ZENER BARRIER
DATA SHEET
PWZ
The ZENER BARRIER is a safety barrier for operating
an electronic instrumentation system as an intrinsically safe
explosion-proof system in processes subjected to explosive
gases or vapor. Various types are available for transmitter,
electro-pneumatic final controlling element, thermocouple
and resistance bulb, and can be combined with the field instrument mounted in a hazardous area to operate the measuring instrument as an intrinsically safe explosion proof system.
FEATURES
1. High safety explosion-proof zener barrier
• This barrier has been designed according to the latest explosion-proofing principles and it complies with the inspection standards of the Research Institute of Industrial
Safety, Ministry of Labor, of the Japanese Government.
IEC recommendations and VDE standards have been
taken into due consideration in design and manufacture.
• The voltage limiter circuit (zener diode) and thick film fuse
are fully incorporated, and the voltage limiter circuit is triplicated. Thus, safety and reliability of the system have
been improved by far.
• The thick film fuse offers a high safety maintenance rating
of 550V AC.
• The hybrid IC circuit forms a small and compact system,
and meets the creeping distance and other standard values. The system can be easily mounted on the instrument panel. Cable connections and separation of both intrinsically safe and non-intrinsically safe circuits is assured.
• In order to prevent handling error, various failproof devices.
(such as bright blue indication of intrinsically safe terminals, use of contact prevention cover, doubling of bus bar
mounting screws, asymmetric design, color identification
according to models, etc.) are incorporated.
• The classification of hazardous areas (division 0) and grouping of explosive gases (i3nG5) are wider than with other
explosion-proof structures.
2. High reliability barrier
• The structure and circuits are simple with fewer parts than
an insulation barrier or repeater amplifier barrier, and feature high reliability.
• Since all processes from product development to manufacturing are performed by intracompany techniques and facilities, system quality is fully guaranteed with adoption of
reliable design techniques such as FMECA, etc., complete
manufacturing and testing facilities, manufacturing quality
control system, etc.
• The manufacturing techniques, manufacturing test facilities, and quality control system for thick film fuse and hybrid IC have been inspected and approved by the Industrial
Safety Institute of the Japanese Government.
• The system also assures high reliability with the use of
strictly selected parts high derating design, reduced soldering due to use of a hybrid IC, deterioration resistance
by thick film fuse, improved vibration resistance, etc.
3. Improved system design
• Since the safety maintenance rating is as high as 550VAC,
receiving instruments can be optionally selected and the
system easily can be connected to a computer control system.
• Various types of barrier assemblies are prepared and easily
selected according to the measuring instruments combined.
• Since this system uses a small-sized relaying terminal
board structure, the instrument panel can be easily designed and connected.
EDS13-9f
Date
Oct. 20, 1989
PWZ
4. Maintenance and checks facilitated
• Check terminals are provided for checks on doubled current limiting circuit functions.
SPECIFICATIONS
Explosion-proofing Specifications
Type of explosion-protection and grouping of explosive
gases:
Intrinsic safety JIS i3nG5
(i3aG5 for ZLA, ZLC)
(i3aG5 used for electro-pneumatic final controlling element and i3aG4 for multi-point
temperature converter.)
Max. safety rating:
550V AC and 340V DC
Installation:
Zener barrier is fastened by two M4 screws
onto copper bus bar in a non-hazardous area.
Class 1 (10Ωor less) bus bar grounding is
required.
Measuring instrument combined:
The measuring instrument to be connected
to the intrinsically safe circuit is subject to
inspection. (See Table 1). (The same inspection certificate as there for the zener
barrier should be attached without fail)
The measuring instruments on the non-intrinsically safe circuit, are not subject to inspection, and those having a voltage of less
than max. safety rating can be optionally
connected.
Ambient temperature of combined measuring
instrument:
The transmitter and electro-pneumatic final
controlling element installed in the hazardous area must be used at an ambient temperature lower than the following;
Instrument
Ambient temperature
FC transmitter
60°C or less
Abgriff transmitter
50°C or less
Electro-pneumatic
final controlling
element
60°C or less
Multi-point
temperature
converter
60°C or less
Modification of combined measuring instrument:
The combined measuring instrument installed in the hazardous area cannot be
modified. (Unit exchange is possible).
Wiring LC:
Use within inspection conditions (See Table
2).
General Specifications
Ambient temperature:
-10 to 50;
Storage temperature:
-25 to 85;
Ambient humidity:
Less than 90%RH
Optional accuracy:
Better than ± 0.1%
External dimensions (H × W × D):
30 × 70 × 55mm
Mass {weight}: Approx. 250g
Case:
Glass fiber resin case(black)
Terminals:
Connected by crimp terminals with M4
screws and insulation sleeve.
Terminals on intrinsically safe explosionproof circuit side are indicated in bright
blue.
Cover:
Transparent plastic cover for protection of
terminals
Operating conditions for measurement:
Circuit resistance, circuit voltage, common
mode, etc. are limited. (See Table 2)
Table 1. Types and ,code symbols for combined measuring instru
ments and inspection certificate number
Type
Code
symbols
Combined
measuring
instruments
Color
idemtification
For transPWZB10A1 FC transmitter*1 Bule
field indicator
mitter (4 to 20mA,
2-wire system)
Abgriff transmitter,
field indicator
FFI multipoint
temperature
converter
PWZB11A1 Multi-point
temperature
converter
(FRL) + Pt
resistance bulb
Bule
Multi-point
temperature
converter
(FRL) +
Thermocouple
Inspection
certificate
No.
30745
29077
42150
42151
For electropneumatic
final control
element
(4 to 20mA,
2-wire system)
PWZB20A1 Electro-pneumatic Green
converter *2
posisioner *3
41022
For thermocouple
PWZB30A1 Thermometer
(FTA, FTB, FTC,
FTD)
20983
For contact
input *4
For resistance bulb
(3-wire system)
Red
Contact*4
PWZB4 A1 Thermometer
(FTF)
21857
Orange
20984
Notes:
*1 Excluding emf transmitter (FRA) and flow transmitter (FJQ).
FC transmitter modification No. is type 2.
*2 Electro-pneumatic converter modification No. is type 4.
*3 Positioner modification No. is type 5.
*4 For contacts located in a hazadous area, an inspection certificate
prate must be attached to a contact not equipped with a power supply.
Also, when an acetylene atmosphere exsts in a hasardous area, ensure
contacts do not include bare copper or copper alloy.
On the receiving signal side of the zener barrier, it is necessary to use
an exclusive intrinsically safe auxiliary relay (PWR).
2
OPERATING PRINCIPLES
•
The zener barrier consists of three safety maintenance
elements: (I) current limiter circuit, (II) voltage limiter circuit, and (III) fuse for voltage limiter circuit protection.
• Wiring resistance of each element increases during normal operation, and does not affect any measurement.
• The current limiter circuit is an intrinsically safe circuit
which limits the current to an intrinsically safe level even if
a short-circuit, ground, or other fault occurs.
• The voltage limiter circuit suppresses the voltage to less
than the zener voltage to maintain the intrinsically safe
functions even if a dangerous voltage exceeding the
working voltage value or less than the rated max. safety
voltage is applied to the nonintrinsically safe circuit due to
a fault.
• The fuse protects the zener diode from self-heating and
burn out thus losing its voltage limiting function. Cut-off
time Tf of the fuse and fusing time Tz of the zener diode
are in cooperation with each other as described below.
Tz > 10Tf
• The zener barrier consists of a circuit containing three
safety maintenance elements sealed in a case having a
relaying terminal board structure.
The intrinsically safe circuit terminals and the
nonintrinsically safe circuit terminals are isolated from
each other so that they are not shorted to one another
thus losing their functions.
The grounding terminal is grounded to the bus bar
which is also grounded with a sufficiently low grounding
resistance.
The zener barrier includes four barriers according to
applications.
• The current limiter circuit generally uses resistors. Part
of the 4 to 20mA current limiter circuit consists of a
hybrid IC doubled to enhance its reliability.
• The voltage limiter circuit consisting of a zener diode or
ordinary diode is triplicated to assure safety and
reliability.
• The newly developed thick film fuse has a high safety
rating of 550V AC or 340V DC, and resists vibrations and
deterioration by corrosion. It features high reliability
from the viewpoint of explosion-proofing and
measurement.
SYSTEM COMPOSITION DIAGRAM
Remarks: (1)
The intrinsically safe circuit must satisfy the conditions for explosion-proofing given in Table 2.
(2) Refer to the separate manual for intrinsically safe explosion-proof wiring and work inside the instrument panel.
3
PWZ
Table 2 Operating conditions for measurement and explosion-proofing
Model
PWZB10A1
Abgriff
transmitter
FC transmitter
Item
Terminal No.
Working conditions for
measurement
PWZB30A1
PWZB40A1
2, 4
2, 4
2, 4
2, 4
2, 4, 6
Non-intrinsically
safe terminal
1, 3
1, 3
1, 3
1, 3
1, 3, 5
Grounding
terminal
7, 8
7, 8
7, 8
7, 8
7, 8
Check terminal
6
6
6
–
–
Rated working
voltage
25.8V±0.5 DC
(across 1 and 7, 8)
25.8V±0.5 DC
(across 1 and 7, 8)
14V DC or less
(across 1 and 3)
14V DC or less
(across 1 and 3)
0.4V DC or less
(across 1 and 3,
1 and 5, 3 and 5)
Total resistance
value
175Ω/20mA
(across 1 and 2)
129Ω±4.5Ω
(across 3 and 4)
175Ω/20mA
(across 1 and 2)
129Ω±4.5Ω
(across 3 and 4)
175Ω/20mA
(across 1 and 2)
89Ω±3.5Ω
(across 3 and 4)
449Ω±14.5Ω
(across 1 and 2,
3 and 4)
59Ω±2.5Ω
(across 1 and 2,
3 and 4, 5 and 6 )
52Ω
40Ω
By receiving
instrument
(approx. 100Ω)
By receiving
instrument
(approx. 50Ω/wire)
0.5V AC rms
0.5V AC rms
10V AC rms
0.1V AC rms
550V AC
340V DC
550V AC
340V DC
550V AC
340V DC
550V AC
340V DC
Max allowable
common
mode voltage
Remarks
PWZB20A1
Intrinsically safe
terminal
Max allowable
external
wiring resistance
Working conditions for
explosionproofing
PWZB11A1
52Ω
0.5V AC rms
Max. safety
rating
550V AC
340V DC
Max allowable
external
wiring capacitance
0.022µF or less 0.22µF or less
0.022µF or less
0.09µF or less
0.25µF or less
Not limited
Max allowable
external
wiring inductance*
1mH or less
1mH or less
1mH or less
0.5mH or less
5mH or less
Not limited
Reference for
wiring distance
according to
working conitions
(approx. distance)
CWS
(1.25mm2)
125m
CWS
(1.25mm2)
110m
CWS
(1.25mm2)
125m
CWS
(1.25mm2)
250m
2.5km
CEVS
(1.25mm2)
250m
CEVS
(1.25mm2)
220m
CEVS
(1.25mm2)
250m
CEVS
(1.25mm2)
500m
100m, although
this depends upon
compensating
conductors. 2.5km
with contact input
* Only one field indicator (FXG)
or one transmitter with built-in
indicator can be used.
When the field indicator is used
ployed, internal resistance
of 12Ω should be subtracted,
* Only one positioner or converter (ZLA,
ZLC) can be
employed.
Remarks (1) The reference for wiring distance differs according to the type of explosive gases, ambient conditions, presence or
absence of shield, wiring diameter, etc. The above table gives values with regard to i3nG5.
Consult Fuji if there is any question.
(2) The maximum allowable common mode voltage depends on the charateristies of the voltage regulating circuit.
Be careful not to exceed this value.
CODE SYMBOLS
1 2 3 4 5 6 7 8
PW Z
A 1
B10
B11
B20
B30
B40
B42
4
Description
Classification
For transmitter (4 to 20mA, 2-wire system)
For FFI multi-point temprature converter
For electro-pneumatic final controlling
element (4 to 20mA, 2-wire system)
For thermocouple, contact input
For resistance bulb (100°C or more) and
ST transmitter
For resistance bulb (50°C or more and
100°C or less)
CONNECTIONS DIAGRAMS
1. Zener barrier for transmitter
(PWZB10A1)
2. Zener barrier for electro-pneumatic
converter and positioner
(PWZB20A1)
3. Zener barrier for thermocouple
(PWZB30A1)
4. Zener barrier for contact input
(PWZB30A1)
5. Zener barrier for resistance bulb
and ST input
(PWZB40A1)
6. Zener barrier for FFI multi-point
temperature converter
(PWZB11A1)
5
PWZ
OUTLINE DIAGRAM (Unit : mm)
SCOPE OF DELIVERY
Zener barrier
RELATED DEVICES
Combined measuring instruments
ORDERING INFORMATION
1. Product name
2. Code symbols
Note: Asterisked (*)items: Non standard.
Caution on Safety
*Before using this product, be sure to read its instruction manual in advance.
Head Office
Gate City Ohsaki, East Tower, 11-2, Osaki 1-chome,
Shinagawa-ku, Tokyo 141-0032, Japan
http://www.fesys.co.jp/eng
Instrumentation Div.
International Sales Dept.
No.1, Fuji-machi, Hino-city, Tokyo, 191-8502 Japan
Phone: 81-42-585-6201, 6202 Fax: 81-42-585-6187
http://www.fic-net.jp/eng
Information in this catalog is subject to change without notice.
Printed in Japan