐Acting Throttling Controllers 9...........
Direct‐Acting On/Off and
Snap‐Acting Controllers 9....................
Reverse‐Acting On/Off and
Snap‐Acting Controllers 9....................
Principle of Operation 10........................
Maintenance 11................................
Removing the Controller From the Sensor 11........
Replacing the Sensor O‐Rings 11.................
Disassembly 11............................
Assembly 13..............................
Replacing the Controller Relay 13................
Replacing the Controller Supply Filter 13..........
Figure 1. Fisher L2 Liquid Level Controller
W8418‐1
Related Documents 14..........................
Parts Ordering 14...............................
Parts Kits 14...................................
Parts List 14...................................
Controller 14.................................
Sensor 16....................................
Introduction
Scope of Manual
This instruction manual includes installation, adjustment, maintenance, and parts ordering information for the Fisher
L2 liquid level controller.
Do not install, operate or maintain an L2 Liquid Level Controller without being fully trained and qualified in valve,
actuator, and accessory installation, operation, and maintenance. To avoid personal injury or property damage, it is
important to carefully read, understand, and follow all contents of this manual, including all safety cautions and
warnings. If you have any questions about these instructions, contact your Emerson Process Management sales office
before proceeding.
Instruction Manual
D103032X012
L2 Controller
July 2015

Instruction Manual
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L2 Controller
July 2015
2
Table 1. Specifications
Available Configurations
Controller: Snap‐acting or throttling
Sensor: Displacer‐type liquid level sensor for
mounting to side of tank. Displacer travel is
transmitted to controller by pivotal movement of
displacer rod
Input Signal
Type: Liquid level or liquid‐to‐liquid interface
Level Change Required for Full Change in Output
Signal in 1.0 Specific Gravity Liquid, with 1.4 Bar (20
Psig) Supply Pressure, Direct Action, and Standard 48
x 305 mm (1‐7/8 X 12‐Inch) Vertical Displacer with
Standard Lever Arm Length:
Control
Mode
Minimum Proportional
Band Level Change, mm
(Inches)(1)
Maximum Proportional
Band Level Change, mm
(Inches)(1)
Throttling 102 (4) 305 (12)
On/Off 127 (5) 305 (12)
Snap‐acting 13 (0.5) 20 (0.8)
Minimum Specific Gravity(2)
Throttling and On/Off Controllers: Minimum specific
gravity, or specific gravity differential for interface
applications, is 0.1 (see footnote 3)
Snap‐Acting Controllers: Minimum specific gravity, or
specific gravity differential for interface applications,
is 0.1
Output Signal
Pneumatic Jon‐off or Jproportional pressure
signal
Ranges:
Throttling: J0.2 to 1.0 bar (3 to 15 psig) or J0.4 to
2.0 bar (6 to 30 psig)
On/Off: 0 (off) or full supply pressure (on)
Action: Field‐reversible between direct (increasing
level increases output signal) and reverse (increasing
level decreases output signal)
Supply Pressure Requirements
Throttling and On/Off Controller
Throttling: 1.4 bar for 0.2 to 1.0 bar output signal (20
psig for 3 to 15 psig output signal) and 2.4 bar for 0.4
to 2.0 bar output signal (35 psig for 6 to 30 psig
output signal)
On/Off: Any desired pressure between 1.4 and 3.4 bar
(20 and 50 psig).
Snap‐Acting Controller: Any desired pressure
between 1.4 and 5.2 bar (20 and 50 psig) direct, and
1.4 bar and 2.4 bar (20 and 35 psig) reverse
Do not use supply pressure below 1.4 bar (20 psig)
Supply Medium
Air or natural gas(4)
Steady‐State Air Consumption(5)
Throttling Controller: ≤0.03 normal m3/hr (1.0 scfh)
at 1.4 bar (20 psig) supply pressure
Snap‐Acting Controller: ≤0.03 normal m3/hr (1.0
scfh) at 1.4 bar (20 psig) supply pressure or ≤0.04
normal m3/hr (1.5 scfh) at 2.4 bar (35 psig) supply
pressure in tripped condition; air consumption
increases during trip
Sensor to Vessel Connection
J2 NPT threaded or JNPS 2 CL150 through 1500
slip‐on flange connection(6)
Controller Connections
Supply: 1/4 NPT internal located on the bottom of the
case
Output: 1/4 NPT internal located on the top of the
case
Case Vent: 1/4 NPT internal with vent screen
assembly located on the back of the case
Standard Displacer Size
48 x 305 mm, 541 cm3(1‐7/8 x 12 inches, 33 in3)
Maximum Displacer Insertion Length(7)
Standard lever arm length plus one 6‐inch extension,
horizontal or vertical
Displacer Material and Maximum Sensor Working
Pressure(8)
PVC Displacer: Consistent with CL1500 pressure
temperature ratings per ASME B16.34 up to
maximum pressure of 258 bar (3750 psig)
For PED (97/23/EC) maximum pressure limited to 200
bar (2900 psig)
S31603 SST Displacer: CL600 pressure temperature
ratings per ASME B16.34 up to maximum pressure of
99.3 bar (1440 psig)
Note: For slip‐on flange connection, maximum sensor
working pressure must be consistent with the flange
ratings
-Continued-

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L2 Controller
July 2015
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Table 1. Specifications (continued)
Displacer Material and Sensor Temperature
Limits(8)
PVC Displacer -29 to 79_C (-20 to 175_F)
S31603 SST Displacer: -40 to 204_C (-40 to 400_F)
Operative Ambient Temperature Limits(8)
Controller: -29 to 71_C (-20 to 160_F)
Standard Supply, and Output Pressure Gauge
Indications
Triple scale gauges in 0 to 60 psig/0 to 0.4 MPa/0 to
4.0 bar
Hazardous Area Classification
Complies with the requirements of ATEX Group II
Category 2 Gas and Dust
Declaration of SEP
Fisher Controls International LLC declares this
product to be in compliance with Article 3 paragraph
3 of the Pressure Equipment Directive (PED) 97 / 23 /
EC. It was designed and manufactured in accordance
with Sound Engineering Practice (SEP) and cannot
bear the CE marking related to PED compliance.
However, the product may bear the CE marking to
indicate compliance with other applicable European
Community Directives.
NOTE: Specialized instrument terms are defined in ISA Standard 51.1 - Process Instrument Terminology.
1. Any deviation from the standard construction described in the input signal specification above requires special displacer sizing considerations. Contact your Emerson Process Management sales
office for information.
2. Depends on float rod/displacer orientation and length. Contact your Emerson Process Management sales office before proceeding for further information.
3. Minimum specific gravity differential with standard displacer is 0.4. Minimum specific gravity differential of 0.1 is possible with special displacer, consult your Emerson Process Management sales
office for displacer sizing information.
4. This product can be used with natural gas as the supply medium.
5. Normal m3/hr—Normal cubic meters per hour (0_C and 1.01325 bar, absolute) Scfh—Standard cubic feet per hour (60_F and 14.7 psia).
6. Converting from a threaded NPT connection to a flange connection is to be done by the end-user. Refer to Converting a Threaded NPT Connection to a Flange Connection instruction Manual
Supplement (D103277X012), available at www.Fisher.com or from your Emerson Process Management sales office.
7. Standard lever arm length.
8. The pressure and temperature limits in this document and any applicable code limitations should not be exceeded.
Description
The rugged L2 liquid level controllers use a displacer type sensor (see figure 1) to detect liquid level or the interface of
two liquids of different specific gravities.
These controllers use a single four‐mode relay to provide the applicable control and action. The device delivers a
pneumatic output signal to a control/dump valve.
Unless otherwise noted, all NACE references are to NACE MR0175‐2002.
Specifications
Specifications for the controller and sensor are listed in table 1.
Educational Services
For information on available courses for L2 Liquid Level Controllers, as well as a variety of other products, contact:
Emerson Process Management
Educational Services, Registration
Phone: [phone] or [phone]
Email: [email protected]
http://www.emersonprocess.com/education

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L2 Controller
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Installation
WARNING
Always wear protective clothing, gloves, and eyewear when performing any installation operations to avoid personal
injury.
To avoid personal injury or property damage caused by the sudden release of process fluid, be certain the service
conditions do not exceed the sensor pressure limits. Use pressure‐limiting or pressure‐relieving devices to prevent service
conditions from exceeding these limits.
Personal injury or property damage may result from fire or explosion if natural gas is used as the supply medium and
appropriate preventive measures are not taken. Preventive measures may include, but are not limited to, one or more of
the following: Remote venting of the unit, re‐evaluating the hazardous area classification, ensuring adequate ventilation,
and the removal of any ignition sources. For information on remote venting of this controller, refer to page 6.
Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.
If installing this into an existing application, also refer to the WARNING at the beginning of the Maintenance section of this
instruction manual.
CAUTION
If the L2 level controller is installed on a vessel that is to be shipped to a different location (e.g. skid mounted units), remove
the displacer and displacer rod extensions before shipment. Failure to do so could result in damage to the displacer rod due
to vibration and impact loading during shipment. After the vessel is installed at its final location, reassemble the displacer
and displacer rod extension.
1. Be sure there are no obstructions inside the tank that will interfere with displacer installation or operation.
2. Provide the appropriate connection in the tank wall to match the sensor connection. Locate the tank wall
connection such that the displacer will be at the desired control level.
Attaching a Vertical Displacer
Refer to figure 7 for part locations.
1. Thread jam nut (key 68) all the way onto the threaded portion of the universal joint assembly (key 69).
2. Thread the displacer (key 81) all the way onto the threaded portion of the universal joint assembly.
3. Tighten the jam nut (key 63) against the displacer (key 81).
Attaching a Horizontal Displacer
Refer to figure 7 for part locations.
1. Thread the displacer (key 81) all the way onto the displacer rod (key 64) or extension (key 82).
2. Tighten the jam nut (key 63) against the displacer (key 81).

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Attaching the Sensor to the Vessel
Insert the displacer end of the controller‐sensor assembly into the tank connection, and screw the sensor threads into
the tank connection. Tighten sufficiently to seal the threads. If necessary, loosen or tighten slightly to obtain the
orientation shown in figure 2. Make sure that the controller case is level.
CAUTION
Do not pick up the controller/sensor by lifting the displacer rod (key 64). This action could place excessive stress on the
displacer rod and cause the unit to malfunction.
Figure 2. Sensor Orientation
CORRECT CONTROLLER MOUNTING
HOLE ORIENTATION WHEN MOUNTED ON VESSEL
A6639
Pressure Connections
WARNING
Personal injury or property damage may occur from an uncontrolled process if the supply medium is not clean, dry, oil‐free
air, or non‐corrosive gas. While use and regular maintenance of a filter that removes particles larger than 40 micrometers
in diameter will suffice in most applications, check with an Emerson Process Management field office and industry
instrument air quality standards for use with corrosive air or if you are unsure about the proper amount or method of air
filtration or filter maintenance.
1. Provide a source of clean, dry air that meets the requirements of ISA Standard 7.0.01 as the operating medium.
Refer to table 1 to determine supply pressure.
2. Connect the supply pressure to the 1/4 NPT internal connection on the bottom of the controller case.
3. Connect the output signal line to the equipment being operated and to the 1/4 NPT output connection on the top
of the controller case.

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Vent
WARNING
If a flammable or hazardous gas is to be used as the supply pressure medium, personal injury or property damage could
result from fire or explosion of accumulated gas or from contact with hazardous gas. The controller/actuator assembly
does not form a gas‐tight seal, and when the assembly is enclosed, a remote vent line, adequate ventilation, and necessary
safety measures should be used. However, a remote vent pipe alone cannot be relied upon to remove all hazardous gas.
Vent line piping should comply with local and regional codes and should be as short as possible with adequate inside
diameter and few bends to reduce case pressure buildup.
The vent opening or the end of the remote vent pipe, if one is required, must be protected against the entrance of all
foreign matter that could plug the vent. Use 13 mm (1/2‐inch) diameter pipe for the remote vent pipe. Check the vent
periodically to be certain it is free of any obstructions.
Changing Controller Action or Mode
WARNING
To avoid personal injury caused by a sudden release of pressure, shut off the supply pressure and bleed pressure from the
supply lines before performing any procedure in this section.
Throttling and On/Off Controller
The action of a throttling and on/off controller may be changed between either direct or reverse, and the control
mode may be changed between either on/off or throttling.
Refer to figure 3. Loosen the four switch retention screws on the relay. Move the switches to the control action and
control mode required by the application. Tighten the four switch retention screws.
Snap‐Acting Controller
The action of a snap‐acting controller may be changed between either direct or reverse. The control mode is always
snap acting.
Refer to figure 4. Loosen the four switch retention screws on the relay. Move the switches to the control action
required by the application. Tighten the four switch retention screws.

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Figure 3. Fisher L2 Throttling and On/Off Controller Switch Positions for Changing Action and Control Mode
DIRECT ACTION THROTTLING
CONTROL MODE
DIRECT ACTION ON/OFF
CONTROL MODE
REVERSE ACTION ON/OFF
CONTROL MODE
REVERSE ACTION THROTTLING
CONTROL MODE
SWITCH RETENTION
SCREWS
SWITCH RETENTION
SCREWS 1
NOTE:
1 ALL FOUR SWITCH RETENTION SCREWS SHOWN ONLY ON THIS VIEW.
OTHER VIEWS SHOW ONLY TWO SWITCH RETENTION SCREWS IN ORDER TO
ILLUSTRATE THE SWITCH CONFIGURATION.
B2339
1
Figure 4. Fisher L2 Snap‐Acting Controller Switch Positions for Changing Action
SWITCH RETENTION
SCREWS
SWITCH RETENTION
SCREWS
DIRECT ACTION REVERSE ACTION
NOTE:
1 ALL FOUR SWITCH RETENTION SCREWS SHOWN ONLY ON THIS VIEW.
OTHER VIEWS SHOW ONLY TWO SWITCH RETENTION SCREWS IN ORDER TO
ILLUSTRATE THE SWITCH CONFIGURATION.
B2340 1
1

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Span Adjustment
Except where indicated, key numbers referenced in the following procedures are shown in figure 8. The span levers
and other proportional band information are shown in figure 5.
Figure 5. Proportional Band Adjustments
MAXIMUM SPAN (LEAST SENSITIVE) POSITION FOR
THROTTLING AND ON/OFF CONTROLLER. MINIMUM SPAN
(MOST SENSITIVE) POSITION FOR SNAP‐ACTING
CONTROLLER
MINIMUM SPAN (MOST SENSITIVE) POSITION
FOR THROTTLING AND ON/OFF CONTROLLER.
MAXIMUM SPAN (LEAST SENSITIVE) POSITION
FOR SNAP‐ACTING CONTROLLER LEVER A CONTACTING
THE DISPLACER ROD
GB0137-2
E0787
LEVER A LEVER B
SPAN LEVER GAP
Preliminary Checks
1. Check the supply pressure gauge (key 10) to be certain that the supply pressure is at the desired value. Adjust the
supply pressure as required.
2. Adjust the displacer rod to the horizontal position with the spring adjustment (key 4).
3. Bounce the end of the displacer rod (key 64, figure 7) up and down to check that the sensor is operating freely.
4. Place the span adjuster (key 9) at the desired position (see figure 5).

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5. Check figures 3 and 4 for correct control action and control mode.
6. Adjust the relay adjustment screw (key 49, throttling controller) or the valve assembly (key 51, snap‐acting
controller) so that the gap between the span levers (see figure 5) is equal when lever A is contacting the displacer
rod.
Direct‐Acting Throttling Controllers
1. Make certain the Preliminary Checks procedure at the start of this section has been completed.
2. Lower the liquid level so that it is below the bottom of the displacer or at the lowest desired operating point on the
displacer. For interface applications, completely cover the displacer with the fluid with the lower specific gravity.
The heavier fluid should be below the bottom of the displacer or at the lowest desired operating point on the
displacer.
3. Adjust the spring adjustment (key 4) until the output pressure is 1 to 2 psig for a 3 to 15 psig output range, or 2 to 4
psig for a 6 to 30 psig output range.
Reverse‐Acting Throttling Controllers
1. Make certain the Preliminary Checks procedure at the start of this section has been completed.
2. Lower the liquid level so that it is below the bottom of the displacer or at the lowest desired operating point on the
displacer. For interface applications, completely cover the displacer with the fluid with the lower specific gravity.
The heavier fluid should be below the bottom of the displacer or at the lowest desired operating point on the
displacer.
3. Adjust the spring adjustment (key 4) until the output is 16 to 17 psig for a 3 to 15 psig output range, or 31 to 34
psig for a 6 to 30 psig output range.
Direct‐Acting On/Off and Snap‐Acting Controllers
1. Make certain the Preliminary Checks procedure at the start of this section has been completed.
2. Lower the liquid level so that it is below the bottom of the displacer or at the lowest desired operating point on the
displacer. For interface applications, completely cover the displacer with the fluid with the lower specific gravity.
The heavier fluid should be below the bottom of the displacer or at the lowest desired operating point on the
displacer.
3. Adjust the spring adjustment (key 4) until the output pressure is at full supply pressure.
4. Readjust the spring adjustment (key 4) until the output pressure goes to zero psig.
Reverse‐Acting On/Off and Snap‐Acting Controllers
1. Make certain the Preliminary Checks procedure at the start of this section has been completed.
2. Lower the liquid level so that it is below the bottom of the displacer or at the lowest desired operating point on the
displacer. For interface applications, completely cover the displacer with the fluid with the lower specific gravity.
The heavier fluid should be below the bottom of the displacer or at the lowest desired operating point on the
displacer.
3. Adjust the spring adjustment (key 4) until the output pressure goes to zero psig.
4. Readjust the spring adjustment (key 4) until the output pressure goes to full supply pressure.

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Principle of Operation
The operation of L2 controllers in combination with the sensor is based on Archimedes Principle, which states that a
body immersed in a liquid will be buoyed up by a force equal to the weight of the liquid displaced. The buoyant force
and resultant movement of the displacer in the liquid is transmitted to the controller which delivers a pneumatic signal
to a control valve.
Figure 6 shows a simple schematic of the controller and sensor. In its normal position, the counterclockwise moment
due to the weight of the displacer about pivot point O is balanced by the clockwise zero spring moment and the
counterclockwise relay zero force moment applied through lever A to the displacer rod. The weight of the displacer
decreases when the liquid level increases and the subsequent buoyant force increases causing a force imbalance
between the zero spring, relay, and displacer forces. This force imbalance is transmitted to the relay by levers A and B.
The relay compensates for the force imbalance by converting it to a pressure output to a control valve and bringing the
forces back into equilibrium.
Figure 6. Operational Schematic
DISPLACER ROD
LEVER B
PROPORTIONAL
BAND ADJUSTMENT
PIVOT
POINT O
DISPLACER
LEVER A
ZERO
SPRING
RELAY
A5592
For throttling control, the relay pressure output will be proportional to the buoyant force. For on/off control, the relay
pressure output will be either zero or equal to the supply pressure over the range of liquid level change. The liquid level
change required to fully operate the relay is adjusted by sliding the proportional band adjustment along lever A to vary
the lever ratio between levers A and B.
With reverse‐acting proportional control, the principle of operation remains the same as that for direct action;
however, the controller delivers an increasing pneumatic signal to the control valve when the liquid level falls.