minimum motor sealing requirement for coal fired power plants

[Tmoose]

We provide some motorized equipment for use in coal fired power plants. Even on indoor installations Pulverized coal dust is everywhere, even in the real clean ones. The question comes up as to whether WP2 with filters or even TEFC sealing is required to protect the windings, etc. Quite a price difference on a 1000 HP motor.

I'm interested in real life experiences.

thanks

Dan T

 

[rmw]

I would pick a TEFC motor every time if one were available in the size I needed. Filters can and will plug and are dependent on good maintenance practices. Still, lots of open motors in coal plants on larger drivers. So....

rmw

 

[MJCronin]

A better forum for this question would be an electrical power/ electrical motor forum.

My understanding is that the motor type must follow the rules contained in NEC 500.

As I understand the problem, the issue is that few power plants chose to designate hazardous areas within the facility and therefore the motor selection becomes a problem.

My opinion only

-MJC

 

[ccfowler]

Tmoose,

Coal dust is only a problem in and immediately adjacent to coal handling facilities and equipment. The "everywhere" dust that your are probably addressing is flyash. Coal dust is a BIG issue because of the risk of fire, but flyash is inert and only a big nuisance.

Coal dust control ALWAYS gets really serious attention, and everything involving coal handling must be and is treated with every possible concern for fire and dust "explosion" hazards. Coal from different sources can have widely differing dusting characteristics and differing requirements for proper, safe handling. This, along with differing firing characteristics, is why plants do not change coal sources without very careful evaluation and preparation.

You can safely presume that no coal fired power plant will allow any non-safety-compliant equipment anywhere near coal dust areas. Everyone in a coal fired plant gets paranoid about coal dust safety issues. Since you are apparently not familiar with this aspect of coal fired plant life, I very much doubt that your equipment has been going into coal handling areas.

I agree with rmw that TEFC motors are generally a good first choice, but there are very good reasons to use other types as well. TEFC motors tend to run slightly higher internal temperatures, and many places in power plants have very high ambient temperatures where open drip-proof motors can work well at much lower cost. Most old power plants (roughly first half of 20th century) used open motors with very good results despite abundant flyash. Where necessary "custom" sheet metal guards or shields were installed to protect the open motors rather than using open drip-proof motor construction. Those old motors were VERY rugged and VERY conservatively rated. I've seen some of those old beasts carry nearly double their rated load without overheating.

 

[rmw]

I had one client that installed nothing but those old U frame motors in his plant and would buy any one he could find surplus anywhere anytime. He had plenty of dust and ash in his plant.

The only TEFC motor I can recall that he had was a boiler ID fan drive that came with the entire back end package.

rmw

 

[MJCronin]

This not a subject matter for the "whatdoyathink" method of engineering.

http://www.ldpi-inc.com/main-site/technical/articles/class-II.htm

 

[Tmoose]

here is an update of the NFPA-85-2007 requirement.

Dan T

 

[7anoter4]

See:
thread237-270000