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megatron21
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"Ia" and "Ib" Difference in Intrinsically Safe Designation

06/30/2010 10:03 AM

What is/are main difference(s) between those two? Would it be the number of protection applied and/or dangerous limits that might cause hazard?
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redfred
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#1

Re: "ia" and "ib" difference in Intrinsically Safe designation

06/30/2010 10:29 AM

Did you at all read the rules for posting here? I'll bet you that you did not. Here's the introduction to these rules and the first three items:

Are there specific rules for posting?

While you are free to post whatever you wish, as long as it does not violate the CR4 Site Use Policy, we ask that you follow these guidelines when posting or commenting on CR4.

  • Look for answers before you post. Check a search engine or two to see if you can find the answer to your question or a collection of useful links. If it's not, or if the answer is unclear, then that's a pretty good justification for asking the question. This is not to stifle questions, but you're less likely to be insulted if you have done a little research ahead of time. (thanks Silas Marner)
  • Provide as much information as possible. The most frustrating questions on this site are like this: "I need a sensor to test water flow - which is the best one." What are you testing for, what are you trying to determine? Is it in a stream, a pipe, an aquifer? Are you looking to measure velocity or mass? Are you testing for particulates, mineral concentration or pollution? Is it wastewater, potable water, slurry, etc.? The more you let us know, the better the chance that someone on the site will be able to help you find an answer (thanks Silas Marner).
  • Give some thought to your post title. Don't use "Hello", "Question" or "Help". Also, simply saying "DC Motor" is not enough. Be specific, e.g., "How Do I Install Replacement Brushes In My DC Motor"

Now as far as the first item, maybe you did look for a similar thread that deals with your topic. But I cannot tell what your topic is because you've clearly violated the second and third rule here.

Now you seem to be trying to find the difference in two categories of a specific documented standard. Refer to the standard itself. At the very least tell us which standard you are trying comply to. Better yet, copy the fraction of the standard that confuses you into your question.

We are not mind readers. Trust me, you are very grateful that I cannot implant an image into your mind right now.

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Carl_E
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#2

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

06/30/2010 8:25 PM

What can be deduced from the descriptive evidence from the table below?
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redfred
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#4
In reply to #2

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 9:33 AM

Good answer, which safety standard is this from?

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megatron21
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#5
In reply to #4

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 9:53 AM

What was the purpose of your "schooling" ? The "ia" mark is well known and my question was addressed to people to have a knowledge of it. Re: safety standards, i.e. IEC 60079-0 and 60079-11.
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redfred
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#6
In reply to #5

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 11:34 AM

My schooling is not in question here. Do you honestly think that there is one and only one unique safety standard that uses the Ia and Ib designations? I asked my question of Carl_E to verify if the standard he was citing was the one in question. Now if you prefer to assume that you are all talking about the same safety standard, then I refer to a common definition of assume.

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PWSlack
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#3

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 9:30 AM

An Ex ib arrangement is safe against igniting an explosive atmosphere in the hazardous area with one circuit fault applied and is suitable for use for Zone 2 and Zone 1.

An Ex ia arrangement is safe against igniting an explosive atmosphere in the hazardous area with two circuit faults applied and is suitable for use for Zone 2, Zone 1 and Zone 0.

<...Would it be the...dangerous limits that might cause hazard?...>

No. The equipment will have been selected beforehand looking at the Zone designation, the Gas Group and the Temperature Class.

For example, Ex ib IIC T4 would be safe for a Zone 1 hydrogen atmosphere, and not suitable for a Zone 0 hydrogen atmosphere. If the gas were carbon disulphide instead, than the temperature rating would need to be T6. If the zone were Zone 0 hydrogen, then Ex ia IIC T4 would be suitable, and Ex ib IIC T4 would not.

Do not select or install electrical equipment for potentially explosive atmospheres without having had training on the subject!

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msamad
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#7
In reply to #3

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 10:43 PM

There are many links available in the internet for detail of the Hazardous area classification and equipment safety category to be used in classified area.

Primarily two standards are used – one in North America (NEC 500, 505) and another in Europe (IEC 60079).

- MS

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megatron21
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#8
In reply to #7

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/01/2010 10:55 PM

Thanks for your replies. There is an American standard from 2009 : ANSI/ISA and ANSI/UL 60079-11 where there are the following terms: apparatus and systems of level of protection "ia" electrical apparatus and systems containing intrinsically safe circuits that are incapable of causing ignition, with the appropriate safety factor when up to two countable faults are applied and, in addition, those non-countable faults that give the most onerous condition. apparatus and systems of level of protection "ib" electrical apparatus and systems containing intrinsically safe circuits that are incapable of causing ignition with the appropriate safety factor when up to one countable fault is applied and, in addition, those noncountable faults that give the most onerous condition. And then: 5.2 Level of protection "ia" With Um and Ui applied, the intrinsically safe circuits in electrical apparatus of level of protection "ia" shall not be capable of causing ignition in each of the following circumstances: a) in normal operation and with the application of those non-countable faults which give the most onerous condition; b) in normal operation and with the application of one countable fault plus those non-countable faults which give the most onerous condition; c) in normal operation and with the application of two countable faults plus those non-countable faults which give the most onerous condition.
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PWSlack
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#9
In reply to #8

Re: "Ia" and "Ib" Difference in Intrinsically Safe Designation

07/02/2010 7:17 AM

The above words could be written more simply!

What those descriptions do not explain is the application of the Zoning techniques, which are different in the north American countries and European Union countries.

For further reading, there is an article in Wikipedia on the topic, though training on the subject is strongly recommended prior to embarking on selection and installation.

Warning: risk of and possibly when it all goes horribly wrong......

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