B73 & Series 75
Installation and Operating Manual
Sealed
External
Cage
Liquid
Level
Switches
Read this Manual Before Installing
This manual provides information on the B73 and Series
75 Liquid Level Switches. It is important that all instruc-
tions are read carefully and followed in sequence.
Detailed instructions are included in the Installation
section of this manual.
Conventions Used in this Manual
Certain conventions are used in this manual to convey
specific types of information. General technical material,
support data, and safety information are presented in
narrative form. The following styles are used for notes,
cautions, and warnings.
Notes
Notes contain information that augments or clarifies
an operating step. Notes do not normally contain
actions. They follow the procedural steps to which
they refer.
Cautions
Cautions alert the technician to special conditions that
could injure personnel, damage equipment, or reduce
a component’s mechanical integrity. Cautions are also
used to alert the technician to unsafe practices or the
need for special protective equipment or specific
materials. In this manual, a caution indicates a
potentially hazardous situation which, if not avoided,
may result in minor or moderate injury.
Warnings
Warnings identify potentially dangerous situations or
serious hazards. In this manual, a warning indicates an
imminently hazardous situation which, if not avoided,
could result in serious injury or death.
WARNING!
Explosion hazard. Do not connect or
disconnect equipment unless power has been switched off
or the area is known to be non-hazardous.
Low Voltage Directive
For use in Installation Category II, Pollution Degree 2.
If equipment is used in a manner not specified by
manufacturer, protection provided by equipment may
be impaired.
Notice of Copyright and Limitations
Magnetrol and Magnetrol logotype are registered trademarks
of Magnetrol International.
Copyright © 2010 Magnetrol International, Incorporated.
All rights reserved.
Performance specifications are effective with date of issue and
are subject to change without notice. Magnetrol reserves the
right to make changes to the products described in this
manual at any time without notice. Magnetrol makes no
warranty with respect to the accuracy of the information
in this manual.
Warranty
All Magnetrol mechanical level and flow controls are
warranted free of defects in materials or workmanship for
five full years from the date of original factory shipment.
If returned within the warranty period; and, upon factory
inspection of the control, the cause of the claim is
determined to be covered under the warranty; then,
Magnetrol will repair or replace the control at no cost to
the purchaser (or owner) other than transportation.
Magnetrol shall not be liable for misapplication, labor
claims, direct or consequential damage or expense arising
from the installation or use of equipment. There are no
other warranties expressed or implied, except
special written warranties covering some Magnetrol prod-
ucts.
Quality Assurance
The quality assurance system in place at Magnetrol
guarantees the highest level of quality throughout the
company. Magnetrol is committed to providing full
customer satisfaction both in quality products and
quality service.
Magnetrol’s quality assurance
system is registered to ISO 9001
affirming its commitment to
known international quality
standards providing the strong-
est assurance of product/service
quality available.
46-620 B73 & Series 75 Liquid Level Switches
B73 & Series 75
Liquid Level Switches
Table of Contents
1.0 Installation
1.1 Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.2 Critical Alarm Function . . . . . . . . . . . . . . . . .4
1.3 Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.4 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
1.5 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.0 Reference Information
2.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.2 Theory of Operation . . . . . . . . . . . . . . . . . . .7
2.3 Operating Cycle . . . . . . . . . . . . . . . . . . . . . . .7
2.4 Switch Differential Adjustment . . . . . . . . . . .8
2.4.1 Low Level Controls . . . . . . . . . . . . . . .8
2.4.2 High Level Controls . . . . . . . . . . . . . .10
2.5 Tandem Float Models . . . . . . . . . . . . . . . . . .10
2.5.1 Installation, Preventive Maintenance,
and Troubleshooting . . . . . . . . . . . . .10
2.5.2 Differential Adjustment . . . . . . . . . . .11
3.0 Troubleshooting
3.1 Check Switch Mechanism . . . . . . . . . . . . . .11
3.2 Check Sensing Unit . . . . . . . . . . . . . . . . . . .12
4.0 Preventive Maintenance
4.1 What To Do . . . . . . . . . . . . . . . . . . . . . . . . .13
4.1.1 Keep Control Clean . . . . . . . . . . . . . .13
4.1.2 Inspect Switch Mechanisms, Terminals,
and Connections Monthly . . . . . . . . .14
4.1.3 Inspect Entire Unit Periodically . . . . .14
4.2 What To Avoid . . . . . . . . . . . . . . . . . . . . . . .14
5.0 Specifications
5.1 Agency Approvals . . . . . . . . . . . . . . . . . . . . .15
5.2 Physical . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.0 Replacement Parts
6.1 Series 75 . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
6.1.1 Parts Identification . . . . . . . . . . . . . . .20
6.1.2 Switch and Housing Reference . . . . . .20
6.1.3 Series 75 with Material Code 1 . . . . .21
6.1.4 Series 75 with Material Code 2 . . . . .21
6.1.5 Series 75 with Material Code 3 or 4 . .21
6.2 Model B73 . . . . . . . . . . . . . . . . . . . . . . . . . .22
6.2.1 Parts Identification . . . . . . . . . . . . . . .22
6.2.2 Switch and Housing Reference . . . . . .22
6.2.3 Model B73 . . . . . . . . . . . . . . . . . . . . .22
6.3 Series 75 Tandem Float Units . . . . . . . . . . . .23
6.3.1 Parts Identification . . . . . . . . . . . . . . .23
6.3.2 Series 75 Tandem Float Units . . . . . . .23
6.3.3 Switch and Housing Reference . . . . . .23
7.0 Model Numbers
7.1 Model B73 . . . . . . . . . . . . . . . . . . . . . . . . . .24
7.2 Model Series 75 . . . . . . . . . . . . . . . . . . . . . .26
46-620 B73 & Series 75 Liquid Level Switches
1.0
Installation
Caution:
If equipment is used in a manner not specified by manu-
facturer, protection provided by equipment may be
impaired.
1.1
Unpacking
Unpack the instrument carefully. Inspect all units for
damage. Report any concealed damage to carrier within
24 hours. Check the contents of the packing slip and
purchase order. Check and record the serial number for
future reference when ordering parts.
1.2
Critical Alarm Function
It is recommended that for critical alarm functions, an
additional level switch be installed as a high–high or
low–low level alarm for maximum protection.
1.3
Piping
Figure 3 shows a typical piping installation of a Magnetrol
B73 and Series 75 control to a pressure vessel. Level decals
on control identify the actuation levels for a unit with a
single switch at minimum specific gravity. See
Section 5.2,
Physical
on page 18 for the actuation levels.
Conduit
outlet
Pressure
vessel
Switch
actuating
level
reference
marks
Shutoff
valve
Use pipe of sufficient strength to support the control. If
necessary, provide a stand or hanger to help support its
weight. All piping should be straight and free of low spots
or pockets so that lower liquid line will drain towards the
vessel and upper vapor line will drain toward the control.
Shut-off valves are recommended for installation between
the vessel and the control. If control is to be used with a
low temperature liquid (one which will boil in the float
chamber if outside heat is absorbed), the chamber and pip-
ing should be insulated. Such boiling in the chamber will
cause false level indications.
Caution:
Do not insulate switch mechanism housing.
Max. 12"
Drain
valve
On controls equipped with pneumatic switch assemblies,
consult bulletin on mechanism furnished for air (or gas)
piping instructions. See
Section 6.1.2, Switch and Housing
Reference
on page 20 for bulletin numbers for pneumatic
switches.
NOTE: D, E, and H75 models are designed for high level service only
and utilize a pressure equalizing self-purging float and stem.
Pressure in the chamber must be raised and lowered slowly to
avoid potential float collapse.
46-620 B73 & Series 75 Liquid Level Switches
Figure 1
Piping Configuration
4
1.4
Mounting
Caution:
This instrument is intended for use in Installation
Category II, Pollution Degree 2.
Adjust piping as required to bring control to a vertical
position. Magnetrol controls must be mounted within
3° of vertical in all directions. A three degree slant is
noticeable by eye, but installation should be checked with
a spirit level on top and/or sides of float chamber.
Controls should be mounted as close to the vessel as possi-
ble. This will result in a more responsive and accurate level
change in the control. Liquid in a long line may be cooler
and more dense than liquid in the vessel causing lower
level indication in the control than actual level in the vessel.
Caution:
Never insulate the switch housing of the level control.
Installation and maintenance of tandem float models are
accomplished in much the same manner as described for
standard models. Additional consideration must be given
to the piping arrangement to allow for alignment of the
two switch actuating level marks on the float chamber
with the desired levels in the vessel.
Caution:
Operation of all buoyancy type level devices should be
done in such a way as to minimize the action of dynamic
forces on the float or displacer sensing element. Good
practice for reducing the likelihood of damage to the con-
trol is to equalize pressure across the device slowly.
1.5
Wiring
Caution:
Level controls are shipped from the factory with the
enclosing tube tightened and the middle set screw, on the
housing base, locked to the enclosing tube. Failure to
loosen the set screw prior to repositioning the conduit con-
nection may cause the enclosing tube to loosen, resulting
in the possible leakage of the process liquid or vapor.
B73 and Series 75 controls are shipped with the conduit
entry of the switch housing placed 180° opposite to the
tank configurations to simplify installation in most cases.
If this configuration is appropriate to the installation, pro-
ceed to Step 4 to begin wiring the unit. If another configu-
ration is desired, the switch housing can be easily rotated
by first following Steps 1, 2, and 3.
NOTE: A switch or circuit breaker shall be installed in close proximity
to equipment and within easy reach of operator. It shall be
marked as the disconnecting equipment.
Screw
Set Screw
Screw
Figure 2
Switch Housing
1. Loosen set screw(s) at base of switch housing. Refer to
Figure 2.
2. Switch housing may be rotated 360° to allow correct
positioning of conduit outlet.
5
46-620 B73 & Series 75 Liquid Level Switches
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