Protection for data and signal lines in intrinsically safe circuits
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The document outlines the importance of protecting data and signal lines in intrinsically safe (IS) circuits, particularly in hazardous environments like petrochemical and pharmaceutical industries, where explosive gases can pose serious risks. It emphasizes using ATEX-approved surge protection devices (SPDs) to shield IS circuits from transient overvoltages, thus preventing potential sparks that could lead to explosions. The guidelines also include installation requirements and classifications related to hazardous areas based on the frequency and duration of explosive atmospheres.
![Application Note: AN013
page 3 | AN013
Protecting data & signal lines
Surge Protection Devices (SPDs) must be
installed at all lightning protection
boundaries, in line with BS EN/IEC 62305,
to protect against transient overvoltages.
Similarly, IS circuits require surge protection at
the boundary between the hazardous and
non-hazardous area - see Figure 1.
Furse ESP SL**X Series protectors are approved
for use in hazardous areas to protect IS circuits
and have a group IIC T4 certification, for
use with all gas/air mixtures (Classification:
Ex II 2 (1) G, Ex ia [ia Ga] IIC T4 Gb).
These protectors are suitable for high speed
digital communication equipment or systems
with long signal lines, where a large number
of wires require protection (e.g. process
control, 4 – 20 mA loops, fire and gas
detectors and shut down systems).
Protectors offer negligible self-capacitance
and self-inductance for minimal interference
when protecting IS circuits.
Note: ESP SL**X protectors provide
surge protection on IS circuits only and
do not replace the IS barrier itself.
1
S
2
3
S
4
Lightning Barrier
From line
LINE CLEAN
Earth
To equipment
Clean
Line
Li = 0µH, Ci = 0µFLi = 0µH, Ci = 0µF
Pi = 1.3W (-40ºC <Ta <40ºC)Pi = 1.3W (-40ºC <Ta <40ºC)
Pi = 1.2W (-40ºC <Ta <60ºC)Pi = 1.2W (-40ºC <Ta <60ºC)
Pi = 1W (-40ºC <Ta <80ºC)Pi = 1W (-40ºC <Ta <80ºC)
WARNING Electrostatic Hazard
Clean ONLY with a damp clothClean ONLY with a damp cloth
05180518
FurseFurse
Wilford Road,Wilford Road,
Nottingham,Nottingham,
NG2 1EB, UKNG2 1EB, UK
IECEx SIR 10.0030XIECEx SIR 10.0030X
Sira 10ATEX2063XSira 10ATEX2063X
II 2 (1) GII 2 (1) G
Ex ia [ia Ga] IIC T4 GbEx ia [ia Ga] IIC T4 Gb
30V30V
37.8V37.8V
Nominal voltageNominal voltage
Max working voltage, UMax working voltage, Uc
Installation
Field instrument
protection should take
place in Zone 1 and as close as practically
possible to the Zone 0 boundary, preferably
within 1 m to prevent transient overvoltages
from entering Zone 0.
The SPD should be housed in the field
instrument, or within a suitable protective
enclosure, mounted on a separate 35 mm
DIN rail to the IS Barriers.
The SPD should be connected in-line (series)
with the data communication, signal,
measurement, or telephone line, with the
dirty line end of the protector connected to
the cable carrying the incoming transient
overvoltages – see Figure 2.
Cables connected to the clean end should
never be routed next to dirty line cables or
dirty barrier earth bonds. If rows of SPDs are
installed close to each other, dirty line cables
(and earth bonds) must be kept at least 5 cm
apart from clean cables - refer to installation
instructions for further information.
The SPD must not be subjected to thermal
and/or mechanical stresses in excess of those
permitted in the certification documentation,
nor installed in a location where it may be
attacked by aggressive substances. Protect
from excessive dust, moisture and other
contaminants by a suitable enclosure.
Figure 2: Series connection of
ESP SL**X surge protectors.
Lightning protection SPDs in
hazardous areas must only be
installed, operated and maintained
by competent personnel.
SPDs for data and signal lines should
form part of an overall Lightning
Protection System for the site,
including mains surge protection,
structural lightning protection,
and an appropriate earthing system,
as required.
For further information, contact Furse.
Product specification ESP SL15X, ESP SL15X/I ESP SL30X, ESP SL30X/I
Protection level1
Combined Category D, C, B Combined Category D, C, B
Protection boundary LPZ 0B to LPZ 3 LPZ 0B to LPZ 3
Maximum working voltage UC 15 V 30 V
Current rating 750 mA 750 mA
Line resistance 1 Ω 1 Ω
Bandwidth (-3 dB) > 85 Mhz > 85 Mhz
Approval references: IECEx SIR 10.0030X, Sira 10ATEX2063X 1
tested to BS EN/IEC 61643-21](https://image.slidesharecdn.com/applicationnotean013-atex-141013082836-conversion-gate02/85/Protection-for-data-and-signal-lines-in-intrinsically-safe-circuits-3-320.jpg)
Protection for data and signal lines in intrinsically safe circuits
- 1. Protection for data and signal lines in Intrinsically Safe circuits Application Note AN013 for data and signal line protectors ESP SL15X and ESP SL30X
- 2. Protection for data and signal lines in Intrinsically Safe circuits AN013 | page 2 Industries such as petrochemical, oil & gas or pharmaceutical face a daily challenge to protect people and property at risk from potentially explosive atmospheres. These atmospheres create hazardous areas, where air mixes with inflammable materials, such as gases, powders, or dusts (for example, petrol fumes during oil refinery), which would combust if ignited. Hazardous areas must be protected against the risk that a spark or other source of ignition would cause an explosion. Electrical equipment and systems (such as process control units) therefore present a considerable risk to safety, as they may be subjected to transient overvoltages from lightning or switching events. Intrinsic Safety/Ex i A major approach to protecting hazardous areas from dangerous sparking is known as Intrinsic Safety (IS). Within an IS environment, sparks from electrical equipment and circuitry are prevented through the use of IS Barriers, which limit the available electrical energy that could cause an explosion, to below ignition threshold. IS Barriers are NOT surge protectors but field instruments which are themselves AT RISK from transient overvoltages. IS circuits therefore need to be protected from transient overvoltages by a suitable (ATEX approved) surge protector. IEC/ATEX Directives The IEC and the EU, through the publication of two ATEX Directives, have introduced specifications for determining hazardous areas, and product suitability for use in IS environments. ATEX Directive 94/9/EC covers equipment and protective systems for potentially explosive atmospheres and the health & safety requirements to which they must conform. Directive 1999/92/EC covers health & safety of employees at risk from explosive atmospheres and requires the avoidance of ignition in explosive atmospheres, where these atmospheres cannot be fully prevented. The IEC has established a classification of gases (3 groups: llA – llB – llC), and of temperatures for material used in zones at risk of explosion (6 groups: T1 to T6). Products for hazardous areas are classified in line with IEC & ATEX to gas group & temperature for application within specific hazardous area zones (see Zone and EX i classification tables opposite). Instrumentation Instrument Earth ESP SL30X/IESP SL30X Control cabinet IP54 enclosure Instrument Earth System Earth Field earth Open end cable screen ZONE0 Hazardous Area Zones 1,2Non-Hazardous Area Isolated coupling IS Barrier Gaseous hazardous area zones are defined based on the expectation of a potentially explosive atmosphere occuring: Zone 0 Hazard is continuously present, for long periods or frequently (> 1000 hours per year) Zone 1 Hazard is likely to arise occasionally during normal operation (10 – 1000 hours per year) Zone 2 Hazard is not likely to arise during normal operation, or is of short duration only (< 10 hours per year) SAFE AREA No hazard is present Symbol Suitable for Category Tested to Ex ia Zones 0, 1, 2 1 EN 50020 Ex ib Zones 1 & 2 2 EN 50039 Figure 1: The ESP SL30X Series can provide protection for the instrumentation as well as providing protection for the IS Barrier. The isolated screen version (ESP SL30X/I) should be used in Zone 1, 2. IECEx
- 3. Application Note: AN013 page 3 | AN013 Protecting data & signal lines Surge Protection Devices (SPDs) must be installed at all lightning protection boundaries, in line with BS EN/IEC 62305, to protect against transient overvoltages. Similarly, IS circuits require surge protection at the boundary between the hazardous and non-hazardous area - see Figure 1. Furse ESP SL**X Series protectors are approved for use in hazardous areas to protect IS circuits and have a group IIC T4 certification, for use with all gas/air mixtures (Classification: Ex II 2 (1) G, Ex ia [ia Ga] IIC T4 Gb). These protectors are suitable for high speed digital communication equipment or systems with long signal lines, where a large number of wires require protection (e.g. process control, 4 – 20 mA loops, fire and gas detectors and shut down systems). Protectors offer negligible self-capacitance and self-inductance for minimal interference when protecting IS circuits. Note: ESP SL**X protectors provide surge protection on IS circuits only and do not replace the IS barrier itself. 1 S 2 3 S 4 Lightning Barrier From line LINE CLEAN Earth To equipment Clean Line Li = 0µH, Ci = 0µFLi = 0µH, Ci = 0µF Pi = 1.3W (-40ºC <Ta <40ºC)Pi = 1.3W (-40ºC <Ta <40ºC) Pi = 1.2W (-40ºC <Ta <60ºC)Pi = 1.2W (-40ºC <Ta <60ºC) Pi = 1W (-40ºC <Ta <80ºC)Pi = 1W (-40ºC <Ta <80ºC) WARNING Electrostatic Hazard Clean ONLY with a damp clothClean ONLY with a damp cloth 05180518 FurseFurse Wilford Road,Wilford Road, Nottingham,Nottingham, NG2 1EB, UKNG2 1EB, UK IECEx SIR 10.0030XIECEx SIR 10.0030X Sira 10ATEX2063XSira 10ATEX2063X II 2 (1) GII 2 (1) G Ex ia [ia Ga] IIC T4 GbEx ia [ia Ga] IIC T4 Gb 30V30V 37.8V37.8V Nominal voltageNominal voltage Max working voltage, UMax working voltage, Uc Installation Field instrument protection should take place in Zone 1 and as close as practically possible to the Zone 0 boundary, preferably within 1 m to prevent transient overvoltages from entering Zone 0. The SPD should be housed in the field instrument, or within a suitable protective enclosure, mounted on a separate 35 mm DIN rail to the IS Barriers. The SPD should be connected in-line (series) with the data communication, signal, measurement, or telephone line, with the dirty line end of the protector connected to the cable carrying the incoming transient overvoltages – see Figure 2. Cables connected to the clean end should never be routed next to dirty line cables or dirty barrier earth bonds. If rows of SPDs are installed close to each other, dirty line cables (and earth bonds) must be kept at least 5 cm apart from clean cables - refer to installation instructions for further information. The SPD must not be subjected to thermal and/or mechanical stresses in excess of those permitted in the certification documentation, nor installed in a location where it may be attacked by aggressive substances. Protect from excessive dust, moisture and other contaminants by a suitable enclosure. Figure 2: Series connection of ESP SL**X surge protectors. Lightning protection SPDs in hazardous areas must only be installed, operated and maintained by competent personnel. SPDs for data and signal lines should form part of an overall Lightning Protection System for the site, including mains surge protection, structural lightning protection, and an appropriate earthing system, as required. For further information, contact Furse. Product specification ESP SL15X, ESP SL15X/I ESP SL30X, ESP SL30X/I Protection level1 Combined Category D, C, B Combined Category D, C, B Protection boundary LPZ 0B to LPZ 3 LPZ 0B to LPZ 3 Maximum working voltage UC 15 V 30 V Current rating 750 mA 750 mA Line resistance 1 Ω 1 Ω Bandwidth (-3 dB) > 85 Mhz > 85 Mhz Approval references: IECEx SIR 10.0030X, Sira 10ATEX2063X 1 tested to BS EN/IEC 61643-21
- 4. UK OFFICE Thomas & Betts Limited Furse Wilford Road Nottingham NG2 1EB United Kingdom Switchboard +44 (0)115 964 3700 Fax +44 (0)115 986 0538 Sales tel +44 (0)115 964 3800 Sales fax +44 (0)115 986 0071 Email: enquiry@furse.com www.furse.com EUROPEAN HEADQUARTERS Thomas & Betts 200 Chaussée de Waterloo B-1640 Rhode-St-Genèse Belgium Tel +32 (0)2 359 8200 Fax +32 (0)2 359 8201 www.tnb-europe.com MIDDLE EAST OFFICE Thomas & Betts Ltd. Br. Office 107 5EA East Wing Dubai Airport Free Zone PO Box 54567 Dubai United Arab Emirates Tel +971 (0)4 609 1635 Fax +971 (0)4 609 1636 Email: furseenquiryme@tnb.com SOUTH EAST ASIA OFFICE Thomas & Betts Asia (Singapore) Pte Ltd 10 Ang Mo Kio Street 65 #06-07 Techpoint Singapore 569059 Tel +65 6720 8828 Fax +65 6720 8780 Email: asia.inquiry@tnb.com The content of this Thomas & Betts publication has been carefully checked for accuracy at the time of print. However, Thomas & Betts doesn’t give any warranty of any kind, express or implied, in this respect and shall not be liable for any loss or damage that may result from any use or as a consequence of any inaccuracies in or any omissions from the information which it may contain. E&OE. Copyright Thomas & Betts Corp. 2010. Copyright in these pages is owned by Thomas & Betts except where otherwise indicated. No part of this publication may be reproduced, copied or transmitted in any form or by any means, without our prior written permission. Images, trade marks, brands, designs and technology are also protected by other intellectual property rights and may not be reproduced or appropriated in any manner without written permission of their respective owners. Thomas & Betts reserves the right to change and improve any product specifications or other mentions in the publication at its own discretion and at any time. These conditions of use are governed by the laws of the Netherlands and the courts of Amsterdam shall have exclusive jurisdiction in any dispute. AN013-0610 Full specifications of all of the products in the Furse ESP range of transient overvoltage protectors can be found in the Total Solution Product Catalogue. To request a copy, contact Furse Sales at the address opposite. Full product data can be downloaded in PDF form from our website at www.furse.com. Copies of the Total Solution Product Catalogue can also be requested from our website. ABBREVIATIONS ATEX = ATmospheres EXplosibles IEC = International Electrical Commission IS = Intrinsic Safety SPD = Surge Protection Device