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Intrinsic Safety in Class I Div 1 Hazardous LocationsCost-effective Alternatives for Simple Devices

Customer Need and Component Solution

Installation of traditional Type 7/9 bolted enclosures for simple devices (for example, push button stations, resistance temperature detectors [RTDs], thermocouples) into a Class I Div 1 environment is a common, but costly, task. Although these enclosures can be necessary for power/switch-gear applications, there are more cost-effective alternatives using simple devices that can meet standards and application requirements..

Concept A: Hazardous Environment rated Brand X model is a great solution for Division 1 hazardous environments. However, the panel designer must follow explosion proof (Ex ‘d’) ratings requirements. This requires use of conduit fitting, tubes, seals, drains, breathers, etc., in addition to interfacing with a properly rated junction box that is installed in the hazardous environment. This is a costly implementation.

Concept B: The 800H push button is a great solution for unclassified environments. Even though the 800H-2HA4R is not rated for use in hazardous environments, because mechanical contacts (non-energy storing devices) are referred to as a Simple Apparatus by the NEC, this allows use of push buttons (mechanical contacts) in hazardous environments when used with an intrinsic safety protection method. The Intrinsic Safety Barrier (Isolator) acts as a medium between the programmable logic controller (PLC) and push button station, limiting energy to the apparatus to create an intrinsically safe circuit. This method takes advantage of more simple cable routing methods and is cost effective.

Concept C: Brand Z RTD temperature sensors with no hazardous ratings can not normally be used in those environments. But, because RTDs (non-energy storing devices) are referred to as Simple Apparatus by the NEC, they may be used in hazardous environments with an intrinsic safety protection method. The Intrinsic Safety Barrier (Isolator) acts as a medium between the PLC and RTD sensor, limiting the energy to the apparatus to create an intrinsically safe circuit that is permitted by the NEC and approval agencies. This method takes advantage of more simple cable routing methods and is cost effective.

Copyright © 2013 Rockwell Automation, Inc. All Rights Reserved.PUBLIC INFORMATIONOrdinary / Unclassified Environment

Push Button Brand XEx ‘d’ Rated Class 1, IIDiv. 1 &2

Concept AExplosion Proof Ex ‘d’

Methodology

Conduits & Seals

Bolted NEMA 7 & 9 Junction Box

Conduits & Seals

X800H-2HA4RNon-Hazardous Ratings

Concept BIntrinsic Safety Ex ‘i’

Methodology

Intri

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Sa

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937TH-DISAR-DC22-Channel Intrinsic Safety Isolator

RTDBrand ZNon-Hazardous Ratings

Concept CIntrinsic Safety Ex ‘i’

Methodology

Intri

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ally

Sa

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ircui

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937TH-AIRRP-DC1 1-Channel Intrinsic Safety Isolator

Allen-Bradley, Rockwell Software, Rockwell Automation, and LISTEN. THINK. SOLVE are trademarks of Rockwell Automation, Inc.

SummaryBulletin 937 Intrinsic Safety modules are an economical solution for implementing simple devices within Class I Div 1 locations. These modules provide a medium between the PLC and simple device to limit electrical energy to safe levels within the hazardous environment. Intrinsic Safety Modules (Associated Apparatus) can be used with mechanical contacts or other simple devices (Simple Apparatus) that do not store or release energy in a circuit to provide intrinsic safety protection in hazardous environments.

For more information on 937 Intrinsic Safety Modules, please visit: http://ab.rockwellautomation.com/Signal-Interface/Intrinsic-Safety.

Ex ‘i’ protection methods are the most cost effective solution for simple devices in hazardous locations

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Ex ‘d’ Method

List Price, USD

Ex ‘i’ Method Ex ‘i’ Method

Push Button by Brand X $529 800H-2HA4R $354 RTD by Brand Z $71

937TH-AIRRP-DC1

Conduit drain / breather $147

Kit, Cement 1lb. $43

Fiber Filler, 4 oz. $91

Tube fitting elbow $25

Junction Box Junction Box $114 Junction Box $114

Tube fittings Tray Fittings $200 Tray Fittings $200

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779$ 970,1$046,3$

$1,344

$1,028

937TH-DISAR-DC2 $296 $477

List Price, USD List Price, USD

937TH-DISAR-DC2

800H-2HA4RPush Button Station 1 N.O., 1N.C.

24V DCPower Supply

Hazardous Area

Division 1 (Zone 0 & 1)

Trademarks not belonging to Rockwell Automation are property of their respective companies.

Publication 937-AT001A-EN-P - April 2016 Copyright © 2016 Rockwell Automation, Inc. All rights reserved. Printed in the U.S.A.