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RLBTM SERIES
W eigh Module Kit
Installation
Guide
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53221
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Contents
1. Introduction........................................................................................ 1
2. Mechanical Installation..................................................................... 2
2.1 General Installation Guidelines for Weigh Modules ...................2
2.2 Installing the RLBTM Module .....................................................3
3. Load Cell Wiring ................................................................................ 5
4. Junction Box Connections, Adjustments & Calibration .................... 5
5. Troubleshooting.................................................................................. 6
6. Maintenance and Replacement Parts ...............................................7
7. Limited Warranty................................................................................ 8
Copyright © 1999 Rice Lake Weighing Systems. All rights reserved.
Printed in the United States of America.
Specifications subject to change without notice.
9/99
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1. Introduction
The RLBTM Series Weigh Modules are designed to accommodate normal vessel
expansion in all directions while still exercising self-checking capabilities. The
RLBTM module is a single-ended load cell design which incorporates a ball and cup
for center pivoting and isolating the load cell from unwanted extraneous forces.
The module is available in plated steel (250 to 5000 lb SE) and stainless steel (1000
lb to 4000 lb).
The installation should be planned by a qualified structural
Caution
engineer. Each installation is unique, and this booklet is meant
to serve only as an overview for installation of the RLBTM
Series Weigh Modules.
Authorized distributors and their employees can view or
download this manual from the Rice Lake Weighing
Systems distributor site at www.rlws.com.
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2. Mechanical Installation
2.1 General Installation Guidelines for Weigh Modules
In circular mounting configurations, the preferred mounting orientation is with the
long axis of the load cell pointing toward the center of the vessel, as illustrated in
Figures 1 and 2 below.
Figure 1
Figure 2
Figure 4Figure 3
Figures 3 and 4 illustrate other mounting configurations. For rectangular vessels,
the long axis of the load cell should be parallel to the long dimension of the vessel.
In any application where a recurring force is present in one direction, such as in a
conveyor belt or roller platform, the long axis of the load cell should align with that
force.
1. Mounting surface for base plate and top plate must be level within ±0.5°
to minimize side loads and extraneous forces. If the mounting surfaces are
not level, then shims or grout may be used to level the module.
If possible, check level and plumb again when container is fully loaded
because deflections in legs and supporting structures may cause additional
side forces which greatly affect accuracy. Reinforcement such as cross
bracing of legs or other support structures may be necessary to correct this.
Deflection of the module’s top or base plate due to loading should not
exceed ±0.5°.
2. The load on each module should vary by no more than 20%. During
installation, add shims where necessary to verify that the correct load
distribution is achieved on each module.
3. During installation, dummy load cells can be used to prevent overload
damage. However, if the actual load cells are used during installation of the
weigh module, extreme care must be
taken to prevent overload damage. A
tank or hopper weighing several tons can
exert huge forces when dropped only a
fraction of an inch.
FLEXIBLE PIPING
4. It is crucial that all piping or conduit be
horizontal and flexible sections are close
to the vessel. If flexible piping is not
used, make sure the distance from the
LEVEL ±0.5°
J-BOX
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vessel to the first pipe support is 20 to 30 times the pipe diameter. In
smaller, lower capacity tanks and hoppers, isolating the resultant forces
becomes extremely critical. When possible, flexible conduit piping should
be used close to the vessel instead of the rigid variety. For details, see our
Weigh Modules & Vessel Weighing Systems manual, PN 43918.
5. Load cells should not be installed in the modules until all welding is
completed. The heat generated from welding current passing through a
load cell can damage the adhesive holding the strain gauge to the body. If
possible, use a dummy load cell when welding to maintain finished height.
If welding is unavoidable after load cell installation, ground in such a
manner as to prevent welding current from passing through the load cell.
Ground the welder as closely as possible to the point of welding. Never rely
on check rods or piping for grounding.
6. When possible, use only hermetically sealed load cells in washdown
applications. Environmentally protected load cells are not suitable for
such applications and will be damaged. If tanks and surrounding equipment are frequently steam cleaned, or if the load cell is subjected to direct
washdown, a protective shroud for the weigh module is recommended.
Proper drainage is necessary so the weigh module is not standing in water.
7. Detailed instructions for installing this load cell module follow. When
installing the load cells, use the bolts provided or Grade 5 or stronger
hardened bolts. Pay particular attention to the recommended torque
values.
LOAD CELL BOLT
LOAD CELL
TOP PLATE
BALL
COTTER PIN
BASE PLATE WELDMENT
PIN
UPPER/LOWER
2.2 Installing the RLBTM Module
1. The type of installation, structure of the vessel supports, and strength of the
mounting surface govern the method of locating, attaching, and assembling the RLBTM Weigh Module. Carefully consider three areas which
commonly cause accuracy problems:
• Are the supporting legs adequately braced so they will not spread when the
system is fully loaded?
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CUP
WASHER
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• Does the supporting structure have the necessary strength to prevent
flexing when the system is fully loaded?
• Is there attached equipment such as skirting, venting, or piping which is
likely to cause binding or lack of flexibility?
2. Determine where to position the module and in which direction it should
be oriented.
3. Assemble the module and load cell according to the drawings shown at the
beginning of this section. For load cells using 1/2" mounting bolts, torque
to 65 ft-lb. Install load cell with the arrow pointing in the direction of load.
4. Lift and block the vessel to the same height as the assembled modules.
5. Lift one corner or side of the vessel enough to slide that module into place.
6. If the module is being fitted under the leg of a vessel, verify that the leg’s
center line passes through the center of the top plate (through the center of
the load cell’s load hole).
7. Attach the top plate by bolting. Do not fully tighten because shimming may
be necessary to level.
8. Repeat Steps 5, 6, and 7 for the remaining modules. The vessel should now
be supported on the modules alone.
9. If necessary, move the vessel to its final position. Verify that there is no
initial misalignment between the base plate and top plate by lifting the
vessel slightly at each support point in turn. This will also indicate if the
load is evenly distributed on all modules. Shim if necessary (this only
applies to systems utilizing more than three modules).
10. Attach the base plates to the foundation using anchor bolts for concrete or
by bolting or welding to a steel structure. Verify that the base plates are no
more than ±0.5° out of level. Shim as necessary.
11. Check that the top plates are no more than ±0.5° out of level. Shim if
necessary and fully tighten the bolts.
12. The load distribution can be more accurately checked by connecting each
load cell to the junction box and indicator in turn and measuring the output
with a voltmeter. To verify wiring scheme, check the installation manuals
for the junction box and indicator. The variation in load among the cells
should be no more than 20%. Shim if necessary.
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3. Load Cell Wiring
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1. Route the load cell cables so they will not be damaged or cut. Cable should
not be routed near heat sources greater than 150 °F (66 °C). Do not shorten
any load cell cable. The load cell is temperature compensated with the
supplied length of cable. Cutting the cable will affect temperature compensation. Coil excess cable and protect it so it will not be mechanically
damaged or be sitting in water.
2. Provide a drip loop in all cables so that water or other liquids will not run
directly down the cables onto either
the load cells or the junction box.
Attach load cell cable to the dead
structure, not the vessel.
3. If conduit protection is necessary
against mechanical or rodent damage
to the load cell cables, use flexible
conduit and conduit adapters at the
load cells.
4. Connect cables for the load cells to the summing board in the junction box
according to the load cell calibration certificate provided with the load cell
and the labels on the terminal strips of the junction box.
5. For better performance, use positive and negative remote sense lines if the
wiring run from the junction box to the indicator is longer than 25 feet.
DRIP LOOP
LOAD CELL WIRE COLOR
Black
Green +SIG
White - SIG
4.
Junction Box Connections, Adjustments & Calibration
• Refer to junction box manual for trimming details.
• Refer to indicator manual for system calibration guidelines.
5
FUNCTION
+EXCRed
- EXC
SHIELDGray or Bare
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5. Troubleshooting
If system powers up and gives some type of stable digital readout that varies with
the load on the system, system problems are probably caused by factors other than
the load cells. All too often, load cells are blamed for a malfunctioning system; 90%
of the time, the problem lies elsewhere. Look for mechanical causes for your
problem first.
If the system can be calibrated but doesn’t return to zero, loses calibration, or
demonstrates non-linearity or non-repeatability, see the following chart for possible
causes and refer to the following list of checks.
Symptom
No return to zero
Non-linearity
Non-repeatability
Lost calibration Out of level or plumb; moisture problem; mechanical binding
Drifting readout Moisture in junction box, cables, or load cell; mechanical binding
Possible Cause
Mechanical binding or debris in seals or under load cells; may have lost system
calibration
Thermal expansion or deflection under load causing binding or side load
Loose load cell mount; drifting caused by moisture, load cell overload or shock
damage; mechanical binding
1. Check load cell module for debris restricting load cell movement or debris
between scale and structure. Check overload stops for proper clearance.
2. Check that tank/vessel and modules are plumb, level, and square at critical
areas.
3. Check all piping and conduit for connections that restrict vessel movement.
4. If check rods are used, loosen all connections to finger tight for testing.
5. Check load cell cables for physical or water damage.
6. Check all electrical connections, especially in the junction box.
If the problem still is not found:
7. Check possible indicator malfunction by using a load cell simulator to
input a known good signal into the indicator.
8. Disconnect each load cell’s signal leads at the junction box and check
individual load cell outputs with a multimeter. Then check input/output
impedances for comparison with load cell manufacturer’s specifications.
If after all these checks the problem still cannot be isolated, reconnect all but one
load cell. Replace the load cell with a load cell simulator. Alternate so that each load
cell is individually disconnected and replaced with a simulator. If there is a problem
with a particular load cell, the symptom should disappear when that load cell is
disconnected and replaced with the simulator.
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6. Maintenance and Replacement Parts
1
8
4
LOAD CELL
3
5
7
2
6
RLBTM Tool Steel Modules
No. Description No. Req. Replacement Part Numbers
250 to 5000 lb SE
1 Top Plate ......................................1.................................... 53055
2 Base Plate Weldment ...................1.................................... 53058
3 Ball ...............................................1 .................................... 18815
4 Upper/Lower Cup.........................2.................................... 33654
5 Cotter Pin .....................................2.................................... 15232
6 Flat Washer ..................................2.................................... 21938
7 Pin ................................................1.................................... 53067
8 Load Cell Bolt...............................2.................................... 15071
RLBTM Stainless Steel Modules
No. Description No. Req. Replacement Part Numbers
1000 to 4000 lb
1 Top Plate ......................................1.................................... 53062
2 Base Plate Weldment ...................1.................................... 53065
3 Ball ...............................................1 .................................... 53507
4 Upper/Lower Cup.........................2.................................... 33654
5 Cotter Pin .....................................2.................................... 15233
6 Flat Washer ..................................2.................................... 15161
7 Pin ................................................1.................................... 53067
8 Load Cell Bolt...............................2.................................... 15075
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7. RLBTM Limited Warranty
Rice Lake Weighing Systems (RLWS) warrants that all RLWS brand load cells
properly installed by a Distributor or Original Equipment Manufacturer (OEM) will
operate per written specifications. All load cell products are warranted against
defects in materials and workmanship for two (2) years. Products marked as
“waterproof” are warranted against defects in materials and workmanship relating
to moisture ingress.
RLWS warrants that the equipment sold hereunder will conform to the current
written specifications authorized by RLWS. RLWS warrants the equipment against
faulty workmanship and defective materials. If any equipment fails to conform to
these warranties, RLWS will, at its option, repair or replace such goods returned
within the warranty period subject to the following conditions:
• Upon discovery by Buyer of such nonconformity, RLWS will be given prompt
written notice with a detailed explanation of the alleged deficiencies.
• Examination of such equipment by RLWS confirms that the nonconformity
actually exists, and was not caused by accident, misuse, neglect, alteration,
improper installation, improper repair or improper testing; RLWS shall be the
sole judge of all alleged non-conformities.
• Such equipment has not been modified, altered, or changed by any person
other than RLWS or its duly authorized repair agents.
• RLWS will have a reasonable time to repair or replace the defective equip-
ment. Buyer is responsible for shipping charges both ways.
• In no event will RLWS be responsible for travel time or on-location repairs,
including assembly or disassembly of equipment, nor will RLWS be liable for
the cost of any repairs made by others.
THESE WARRANTIES EXCLUDE ALL OTHER WARRANTIES, EXPRESSED
OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. NEITHER RLWS NOR DISTRIBUTOR WILL, IN ANY EVENT, BE LIABLE FOR
INCIDENTAL OR CONSEQUENTIAL DAMAGES.
RLWS AND BUYER AGREE THAT RLWS’S SOLE AND EXCLUSIVE LIABILITY HEREUNDER IS LIMITED TO REPAIR OR REPLACEMENT OF
SUCH GOODS. IN ACCEPTING THIS WARRANTY, THE BUYER WAIVES
ANY AND ALL OTHER CLAIMS TO WARRANTY.
SHOULD THE SELLER BE OTHER THAN RLWS, THE BUYER AGREES TO
LOOK ONLY TO THE SELLER FOR WARRANTY CLAIMS.
No terms, conditions, understanding, or agreements purporting to modify the terms of
this warranty shall have any legal effect unless made in writing and signed by a corporate
officer of RLWS and the Buyer.
©1999 Rice Lake Weighing Systems, Inc. Rice Lake, WI USA. All Rights Reserved.
RICE LAKE WEIGHING SYSTEMS
230 WEST COLEMAN STREET
• RICE LAKE, WISCONSIN 54868 • USA
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