Maintenance of explosion proof motors by plant personnel. 10

[electricpete]

We have a very few explosion proof motors at our plant. I'm not very experienced in the requirements related to these motors.

I am aware the motor receives a certification from UL and that motor repair shops can also receive some sort of certification to work on UL motors.

MAIN QUESTION: Are plant personnel (with motor experience but no special UL certification) permitted to disassemble the motor to replace bearings?

Related/contrasting question: Can plant personnel open the terminal box to access connections (it seems to me that it obviously must be allowed for motor installation... removing terminal box cover to access terminations seems somewhat analogous to removing endbells for bearing replacement).


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(2B)+(2B)' ?

 

[ScottyUK]

Hi ePete,

It has the appearance of a flamepath, with a spigot and a broad flat face to slow and cool the explosion by-products. The cover fixings are a little more widely spaced than I would expect on a British design but that certainly doesn't mean it's wrong.

In what way is it different? Arguably it's not. Sometimes rules are just rules: I previously held a COMPEX cert but mine has lapsed and I doubt I will renew it in my current role. Do I still have the skills to make off a cable gland for use in a hazardous area? Sure, but I'm not allowed to: it's the rules.

 

[controlsdude]

Maybe call the local electrical inspector in your area. Also, your insurance carrier would usually have someone they use for insurance claims that happen in this area of expertise. I know in my area there is also some distributor that carry these explosion proof products that have someone they can direct you to contact for the questions you are asking.

 

[Compositepro]

Itsmoked, I do not believe that venting in order to limit over-pressure is actually one of the objectives of explosion-proof design. The pressure increase of an explosion in the casing is so fast that the rate of venting through gaps is insignificant. My understanding has been that the design philosophy is that the casing is designed to contain the maximum pressure without damage and that the joints are designed so that any leakage will be cooled by the long and narrow leak paths so it cannot cause ignition outside the casing.

Maximum explosion pressure of any mixture at ambient pressure is limited by the amount of oxygen in the air to about 150 psi.

 

[itsmoked]

Makes sense Comp. Thanks for that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[electricpete]

fwiw, I did notice there is an EASA webinar related to requirements for servicing hazardous location motors on 3/21/18 at a cost of $200 for non-members

https://www.easa.com/education/even...equirements-service-hazardous-location-motors

I might end up attending that webinar, will report back if I do.

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(2B)+(2B)' ?

 

[MagneticFlux]

"MAIN QUESTION: Are plant personnel (with motor experience but no special UL certification) permitted to disassemble the motor to replace bearings?"

1) In a nutshell, if it has a UL rating, it must be serviced by a UL registered shop to keep that UL rating. (they actually re-certify the equipment after service)

2) Can this type of work be "self performed"? IMO, this would be determined by the highest levels of management. Reason being, they are ultimately liable for the actions (or inaction) of their employees. Depending on your organization, you may have staff/engineers that are considered as 'competent' per local law(s) (NEC, IEC, etc...). That being said, your organization may authorize you to work on such equipment under your own or some sort of 'competent' supervision. Its all about liability!