Existing Ventilation Fan Issues -- Looking for industry standards re: installation and configuration

[henerythe8th]

I have inherited (new job) a fairly large ventilation fan system that has two fans -- I'll refer to them as Fan 1 & Fan 2. They operate one at a time and are dampered out when not in operation.
Fan 1 -- I consider a good installation and Fan 2 -- I believe is a poor installation.

I have basic installation instructions for the fan that I consider poorly installed.
I have contacted the manufacturer of both the fan itself and the company that assembled the fan skid, neither of them was of any help.
I'm looking for industry standards, codes, handbooks, etc. relative to the installation methods of large fans and their configuration.

These fans are rated at about 36,000 cfm and are driven by 100 (Fan 1) and 60 (Fan 2) hp electric motors. Both units have been in service about 20 years.

Fan 1 is installed with flexible couplings at both the suction and discharge, has a large concrete foundation and the skid has grout placed between the steel skid base and the concrete foundation. This fan runs smoothly and has had few problems over it's life.

Fan 2 has steel duct connected directly to both the suction and discharge (no flex connections). This skid is on a concrete foundation, does not have a grout interface between the steel structure and the concrete foundation and appears to have some missing shims. This fan has experienced a number of issues over the course of the last year or two; bearings in electric motor failed, fan shaft bearings failed, fan shaft replaced, and a cracked adjustable motor base.

I want to substantiate the changes I consider essential to long time health and continued operation of Fan 2.
Any recommendations?

 

[willard3]

A good place to start is The Air Movement and Control Assoc. (AMCA) standards

 

[krb]

It may be overkill in your situation, but I use API 686 Recommended Practice for Machinery Installation and Installation Design. It has good information on some of the issues you describe.

 

[henerythe8th]

Thank you for the help so far!

 

[capliard]

Any idea on the level of vibration the fans are experiencing when in operation ?

I use this on Iphone to monitor Vibrations : Link

A stalled condition produces vibration and will damage equipment at some point.

Are the fans identical apart from rated HP? If so, why are they different? If not, why is rated HP different?

Axial fans or Centrifugal fans ?

The solution might be to stop pouring money on the ''bad'' 60hp fan and put a VFD on the 100HP fan to achieve required point of operation.

CAPL



Ingenieur Minier. QuTbec, Canada.

 

[henerythe8th]

The fans are not stalled.
They are periodically monitored for vibration.

The 100hp motor for Fan 1 is currently limited via a VFD.
The 60hp motor for Fan 2 does not have VFD.

The fans are not identical. Because they were purchased at different times and circumstances.

Whatever the action with the fans I need documentation...

 

[berkshire]

henerythe8th
Do you have any service logs for either of these fans ?

It would appear from your comments that you do not have an issue with Fan 1

Whilst I would agree that the ducting on Fan 2 should have flex connectors or canvas joints, sometimes but not always,
installers connect direct and get away with it. Examine the connections and see what they are : Slip joint with pop rivets or self tapping screws , S & drive joint, Duct Mate flanged connection, or Rigid angle iron paired flanges.
S and drive joints have a certain amount of flexibilty to them, and can tolerate some vibration for a while before they fret holes. The other connectors will only tolerate very mild vibration , they will fret fastener holes. Check for noises in the ducting especially at start up . If the fan casing is restrained from vibrating by the ducting, that will impose additional loads on your fan bearings and may be a source of early failure. Good luck.

B.E.


You are judged not by what you know, but by what you can do.