I'd like to hear your opinions on having a new wheel and shaft assembled. Is it best to use a carbon steel blade, or stainless?

I heard no to stainless because of it's expansion rates. Hot fan applications...

We're having some issues with drives belts too which I'll start another thread on.

Thanks,

Why use stainless, is it corrosive environment?

Yes, very much so. This is what we call a tailgas fan. It contains a flammable gas, steam, and parts of sulphur...

I would just as soon use carbon steel. Some of these fans don't have alot of room axially in them, and the expansion rates I believe are more than carbon steel. Could create a rubbing with the blade.

Here is a photo of the fan I'm having heat problems with. I wish they would trash these used blades, instead of re-using them...Here's the culprit...See pic

I've never seen problems on shut-downs and start ups when using new 1/4 thick blades, in hot fans.

Anyone have a different experience?

Rod,

Coefficients of thermal expansion:

carbon steel 6.33 x 10^-6
304 stainless 9.6 x 10^-6 up to 212 deg f
9.9 x 10^-6 from 213-600 deg F.

So you can expect about 1.5 times as much growth. It gets worse the hotter it gets.

304L (Low Carbon) is more commonly used for fabrication but I don't have data for that. 316 is about the same.

Did those blades start at 1/4" thick? How thick are they now and after how long?

Rod,

I have been doing some work at a plant that uses both stainless and carbon steel blades in the tailgas stream. I agree that a new fan runs a lot better than one with 6 months or more time on it. We clean the dickens out of them, and they just get worse. You can balance them today and next week they are showing signs of high vibes again. The stailnless ones do last longer than carbon steel, but we don't have any areas that are too close so expansion isn't a problem. Carbon black coating is our biggest problem. I believe these folks went to carbon steel simply from a cost stand put.
I don't think they have ever said which one lasts longer.

Danny,
From the picture, that is typical of one in the tailgas stream (that stuff is nice around one with a leaking seal). The supporting frame, catwalk, and everything around looks similiar. The rust flakes off in big palm size areas.
The catwalks bother me.

Dave