Fan Problems

at the first glance. I suspect your fan's bearing get cease and the shaft is turning againt the bearing. but then you mention that the bearing is very difficult to separate with the shaft, so I don't think that is the reason.

Corrosion might be a more logical explanation. You mention that the fan is operating in high humidity area and normally water or other dust collect outside of the shaft when a step(or resting ground) is there. The shaft get corroded and that's why there is a necking there.

easiest way to solve this is to just paint the shaft with anti corrosion material. establish a system to repaint and protect the shaft and also grease the bearing is the long term solution.

I read your reply for fan problems, I am a saleswoman in foreign trade for fan. I was puzzle for what technical parameterf the users will focus on and how I find the purchaser of industrial fan directly. As I am responsible in foreign trade. Could you do me a favor and give me some advice.

Thanks very much for your attention.

My MSN: mycndf@hotmail.com

Hi.zichau

thank you for your answer.

But I want to explain sth : the seperation of shaft from hub was difficult and we had to destry the hub. and the places on shafts that are incontact with bearing necked and had corrosion.

the material of shaft is C40 and the capacity of fan is 200000 m3/h

If the material is proper for this humidity condition or not?

whitch material is useful for prevent to corrosion and paint the shaft.?

what is the best method for install and disassemble the shaft and bearing and hub?

what is your recomended for maintenance?

If the bad mentenance is a source for this problem that I mentioned?

what is your mean about step(resting ground) in last answer.

I would be grateful for replying me.

I work in air conditioning and refrigeration here in florida. we have alot of problems with fan shaft corrosion with the salt air. when ever I come across a new unit either that i am installing or am servicing, I do some preventative work to make future servicing easier. to keep the fan hubs fom rusting onto the motor shafts, i take the fan apart and apply a graphite substance called "never seize" to the shaft and hub. it forms a protective coating and makes it a whole lot easier to work on later.

for separating the pulley from the shaft .,....

may be u can heat the shaft at the pulley side ..???

for preventing direct heating by oxy flame ..maybe u can apply high voltage to not affect the properties of the shaft..!!!

am I right ?? or it is a stupid idea?

Hi.

thank you for your answer.

But I want to explain sth : the seperation of shaft from hub was difficult and we had to destry the hub. and the places on shafts that are incontact with bearing necked and had corrosion.

the material of shaft is C40 and the capacity of fan is 200000 m3/h

If the material is proper for this humidity condition or not?

whitch material is useful for prevent to corrosion and paint the shaft.?

what is the best method for install and disassemble the shaft and bearing and hub?

what is your recomended for maintenance?

If the bad mentenance is a source for this problem that I mentioned?

what is your mean about step(resting ground) in last answer.

I would be grateful for replying me.

"why the shaft in places that are incontact with bearings are necked?"

There is three possible reasons for this, the first you have eluded to with the humidity and simple oxidization, High humidity will accelerate oxidation.

The second and most likely possibility is that the shaft and fan are made of dissimilar metals. This causes one metal to bleed into the other over time, ( I forget the term right now but it is much the same way a battery works). The erosion of metal near the point of contact of another metal is a prime symptom. In my experience fans are usually made of some lightweight material such as aluminum, and shafts are made of steel.

The third option is that pollution and dirt (which is typically acidic) has built up and dissolved the metal over time.

The easy cure for the first two is what number 3 replied. Any coating to slow down oxidation or provide seperation of the metals will slow the erosion.

For dissimilar metals, there are a number of cures, some of these are:

1. add a sacrificial metal much the same way they protect metal ships from corroding in salt water.
2. make sure the shaft and fan are made with the same metal. (correct cure)
3. add a teflon bearing (or other insulator) between the shaft and fan

For the third problem, regular maintenance to clean the fan will help

the bearings and shaft could also be "dissimilar Metals"

Yes, this is a very common problem in assemblies with dissimilar materials and corrosive conditions, and is called galvanic corrosion. It is the same principle that occurs in conventional batteries and, in some material associations, one would even light a bulb if connected to the different parts...:

1. Try some coating during or prior assembly, to isolate one material from another.

2. If possible, any galvanic protection in the shaft would help, if painting is not possible.

3. Periodic lubrication always help.

thank you for your reply.

the material og shaft is C40.

which material you suggest to use for shafts?

The material seems ok for the application. If its worth for the mechanical properties it has to have, let it be.

As another colleague stated, theres a "never-seeze" compound that's made from grease plus graphite, that works really well preventing rust, even in bolts attached to hot areas in jet engines!

If the tolerances of the bearings and the shaft allow, paint the shaft with off-the-shelf paint or primer from your local supplier, it will certainly solve your problem. I'm not familiar to this products sold abroad, except for some products used in aircraft, which I don't think you're gonna like too much

If the paint cannot be applied in the bearing contact areas, isolate these areas, paint the remaining parts of the shaft and apply never-seeze to the bearing contact areas.

Also, I didn't see if the fan itself is made of light alloy or something like this. If this is the case, the shaft is galvanically protecting your fan. Check if the paint can be applied to the fan to shaft contact area, in a way it can be eletrically isolated.

Rgds.