Explosion Ratings - Propylene Refrigeration Cycle

[awhicker]

I am putting a bid together for a customer in the propylene refrigeration sector. We will be using a multistage compressor. What, if any, explosion ratings are needed by NEC? My current classification is Class I , Group B,C,D , Division 2. Please let me know if you need more information. Thank you.

[US Iceman]

Hi,

Welcome to the RE forums.

The classification area is usually defined by the owners insurance company based on my experience. Some will require a full explosion-proof rating for control panels and other devices (the cast aluminum panels and hard conduit, etc.)

Others may allow the use of a NEMA-4 or 4X panel if an air-purged panel is utilized.

I would not volunteer to specify the electrical classification, but rather ask the owner what they want, or are required to have.

The same applies for the motor enclosure type also.

[awhicker]

Explosion ratings, therefore, are not decided by either IEC or NEC classification? This was my underlying question. I was partly expecting you to answer the question the way you did. I can not seem to find anything in the customer specifications besides a NEMA 4X callout that can guide me towards any type of protection. Because the working gas is propylene, however, I would assume that the customer wants some type of explosion rating. I was thinking that since this was not explicitly given to me that there was a common explosion proof protection for these processes.

[Brian_UK]

Without knowing anything about your countries regulations I would pass your concerns back to the customer for clarification.

If you happen to get things wrong and someone points this out after the event (installation, accident, etc.) then you could fall liable.

Also, I believe that it should be the responsibility of the client to be specific when requesting bids, quotes, tenders especially if dangers exist.

[US Iceman]

...I would assume that the customer wants some type of explosion rating.

Never, ever, assume anything on projects like this unless you willing to accept full responsibility for anything and everything...which I would not recommend (EVER)!

If the customer can't tell you what they need, then don't quote it! Because, if you do guess and guess wrong, then guess who gets blamed?

NEMA 4X is not explosion proof, unless it has an air purging capability and the ability to measure and control the purge atmosphere pressure in the panel. They should be able to tell you if this is acceptable with a purge for that atmosphere classification.

NEMA 4x just tells you the box/panel is watertight and corrosion resistant. That certainly does not have anything to do with explosion proof!

The IEC and NEC only specify how you deal with the area classification ONCE it has been designated by the owner or others (usually the owners insurance company).

I was thinking that since this was not explicitly given to me that there was a common explosion proof protection for these processes.

Again, do not assume anything! Make them tell you what they require and get it in writing with the persons name, date, and phone number. And, make sure they say in writing they are DIRECTING you to use that specific method (whatever it is).

Same thing for motors and other electrical requirements. Sometimes there are specifics on what you can and cannot do with conduit, terminations, intrinsically safe devices for controls, etc.

[awhicker]

Thank you for your help.

I would like to point out that I was not going to put into writing any assumptions, I was wondering if I should look further into this lack of explosion protections. I was also inquiring whether NEC or IEC standards have any relation to the explosion ratings, I now understand that they do not. Again, thanks for all the help.

Just out of curiousity:
I have never seen IP W24 before this job. I have a poster "expert guide to hazardous locations" but I don't have anything on what the "W" means.

[Brian_UK]

The W stands for Weather but for some more reading on it try here...

http://en.wikipedia.org/wiki/IP_Code