The following video from Cooper Crouse Hinds shows the importance of quality control and proper installation practices required when using Explosion Proof enclosures. http://www.crouse-hinds.com/smart/Videos/Haz%20Loc%20Equip.wmv. However when viewing the video I find that the following two sequences tend to reinforce in my mind why we used Intrinsic Safe practices at my former employer in the oil sands.
There are two places in the video that reinforce to me how vulnerable Explosion Proof practise are to human failure. The first of these is in the discussion on the Importance of Construction & Installation Practices at the 5:40 to 7:00 minute mark of the video. The second piece is a continuation of the video between the 7:00 – 9:00 minute marks reinforces the need for proper maintenance of the enclosure.
It is interesting that a single scratch on the face of the flange can eliminate the effectiveness of the enclosure yet I have seen numerous enclosures that do have scratches across the full flange face (easy enough to do if something accidentally drags across the surface). Of course replacing an explosion proof enclosure is not a trivial task, since all the connections need to be pulled back (you are using couplers directly threaded to the enclosure aren’t you? (Electrical code allows you to place a coupler between the enclosure and the seal in most applications)), and then reconnected, several hours work and potential lost production time.
What is not shown, though can easily be surmised is that if ALL the bolts on the enclosure are not properly installed and with the minimum required torque this is worse than the small scratch used to such effect in the video. Most of the people I talk to indicate that if an explosion proof box is opened for maintenance after the project ‘punch list’ is complete it is very unlikely that all the bolts have the proper torque, if they have been more than finger tightened or installed at all.
You may not think this has anything to do with Industrial Networks, however we DO need to install equipment in Hazardous areas and fortunately there are IS options available.
If the video does not make you consider the use of IS and its support for live working as an alternative, hopefully you will consider using the video at a safety meeting to reinforce with your workers the importance of maintaining the integrity of your Explosion Proof enclosures. We have had enough ‘exciting news’ as a result of explosions and accidents in the last while.