Boiler ID Fan 2

[Bigbob1941]

We have a 400HP, 480Volt, ID Fan being installed in a bag house for a 100,000 lb/hr boiler. The fan is made by Clarage and they have specified dampers on the discharge side of the fan only. There are no dampers on the inlet. The motor is powered by a VFD. It's designed so the outlet dampers will be wide open and the speed of the fan will be controlled through the VFD.

Is it possible to only have an outlet damper and not inlet dampers on an ID Fan? Wouldn't the lack of inlet dampers make the fan draw maximum current and pressurize the housing of the ID fan when starting?

 

[pablo02]

As I recall, this is typical of an ID fan driven by a VFD...

The VFD will start the fan and gradually come up to (as dictated by control program) speed --the motor starting current and initial air flow are significantly reduced compared to the non-VFD starting methods...

 

[quark]

If it's a radial centrifugal fan, you won't have any problems. If it's axial fan then you have to have only suction control. However, your variable speed system will take care of these problems.

Just take care about the ramp up time during starting of the fan.

You should also note that the power drawn by any fluid handling device is proportional to the mass flow rate of the fluid across the device. So when you partially close the discharge, less fluid will be moved and so less power consumption.

Regards,

 

[Bigbob1941]

I think your answers have solved my problem. Thank you very much for the assistance.

 

[yogibear1]

Bob: Note that this motor should be inverter duty. Your Electrical Engineer will have specified a VFD drive that is compatable with this specific type of motor. These drives go from very simple to very complex depending upon your particular needs. If your staff ET is not familiar with these drives it is time to send him to school or hire that service (usually from the vendor/installer).