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Anonymous Poster

Intrinsic safe

02/14/2007 8:19 AM

what is known as intrinsic safe ?

& where it can be used?

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Guru
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#1

Re: Intrinsic safe

02/14/2007 9:02 AM

A loose definition is as follows:

Intrinsic safety is a concept whereby the maximum energy available in an electrical circuit is insufficient to cause the ignition of a flammable gas/air mixture (define the gas group and temperature class to which it applies) with a number of faults applied to the circuit.

EEx 'ib' is safe with one fault applied and can be used in hazardous areas Zone 1 and Zone 2.

EEx 'ia' is safe with two faults applied and can be used in hazardous areas Zone 0, 1 and 2.

Apart from equipment specially certified for Zone 0, EEx 'ia' is the only technique that is permissible in Zone 0.

Zone 2 is defined as where a flammable gas/air mixture is present under abnormal operation and only for a short time.

Zone 1 is where it is present normally and only for a short time.

Zone 0 is where it is present normally, more or less continually.

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#2

Re: Intrinsic safe

02/14/2007 9:05 AM
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Guru
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#4
In reply to #2

Re: Intrinsic safe

02/15/2007 3:34 AM

The website is a bit outdated: for the whole European union the ATEX directive is law. You need to use material which is approved for the task that you want to use it for. There is no relation between a country of usage and the certified body that certified the unit. The rules are the same for the whole union and something that is approved in Greece can be used without problem in Scotland.

The ATEX directive imposes an evaluation of the risk of an explosion in your company.

In case this is possible (even in very abnormal conditions) you need to protect yourself and your environment for the risk.

There are different methods of avoiding the ignition of a potentially explosive environment (it can be a gas-air mixture or dust)

Intrinsically safe is one of those methods: the basic idea is that you do the necessary measurements/action with so little power that is is impossible that you ignite. (this is different for different gases/dusts, the used barriers are classified)

Normally it is used for measurements in a zone 0 (potential explosive atmosphere is normal, eg inside a storage tank) with sensors which are not approved for this task.

But you could use it where you need to do a measurement in a zone, departing from a non approved measurement device outside the zone and its sensor (not approved) in the zone. (in case you don't find an approved sensor to work with your apparatus)

Depending on the zone classification you can self certify (zone 2) the solution or ask a third party (certified body) to do it. But in all cases you need to document the solution.

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#3

Re: Intrinsic safe

02/15/2007 1:11 AM

Visit Ronan website : www.ronan.com

and download the pdf file "ART of I.S" which is a detailed description of I.S and its applications.

Enjoy

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#5

Re: Intrinsic safe

02/15/2007 7:16 AM

An intrinsically safe circuit is one that is designed so that it's physical and electrical characteristics do not allow sufficient electrical energy (millijoules) in an arc or spark to ignite or produce sufficent thermal energy from an overload condition to exceed the ignition temp of a specific gas or vapor under normal operating conditions. There are intrinsically safe apparatus, intrinsically safe circuits and intrinsically safe systems. The US standard for intrinsically safe systems is ANSI/UL 913, which is similar to the standards of other countries. All standards are based on the IEC standard. ANSI/UL 60079-11 is based on the IEC 60079-11 standard and contains the US deviations, which allow it to be comatible for installations in the US. The NEC offers the choice of designating hazardous locations as two divisions, 1 and 2 or three zones 0, 1 and 2. ANSI/UL 913 requirements are based on the IEC Zone 0 requirements, which are the most stringent. Equipment certified by a testing facility as meeting the requirements for installation in a Zone 1 area would not necessarily meet the ANSI/UL 913 requirements for a Div 1 area.

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