explosion proof enclosures

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gunthman

Member
Q. Is a machine shop allowed to drill and tap any type of explosion proof enclosure and assume that it is safe.? How does this affect the UL and or manufacturers rating of the enclosure.? Should / does the enclosure need to be re-certified.?

Thanks,

Charles Guenther
Electrical Planner / Estimator
Sunoco Oil Refinery
 

ryan_618

Senior Member
gunthman said:
Q. Is a machine shop allowed to drill and tap any type of explosion proof enclosure and assume that it is safe.? How does this affect the UL and or manufacturers rating of the enclosure.? Should / does the enclosure need to be re-certified.?

Thanks,

Charles Guenther
Electrical Planner / Estimator
Sunoco Oil Refinery

I would never, ever pass an explosion proof enclosure that was modified to that extent, and I am pretty liberal about modifying listed products. When you consider what the enclosure is there for (to contain internal explosions), I would require a feild evaluation from UL (or other NRTL). I have seen videos of the manufacturing and testing processes for Class 1 equipment, and can tell you that the engineering and the care put into the products is remarkable.
 

barbeer

Senior Member
ryan_618 said:
I would never, ever pass an explosion proof enclosure that was modified to that extent, and I am pretty liberal about modifying listed products. When you consider what the enclosure is there for (to contain internal explosions), I would require a feild evaluation from UL (or other NRTL). I have seen videos of the manufacturing and testing processes for Class 1 equipment, and can tell you that the engineering and the care put into the products is remarkable.

My thoughts exactly!:smile:
 

lpelectric

Senior Member
gunthman said:
Q. Is a machine shop allowed to drill and tap any type of explosion proof enclosure and assume that it is safe.? How does this affect the UL and or manufacturers rating of the enclosure.? Should / does the enclosure need to be re-certified.?

Thanks,

Charles Guenther
Electrical Planner / Estimator
Sunoco Oil Refinery

As an inspector, I would fail this under unacceptable field modification.
 

nakulak

Senior Member
It might be prudent to consult the manufacturer and ask them what they suggest for a remedy (if needed) (if the modification was minor and they felt it was compliant then you would also have a record paper trail)
 

LJSMITH1

Senior Member
Location
Stratford, CT
Explosion Proof enclosures are specially designed to handle internal pressures. Wall thicknesses, gussets, and radii all are designed to make sure the box does not turn into shrapnel if it explodes. Most EP enclosures have special threads (on covers, plugs, etc.) that allow gasses to escape at a controlled rate.

Modification of the enclosure may affect the way the explosion is controlled. My advice would be to contact the manufacturer and ask them to certify the modification. In most cases, they would do a test to confirm that the product still meets the requirement. However, you still may need a UL field evaluation (along with a mfr certification) to prove that there is no ill effect from your modification.

Good Luck!
 

tkb

Senior Member
Location
MA
Crouse Hinds has many Class 1 Div 1 enclosures that are listed for field machined taped conduit openings.

They are mostly the larger size boxes.

I don't think that all of the boxes are listed for field tapping.
 
gunthman said:
Q. Is a machine shop allowed to drill and tap any type of explosion proof enclosure and assume that it is safe.? How does this affect the UL and or manufacturers rating of the enclosure.? Should / does the enclosure need to be re-certified.?

Thanks,

Charles Guenther
Electrical Planner / Estimator
Sunoco Oil Refinery

The enclosure manufacturer specifies the allowed locations, type(NPT) and size of the allowed openings. In the absence of those, THOU SHALL NOT MODIFY XP ENCLOSURES IN ANY MANNER.(Second cardinal sin of electrical installations.):D
 

megloff11x

Senior Member
This is why it's so expensive to deal with hazloc!

If you think this is bad, try finding a listed sensor. Take $10-$100 device and pay UL, TUV, or CSA $10000 to test its ability to start fires.

Reminds me of when NORAD modified their comm wiring and lost all of their EMP protection.

Matt
 
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