Screw conveyor sagging

[Dan12345]

I was called to work on a screw conveyor that is sagging. I have very little experience in working with them, so any help is appreciated. The auger is made from what looks to be heavy wall pipe, about 10" dia, and about 20' long. There are no supports in the middle, just one on each end. The trough is an asme pressure jacket as steam is injected into it, and is only supported at the ends as well.

The auger is digging into the trough and causing some bad galling. The galling is happening not in the middle so much, but heavily between the middle and the supports, so about 1/3 of the way in from the supports.

I am just trying to see if anyone has any suggestions on what could be done to remedy the problem. Since the auger is not scraping in the middle could that be a sign that the trough itself is sagging? or could the auger be sagging as well. We are still in the process of figuring things out, I was thinking of pulling a string across the trough to see if it was indeed the trough or the auger. any other sort of methods? How about for checking straightness of the auger? We were thinking of a dial indicator, but we could only get so far as the flights would knock it off.

Well any help is appreciated.

Thank you

Dan

 

[micalbrch]

As you are asking for any help, I dare to answer although I only have some experience with double shaft augers in WWTPs. Sagging of the auger shafts can be caused by bearing failures (depending upon the kind of bearing you have) or by wear of the screw flights. Usually the gap between screw blade and trough is very small. If the screw blades are worn the whole shaft will longer be supported by the trough but starts to swing and this can cause the galling and - worst case - shaft breake.

 

[Dan12345]

The bearings on the supported side are graphite, and one is a pillow block. The pillow block bearing had some galling on the bottom side of the bearing. The top half of the bearing was smooth. I dont know if that would be a cause of the shaft sagging, or if that would happen when the flights would dig into the trough.

 

[berkshire]

Dan,
When the screw is running, can you observe any up and down oscillation of the screw?
Also is this a pillow block at the drive end and a radial bearing in the end cap of the conveyor, or is the conveyor open ended with a hanger bearing.
The most obvious cause of the problem would be wear in the bearings allowing the auger to sit below its design position in the trough and touching the case.
I suspect that it is not that easy, or you would not be asking for help.
Another thing to check would be to see if anybody has turned the steam pressure up on the jacket even for a short while. This may have bulged the trough.

Without more information on the size and style of the conveyor I cannot offer more suggestions.
B.E.

 

[Dan12345]

B.E.,

I myself haven't been able to see the screw run. The system itself is a blentech jacketed system. It cooks onions by turning about 1-1/2 revolutions forward then backward 3/4 rev. the driven and supported side have a radial bearing as well as a pillow block. The trough has a hole on the driven side that is piped to so all the onions fall into.

I suppose it is likely the trough could have bulged, but it is made of 3/8" thk. T304 ss. It is definitely worth looking into though.

Like I said, I know very little about conveyors, so unfortuneatly I am not able to provide anymore information at this time.

Thanks for your reply, and when we get it figured out, i will update the status, incase anyone cares for the future.

Dan