eex ia instrumentation and fittings.

  • Thread starter Charles Anthony
  • Start date
C

Thread Starter

Charles Anthony

Can anybody point me in the right direction with advise and tell me where to find a copy of a specification for equipment to be used in classified areas on petro-chemical plants?

There are some 'eex ia' certified transmitters located in a hazardous area (zone I) on a plant where I am currently working in Kuwait.
The 4-20mA signal cables feed into these transmitters via "Copex" type flexible conduit and glands, which themselves are not cerified for use in hazardous areas.

Can the installation contractors be allowed to do this type of installation, using the fact that the system is fed via "eex ia' certified barriers, therefore the glands and conduit do not need to be certified, as a get out clause?
Remember, there is insufficient power in the system to cause a spark even under fault conditions.
 
A
Hello,
Once you have used barriers, then the field side is well protected and hence you can use ordinary systems in the field like weather proof jb's, conduitys etc., provided these are not capable of generating charges or storing energy by themselves. if you have an electronic or electric component then that has to be certified.

Regards,
Anand
 
> Can anybody point me in the right direction with advise and tell me where to find a copy of a specification for equipment to be used in classified areas on petro-chemical plants?

Most instrument/barrier manufacturers have their own booklets/PDF files with a list of all classifications of equipment and what zones, gas/dust groups permit which classification. Elcon, MTL, Pepperl & Fuchs all have free information.

Do a web search for 'hazardous area' 'intrinsically safe' you will get lots of hits.


> There are some 'eex ia' certified transmitters located in a hazardous area (zone I) on a plant where I am currently working in Kuwait.

Eex ia - this is a European certified instrinsically safe device.


> The 4-20mA signal cables feed into these transmitters via "Copex" type flexible conduit and glands, which themselves are not cerified for use in hazardous areas.
> Can the installation contractors be allowed to do this type of installation, using the fact that the system is fed via "eex ia' certified barriers, therefore the glands and conduit do not need to be certified, as a get out clause?
> Remember, there is insufficient power in the system to cause a spark even under fault conditions.

Apart from good electrical installation practice, IS circuits require particular attention:

1. The electrical cable, fittings, fixtures have to have a 'reasonable' IP rating. Personally I will not accept less than IP65 - not sure what 'copex' type fittings give?

2. Generally IS circuits have to be easily identifiable from other non-IS circuits, such as flame/explosionproof ciruits - this is usually achieved by using a blue cable and blue junction boxes, clear labelling etc on the IS circuits. They should have some degree of segregation from other ciruits - standards vary, the lowest I have come across is 100mm on cable tray. Site electrical standards should specify exact requirements!

You will benefit from speaking to the barrier manufacturer regarding wiring. Depending on the site you might require 'system certificates' for barrier,cable & instrument combinations?

Its also important to have to hand the full area classification - zone, gas group, temperature class.

Not saying that you will, but don't take any risks!
 
B

Bruce Durdle

Charles,

Under IEC rules, it is acceptable to use IS systems with any form of wiring - there are no special requirements for glands and conduits,

Having said that, check your local interpretation of the requirements for barrier glands to prevent vapour migrating along the cable - there is
sometimes an issue with this. (But how anyone expects a good barrier around a multi-pair instrument cable defeats me ... )

Bruce.
 
W
You pot the gland. Of course this means that you have to basically remove
the conduit and wiring to rewire it.


Walt Boyes

---------SPITZER AND BOYES, LLC-------------
"Consulting from the engineer
to the distribution channel"
www.spitzerandboyes.com
[email protected]
21118 SE 278th Place
Maple Valley, WA 98038
253-709-5046 cell 425-432-8262 home office
fax:801-749-7142
 
B

Bruce Durdle

Hi Walt,

I'm talking about a cable-only system.The Australian standard for Ex d or explosion-proof equipment was revised in 1995 to require all cables to be fitted with a barrier gland (having a ferrule where all cores were supposed to be separated out and packed with epoxy to make a gas-tight barrier and prevent vapour or gas migrating along the cable), unless the cable had a cross section completely filled with extruded filler. Since there is no reason why the same can't happen with other methods of protection, this
ruling was extended to all other types of protection, including Intrinsically Safe.

As I said, while it may be practicable to do a good job with a barrier gland with a multi-core control cable, I cannot see how it can be done
using a multi-pair individually-screened instrument cable - and without separating out the cores and screen at the gland, it would appear to be rather pointless anyway. I think this is one of those requirements that gives the regulators a good feeling but makes life hell for those who have to comply.

Fortunately, in the latest version of the over-riding standard, they require barrier glands on cables only if there is a possibility of
significant pressure-drop along the cable.

Just out of iterest for those of you who have to use conduit seals - I recently had a class prepare conduit seals using compound from a bag that had been open to the atmosphere for a while. 3 weeks later it is still soft and chalky.

Bruce.
 
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