L.V FUSES IN HAZARDOUS ZONE - ZONE 2

[bobziva]

The client is trying to install switching devices ( fuses)in hazardous zone - zone 2, what is not acceptable to me. The distribution voltage is 240V.
They are trying to explain that encapsuled device (fuse) can be acceptable solution.
a) I didn't find proper manufacturer making this product in America / Canada.
b) Also an installation of new fuses after breaking of old ones requires a special procedure. I didn't find any article describing that procedure.
For me is better solution a breaker encapsuled in zone 2 casing.
I welcome any link describing my problem.

 

[alehman]

A fuse in a hazardous zone must be in an appropriately rated and sealed enclosure. I don't think you will find a fuse rated for hazardous environments.

 

[bigamp]

Check out Stahl on

http://www.rstahl.com

Zone 1 certified fuses on pages 11/46 to 11/50 in their dreaded catalogue. Ranging from small ones 8560 series (32mA to 5A), bigger ones 8561/01 series (2A to 25A) to large ones 8561/02 (2A to 63A). For the 8561 fuses at least, a defective fuse can be detected externally by means of the indicator and fuse links may only be exchanged after disconnecting the supply. I expect the fuses need to be mounted in a Stahl enclosure of some sort.

Stahl also do a nice range of zone 1 dist boards with MCB's (Ex de protection). As you suggest, these appear to be a much better approach than fuses.

 

[Kiribanda]

Hello bobziva,

Your client is absolutely correct. Some users in the petrochemical industry are very worried about issues like these. But if you think about the fundamentals of hazardous area classification you will get the answer.
Fuses to be installed in a suitable enclosure as per followings. That means you cannot install them in open air even though they are weather protected like expulsion fuses on MV.

Class 1 Div 1 Area: Fuses are allowed provided the enclosure you are going to use has to be certified for Class 1 Div 1 area. ( NEC 501-6).

Class 1 Div 2 Area: Fuses are allowed provided the enclosure you are going to use has to be certified for Class 1 Div 2 area. ( NEC 501-6) Also you can install them in a general purpose enclosure (weather proof only) provided those fuses have got its operating element immersed in oil, enclosed within a hermitically sealed chamber or covered with sand ( HRC current limiting cartridge or so called plug type fuses ). Therefore glass fuses are not allowed in general purpose enclosures.

In the IEC world (IEC 60079) it is the same concept. Only difference is you have to install certified enclosures for Zone 1 or Zone 2 as the case may be.

You don’t need a special method to replace the burnt fuses. Only thing is the maintenance personal have to make sure that they have isolated from upstream before removing the fuses.

Does this answer your questions?

Regards!

Kiribanda :->

 

[bobziva]

Thank you everyone for the good comments.
STAHL - suggested by BIGAMP is German company. They are making that what I need. But these products are probably not approved, certified for specific hazard area for sale on American Market. On other side I found British and German Cerificates etc. but not American and Canadian .
Must be certified by NRTL, UL, ETL or CSA, otherwise we have not right to buy it and install on the site.
The fact is that these products are better than American, but not certificated for our market ....

 

[advidana]

I get client like that to.
advidana

 

[ilan7]

Bit late but better then Never.
I used the Stahl fuses at a Class I Div. 2 area in Alberta Canada and the installation passed the local CSA inspection.

As those fuses are very expensive I used "Regullar" glass fuses but filled with sand at the glass. I got a letter from the manufacturer that those type of fuses allowed in Class I Div. 2. Used them in a small project in Nevada and the inspector did not ask about them. Now we have a project in New Zealand, and as those guys are more piky, I think of going back to the expensive Stahl fuses. If you wish, I can look for the letter and Email it.
Regards
ilan
ilan_a7@yahoo.com

 

[bobziva]

Ilan7,
Thank you for the comments. If you have any detail about "regular" glass fuses filled with sand at the glass, as acceptable fuses in ClassI Div2. , please send to me. You said that you have a letter from manufacturer.
Regards
Bob
bobziva@yahoo.com

 

[jbartos]

Suggestion: The circuit breaker appears to be the better solution for hazardous locations since it trips and it can be reset from outside. There is no need to open the XP enclosure.