Service on a ATEX EEx P cabinet

[Esporp]

Hi
We have a pressurized cabinet located in a Zone 1 area. The user manual states that before performing service we have to check that the area does not contain any explosive gases (checking would be doen by a handheld instrument). Servce involves opening the cabinet and with the power on.

I am no expert on the ATEX laws, but something about this procedure does not seem right.

Does anybody here have any expereience with this sort of issue?

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[micalbrch]

I guess that all build-in components of the cabinet are not Ex-proofed but only the closed cabinet. That's why it is pressurized. Before you open the cabinet you must check whether explosive atmopshere is present or not. If not, you can open the cabinet (= ATEX does not apply in this moment because there is no explosive atmosphere). If such an atmosphere is present, you must not open the cabinet. Is that what the manual says?

 

[Esporp]

Yes, you have to check if any explosive gases are present before opening the cabinet.

My question is then really; although the cabinet is located in a Zone 1 area, is it allowed to open the cabinet if there are no explosive gases present?

Are there any requirements to the check of the atmosphere?

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[micalbrch]

Yes, it is allowed to open the cabinet although it should be disconnected from power before you do that. That is something I did not understand from your initial post. What service do you have to do with power on? If that is really necessary (power on) you have to make sure that there is no explosive atmosphere around. Zone 1 means that an explosive atmosphere can be present but is not present all the time. The cabinet must be safe under these conditions during operation (and it is because it is pressurized) and predictable malfunctions. Nothing is said about service.

In general: You do not have to move ATEX equipment from the site to the workshop for service although you might do work (dismantling) that takes safety devices out of operation. But during service work the machines are usually not in operation.

 

[geesamand]

This might be a very rudimentary understanding, but Zone 1 means infrequently explosive environment. For example, next to a fuel storage tank nozzle. Therefore you can identify when it is and is not explosive. The equipment need only be safe against explosion during normal operation (i.e. when the cabinet is closed and pressurized) but not outside of that assumption (opened for service). Of course, what constitutes "normal operation" for a device is the golden question but in the case of the cabinet it seems that opened is outside of that.

David

 

[Esporp]

Thanks for your answers.

This cabinet is located in a pump room on-board a crude oil tanker. It is a measuring device using consumables, so the consumable has to be refilled when empty. After the refilling is completed the internal tubing has to be primed, this is done by initiating the priming function, meaning the power must be on and the door open.
I take it form your answers that this is allowed as long as we can be certain that the area is free of any explosive gases.

Is the checking for explosive covered in the ATEX directive, or is it sufficient to follow the procedure of whatever instrument is used for the checking?

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