Problem with water-tube boiler exhaust fan 1

[lucaspenalva]

Hello there,

So this power plant has this exhaust system working for 10 years. They bought the fan design project and built it themselves.

Fan specs (design):
770 rpm
194 bhp
183 kgf.m
146.000 m³/h

Motor specs
6 poles
250 hp
148 kgf.m
nominal amps 340A

Pulley specs
600mm - 390mm

They don't like pulleys and decided to remove it - however, without doing any calculations if this would work or not.
Its now direct coupled but not working effectvely - when it reaches ~500 rpm, amps go 340A+ and motor stops.

Back to pulley or go with gear reducer?

Image of the system is attached

 

[DrRTU]

This is an induced draft fan not exhaust fan. You have presented a small fraction of information required to solve this. The fan / motor combination must be mated to the application over the complete operational envelope. This must include startup and shutdown. The statement of they don’t like belting is very odd. To change from belting to direct coupled requires proper engineering. Fan curves are very important due to this fan will be subject to varying density and flow rates. I suggest they hire an independent AE firm or deal with the boiler mfg.

 

[LittleInch]

Agree you need to get the fan speed load curve and the motor speed load curve. Sounds like the motor doesn't have enough low down torque to accelerate the fan so the motor is becoming overloaded and very high slip.

There was a good reason the pulley system was there. Ever heard of the phrase "if it isn't broken don't fix it?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.