First things to check are:

1. Are all springs properly matched and not broken?
2. If there are any rubber side sway bumpers ensure they are not directly touching the screen. There should be a small clearance when stopped.
3. Make sure the there is ample clearance around the screen and no part is hitting the structure during the operation of the screen.
4. Make sure that all counterweights are properly balanced. When you say they are welded on - that is a major concern for me.
5. Have you talked to the screen manufacturer?

■

What is 'working great'? If one pair of diagonally opposed corners is almost stationary then the deck is almost confined to roll about those corners. Just think about the possible degrees of freedom. The most improbable situation is that the counterweights are diametrically opposed: which situation could cause this unusual mode of vibration. I doubt that any screen manufacturer would get involved in such a scenario. Gary's concern about welded counterweights says it all. If the weights are not accurately located then the 'most improbable situation' mentioned above is likely to occur to some extent. Development of a roll axis will encourage interference with stationary bits.

Stand clear because the weights are going to fly away sometime.

There are more cowboys in the quarries than on the prairie! ■

Originally Posted by Sir Pans Alot

Good evening all!

I am hoping that you can help me with an issue a friend is having on his 2 bearing center shaft double deck screener. (Not sure if that is the right terminology as I am a trommel guy). Single pully drive and offset weights welded onto each disk.

So the issue is that the top left and bottom right of the screen deck is working great, but the bottom left and upper right is barley vibrating and not shooting the rocks off. It is like the material travels diagonal across the decks. It is strange how it is just not one side that is not working, but kiddy corners.

I have tried searching trouble shooting guides for factory decks and this forum but cannot find out where to start? Any idea's would be very much appreciated!

Thank you!

==================================================================================================== ==========

Just what are you screening with this thing???????????

Is the screener supported with airbags or springs or is it a wire rope cable suspended screen? It may be that the old wire rope cables need to be replaced.

Welded counter weights are a big no no!!!!!!!!!!! its entirely possible that the shaft half is fighting against itself with weights that are at complete oppossition to each other on the opposing half shaft rather than acting in tandem to throw material back up the screen deck.

AS my dear friends have so correctly stated "you have trouble in River City and it has nothing to do with pool tables or sheep ranchers.

What is the tonnage per hour or per minute being pushed across the screener??

Are the two screen decks rubber coated?? This screen has an elliptical orbit BTW.

What are the sieve sizes of the two screens?, this needs answering first.!!

Has any one checked to see if the upper or lower screen decks weaving/welds is/are broken or breaking away from its anchor points in the side plates??

Most if not all elliptical screeners pull the material back up the screen deck with the elliptical orbit going clock wise as you face the right side plate to

screen material as it is fed to the top of the screen deck.

What maintenance has been done on this beast lately? have new drive belts been installed??

Is this elliptical screener fed by a hopper draw point or by a belt conveyor?

Is the material being fed evenly across the top of the screener?-A partially plugged chute will cause this if there is a large build up

of material on one side of a chute.

If the upper or lower screen deck is blinded by material its not being properly maintained and kept clean by washing it and will cause the screener to miss behave

Your friend could have a very large basket of problems with this screener,especially if the unit has rubber vibration absorbers

that are plugged with dirt not allowing them to move properly and as a result creating huge forces that are transmitted when

the screen is at operating speed affecting its orbit as Gary has mentioned.

Your friend is dealing with physics reacting to an unknown or unseen cause like broken side plates or broken screen decks or screen deck mounts,

or caused by a maintenance that was not done properly-I.E. overtightened V belts, V belts that are not from the same lot group-a big no no there,

or a blinded screen deck which is a sign of a much bigger problem with a two deck elliptical screener.

Your friend has to start at the very beginning and clean and clean and inspect the screener from bottom to top as it sounds like a side plate is cracked and the G forces created by the screener at speed are being transmittted diagonally IF WORSE COMES TO WORSE.

I hope for your friends sake it is simply an overtightened set of V belts but if the opposing counter weights are not exactly in the same position WOE is the word here.

I hope that he has these welded weights removed and installed properly.

John you are so right about cowboys in quarries!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Help us to help us help you solve your friends predicament or no basket of fuzzy four week old german shepard puppies or Maine Coon Cat kittens will be given as a door prize. ■

let's give this problem a go:

1. how old is the screen?

2. has any work been done on the support decks?

3. if welded on, or rebuilt new and refitted...the may not be absolutely SQUARE

4. if not square = screen will RACK

5. if not square = screen will SQUIRREL down the deck in a GOOFY pattern ...side to side or other

6. vbelt drive belts may not if ALIGNED and be pulling obtusely on an angle vs square and aligned

7. broken springs = YEP = OLD vs new or cracked and compressed due to age = poor floatation and erractic material action on the deck

8. loose wirecloth will cause this also

9. wirecloth should be drum head tight....caution on the side of overtight vs loose

10. check screen RPM...tell the wirecloth openings and I will tell you the SPEED/STROKE AND SLOPE Needed to do the job correctly.

Yours in GOOD VIBRATIONS....

George Baker

MODERATOR

[*]Are all springs properly matched and not broken?[*]If there are any rubber side sway bumpers ensure they are not directly touching the screen. There should be a small clearance when stopped.[*]Make sure the there is ample clearance around the screen and no part is hitting the structure during the operation of the screen.[*]Make sure that all counterweights are properly balanced. When you say they are welded on - that is a major concern for me.[*]Have you talked to the screen manufacturer?[/LIST][/QUOTE] ■

Originally Posted by Sir Pans Alot

Good evening all!

I am hoping that you can help me with an issue a friend is having on his 2 bearing center shaft double deck screener. (Not sure if that is the right terminology as I am a trommel guy). Single pully drive and offset weights welded onto each disk.

So the issue is that the top left and bottom right of the screen deck is working great, but the bottom left and upper right is barley vibrating and not shooting the rocks off. It is like the material travels diagonal across the decks. It is strange how it is just not one side that is not working, but kiddy corners.

I have tried searching trouble shooting guides for factory decks and this forum but cannot find out where to start? Any idea's would be very much appreciated!

Thank you!

It is a typical natural frequency problem - torsional frequency. Get it tested and adjust the running speed.

Regards

Ziggy Gregory ■