HBM SB01A User manual
A1020-4.0 en/de/fr
Safety Barriers
Zenerbarrieren
Barrières de Zener
SB01A
Mounting Instructions
Montageanleitung
Notice de montage
English Page 3 - 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deutsch Seite 19 - 34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Français Page 35 - 50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Contents Page
English
Safety instructions 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 Scope of delivery 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 General 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Application 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Maintenance, service 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Fault elimination 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Insulation coordinates for units with Ex certification according
to EN 60079‐11 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Ambient conditions 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 Operating principle 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Installation notes 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Specification of the Zener barriers 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 Electrical connection 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Barrier nominal (rated) data 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Dimensions 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Safety instructions
Appropriate use
Zener barriers are used in control and instrumentation systems for the
processing of lower voltages and currents. Zener barriers contain intrinsically
safe circuits that are used to drive intrinsically safe field devices (load cells) in
potentially explosive atmospheres.
Devices which have been operated in general electrical systems, must not be
used afterwards in electrical systems that are in connection with potentially
explosive atmospheres.
To ensure safe operation, the device may only be operated in accordance with
the information given in the Operating Manual. It is also essential to comply
with the legal and safety requirements for the application concerned during
use. The same applies to the use of accessories.
The equipment must not be attached directly to the mains.
General dangers of failing to follow the safety instructions
The Zener barriers correspond to the state of the art and are fail‐safe. The
devices may give rise to remaining dangers if they are inappropriately
installed and operated by untrained personnel.
Any person entrusted with the installation, commissioning, maintenance or
repair of the devices must have read and understood the Operating Manual
and in particular the technical safety instructions.
Conditions on site
Protect the equipment against direct contact with water (IP 20).
Maintenance and cleaning
The Zener barriers are maintenance free. Please note the following points
when cleaning the housing:
- Before cleaning, disconnect the device from the power supply.
- Clean the housing with a soft, slightly damp (not wet!) cloth. In no case
shall you use solvent.
- When cleaning, ensure that no liquid gets into the device or connections.
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Remaining dangers
The scope of performance and supply of the Zener barriers covers only part of
the range of measurement technology. In addition, equipment planners,
installers and operators should plan, implement and respond to the safety
engineering considerations of measurement technique in such a way as to
minimize remaining dangers. Prevailing regulations must be complied with at
all times. There must be reference to the remaining dangers connected with
measurement technique.
Any risk of remaining dangers when working with the Zener barriers is pointed
out in this manual by means of the following symbols:
Symbol: CAUTION
Meaning: Potentially dangerous situation
Warns of a potentially dangerous situation in which failure to comply with
safety requirements could result in damage to property or some form of
bodily injury.
Symbols pointing out notes on use and waste disposal as well as useful
information:
Symbol: NOTE
Means that important information about the product or its handling is being
given.
Symbol:
Meaning: CE mark
The CE mark enables the manufacturer to guarantee that the product com
plies with the requirements of the relevant EC directives (the declaration of
conformity is available at http://www.hbm.com/HBMdoc).
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Qualified personnel
This instrument may only be installed and used by qualified personnel, strictly
in accordance with the technical data and the safety requirements and
regulations listed below. It is also essential to comply with the legal and safety
requirements for the application concerned during use. The same applies to
the use of accessories.
Qualified personnel means persons entrusted with the installation, assembly,
commissioning and operation of the product who possess the appropriate
qualifications for their function. Maintenance and repair work at the open, live
device may only be performed by trained personnel who are aware of the
potential danger.
CAUTION
Start‐up and installation are to be implemented only by technical personnel
for this special‐trained.
Installation of the devices outside the potential explosive atmosphere
SThe Zener barriers are constructed to comply with protection class IP20
according to EN 60529 and must be protected accordingly from adverse
environmental conditions such as water spray or dirt exceeding the degree of
soiling 2.
SZener barriers must be installed outside the potential explosive atmosphere!
SThe intrinsically safe circuits of the devices (light blue marking at the devices)
can be - depending on the type of protection - conducted through potential
explosive atmospheres. In this connection, it is particularly important to ensure
the safe isolation of all non‐intrinsically safe circuits.
SWhen intrinsically safe field devices (load cells) are interconnected with the
intrinsically safe circuits of the related Zener barriers, the respective maximum
values for the field devices (load cells) and the Zener barriers - in the sense
of explosion protection - must be observed (proof of intrinsic safety).
EN 60079‐14 / IEC 60079‐14 has to be observed. For the Federal Republic of
Germany the national foreword of the DIN EN 60079‐14 / VDE0165 part 1 has
to be observed additionally.
SThe EC Certificates of Conformity or EC‐Type Examination Certificates have
to be observed. It is especially important to observe the ”Special conditions”
where these are contained in the certificates.
SWhen intrinsically safe circuits are used in explosive atmospheres caused by
dust (Ex‐Area 'D') only approved field devices (load cells) must be used.
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1 Scope of delivery
•2 pcs Zener barriers type Z 764
•1 pc Zener barrier type Z 763
•EC type examination certificate BAS01ATEX7005
•Certificate of Conformity BAS No. Ex 02E2186
•Mounting instructions
2 General
The SB01A Zener barrier combination comprising two pcs of type Z764 and one
pc of type Z763 was specially developed by Pepperl + Fuchs in cooperation with
HBM for the use of load cells with DC weighing indicators. It is characterized by
a low line resistance in the excitation lines.
For this circuit arrangement the BASEEFA (British Approvals Service for
Electrical Equipment in Flammable Atmospheres) has granted a system
Certificate of Conformity (BAS No. Ex 02E2186).
The complete certificates of conformity can be found on our web site:
http://www.hbm.com/HBMdoc
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3 Application
3.1 Maintenance, service
The transfer characteristics of the devices remain stable, even over long periods
of time, thus eliminating the need for regular adjustment. Maintenance is there
fore not required.
3.2 Fault elimination
Units that are operated in connection with potentially explosive atmospheres
must not be modified in any way. Repairs on a unit may be carried out only by
specially trained and authorized specialist personnel.
3.3 Insulation coordinates for units with Ex certification
according to EN 60079‐11
The units are determined for use in degree of soiling 2, per EN 60664.
3.4 Ambient conditions
Ambient temperature: -20 °C ... +60 °C ( -4 °F ... +140 °F )
Storage temperature: -25 °C ... +70 °C ( -13 °F ... +158 °F )
Humidity: max. 75 % relative humidity without condensation
3.5 Operating principle
Safety barriers form the interface between intrinsically safe and
non‐intrinsically safe circuits. It is their task to limit the energy transmitted from
the non‐Ex area to the Ex area, both in normal operation and in the event of a
fault.
The barrier limits the current and voltage in the intrinsically safe circuit if the
voltage on the non‐intrinsically safe side reaches excessively high values or if
a short circuit occurs on the intrinsically safe side.
In normal operation the voltage between terminals 7 and 8 or 5 and 6 is less
than the breakdown voltage UZof the Zener diodes, and therefore there is
only a small leakage current through the diodes.
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Safe areaHazardous area
7
6
5
81
2
3
4
x3
x3
Load cell
Amplifier
R1
R1
Fig. 3.1: Schematic diagram of the internal structure of a Zener barrier
If the voltage between terminals 7 and 8 or 5 and 6 increases beyond the
breakdown voltage of the diodes, the Zener diodes become conducting. If the
current is too high, the fuse trips and protects the Zener diodes from
overloading.
If the fuse is destroyed the damage is irreparable, and the whole barrier has
to be swapped out.
In the event of a short circuit on the intrinsically safe side, the resistance R1
limits the current on terminals 1 and 4 to IK= UZ/ R1.
The data for voltage, resistance and short‐circuit current is specified on the
Zener barriers.
The Zener barrier can only limit the voltage and current in the intrinsically safe
circuit effectively if the energy stored in the intrinsically safe circuit is also
limited. Therefore the capacitance and inductance in this circuit, also taking
account of the cable properties, must not exceed defined values.
The SB01A Zener barrier set is intended for operating strain gage full‐bridge
transducers on measuring amplifiers that have a DC bridge excitation.
Grounding Zener barriers
The purpose of the dual‐channel structure of the Zener barrier is not only to
limit the voltage and current between the two channels with terminals 5 and 8,
but also to make sure they are limited relative to the ground potential.
NOTE
In order to operate the barrier safely it must always be grounded
through a potential equalization line.
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The cross‐section of the ground connection in the case of a copper conductor
must be at least 4mm2(for further requirements see EN60079-14, section
12.2.4).
CAUTION
Double grounding of intrinsically safe circuits is not prohibited.
The isolation voltage of lines and field devices (load cells), measured against
ground, must be greater than 500 VAC.
CAUTION
In the case of cable lengths over 50 meters the shield must not be put
on on both sides.
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