Re: Uneven Vibration
Originally Posted by TexasAsphalt
We have an old screen deck that was put back into service a few years back. No markings or identification found anywhere on the screen deck. The screen has been running well but a couple of weeks ago it started vibrating unevenly. It is a inclined deck with a shaft straight through, bearings and weighted flywheels on each side, sheave and belt drive on one side. What it is doing is the rise and fall of the vibration cycle is alternating from one side to the other. So when one side of the deck is rising the other side is falling. We have check the weighted flywheels to ensure no weights have shifted or dropped and that the flywheels have not shifted. we have checked the springs for fatigue or cracks. We have checked for clearance problems or structure failures. We have checked the bearings for play or failure. I have not seen a screen deck dance like this before. Does anyone have any thoughts on what might be causing this problem. Thanks.
Check for natural vibration - screen and supporting structure
Regards
Ziggy Gregory ■
Checks At Screen
Hello,
if possible, check whether the vibration disbalance is itself a cyclic process (regular time interval for ame positions of disbalance), then check back vs. all rotating (i.g. prb. inducing) processes, whether you find a common factor. Pls. check also, whether the disbalances starts always at the same place and try to get a wider picture about start-up and close-down situation. Doesn't it vibrate quite irregularly when closing down?
My guess is however a) the oscillators have a (slight?) disbalance / out of tune or b) spring characteristics are (slightly) different from previous condition when everything was running smooth. Springs are undergoing such complicated internal stress cycles from the shaping alone --> there comes the problem of fatigue into play, and you mentioned a timespan of years. Any chance to have the springs changed / checked by a reliable / knowledgeable supplier somewhere around?
L b n L: Does the starting of the disbalance coincide in time with some event / changement happening in the vicinity of / at that machine? Call it an collision, new operator, overload, breakdown, sthg. else.
Regards
R. ■
Wobbling Screener
Originally Posted by TexasAsphalthref="showthread.php?p=78211#post78211" rel="nofollow">
We have an old screen deck that was put back into service a few years back. No markings or identification found anywhere on the screen deck. The screen has been running well but a couple of weeks ago it started vibrating unevenly. It is a inclined deck with a shaft straight through, bearings and weighted flywheels on each side, sheave and belt drive on one side. What it is doing is the rise and fall of the vibration cycle is alternating from one side to the other. So when one side of the deck is rising the other side is falling. We have check the weighted flywheels to ensure no weights have shifted or dropped and that the flywheels have not shifted. we have checked the springs for fatigue or cracks. We have checked for clearance problems or structure failures. We have checked the bearings for play or failure. I have not seen a screen deck dance like this before. Does anyone have any thoughts on what might be causing this problem. Thanks.
As you have an inclined deck screen it has an elliptical orbit,
first I have to ask if you have used stroke card to check the screener????????????????????????????????????????????????????????????
You have to do this before you go any further as this elliptical screener has issues!!!!!!!!!!!!
As far as the springs go nothing can be deterimined unless and until the exisiting springs
are measured in comparison to A NEW UNMOUNTED SPRING-that is the only way.
Thats the nice thing about air bag supports as they never go bad unless the bag tears.
You cannot make any assumptions until and unless you use a stroke card to determine the
screens behavior.
A lot of things could be wrong but it sounds as if one of the connecting shafts to the side plates is bad and the screens
orbit is distorted.
Until you use a stroke card ON BOTH SIDES of the screener all is moot!!!!!!!!!!!!!!!!!!!!!!!
Attachments
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Uneven Motion On Your Screener.
SOME things to consider:
1. When you say dance...this means erratic
2. Erratic motion means unbalanced motion
3. Do the stroke check, A must, to confirm the circles are identical on all 4 corners and at each side at the centre above the shaft position
4. If all the circles are kinda identical...it means the machine is in a balanced configuration
5. if most look kinda the same but, one corner looks way different...the problem is in that goofy corner
6. check for OLD COIL SPRING...could be it....but, replace all springs at once
7. could be running too fast, will make the screen DANCE erractlcally...DO tachometer check for speed and let us know
8. could be wrong sheave on screen or wrong sheave on motor or wrong vbelt profile for the sheave section.
9. one side up other side down, describes what will call "RACKING" Or a twist which typically identifies a loose support member under the wirecloth, which is moving on its own axis vs with the rest of the machine and would act as you describe.
10. CHECK all around for cracks.
11. if unit if overloaded and material is not moving on and off/ then we create a static load on the screener when operating and it will "HUMP" up and down vs doing a nice circular motion and a nice free floating action as designed.
12. Sometimes old machines need a little TLC.
let us know how she goes. Izaharis is correct is asking to do a stroke check to confirm it is balanced for sure.
Wishing you good vibrations......George Baker MODERATOR
Originally Posted by lzaharisfirst I have to ask if you have used stroke card to check the screener????????????????????????????????????????????????????????????
You have to do this before you go any further as this elliptical screener has issues!!!!!!!!!!!!
As far as the springs go nothing can be deterimined unless and until the exisiting springs
are measured in comparison to A NEW UNMOUNTED SPRING-that is the only way.
Thats the nice thing about air bag supports as they never go bad unless the bag tears.
You cannot make any assumptions until and unless you use a stroke card to determine the
screens behavior.
A lot of things could be wrong but it sounds as if one of the connecting shafts to the side plates is bad and the screens
orbit is distorted.
Until you use a stroke card ON BOTH SIDES of the screener all is moot!!!!!!!!!!!!!!!!!!!!!!!
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Re: Uneven Vibration
Originally Posted by TexasAsphaltWe have an old screen deck that was put back into service a few years back. No markings or identification found anywhere on the screen deck. The screen has been running well but a couple of weeks ago it started vibrating unevenly. It is a inclined deck with a shaft straight through, bearings and weighted flywheels on each side, sheave and belt drive on one side. What it is doing is the rise and fall of the vibration cycle is alternating from one side to the other. So when one side of the deck is rising the other side is falling. We have check the weighted flywheels to ensure no weights have shifted or dropped and that the flywheels have not shifted. we have checked the springs for fatigue or cracks. We have checked for clearance problems or structure failures. We have checked the bearings for play or failure. I have not seen a screen deck dance like this before. Does anyone have any thoughts on what might be causing this problem. Thanks.
Dear Mr.TexasAsphalt,
Is there any cardon shaft used ? Could you please post the General Arrangement drawing of the screen ?
Regards, ■
Uneven Vibration
Hello,
We have an old screen deck that was put back into service a few years back. No markings or identification found anywhere on the screen deck. The screen has been running well but a couple of weeks ago it started vibrating unevenly. It is a inclined deck with a shaft straight through, bearings and weighted flywheels on each side, sheave and belt drive on one side. What it is doing is the rise and fall of the vibration cycle is alternating from one side to the other. So when one side of the deck is rising the other side is falling. We have check the weighted flywheels to ensure no weights have shifted or dropped and that the flywheels have not shifted. we have checked the springs for fatigue or cracks. We have checked for clearance problems or structure failures. We have checked the bearings for play or failure. I have not seen a screen deck dance like this before. Does anyone have any thoughts on what might be causing this problem. Thanks. ■