Explosion Proof Design
Explosion Proof Design
(OP)
I am looking at an application for an automated material handling system in an explosion proof environment (flammable substance: mineral spirits) and am trying to find standards, regulations, etc on the design of such equipment. I understand that all motors and electrical components need to be designated as "explosion proof" but what about issues such as metal to metal contact?
Thanks,
Matt
Thanks,
Matt





RE: Explosion Proof Design
You need to be looking in the NEC, specifically Article 500 and subsequent articles. The main driver is the classification of the hazardous area, ex: Class I Div II. This will dictate what requirements you need to meet. The hazardous area could also be designated using the newer Zone definitions. Either way, items such as bonding, grounding, hazard proofing, etc are all discussed in Article 500. The NEC Handbook does a real good job expanding on the code text and provides a lot of examples.
Based on the information you provided, you are looking at a Class 1 (flamable liquids and gases) area. The Division takes a little more analysis to define.
Remember that it doesn't have to be explosion proof. It has to be Hazard Proof. Explosion proof is just one method of achieving the Hazard proof requirement. There are numerous methods of making the system safe such as intrinsic systems, purged and pressurized enclosures, hermetically sealed, oil emersion, non-incendive circuit/equipment and explosion proof.
I hope this has been of some help.
Jim Muir
Principal Project Engineer
Innoventor Engineering, Inc.
10 Kimler, Suite A
Maryland Heights, MO 63043
314.692.9998
314.692.9942 (Fax)
jmuir@innoventor.net
RE: Explosion Proof Design
RE: Explosion Proof Design
RE: Explosion Proof Design
I also used to deal with a similar issue all the time with refinery sewer systems. They could potentially have explosive mixtures at any time, and the junction boxes often had a pump and/or mixer installed. We always recommended blanketing the sumps to remove one of the three components of fire triangle, considering any metal on metal contact could have provided the source for ignition. Nonetheless, one of the major oil companies always ignored our recommendations and had the occasional sewer fire but considered that "normal". Go figure.
This may not be the answer you wanted to hear, but as far as I can tell you will always have the possiblity of fuel and a source of ignition (spark from metal on metal), so I would suggest you get rid of the source of oxygen.
RE: Explosion Proof Design
James D. Kieffer, PE
Kieffer & Associates Inc.
www.kiefferassociates.com