Conduit Seal between explosion proof motor and pressurized enclosure for Class I Division 1 location.

[paulbr]

We are at design stage now. We need to run conduit between pressurized enclosure and explosion proof motor. Distance is about 48". Do we need two conduit seals, one at each end of conduit, or just one at pressurized enclosure will be enough?
Is explosion proof motor still enclosure Per 501.15 (A)?
Any suggestions?

 

[rbalex]

We are at design stage now. We need to run conduit between pressurized enclosure and explosion proof motor. Distance is about 48". Do we need two conduit seals, one at each end of conduit, or just one at pressurized enclosure will be enough?
Is explosion proof motor still enclosure Per 501.15 (A)?
Any suggestions?

Yes, the motor's enclosure is still an enclosure.

Assuming the pressurized enclosure is sealed per Section 501.15(A)(2) there are still a couple of questions about the motor'enclosure:

• Is the motor terminal box factory sealed separately from the motor chamber itself?
• What size is the conduit entry to the motor terminal box?

 

[paulbr]

Conduit entry to motor terminal box is 1.25".
We will try to investigate if motor terminal box factory sealed separately from the motor chamber.
Please, elaborate on "motor's enclosure is still and enclosure".
Motor terminal box does not contain components listed in 501.15 (A) (1). Do you think motor temperature may be factor that will require seal?

Paulbr

 

[rbalex]

Conduit entry to motor terminal box is 1.25".
We will try to investigate if motor terminal box factory sealed separately from the motor chamber.
Please, elaborate on "motor's enclosure is still and enclosure".
Motor terminal box does not contain components listed in 501.15 (A) (1). Do you think motor temperature may be factor that will require seal?

Paulbr

You asked if it was an enclosure and I said it was. You probably meant to ask if it needed to be sealed per Section 501.15(A). Had I understood it correctly at the time, the answer would have been, "It depends." and I would still have asked the two questions.

The conduit entry question was to determine if Section 501.15(A)(1)(2) applied. it doesn't appear to.

Rather than asking about factory sealing, I should have asked if the motor was single-phase or three-phase. (Single-phase is unlikely with a 1-1/4" conduit entry) Single-phase motors often have a switching mechanism and a seal would be required either external to the motor terminal box or a factory sealed motor terminal box. If it is three-phase a seal may be unnecessary. The internal temperature can indeed be a factor. It usually isn't, but it should be checked.

 

[paulbr]

This is three phase motor. Temperature rise marked on nameplate of the motor is 54C. Process engineer on the project confirmed that auto-ignition temperature is much higher than 80% of (54C + ambient). Seems that only one seal is required. Do you agree?

 

[rbalex]

This is three phase motor. Temperature rise marked on nameplate of the motor is 54C. Process engineer on the project confirmed that auto-ignition temperature is much higher than 80% of (54C + ambient). Seems that only one seal is required. Do you agree?

Yes. A single seal at the pressurized enclosure per Section 501.15(A)(2) sounds reasonable.