Siemens SIWAREX R Operating Instructions Manual
s
SIWAREX R
Load Cells
Operating Instructions Edition 06/2009
Table of Contents:
Safety Instructions............................................................................3
General Information..........................................................................4
Notes on product liability.................................................................4
1 Technical Description.......................................................................5
1.1 Area of Application.............................................................................. 5
1.2 Structure ............................................................................................. 5
1.3 System Configuration.......................................................................... 7
2 Installation/Assembly..................................................................... 10
2.1 Installation......................................................................................... 10
2.2 Assembly .......................................................................................... 13
2.3 Disassembly...................................................................................... 16
3 Commissioning............................................................................... 17
4 Service.............................................................................................19
4.1 Care and Maintenance...................................................................... 19
4.2 Troubleshooting ................................................................................ 19
5 Technical Data.................................................................................22
5.1 Functional Data................................................................................. 22
5.2 Unit Version ...................................................................................... 24
5.3 Explosion Protection ......................................................................... 25
5.4 Electromagnetic Compatibility........................................................... 26
5.5 Dimensions ....................................................................................... 27
6 Ordering Data.................................................................................. 34
SIWAREX R Load Cells Operating Manual
A5E00159640
2
Safety Instructions
DANGER
indicates that death, severe personal injury or substantial property damage will
result if proper precautions are not taken.
WARNING
indicates that death or severe personal injury can result if proper precautions are
not taken.
CAUTION
This text accompanied by a warning triangle indicates that minor personal injury
can result if proper precautions are not taken.
Qualified personnel as used in the safety instructions in this manual and on the
Copyright © Siemens AG 2009 All rights reserved
The reproduction, transmission or use of this document or its
contents is not permitted without express written authority.
Offenders will be liable for damages. All rights, including rights
created by patent grant or registration of a utility model or design,
are reserved.
Siemens AG
Bereich Automatisierungs- und Antriebstechnik
Geschäftsgebiet Process Instrumentation and Analytics
D-76181 Karlsruhe
CAUTION
This text without an accompanying warning triangle means that property damage
may occur if proper precautions are not taken.
ATTENTION
indicates that an undesirable result or state may result if the proper steps are not
taken.
NOTE
indicates a potential benefit if recommendations are followed.
product itself are individuals who are familiar with the installation, assembly, initial
start-up and operation of this product. They must be authorized and qualified to
install, start and maintain devices, systems and circuits in accordance with
national safety rules and regulations.
Disclaimer of Liability
We have checked the contents of this manual for agreement with
the hardware and software described. Since deviations cannot be
precluded entirely, we cannot guarantee full agreement. However,
the data in this manual are reviewed regularly and any necessary
corrections included in subsequent editions. Suggestions for
improvement are welcomed.
©Siemens AG 2009
Technical data subject to change.
SIWAREX R Load Cells Operating Manual
A5E00159640
3
General Information
Use for the intended purpose
Use for the intended purpose means that this product may only be used within the
limits of the technical specifications and statement of purpose of this operating
manual.
This device will not be a source of danger provided it is used for the intended
purpose under consideration of the safety instructions.
Perfect, safe operation of this device is conditional upon proper transport, storage,
installation and assembly.
Proper operation of this device can only be ensured if the specifications provided in
technical data are observed.
Improper handling can result in death, severe personal injury and property
damage.
Notes on product liability
We expressly point out that the nature of the product is described exclusively and
conclusively in the contract of sale. The contents of this product documentation are
not part of an earlier or existing agreement, acceptance or legal relationship nor do
they affect these in any way. The particular contract of sale determines the sum of
obligations to be met by Siemens and the guarantee regulation container therein is
complete and is the sole regulation that shall apply. This contractual guarantee
regulation is neither extended nor limited by the information provided in this
document.
Information on delivery
The scope of delivery in accordance with the valid contract of sale is listed in the shipping
documents enclosed in the delivery.
Please observe any relevant instructions when opening the packaging. Check the
shipment for completeness and possible transportation damage. In particular,
compare the order number on the rating plate with the order information.
Please read this operating manual before starting work! It contains important
information and data that, if observed, ensure the overall safety and functionality of
this device. Following these instructions will make it easier for you to use handle
this product and ensure reliable measuring results.
SIWAREX R Load Cells Operating Manual
A5E00159640
4
1 Technical Description
1.1 Area of Application
SIWAREX R load cells are used for static and dynamic measurements of forces
and weights. They can be used for almost all applications in industrial weighing
technology. These may be for example:
• container, hopper or platform scales,
• rollway, belt or crane scales,
• filling/packing plants, proportioning and mixing,
• filling level and completeness inspection,
• equipment for monitoring pressing and clamping procedures,
• dynamic scales
All applications can be located in areas with mandatory calibration or in hazardous
areas.
1.2 Structure
The SIWAREX R load cells are equipped with wire strain gauges (WSG). WSG
load cells are transducers for converting mechanical forces into electrical signals.
The functional principle is always the same despite different designs.
The basic element is a special spring body. The spring body is deformed elastically
when a force is applied. The integrated WSGs then change their ohmic resistance
(figure 1-1)
Figure 1-1 Principle diagram shown by the example of a bending rod load cell
SIWAREX R Load Cells Operating Manual
A5E00159640
5
Edition 06/2009
At least four WSGs per load cell are connected in a full Wheatstone bridge. The
stretched or upset WSGs are wired so that the positive or negative changes in
resistance add up to a total upset of the bridge.
The feed voltage (in 6-wire technology also the sensor voltage, SENSE) is applied
at one bridge diagonal. The measuring voltage is tapped at the other diagonal.
At a constant feed voltage (EXC), the measured voltage (SIG) changes
proportionally to the applied load (figure 1-2). In practice load cells contain other
resistors for temperature compensation, zero point and parameter adjustment.
These may be in the input or output of the load cell depending on the type and on
requirements.
Technical Description
Figure 1-2 Principle diagram of a Wheatstone bridge
The SIWAREX R load cells are usually made of high-grade steel and are welded
hermetically sealed. This provides high corrosion protection and protection rating.
Most series are licensed for use in scales with mandatory calibration of class III
according to DIN EN 45501 and comply with OIML R60 3000d. Load cells with
greater accuracy and/or EEx (i) approval are available on request.
SIWAREX R load cells are electrically calibrated as standard. As a result, no
reference load adjustment is necessary for example when commissioning a
platform scales. A load cell can also be exchanged without readjustment.
An exception to this rule is the series K and possibly load cells delivered outside
the standard scope of delivery. The respective technical data apply for these load
cell types.
SIWAREX R Load Cells Operating Manual
A5E00159640
6
Edition 06/2009
1.3 System Configuration
In weighing technical systems one or more load cells are connected to a weighing
module for evaluation of the measured signal. Several load cells of a scales are
connected in parallel in a junction box to supply a common output signal.
Load cells may only be connected in parallel when they have the same
characteristic value, the same rated load and the same internal resistance.
ATTENTION
The total resistance in parallel connected load cells may not drop below the
minimum resistance specified in the technical data of the weighing module.
The maximum number of load cells that can be connected to a weighing module
depends on the total resistance of the parallel connected load cells. This must be
within limits of the weighing module specified for the load resistance. The length of
the lines and the data of other elements, e.g. Ex i-Interface, must also be taken into
account.
CAUTION
If several load cells are connected in a scales it cannot be determined whether
individual load cells are overloaded in the event of uneven load distribution.
The maximum cable length between the load cell and the weighing module can be
found in the technical data of the weighing module. For Ex applications the data of
the Ex-i interface must also be taken into account.
A shielded 6-wire cable, e.g.. Li2Y(ST)CY 6x0.75 mm
702-8AB or, for Ex applications, 7MH4 702-8AA must be used to connect the
junction box to the weighing module, to extend a load cell connecting cable or for a
cross-connection between two junction boxes.
Overloads should be avoided in the layout of load cells by creating a safety
reserve. The safety reserve for three application points should be 20%. In the case
of statically aspecific use of more than three application points, the safety reserve
must be at least 50% if it cannot be ruled out that the load is only resting on two
diagonally opposite load cells. The reason for this may be drops in the foundation
or improper assembly. Accidental overloads or overloads due to the process must
be taken into account or kept away from the load cells by overload protection
devices. Overloads are caused for example:
• in the case of uneven load distribution as a result of attachments or tipping
mounds,
• when rolling/pushing the load onto platform or rollway scales,
• by hard setting down of the load,
• by setting down the load in free fall,
• when persons are leaning/standing on the scales,
• by wind forces on the side of a silo facing away from the wind.
Technical Description
2
, Siemens order no.: 7MH4
SIWAREX R Load Cells Operating Manual
A5E00159640
7
Edition 06/2009
Overloads may also occur in lifting direction when the force application is
permanently mounted to the load cell such as elastomer bearings on load cells of
series BB.
Lift off protection is necessary where there is a risk of the load carrier lifting off or
tipping over. This is essential for lightweight containers or high silos outdoors.
CAUTION
Overload protection devices must always be provided for load cells with low rated
loads to protect the cells from being damaged.
Use of the load cells beyond the maximum working load or maximum transverse
load can lead to irreparable faults and even breakage of the load cell.
Load cells may not be overloaded, e.g. by tightening screws, when adding
installation components.
NOTE
If load cells are loaded beyond their rated load this can lead to an error message
in the weighing module.
If load surges during the measuring mode cannot be ruled out, for example when
the load is set down in free fall, suitable precautions must be taken to avoid
damage to the load cell (e.g. elastomer bearings or higher load cells).
The load must be applied in exact measuring direction of the load cell. Torsion and
bending torques, off-center loads and transverse loads are disturbances which on
the one hand falsify the measuring result and on the other hand can damage the
load cell when they exceed the permissible limits. Load cells must therefore be
installed with suitable installation components (e.g. SIWAREX R installation
components). The possible errors mentioned above are then largely avoided. The
installation components allow enough freedom of movement to prevent heat
expansion leading to transverse loads.
Transverse forces such as are caused by wind, acceleration or conveyor belt
friction must be compensated by deflections or stops. Deflections must be installed
exactly vertical to the direction of action of the load cells so that no force
components occur in measuring direction. The deflections must be installed in such
a way that they do not twist for example when the application points expand. This
is most easily avoided by arranging the deflections in the same direction of
rotation.
The deflections to be installed should correspond to the principles used in weighing
technology. Ball-jointed deflections are available for most SIWAREX R combiinstallation units. Ball bolt deflectors up to a transverse load of 1000 kN are
available on request.
No parallel forces may be applied by filling and emptying devices and supply lines.
Technical Description
SIWAREX R Load Cells Operating Manual
A5E00159640
8
Edition 06/2009
DANGER
Load cells are machine elements not constructed with the usual safety factors.
Therefore appropriate crash protection or catastrophe protection must be provided
which suit the danger potential.
CAUTION
For protection against undesirable electrical currents such as they occur when
welding or from lightning, the load cells must be bridged with a highly flexible
grounding cable (e.g. SIWAREX R grounding cable 7MH3 701-1AA1).
The substructure must withstand the planned loads. The application surface must
have a roughness of a max. 1.6 µm.
The values in the technical data must be observed for the ambient conditions.
Note
The load cell must be protected from direct sunlight. The permissible operating
temperature could otherwise be exceeded and thus the accuracy impaired.
Technical Description
SIWAREX R Load Cells Operating Manual
A5E00159640
9
2 Installation/Assembly
2.1 Installation
SIWAREX R load cells may only be assembled and connected by qualified
personnel.
If a scales is equipped with a single load cell, this can be connected directly to the
weighing module if space allows. To bridge greater distances the connecting cable
can be extended through a junction box.
Several load cells are connected in parallel in a junction box.
Load cells can be fitted with 4 or 6-wire connecting cables.
Four-wire connecting cables should not be shortened or lengthened because the
line resistance is temperature-compensated. If the length of the connecting cable is
altered, the input and output resistance also changes. This change can be
corrected by adjusting the scales but this does not compensate temperaturerelated changes in resistance of the missing or lengthened piece of cable. The
value of the remaining temperature error is shown in the table below. The
SIWAREX measuring cable 7MH4702-8AA / -8AB is used as the basis for these
observations. The feed lines are connected in parallel (double).
Table 2-1 Remaining temperature error of a cell per 10 K in %:
Change in Series
length K RN BB CC SB
3 m 0.0012 0.0003 0.0007 0.0007 0.0009
5 m 0.0020 0.0005 0.0012 0.0011 0.0014
10 m 0.0040 0.0009 0.0024 0.0022 0.0029
If 3 or 4 cells are operated in parallel and the cable of a cell is lengthened, the
additional error is about a third or a quarter. Prerequisite is an even load
distribution on the cells.
ATTENTION
Only EMC-safe housings (e.g. SIWAREX JB) may be used to
extend connecting cables.
On 6-wire connecting cables, the feed voltage is fed back as a reference voltage to
the weighing module. Shortening or lengthening has no effect on the measuring
result.
Figures 2-1 and 2-2 show the parallel connections of load cells in 4 and 6-wire
technology.
SIWAREX R Load Cells Operating Manual
A5E00159640
10
Edition 06/2009
ATTENTION
If load cells with 4-wire connecting cables are used, two bridges must be inserted
additionally:
Bridge 1: EXC- to SENSEBridge 2: EXC+ to SENSE+
Installation/Assembly
Load cells
Junction box
Weighing
module
Figure 2-1 Parallel connection in 4-wire technology
SIWAREX R Load Cells Operating Manual
A5E00159640
11
Loading...