Rice Lake Weigh Modules Mount Assemblies User Manual
INST ALLA TION AND
SYSTEM GUIDELINES
43918
CONTENTS
Vessel W eighing System Design......................................................... Section 1
Bulk Material Weighing Systems • Load Introduction Principles • Maximizing System Accuracy •
Selecting Number of Supports & Load Cell Capacity • Choosing the Correct Load Cell • Calibrating
Thermal Expansion of Vessels & Stay Rods • Calculating T ank V olumes • Densities of Common Materials
• Load Cell Bolt Torque Values • Wind and Seismic Effects on Vessel Stability
Weigh Modules ................................................................................ Section 2
Single-End Beam Load Cell Modules • Double-End Beam Load Cell Modules • Compression Canister
Load Cell Modules • S-Beam Load Cell Modules • Mounting Assemblies and Compatible Load Cells
Vessel Attachments .......................................................................... Section 3
Attaching Piping to Weigh Vessels • Piping Guidelines • Vessel Restraint Systems • Low-Accuracy
Systems: Partial Mounting on Flexures
Installation & Service Tips ............................................................... Section 4
Before Installing • Determining Microvolts per Graduation • Load Cell Mounting Hardware Safety
Guidelines • Load Cell T rimming • Load Cell Troubleshooting • Selecting Replacement Load Cells •
Load Cell Wiring Guide • Calibrating Vessel W eighing Systems
Glossary.......................................................................................... Section G
!
All vessel weighing system installations should be planned by a qualified structural engineer.
Warning
This manual is intended to serve only as a general guide to planning, installation, and servicing of these
systems; no attempt has been made to provide a comprehensive study of all possible system configurations.
Copyright © 1997 Rice Lake Weighing Systems. All rights reserved. Printed in the United States of America.
Specifications of products described in this handbook are subject to change without notice.
December 1997
SYSTEM DESIGN
VESSEL WEIGHING SYSTEM DESIGN
Bulk Material Weighing Systems ...................................................................................1-2
Custody T ransfer................................................................................................................................................................ 1-2
Material Proportioning ...................................................................................................................................................... 1-2
Loss in Weight ................................................................................................................................................................... 1-2
Common Hopper Scale Arrangements .............................................................................................................................. 1-3
Load Introduction Principles......................................................................................... 1-6
The Ideal... ......................................................................................................................................................................... 1-6
Angular Loading ................................................................................................................................................................ 1-6
Eccentric Loading.............................................................................................................................................................. 1-6
Side Loading ...................................................................................................................................................................... 1-7
Twisting Loads ................................................................................................................................................................... 1-7
Contents
Maximizing System Accuracy ........................................................................................ 1-8
Environmental................................................................................................................................................................... 1-8
Load Cell and Mount.......................................................................................................................................................... 1-8
Mechanical/Structural ....................................................................................................................................................... 1-8
Calibration ......................................................................................................................................................................... 1-8
Operational Considerations ............................................................................................................................................... 1-8
Selecting Number of Supports & Load Cell Capacity....................................................... 1-9
Number of Supports .......................................................................................................................................................... 1-9
Load Cell Capacity ............................................................................................................................................................. 1-9
Choosing the Correct Load Cell ................................................................................... 1-10
Environmentally Protected...............................................................................................................................................1-10
Hermetically Sealed ..........................................................................................................................................................1-10
International Protection (IP) Rating Guide ......................................................................................................................1-11
Calculating Thermal Expansion of Vessels & Stay Rods ................................................ 1-12
Stay Rod Expansion/Contraction.................................................................................................................................................1-12
Vessel Expansion/Contraction .....................................................................................................................................................1-12
Calculating Tank Volumes........................................................................................... 1-14
Formulas for Various Tank Shapes and Sections ..............................................................................................................1-14
Calculation Examples .......................................................................................................................................................1-17
Densities of Common Materials ................................................................................... 1-19
Load Cell Bolt Torque Values....................................................................................... 1-23
Wind and Seismic Effects on Vessel Stability................................................................ 1-24
1-1
SYSTEM DESIGN
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Bulk Material W eighing Systems
Bulk materials are weighed for various reasons. Although this discussion focuses on the weighing of bulk solids, many of the principles
are equally applicable to the weighing of bulk liquids. For the sake of convenience, we have classified bulk material weighing into three
general types:
Custody Transfer
Figure 1-1
Weighing bulk material on a truck scale is a typical example of
custody transfer weighing where material is being traded for
dollars. The filled truck is weighed and the known tare weight of
the truck is subtracted to determine the net weight of product. This
may be done for invoicing or inventory-control purposes. Typically, achieving a predetermined weight is not important in this
situation. What is important is knowing how much material
entered or left the facility.
Material Proportioning
Figure 1-2 shows various ingredients being weighed on separate
scales, then mixed. Each scale must be accurate, or there could
be a detrimental effect on the proportions of each ingredient in
the finished product.
Figure 1-3 shows several materials being mixed to a given recipe
and batched one at a time into a single weigh hopper. As all
ingredients are weighed in the same weigh hopper, the weighing
system must be linear to achieve correct proportioning. It does not
need to be calibrated accurately if the final net weight of product
is not critical.
Loss in Weight
Figure 1-4 shows a situation where the weigh hopper is first topped
up and when the filling process stops, the material is fed out at a
controlled rate. The total amount of material supplied to the
process may be important, but the rate at which product is fed into
the batching process from the weigh hopper is usually more
important.
Bulk Material Weighing Systems
Figure 1-3
Figure 1-2
Figure 1-4
1-2
Bulk Material Weighing Systems
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Common Hopper Scale Arrangements
SYSTEM DESIGN
A. One of the simplest hopper weighing systems is illustrated
below in Figure 1-5. The weigh hopper may be filled using a
feed conveyor, front-end loader, auger, etc., and the material
may be removed from the hopper using a discharge conveyor.
Figure 1-5
Advantages of this system are:
• Low cost compared to other systems.
• Low overall height.
Disadvantages of this system are:
• Slow fill and discharge (low throughput).
• Difficult to achieve an accurate prescribed weight because
of inconsistency in input material flow.
B. Figure 1-6 below illustrates a weigh hopper positioned
directly under the storage silo.
Advantages of this system are:
C. A conveyor-fed system can be improved by adding an upper
surge hopper as shown in Figure 1-7. The surge hopper allows
the conveyor to be run continuously and isolates the weigh
hopper from the sometimes erratic flow of material from the
conveyor.
Figure 1-7
Advantages of this system are:
• Weigh hopper isolated from the feed conveyor.
• The input conveyor can run continuously.
• Surge hopper serves as a buffer to smooth out demand.
• 2-speed fill is possible.
• Faster fill and higher throughput possible.
Disadvantages of this system are:
• Higher overall height.
• Higher cost.
• More complex controls and mechanical arrangement.
Figure 1-6
• The weigh hopper is gravity-fed, simplifying the feed process
and providing a more uniform flow.
• Faster fill cycle and hence greater throughput.
• 2-speed fill may be used for greater target accuracy.
Disadvantages of this system are:
• Higher overall height.
• Material must be conveyed higher to storage silo.
1-3
SYSTEM DESIGN
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D. This arrangement is similar to Example C, however, a lower
surge hopper has been added to speed up the discharge cycle.
This system, shown in Figure 1-8, is typically used in multidraft grain loadout systems where multiple drafts are required to fill a rail car or barge. The weight of each draft can
be accumulated and the target weight of the final draft
adjusted to achieve the desired car net load.
Figure 1-8
Advantages of this system are:
• Weigh hopper isolated from feed conveyor.
• Surge hopper serves as a buffer to smooth out demand.
• 2-speed fill is possible.
• Faster fill, discharge, and throughput possible.
Bulk Material Weighing Systems
Figure 1-9
F. Figure 1-10 illustrates a loss in weight system. This is used
where a process needs a batch of material (not more than the
capacity of the weigh hopper), but that material needs to be
fed to the process at a controlled rate.
The process starts by filling the hopper with at least enough
material for the upcoming process. The fill is then stopped
and the discharge commences. The rate at which the discharge takes place is controlled by monitoring the “loss in
weight” of the hopper and then modulating the discharge
rates to maintain the desired flow rate. The discharge may be
ended at the completion of the process step, or when a specific
amount of material has been discharged.
Disadvantages of this system are:
• Higher overall height.
• Higher cost.
• More complex controls and mechanical arrangement.
The systems described up to this point deliver a single material in
pulses rather than from a continuous flow. They may be used for
in-plant process weighing or custody transfer. Figures 1-9 and 110, described below, provide a continuous material flow and are
more often used for process weighing.
E. Figure 1-9 illustrates a single storage silo with two weigh
hoppers suspended underneath. This arrangement can be
used to provide material continuously to a process. As one
hopper is emptying, the other can be filling If the system is
sized correctly, there is no interruption to the material flow
on the discharge belt.
Advantages of this system are:
• Continuous material flow.
• High throughput possible.
Disadvantages of this system are:
• Higher overall height.
• Higher cost than pulse discharge systems.
• More complex controls and mechanical arrangement.
Advantages of this system are:
• Gives the ability to supply material at a constant rate
Disadvantages of this system are:
• Complex controls and mechanical arrangement
• Higher cost than pulse discharge systems.
Figure 1-10
1-4
Bulk Material Weighing Systems
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SYSTEM DESIGN
G. Figure 1-11 illustrates a multiple-ingredient batching sys-
tem where all the ingredients are weighed one at a time in a
single weigh hopper.
Figure 1-11
Advantages of this system are:
• Lower cost than multiple-weigh hoppers
• Scale calibration may not be critical, as all ingredients are
weighed in a single scale, assuring correct proportions.
Disadvantages of this system are:
• The accuracy of minor ingredients may suffer where the scale
capacity is large compared to the weight of ingredient.
• System is somewhat slow because each material must be
batched in one at a time, and the cycle cannot repeat until the
weigh hopper has been discharged.
H. The system illustrated in Figure 1-12 below is a multi-
ingredient batching system which has a separate weigh hopper for each ingredient.
Figure 1-12
Advantages of this system are:
• Weigh hopper capacity can be sized appropriately for each
material so that each weighment is close to the scale capacity,
providing greater accuracy.
• Faster throughput, since all materials can be weighed and
discharged simultaneously.
Disadvantages of this system are:
• Higher cost.
• Each scale must be accurate to ensure correct proportioning.
Note: We recommend that you do not attempt to weigh a batch of
material which is less than 20 scale divisions since the accuracy
will be questionable.
For example, if a hopper scale has a .5 lb division size, we recommend that you not weigh less than a 10-lb batch on that scale. It’s
better to weigh minor ingredients accurately on a scale suited to
the purpose, and add those ingredients to the batch by hand. For
example, if making raisin oatmeal cookies, it may not be too much
of a problem to batch-weigh the raisins along with the oatmeal.
However, it may be prudent to weigh the salt on a more sensitive
bench scale and hand-add it to the hopper at completion of the
weigh cycle.
1-5
SYSTEM DESIGN
Load Introduction Principles
Load Introduction Principles
A clear understanding of the exact manner in which a load must be placed on a load cell will assist you in both designing a vessel that is
to be equipped with load cells, and in choosing the correct type of load cells and mounts for your application.
The Ideal...
Load cell specifications are derived under laboratory conditions,
where load is applied to the cell under near-perfect conditions. The
performance of load cells in an actual process weighing application
can be greatly degraded if care is not taken in the means by which
the load is applied to the cell.
If the direction of the force is constant, calibration will compensate
for this and the scale will weigh accurately. However, if the angle
changes as the force is applied, it will cause nonlinearity and if
there is friction in the mechanical system, hysteresis will also be
present. Angular loads can be caused by mounts that are out of
level, a nonrigid foundation, thermal expansion/contraction, structure deflection under load, and the unavoidable deflection of the
load cell itself.
C
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Figure 1-14
Figure 1-13
Figure 1-13 shows a typical mounting arrangement for a singleended beam. The fixed end is fastened to a “rigid” foundation, while
the free end is cantilevered to allow downward deflection as load
(F) is applied. Under ideal conditions, the mounting surface would
be flat, horizontal and perfectly rigid. The load F would be introduced vertically with minimal extraneous forces applied, and the
load cell would be totally insensitive to all forces other than
precisely vertical ones.
However, in the real world, load cell mounting and loading conditions are far from ideal. Incorrect loading is by far the most
common cause of accuracy problems encountered by service
technicians. Understanding the following common load introduction problems will prevent loading errors in your vessel weighing
application.
Though the discussion is confined to single-ended beams, many of
the principles apply equally to other load cell types.
Angular Loading
This is a condition where the load F is introduced through the
loading hole, but at an angle to its center line. This angular force
can be broken up into its vertical component along the loading
hole center line which the cell will register and its horizontal
component at 90° from the center line. This horizontal component
is a side force to which, ideally, the load cell would be totally
insensitive. For example, if force F is inclined to the load hole
center line at an angle of 5°, then the force registered by the cell is
reduced by .4% while a side force of .01F is also applied.
Eccentric Loading
This is a condition where the force F is applied vertically to the cell,
but its line of action is shifted away from the vertical line through
the loading hole. This is not a detrimental condition if the force is
applied consistently at the same point, since calibration will
compensate for this effect. However, if the point of application
moves horizontally as the scale is loaded, it will cause nonlinearity
and possibly hysteresis. Eccentric loads may be caused by poorlydesigned mounting arrangements and thermal expansion/contraction of the scale.
Figure 1-15
1-6
Load Introduction Principles
SYSTEM DESIGN
Side Loading
Figure 1-18 illustrates a torque of magnitude Fy exerted as the
result of the load F being applied at a distance y from the loading
hole center line.
Figure 1-16
This is a condition where the vertical force F (which you are trying
to measure) is accompanied by a side force R applied at 90° to F.
This force can be constant, but more typically is a force that varies
over time and hence affects the linearity and possibly the hysteresis
of the scale. The ideal load cell would be totally insensitive to side
loads. However, in practice these extraneous forces do affect the
Mounts which are out of level, thermal expansion/contraction,
structure deflection under load and dynamic side forces (caused by
rotating mixers, etc.) all cause twisting of the load cell. Since these
forces tend to vary in magnitude as a function of time, temperature
and/or load, the effects are not predictable, and will degrade system
accuracy.
output of the cell and two seemingly identical cells can react
differently to the same side load. A related condition is the END
FORCE, P, which is similar to a side force, except that it acts on the
end face of the cell. Side forces are the result, typically, of thermal
expansion/contraction, mounts which are not level, and vessel
dynamics (caused by mixers, etc.).
T
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Figure 1-18
Twisting Loads
T
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(a) (b)
Figure 1-17
Typically, a side force does not act exactly at the neutral axis and
hence produces a torque or twisting effect in addition to the side
force. A load cell can be subjected to a torque (T) in a number of
ways. Figure 1-17 (a) illustrates a condition where the line of action
of a side force is moved away from the neutral axis by a distance h
resulting in a torque of Rh. Figure 1-17 (b) illustrates a situation
where the load is hung from the cell using a bolt. Any side force
applied by this arrangement has a much larger twisting effect on
the cell because of the increased distance h1 to the neutral axis.
h
1
1-7
SYSTEM DESIGN
Design Elements
Maximizing System Accuracy
High-accuracy systems are generally considered to have system errors of ±.25% or less; lower accuracy systems will have system errors
of ±.50% or greater. Most weight indicators typically have an error of ±.01%, hence, the main source of error will be the load cells and,
more importantly, the mechanical arrangement of the scale itself. In vessel weighing, each installation is unique in terms of the
mechanical arrangement, site conditions and environmental factors. Therefore, it is impossible to be specific in this publication about
the system accuracy that can be achieved. The first requirement is to determine what the customer’s accuracy expectations/requirements
are, then design the system accordingly. Grouped under various subheadings below are various recommendations that contribute to high
accuracy. It will not be possible to comply with all these recommendations; however, they should be kept in mind when designing a system.
Environmental
■ Install the vessel in a controlled environment where seasonal
temperature fluctuations are minimized. If this is not feasible, use load cells with temperature compensation specifications that will allow satisfactory performance over the expected temperature range.
■ Use a metal shield to protect the load cells from radiant heat
sources. Use an insulating pad between the vessel and load cell
mount if heat is being conducted.
■ If thermal expansion/contraction of the vessel is expected,
choose a mount which will allow unhindered lateral movement. If stay rods are required, position them so that thermally-induced movement is minimized. See Vessel Restraint
Systems in Section 3 for more information.
■ Place the vessel indoors, if possible, where it will be protected
from wind and drafts.
■ Do not place the vessel in an environment where its support
structure is subject to vibration. Ensure that vibrations are
not transmitted via attached piping or stay rods.
■ Select load cells and mounts that will give the degree of
corrosion protection required.
■ Use load cells that have the degree of environmental protection required for the application. For example, avoid possible
drifting problems with standard load cells in washdown applications by specifying hermetically-sealed cells.
Load Cell and Mount
■ Choose load cells whose accuracy is consistent with the
desired system accuracy.
■ Do not grossly oversize the load cells; see Load Cell Capacity
on page 1-9. Best accuracy will be achieved when weighing
loads close to the vessel capacity. As a general rule, do not
attempt to weigh a load of less than 20 graduations.
■ If it is not possible to trim the corners, use load cells with
matched outputs, particularly if the vessel is not symmetrical
and/or the material is not self-leveling. Otherwise, use a
pretrimmed junction box.
■ Support the vessel entirely on load cells; do not use dummy
cells or flexures that would hinder a good calibration. See
Partial Mounting on Flexures on page 3-11.
■ Use proven load cell mounts that will provide optimal loading
conditions.
■ Orient the mounts as recommended in the installation manual.
Mechanical/Structural
■ Support the load cell mounts on a rigid structure; this will
ensure a high natural frequency and reduce the amount of
bounce and instability. All support points must be equally
rigid to avoid tipping of the vessel as load is applied. Minimize
interaction between adjacent weigh vessels mounted on the
same structure. Vehicular traffic must not cause deflection of
the vessel’s support structure.
■ Ladders, pipes and check rods, etc. should not be allowed to
shunt the weight that should rest on the load cells.
■ Where piping or conduit must be attached to the vessel, use
the smallest diameter acceptable for the application. Use the
longest unsupported horizontal length of pipe possible to
connect to the vessel.
■ Use an indicator that is EMI/RFI protected. Provide grounding and transient protection in accordance with the
manufacturer’s recommendations. In general, take measures
to reduce electrical interference.
■ Use a good-quality junction box which remains stable with
changing temperatures. Look for a junction board which has
a solder mask at a minimum and which preferably is
conformally coated also. Ensure that the enclosure is suited
to the environment.
Calibration
■ Design in a convenient means of hanging weight from the
corners of the vessel to trim the load cell outputs and for
calibration. Use weights as described above, or known weight
of material to perform the calibration. See Calibrating Vessel
Weighing Systems in Section 4.
Operational Considerations
■ Maintain an even and consistent flow of material.
■ Avoid simultaneous fill/discharge of weigh vessel.
■ Slow down the filling cycle as much as possible and/or use a
2-speed fill cycle.
■ Reduce to a minimum the amount of “in flight” material.
■ Use preact learning to predict the optimum cutoff point based
on past performance.
■ Use Auto Jog to top off contents after fill.
■ If possible, switch off any vibrating or mixing equipment
while the weight is being determined.
■ Reduce to a minimum the surging of liquids while a weight
reading is being taken.
1-8
Design Elements
VESSEL WEIGHING SYSTEMS
Selecting Number of Supports & Load Cell Capacity
Number of Supports
The number of supports to be recommended is dependent on the
geometry, gross weight, structural strength and stability of the
vessel. The number of supports chosen for a vessel obviously
influences the capacity of the load cells required. In general, no
more than eight supports should be used. It becomes more difficult
to get even weight distribution on all supports as the number
increases beyond three. Below is a look at a number of examples.
Suspended Vessels
These vessels are very often suspended from an existing structure
which will sometimes dictate how many supports will be used. In
general, one or more supports may be used. Using three supports
or fewer has the advantage of not requiring adjustment of
the length of the support linkages to distribute the load
equally between all supports (assuming the cells are arranged
symmetrically on the vessel).
Upright cylindrical vessels in compression
The most convenient method of mounting is with three supports
arranged at 120° degree intervals. Correct weight distribution is
inherent to 3-point support and is preferred whenever possible.
With tall slender vessels or vessels subject to fluid sloshing, wind
or seismic loads, stability against tipping becomes a consideration.
In these situations, four or more supports should be considered.
See Appendix section on wind and seismic effects.
Square, rectangular or horizontal cylindrical
vessels mounted in compression
Because of geometry, it is usually most convenient to mount these
vessels on four supports, close to each corner. Higher capacities
may, of course, require more than four.
Load Cell Capacity
It is vital to the performance of a weighing system to select load
cells of the correct capacity. Here are some guidelines:
■ All load cells selected must be of the same capacity.
■ Estimate the vessel dead weight, including all piping, pumps,
■ Add the maximum live weight of product to be weighed to the
■ Divide the gross weight by the number of legs or support
■ Select a load cell with a capacity somewhat greater than the
A good rule of thumb is to select a load cell with a capacity 50 –
100% in excess of the calculated nominal load per cell. Once the
load cell capacity has been determined, check that the live weight
signal is adequate for the instrumentation selected; see Section 4
for information on how to determine the microvolt-per-graduation for your system. This is particularly important when the ratio
of dead weight to live weight is high.
■ Additional factors to consider:
■ See page 2-22 for compatibility information on mounts and
agitators, insulation and vessel heating fluids.
dead weight. This is the gross weight of the vessel and
contents.
points. This is the nominal weight which will be carried by
each load cell.
nominal weight. The following should be considered when
determining how much greater the load cell capacity should
be:
1. Is your dead weight accurate?
2. Will the load be evenly distributed on all cells?
3. Is the vessel fitted with an agitator or subjected to shock
loading?
4. Is it possible the vessel will be overfilled, exceeding your
live weight value?
5. Will the vessel be subjected to wind or seismic loading?
For more information, see Wind and Seismic Effects on
Vessel Stability.
Load Cell Construction Material — In a corrosive environment, stainless steel outperforms nickel-plated alloy steel.
Load Cell Protection — The ultimate degree of protection
can be achieved with hermetically-sealed load cells which
ensure the integrity of the strain gauge section of the cell in
corrosive or washdown applications.
Cable Length — Check that the standard cable length will
be adequate for your installation. Longer cable lengths are
available on special order.
load cells by capacity. Capacity requirements may limit
practical applications of many models.
1-9
SYSTEM DESIGN
Choosing the Correct Load Cell
Misuse of any product can cause major cost and safety problems;
load cells are no exception. Unfortunately, the load cell protection
rating systems used in the industry today are inadequate in some
ways. That’s why Rice Lake Weighing Systems, with years of load
cell experience, has developed its own rating system for load cells.
Our system categorizes load cells in two major groups: hermetically-sealed (HS), and environmentally-protected (EP). Hermetically-sealed cells are then further characterized by IP (International Protection) numbers. We feel this system effectively matches
load cell to application for optimal results.
To choose the proper load cell protection qualities, a fundamental
understanding of the differences between “environmentally-protected” and “hermetically-sealed” load cells is necessary. The
inappropriate use of environmentally-protected load cells in harsh
conditions is a prescription for load cell failure. Because of the
extra manufacturing steps, hermetically-sealed load cells cost
more than environmentally-protected versions. Despite the higher
initial cost, hermetically-sealed load cells may be the best longterm choice for harsh chemical, washdown, and unprotected
outdoor applications.
Environmentally Protected
Environmentally-protected load cells are designed for “normal”
environmental factors encountered in indoor or protected outdoor
weighing applications. By far the most popular type, these load
cells may employ strategies like potting, rubber booting, or redundant sealing to afford some protection from moisture infiltration.
Potted load cells utilize one of several types of industrial potting
materials. The liquid potting material fills the strain gauge cavity
then gels, completely covering the strain gauge and wiring surfaces. While this may significantly diminish the chance of moisture contamination, it does not guarantee extended waterproof
performance, nor does it withstand corrosive attack.
A second method of protection uses an adhesive foam-backed plate.
This protection affords some moisture and foreign object protection, but less than potted cells. In many cases, manufacturers will
use a caulking material to seal the plate to decrease the potential
for cavity contamination. A common approach among manufacturers to further decrease the entry of moisture to the strain gauge
combines both a potted cavity and a foam-backed plate, in a process
called redundant sealing.
Yet another strain gauge cavity protection strategy is the rubber
boot. Commonly employed with cantilever and bending beam
models, the boot covers the cavity and is secured by clamps. While
this provides easy access for repairs, the boot may crack if not
lubricated regularly, allowing contaminants into the load cell
cavity. Lubricating the rubber boot during routine inspections will
contribute to the long-term durability of the load cell.
Protecting the strain gauge cavity is just one consideration in
protecting a load cell from contamination. Another susceptible
area is the cable entry into the body of the load cell. Most environmentally-protected load cells incorporate an “O” ring and cable
compression fitting to seal the entry area. This design provides
protection only in applications with minimal moisture. In highmoisture areas, it is safest to install all cabling in conduit, providing both a moisture barrier and mechanical protection.
Although environmentally-protected load cells keep out unwanted
contaminants, they are not suited for high moisture, steam, or
direct washdown applications. The only long-term strategy for
these applications is to use true hermetically-sealed load cells.
Hermetically Sealed
Hermetically-sealed load cells offer the best protection available
for the weighing market. Using advanced welding techniques and
ultra-thin metal seals, these load cells handle the extremes of
harsh chemical and washdown applications. What makes the seal
unique is the process of laser-welding metal covers to protect the
strain gauge and compensation chambers. The cavities are then
injected with potting or, in the case of glass-to-metal seals, filled
with a pressurized inert gas, providing a redundant seal. As a final
assurance of the integrity of the seal, a leak test is conducted to
reveal any microscopic flaws in the sealing weld.
True hermetic protection addresses both the strain gauge cavity
and cable entry area. The most advanced cable entry design
employs a unique glass-to-metal bonding seal which makes the
cable termination area impervious to moisture. Cable wires terminate at the point of connection to the load cell, where they are
soldered to hermetically-sealed pins that carry signals to the sealed
strain gauge area through a glass-to-metal seal. Water or other
contaminants cannot “wick up” into the load cell, since the cable
ends at the entry point. This design allows for field-replaceable
cable, since the connection is outside the load cell.
A word of caution: stainless steel load cells are not synonymous
with hermetically-sealed load cells. While environmentally-
protected stainless steel load cells may be suitable for dry
chemical corrosive environments, hermetically-sealed stainless
steel models are the appropriate choice for high moisture or
washdown applications.
Design Elements
1-10
Design Elements
VESSEL WEIGHING SYSTEMS
International Protection (IP) Rating Guide
If a hermetically-sealed cell is necessary, further classification is needed to be sure of the type of protection a particular cell offers. For
hermetically-sealed cells, Rice Lake Weighing Systems uses the International Protection (IP) rating system. We find the IP numbers and
their definitions are suitable for the classification of hermetically-sealed load cells, and only apply IP numbers to such cells. The IP
numbers on a hermetically-sealed cell further specify the treatment a specific cell can endure in environments more severe than simple
washdown. The following tables define the IP numbers alone and in conjunction with the hermetically-sealed rating.
▲
Example: Protection level offered
by an IP67 rated product
▲
Protection against solid objects
First number (in this case 6)
No protection
0
1
Protected from solid objects up to 50 mm (e.g., accidental touch
by hands)
2
Protected from solid objects up to 12 mm (e.g., fingers)
3
Protected from solid objects more than 2.5 mm (e.g., tools and
small wires)
4
Protected from solid objects more than 1 mm (e.g., small wires)
5
Protected from dust; limited entrance (no harmful deposit)
6
Totally protected from dust
IP 67
Manufacturers may give a NEMA rating to
cells. This system was established for electrical enclosures and is difficult to apply to load
cells. However, if you see a NEMA rating and
need a general idea of what it means, IP67
and NEMA 6 cells are comparable and meet
similar requirements.
Time invested in a well-considered choice
offers large returns in the long run. If there
is any doubt as to which cell to use, consult
with a company such as Rice Lake Weighing
Systems that offers experience and knowledge with every load cell.
▲
Protection against liquids
Second number (in this case 7)
No protection
0
1
Protected from vertically-falling drops of water (e.g.,
condensation)
2
Protected from direct sprays of water up to 15° from vertical
3
Protected from direct sprays of water up to 60° from vertical
4
Protected from water sprayed
entrance allowed
5
Protected from low pressure jets of water from all directions;
limited entrance allowed
6
Protected from strong jets of water (e.g., for use on ship decks);
limited entrance allowed
7
Protected from the effects of immersion between 15cm and 1m
8
Protected from extended periods of immersion under pressure
from all directions; limited
IP Numbers with Hermetically Sealed (HS) or Environmentally
Protected (EP) Ratings
Rating Protection
EP
HS-IP65
HS-IP66
HS-IP67
HS-IP68
HS-IP66/68
Dust proof, not protected from moisture or water
Dust proof, protected from splashes and low-pressure jets
Dust proof, protected from strong water jets
Dust proof, protected from temporary immersion in
water 1 meter deep for 30 minutes
Dust proof, protected from continuous immersion in
water under more severe conditions than IP67
Dust proof, protected from strong water jets and/or
constant immersion
1-11
SYSTEM DESIGN
Thermal Expansion
Calculating Thermal Expansion of V essels & Stay Rods
Stay Rod Expansion/Contraction
Stay rods attached to vessels subjected to thermal changes can
introduce significant forces which affect system accuracy. The
method of attachment and the length of the stay rods directly affect
these forces.
Figure 1-19 illustrates a stay rod rigidly attached to a bracket on
each end—one bracket is rigidly mounted, the other is unattached,
thus allowing the rod to expand and contract freely. As the temperature rises or drops, the length of the rod will increase or
decrease respectively. The change in length (∆L) is proportional to
the original length (L), the change in temperature (∆T), and the
This shows that a 48" steel rod will increase by .019" as a result of
a 60°F temperature rise. This may seem insignificant, until you
consider the forces which can result if the stay rod is confined
rigidly at each end, as in Figure 1-20.
In Figure 1-20, a 1" steel rod 48" long is attached to a bracket on
each end, and both brackets are rigidly attached. If the rod is
initially adjusted so that there is no strain, a subsequent 60°F rise
in temperature will cause the rod to exert a force of 9,000 lb on each
bracket. Hence, vessel restraint systems must be designed and
installed properly so that they don’t move and/or apply large lateral
forces to the weigh vessel.
coefficient of linear expansion (a) which is a characteristic of the
rod material.
∆L can be calculated from the following equation:
∆L = a x L x ∆T
L
Vessel Expansion/Contraction
Figure 1-19
Table 1-1 below lists the coefficient of thermal expansion (α) for
various materials used to construct vessels and stay rods.
Example:
If the rod in Figure 1-19 is made from 1018 steel, then a = 6.5 x 10
6
from Table 1-1. If the rod is 48" long and the temperature
increases by 60°F, the length of the rod will increase by:
∆L = a x L x ∆T
∆L = 6.5 x 10-6 x 48" x 60
∆L = .019
Temperature fluctuations will cause weigh vessels to grow and
contract. Figure 1-21 on the following page best illustrates this.
Shown is a top view of a rectangular vessel. The solid line repre-
sents its size at 70°F and the inner and outer broken lines represent
its size at 40°F and 100°F respectively. The amount that the sides
-
will increase/decrease in length can be found using the expansion
formula discussed previously.
48"
1" Dia
Figure 1-20
Therefore: ∆L = X x L x ∆T
lairetaM
leetSwoL
nobrac
)8101(
leetssselniatS20301x6.9
303
403
61301x9.8
munimulA160601x0.31
Table 1-1
1-12
6-
01x5.6
6-
6-
6-
noisnapxEraeniLfotneiciffeoC
repsehcni( ° )F
Thermal Expansion
Vessels with attached piping can be subjected to severe side forces
as a result of temperature variations if the connections are not
executed properly. It is worth noting that vessels expand and
84.0"
144.0"
Figure 1-21
If the vessel is made from mild steel, the length will vary by ± .028"
(6.5 x 10-6 x 144 x 30), and the width will vary by ± .016"
(6.5 x 10-6 x 84 x 30) as the temperature fluctuates by ± 30°F. It will
be apparent that if the load cell is held rigidly by the mount,
enormous side forces will be applied to the cell, hence the need to
use a mount which can accommodate vessel expansion/contraction due to changes in temperature.
In the case of a cylindrical vessel, the change in diameter (∆D)
resulting from a change in temperature (∆T) is given by:
∆D = a x D x ∆T
contract vertically as well as horizontally with changes in tempera-
ture. Rigidly-attached piping may magnify the effects of this
expansion, as seen in Figure 1-23. See Attaching Piping to Weigh
Vessels in Section 3 for detailed guidelines on this subject.
SYSTEM DESIGN
D
Figure 1-22
Example:
If a cylindrical vessel is 96" in diameter and made from 304
stainless steel and is subjected to a temperature rise of 80°F
as the result of being filled with a hot liquid, then the diameter
will increase by:
∆D = 9.6 x 10-6 x 96 x 80
= .074"
Figure 1-23
1-13
SYSTEM DESIGN
Calculating Tank V olumes
Calculating Tank Volumes
Formulas for V arious Tank Shapes and Sections
Cylinder
π
Volume =
D2H
4
H
D
Portion of Cylinder
π
2
Volume =
hD
8
h
D
Horizontal Cylinder (Partially Filled)
Volume =
π
D2L −
4
π
720
D2Lcos
2h − D
()
−1
D
+h−
D
2
LhD−h
2
Frustum of Cone
π
hD2+dD+ d
Volume =
()
12
D
h
d
h
L
π
4
D
D2L
2
In the special cases where h=D (that is, the vessel is filled com-
pletely) then this formula reduces to:
Volume =
D
h =
(that is, the vessel is filled half way) then this formula
2
reduces to:
π
Volume =
D2L
8
1-14
Calculating Tank Volumes
SYSTEM DESIGN
Hemispherical End
3
π
D
Volume =
12
Spherical Segment
2
Volume =
π
L
2
D
L
+
8
6
Square Prism
(Rectangular Cross Section)
Volume =ABH
D
H
D
2
A
B
Square Prism (Square Cr oss Section)
D
Volume = A2H
L
The radius of the sphere from which the segment is cut is
2
D2+ 4L
r =
8L
D
Note: r
≠
(D is the diameter of the vessel)
2
Hemispherical End (Partially Filled)
π
Volume =
(3h2D− 2h3)
12
h
Wedge I
Volume =
D
a + A
H
A
A
Bh
2
A
h
a
B
1-15
SYSTEM DESIGN
13'
4.5'
15'
Wedge II
Volume =
hAB
2
Calculating Tank Volumes
h
h
A
B
Frustum of Pyramid
Volume =
h
2 AB + Ab + aB + 2ab
()
6
A
h
a
B
b
α
D
Figure 1-24
The volume of any cone is:
height
x area of base
3
In calculating the volume of material in a vessel, an adequate
approximation can be made by adding 1/3 of the height of the cone
to the height of material up to the cone.
For example, in Figure 1-25, assume the height of the material in
the cylindrical vessel to be 15'+1.5'=16.5 feet.
Thus the volume is calculated using the following formula:
Volume =
π
4
D2h
=
3.14
x (13)2 x 16.5 = 2190 cubic feet
4
Angle of Repose
When a granular material is dropped from above onto a flat surface
it tends to form a cone, as shown in Figure 1-24. The shape of this
cone is described by the angle of repose, α, which is a characteristic
of the material. The angle of repose varies somewhat with particle
size, moisture content, etc. The relationship between α, h, and D
(see Figure 1-24) is:
α
D tan
h =
2
1-16
Figure 1-25
Calculating Tank Volumes
SYSTEM DESIGN
Calculation Examples
Example 1
Calculate the volume of liquid in the horizontal tank shown below.
It has hemispherical ends and is filled to a height of 4.5 feet.
4.5'
3' 20' 3' 6'
For ease of calculation, this can be broken into 3 sections
Example 2
If, in the last example, the vessel were filled completely, then the
volume would be:
Total Volume = Volume(a) + Volume(b) + Volume(c)
Example 3
If the vessel in Example 2 is filled with linseed oil, calculate the
weight of material when the vessel is full.
From the section Density of Common Materials, we know that the
density of linseed oil is 58.5 lb/cu. ft. From Example 2, we know
(a) (b) (c)
Step 1
The volume of section (a) or (c) is given by the formula:
Volume =
π
12
where
(3h2D – 2h3)
π
= 3.14,
h = 4.5
,
D = 6
that the volume of the vessel is 678.2 cubic feet.
Weight of Material = Volume x Density
3
π
D
π
D2L
π
D
+
12
3.14(62) x 20
4
= 678.2 x 58.5
= 39,675 lb
12
3.14(63)
12
+
4
+
=
= 56.5 + 565.2 + 56.5
= 678.2 cu ft
3
3.14(63)
+
12
=
3.14
=
=
= 47.7 cu ft
((3 x 4.52 x 6) – (2 x 4.53))
12
3.14
(182.25)
12
Step 2
The volume of (b) is given by the formula:
πD2L
4
3.14 x 62 x 20
π
–
720
where π = 3.14, h = 4.5, D = 6, L = 20
4
=
565.2 – 3.14cos
= 565.2 – 188.4 + 77.94
= 454.7 cu ft
2h – D
D2Lcos
–1
( )
3.14 x 62 x 20cos
–
720
+ h –
D
–1
(.5) + 30√6.75
D
( )
2
–1
2 x 4.5 – 6
( )
6
Step 3
Total Volume=Volume(a)+Volume (b)+Volume(c)
= 47.7 + 454.7 + 47.7
= 550.1 cu ft
L√hD – h
+ 4.5 –
( )
2
6
20√4.5 x 6 – 4.5
2
2
1-17
SYSTEM DESIGN
5'
3'
3'
(b)
9.7'
Volume (a)
Volume (b)
3'
Calculating Tank Volumes
Example 4
Calculate the volume of material in the hopper shown below.
Step 2
The volume of section (b) is given by:
Volume =
12'
5'
2'
6'
3'
3'
7'
5'
Step 3
For ease of calculation, this may be broken into 2 sections as
follows:
Step 1
The volume of section (a) is given by:
Volume = ABh
= 5 x 7 x 6.7 = 234.5 cu ft
Example 5
If, in the last example, the vessel was filled to overflowing, then the
volume would be :
5'
Volume(Total) =Volume (a) + Volume (b)
Volume(b) is same as the previous example (73.0 cu ft)
2'
Volume(a) = 5 x 7 x 9.7 = 339.5 cu ft
h
2AB+ Ab + aB +2ab
()
6
3
6
3
6
= x ((2 x 5 x 7) + (5 x 5) + (3 x 7) + (2 x 3 x 5))
= x 146 = 73.0 cu ft
Total Volume=Volume (a) + Volume (b)
= 234.5 + 73.0
= 307.5 cu ft
6'
(a)
6.7'
where the “leveled height” is assumed to be 6.7'.
1-18
Volume(Total) = 339.5 + 73.0 = 412.5 cu ft
Material Densities
Densities of Common Materials
SYSTEM DESIGN
Bulk Density Angle of
Material lb/cu. ft. Repose
Abrasive 150
Abrasive Mix 153
Acetylenogen 70-80
Acid Phosphate 60
Adipic Acid 45
Alfalfa, ground 16 45
Alfalfa, seed 48
Almonds, broken or whole 28-30
Alum, pulverized 45-50 30-45
Alumina 60-120 30-45
Aluminate Gell 45
Aluminum Chips 7-15
Aluminum Etchant 54
Aluminum Filament 74
Aluminum Ore (Bauxite) 89-94
Aluminum Powder 47-79
Aluminum Sulfate 58-69
Amianthus 20-40
Ammonium Chloride 52
Ammonium Nitrate 45-62
Andalusite 49
Antimony Oxide 45
Apple Slices, dried 15
Apple Pumice, dried 15
Arsenic 30
Arsenic Oxide 100-120
Asbestos Fiber 19
Asbestos Ore 81
Asbestos Shorts 25
Ashes, dry 35-40 45+
Asphalt, crushed 45 30-45
Bagasse 7-10 45+
Bakelite, powdered 30-40
Barite 100-160
Barium Carbonate 45-97
Bark, wood 10-20 45+
Barley 38 up to 30
Basalt 184
Batch, glass 90-100
Bauxite, crushed 75-85 30-45
Beans, castor 36 up to 30
Beans, navy 48-54 up to 30
Beans, soy 45 up to 30
Beets 45
Beet pulp 25-45
Benzene Hexachloride 56
Bicarbonate of Soda 41
Binder 812 41
Black Coloring 30
Blood, ground 30
Bluestone 60-70
Bulk Density Angle of
Material lb/cu. ft. Repose
Bones, crushed 35-40
Bones, ground 50
Boneblack 20-25
Bonechar 40
Borax 60
Borax, powdered 53
Borton 75
Bran 10-20 30-45
Brass, cast 519
Brass, rolled 534
Brewers grain, wet 55-60 45 & up
Brick, best pressed 150
Brick, tire 137
Brick, soft interior 100
Bromoseltzer 37
Bronze chips 30-50
Bronze powder 75
Cab O Sil 1
Calcin flour 75-85
Calcium Fluoride 82
Calcium Lactate 26-29
Calcium Phosphate 40-50
Carbon activated 8-20
Carbon, black pellet 25 up to 30
Carbon, black powdered 4-6
Carbon lampback 7
Carbon, masterbatch 40
Carborundum 100
Casem 38
Caustic, soda 88
Caustic, soda flakes 47
Celation FP4 14
Celite 535 9
Cement Bulk 75-95
Cement, clinker 75-85 30-40
Cement, portland 90 30-45
Cement, slurry 90-100
Chalk, crushed 85-90
Chalk, ground 70-75
Chalk, lumpy 82-95 45 & up
Chalk, pulverized 70-75
Charcoal 18-25
Cherry wood 42
Chickory 33
Chili spice 45
Chocolate powder 40
Chrome ore 125-150
Cinders, coal 40 25-40
Clay, ceramic, dry 65-80
Clay, fire 40
Clay 96
1-19
SYSTEM DESIGN
Material Densities
Bulk Density Angle of
Material lb/cu. ft. Repose
Clay, potters 100-120
Clay, product 36
Clover, seed 48
CMC Powder 52
Coal Anthracite (solid) 94
Coal Bituminous (loose) 43-50 30-45
Coal Char 24
Coal, dust 35
Coal, sized 50
Cobalt Oxide 114
Cocoa, beans 30-45
Cocoa, flavoring 55
Cocoa, powdered 33-35
Coconut 20-22
Coconut, shredded 20-25 45 & up
Coffee 20
Coffee, fresh beans 30-40 30-45
Coffee, green beans 32-45
Coffee, roasted bean 22-30 up to 30
Coffee, soluble 19
Coke, calcined 35-45
Coke, loose 23-32 30-45
Collupulin 19
Compost 28 30-45
Concrete, sand & gravel 150
Cookie Meal 38
Copper, cast 542
Copper, ore 120-150 30-45
Copper, sulfate 60-70 31
Copra 22-33
Copra, cake ground 40-45
Copra, meal 40-45
Cork, granulate (1/2) 12-15
Cork, granules 4
Cork, solid 15
Corn, cracked 40-50
Corn, grits 40-45 30-45
Corn, meal 32-40
Corn, seed 45
Corn, shelled 45 up to 30
Cottonseed, cake 40-45 30-45
Cottonseed, flakes 20-25
Cottonseed, meals 35-40 30-45
Cottonseed, meats 40 30-45
Cryolate (1/2) 90-110 30-45
Cryolite (100) 50-75
Diatomaceous Earth 11-17
Dracalcium Phosphate 40-50
Disodium Phosphate 25-31
Dolomite 83
Dolomite, lumpy 90-100 30-45
Bulk Density Angle of
Material lb/cu. ft. Repose
Dolomite, pulverized 46
Donut Mix 45
Earth 76
Earth, common dry 70-80 30-45
Earth, moist 30-35 30-45
Ebonite 65-70
Egg Yolk 23
Elm, dry 35
Feldspar (1/8) 100-160
Feldspar, (1-100) 65-75
Feldspar, ground 65-70
Feldspar, lumps 85-95 34
Ferro Silicon 87
Ferrous sulfate 50-75
Fine, powder 127
Fit 24-33
Fish, scrap 40-50
Flaxseed 43-45
Flaxseed, meal 25
Flaxseed, whole 45 up to 30
Flour 42-48
Flour, wheat 35-40 45 & up
Flue, dust, dry 110-125
Fluospar 82
Fluospar, lumps 80-110 45 & up
Fluospar, solid 200
Fly ash 61-95
Fly ash, dry 35-40
Foundry sand, loose 80-90
Foundry sand, rammed 100-110
Frodex 24 38
Fullers Earth (burnt) 40 23
Galena 240-260
Garbage 30
Geon Resin 22
Gilsonite 37
Glass, broken 80-100
Glass, frits 128
Glass (window and plate) 161
Glue 52
Glue, ground 40
Glue, pearl 40
Gluten meal 40 30-45
Gold powder 53
Granite, lumps 96 30-45
Granite, solid 150-170 30-45
Granular material 48
Graphite, flake 40
Graphite, ore 65-75
Grape pomace 15-20
Grass, seed 10-12
1-20
Material Densities
SYSTEM DESIGN
Bulk Density Angle of
Material lb/cu. ft. Repose
Gravel, dry 90-100 30-45
Green powder 57
Green stone 107
Ground bone 50
Guar Gum 35
Gumbase 42
Guano 70
Gypsum, crushed 90-100
Gypsum, ground 75-80
Hash, spice 66
Hay, loose 5
Hell blue dye 19
Hemlock 25
Hexanedioic Acid 45
Hickory, dry 25
Ice, crushed 35-45 up to 30
Ice, solid 57.4
Insecticide 46
Ional 47
Iron, cast ductile 444
Iron, cast gray 450
Iron Ore 120-180
Iron oxide 174
Iron oxide, black 160
Iron Sulfate 50-75
Kaolin, clay 160
Kaolin, talc 42-56
Lactose 32
Lamisay flour 34
Latikra 34
Lead, arsenal 72
Lead, carbonate 240-260
Lead, ore 180-230
Lead, red 230
Lead, white 250-260
Lignite 42-55 30-45
Limanite 120
Lime, bricks 41-83
Lime, ground 60
Lime, hydrated 40 30-45
Lime, pebble 53-56
Lime, quick 54
Limestone 100
Limestone, agriculture 68
Limestone, dust 55-95
Limestone, filler 63
Limestone, loose 100
Limestone, pulverized 85-90 45 & up
Lindane 56
Linseed, cake 48-50
Linseed, whole 45-50 up to 30
Bulk Density Angle of
Material lb/cu. ft. Repose
Magnesia 77
Magnesium chloride 33
Magnesium oxide 10-135
Magnesium, sulfate 40-50
Mahogany Spinach 53
Maize 45
Malt, flour 40
Malt, meal 36-40
Malt, powder 40
Malt, wheat 41
Manganese Ore 125-180
Manganese Oxide 120
Manganese Sulfate 70
Manganese Solid 475
Manure 25
Marble, crushed 80-95 30-45
Maple 49
Masonry 185
Material 199 67
Meat 50-55
Mercury 849
Metallic, flake 35
Mica, ground 13-15 30-45
Mica, flakes 17-22
Mica, solid 181
Mica, soapstone 46
Milk, malted 27-35 45 & up
Milk, powdered 36 45 & up
Mill Scale 100-125
Milltown 35
Mineral Oxide 35
Molybdenum 107
Mortar, wet 150
Moulding compound 42
Muriate of Potash 77
Mustard, powdered 16
Mustard, spice B 45
Naphthalene Flakes 36
Neutral Granules 24
Nickel Ore 150
Nicotinic Acid 35
Oskite 60
Oak, live, dry 59
Oats 25-35 32
Oat flour 33
Oil cake 48-50
Oil, linseed 58.8
Oleomargarine 59
Orange Peel, dry 15
Paper Pulp (15%) 62
Paper Pulp (6 15%) 60-62
1-21
SYSTEM DESIGN
Material Densities
Bulk Density Angle of
Material lb/cu. ft. Repose
Parazate 18
Peanut Brittle 36
Peanuts, unshelled 15-24 30-45
Peas 45-50
Pentserythritol 43
Peppermint 32
Pharmaceutical Mix 39
Pharmaceutical Lubricant 9
Phenol Formaldehyde 30
Phosphate 94
Phosphate, crushed 75-85 26
Phosphate, granular 90-100
Phosphate, soda 25-31
Phosphoprotein 36
Pie Crust Mix 34
Pine, white, dry 26
Pine, yellow south 45
Pitch 72
Plastic beads 46
Plastics, chopped 37
Plastics, lrg. flakes 19
Plastics, small flakes 34
Plastics material color 34
Plastics, spheres 42
Plastics, Powder B 25
Plastics, Scrap 40
Polyester, film 5
Polyethylene 42
Polyethylene, flakes 6
Polyethylene, pellets 35
Polyvinyl Chloride 40
Pork Spice 72
Potassium Bromide 114
Potassium Chloride 73 30-45
Potassium Iodate 128
Potassium Nitrate (1/2) 76
Potassium Sulfate 42-48
Potatoes, dried 58
Pie Mix 34
Protein Supplement 33
PVC Powder 30
Quartz 85
Raisins 48
Red Oxide 72
Red Color Concentrates 32
Redwood 26-30
Resin 30-37
Resin Luron 39
Rice, chopped 64
Rice, grits 42-45 up to 30
Rice, rough 32-36 30-45
Rip Rap 80-105
Bulk Density Angle of
Material lb/cu. ft. Repose
Rolaids 64
Rosin 67
Rubber Composition 33
Rubber Caoutchouc 59
Rubber, mfg. 95
Safflower 45
Safflower, cake 50
Sal Ammoniac 52
Salicylic Acid 29
Salt (1/8) 50
Salt, coarse 45-55 30-45
Salt, dry coarse 45-50
Salt, fine 70-80
Sand, damp 110-130 45 & up
Sand, dry 90-110
Sand, foundry (1/8) 90
Sand, foundry (1/2) 90
Sand, rammed 100-110
Sandvoids full of H2O 110-130 15-30
Santonox 18-45
Saran Powder 35
Sawdust (wet) 24
Scale 125-160 36
Sewage 40-50
Shale, crushed 85-90 39
Shale, solid 162
Shavings, wood 15
Silene 15
Silene & Zinc 15
Silica Gel 42
Silicon Carbide 15-88
Silver Powder 69
Sinter 90-110
Slag Furnace (+1/2) 60-65
Slate, crushed 80-90 28
Slate, solid 165-175
Sludge 45-55
Snow, packed 15-35
Soap, flakes 5-20 30-45
Soap, powdered 20-25 30-45
Soapstone 40-50
Soda Ash, heavy 55-65 30-45
Sodium Aluminate 72
Sodium Bisulfate 90
Sodium Chloride 84
Sodium Nitrate 70-80 24
Sodium Phospho Aluminate 67
Sodium Pysophosphate 63
Sodium Sulfate, dry (1/8) 65-85
Sodium Tripolyphosphate 58-64
Sorghum, seed 32-52
Soybeans, cake 40-43
1-22
Material Densities
SYSTEM DESIGN
Bulk Density Angle of
Material lb/cu. ft. Repose
Soybeans, flakes, raw 20-26
Soybeans, meal, cold 40
Soybeans, meal, hot 40
Spice (Vienna) 63
Spruce 28
Stabilizer 71
Sta-nut 52
Steatite 25-50
Steel, solid 469.6
Steel Turnings 60-120 45 & up
Sugar Beet, dry 12-15
Sugar Beet, wet 25-45
Sugar, powdered 50-60
Sugarcane 15-18 45 & up
Sulphur, crushed 50-60
Sulphur, dust 50-70 30-45
Sulphur, powdered 50-60
Taconite 116-130
Talc, granulated 50-65
Talcum powder 55
Tanbark 55
Tar 69-75
Tea 27
Tin Cast 459
Timothy, seed 36
Titanium Sponge 60-70
Bulk Density Angle of
Material lb/cu. ft. Repose
Tobacco, scraps 15-25 45 & up
Tobacco, stems 16-25 45 & up
Traprock, compact 187
Tricalcium Phosphate 40-50
Trichlorocyanuric Acid 50
Triple Super Phosphate 50-55
Trisodium Phosphate 60 40
Tumeric 51
Ulexite 75
Vermiculite 62
Vermiculite, ore 80
Vicrum 35
Vinyl Resin 36
Vitamin Mix 43-49
Walnuts 35-40
Wax 26
Wheat, cracked 46 30-46
Wheat, cut 45-48
Wheat germ 35-40
White Powder 28-45
Wood, bark 10-20
Wood, chips 10-30 45 & up
Yellow Corn Flour 33
Zinc Concentrate 75-80
Zinc Hydrosulphate 44
Zinc Oxide, heavy 10-15 45 & up
Load Cell Bolt Torque Values
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"61/512325203
"8/383040506
"61/755065859
"2/15859521041
"61/9521041571591
"8/5571012542072
"4/3003033524064
"8/7054094066007
"10865170990501
"8/1-158809907415561
"4/1-15521083100120132
"8/3-15361578105720113
"2/1-10812034204630014
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Notes:
1) Based on dry assembly. Variables such as lubrication, plating, etc. may
reduce the values listed above as much as 20%, and must be taken into
consideration.
2) General formula for calculating Torque is as follows: Torque in Inch
lb=0.2 x Nominal Diameter of Screw x Load in lb, where load = 80% of yield
strength, expressed in lb, not pounds per square inch.
3) The tension induced in a cap screw may be checked by measuring overall
length before torquing and then under torque load. The screw stretches
.001" per inch of screw length for each 30,000# PSI induced tension.
Applies only to loads below the yield point.
1-23
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