C1D2 customer comments

[petersonra]

One of my favorite customers called a little while ago. One of his customers has asked he supply some "explosion proof" equipment. It was further stated to be C1D2, and also purged.

I sent him back to his customer to get some clarification, as it did not make a lot of sense what was being asked for.

There are some solenoid valves. As I read the code, solenoids are specifically allowed to be general purpose in a C1D2 area, so nothing special would be required there. It does not appear any seals would be required.

It appears that the purging system may actually be there to deal with some limit switches. I don't see any reason that the conduit to the limit switches can't be routed so that they are protected by the purge/pressurization system.

Am I missing something important here? As best I can tell the only electrical equipment I have to worry about are some solenoid valves and some limit switches.

 

[rbalex]

Basically, I agree with you. The solenoids can be ?general purpose? in Class I, Division2. I?d like to know more about the general setup and the limit switches themselves; e.g., if there is a ?factory sealed? version or not. Depending on the overall setup, purging an entire conduit system, without seals, can be prohibitively expensive.

 

[petersonra]

Basically, I agree with you. The solenoids can be “general purpose” in Class I, Division2. I’d like to know more about the general setup and the limit switches themselves; e.g., if there is a “factory sealed” version or not. Depending on the overall setup, purging an entire conduit system, without seals, can be prohibitively expensive.

expense is not my problem if the customer asks for it. the equipment is going to a large chemical company. presumably they know what they want.

I suspect there are prox switches that could be used that are listed for C1D2 that could be substituted for the hard limit switches if cost was the issue. I don't know why they want hard limit switches on the valves in lieu of something more cost effective. It seems odd that they would spec XP limit switches and then want to purge them. I would just put seals on them and be done with it. I can't think of any good reason to use XP switches if it is going to be purged either.

BTW, is there any reason we would have to pour the seals here? I can't think of any, and normally in the past we didn't, thinking it would be a lot easier if they needed to rewire something in the field not to have to mess with the sealing compound.

 

[rbalex]

expense is not my problem if the customer asks for it. the equipment is going to a large chemical company. presumably they know what they want.

I suspect there are prox switches that could be used that are listed for C1D2 that could be substituted for the hard limit switches if cost was the issue. I don't know why they want hard limit switches on the valves in lieu of something more cost effective. It seems odd that they would spec XP limit switches and then want to purge them. I would just put seals on them and be done with it. I can't think of any good reason to use XP switches if it is going to be purged either.

BTW, is there any reason we would have to pour the seals here? I can't think of any, and normally in the past we didn't, thinking it would be a lot easier if they needed to rewire something in the field not to have to mess with the sealing compound.

From the description so far, I don?t see an underlying rationale. I can?t seem to speculate on one either.

The number of people that truly understand hazardous location installations has always been small and that number has been dwindling for some time; so ?presumably they know what they want? is not certain. For many it?s ?belts and suspenders;? that?s been true for a long time too.

In Division 2, explosionproof (poured) seals are only required to maintain the integrity of explosionproof equipment. Boundary seals are no longer required to be explosionproof.

?Rewiring? can be a problem though. Many explosionproof seals are overlooked to start with. In Division 2 that may or may not be a big a deal although I certainly wouldn?t encourage it. In Division 1 they?re essential. Where a non-explosionproof seal was used to maintain pressure, it could be a problem if it's forgotten after a rewiring. Then pressure monitoring becomes the key.

 

[weressl]

Basically, I agree with you. The solenoids can be ?general purpose? in Class I, Division2. I?d like to know more about the general setup and the limit switches themselves; e.g., if there is a ?factory sealed? version or not. Depending on the overall setup, purging an entire conduit system, without seals, can be prohibitively expensive.

How could you even purge a conduit system? Pressurizing isn't the problem, purging is. Bleed-off solenoids all over?

 

[petersonra]

How could you even purge a conduit system? Pressurizing isn't the problem, purging is. Bleed-off solenoids all over?

It is not that hard for a small system. Not a lot different than purging multiple enclosures.

This is a all stuff that will be in an area no more than 10 X 10 feet.

I really don't get what it is they think they will be accomplishing. it does not seem like something that serves any useful purpose.

OTOH, I often get told stuff like this that has gone thru 4 or 5 salesmen and gets garbled along the way.