Re: Excessive Vibration Problem
George
It sounds like a typical natural frequency problem of the structure - structure should be checked for a natural frequency and the screens detuned. ■
Right On
CORRECT you are Ziggy. ■
Re: Excessive Vibration Problem
Originally Posted by George Baker
10 big 8x20 Horizontal flat LINEAR DRIVE screens all on the same floor doing the same TPH. The problem described was excessive vibration, MEGA SHAKING OF THE SUPPORT STRUCTURE IN, ON AND AROUND THE SCREENING FLOOR.
Could I help with any suggestions.
''''''''''''''''''''''''''''''''''''''''
Many many number of times over my 32 years in this business, I have flown out to distant locations on this exact type of problem to try and troubleshoot what the problem and or cause might be.
Here I suggest:
1. All units here are running at the same RPM, ALL 10 units together.
2. What quite often occurs is the machines all try to SYNC up to each other RPM and you actually get a RAMPING UP AND RAMPING DOWN OF flexation in the structure.
3. The question is: is it the structure that is not engineered with enough safety factor in it or are the machines basically causing the problem with similar RPM's all running kinda the same all on the same beams
4. We quite often have the customer change the RPM of one two or three of the machines to STOP the machines from TRYING TO SIMULATE each others rythym. This quite often STOPS this excessive vibration and eliminates the problem.
5. Sometimes we have to THROW some more X BRACING steel beneath the structure supporting the units to tighten up the SUPPORT.
6. Sometimes we find the support beams DO NOT carry straight down to solid concrete footings and causing excessive vibration to everything in the area.
I actually got this senario on a PM but, was unable to reply due to wrong email address or whatever, so I will try to address here generically.
The safest way is to apply screens with direct deck excitation and static housing.
As it seems to late in your case you may try frequency converter to find out whether it is a natural frequency issue. If not, replace coil springs with ROSTA insulating mountings. If not enough, a reactive compensating mass between the screen and floor will be necessary. ■
Re: Excessive Vibration Problem
Kris
Rosta mounts will stiffen the screen in horizontal direction and therefore you will change the natural frequencies. Compensating mass/frame would solve the problem but it would add height so your feed and discharge chutes would have to be modified and that could be difficult to do in an operating plant.
regards
Ziggy ■
Screening The Issue
Originally Posted by ziggyRosta mounts will stiffen the screen in horizontal direction and therefore you will change the natural frequencies. Compensating mass/frame would solve the problem but it would add height so your feed and discharge chutes would have to be modified and that could be difficult to do in an operating plant.
regards
Ziggy
Ah yes, sympathetic vibrations;
Air bag shock absorbers for screen damping and support work too if there is room. ■
Excessive Vibration Problem
I had an inquiry from half way around the world, with the following problem:
10 big 8x20 Horizontal flat LINEAR DRIVE screens all on the same floor doing the same TPH. The problem described was excessive vibration, MEGA SHAKING OF THE SUPPORT STRUCTURE IN, ON AND AROUND THE SCREENING FLOOR.
Could I help with any suggestions.
''''''''''''''''''''''''''''''''''''''''
Many many number of times over my 32 years in this business, I have flown out to distant locations on this exact type of problem to try and troubleshoot what the problem and or cause might be.
Here I suggest:
1. All units here are running at the same RPM, ALL 10 units together.
2. What quite often occurs is the machines all try to SYNC up to each other RPM and you actually get a RAMPING UP AND RAMPING DOWN OF flexation in the structure.
3. The question is: is it the structure that is not engineered with enough safety factor in it or are the machines basically causing the problem with similar RPM's all running kinda the same all on the same beams
4. We quite often have the customer change the RPM of one two or three of the machines to STOP the machines from TRYING TO SIMULATE each others rythym. This quite often STOPS this excessive vibration and eliminates the problem.
5. Sometimes we have to THROW some more X BRACING steel beneath the structure supporting the units to tighten up the SUPPORT.
6. Sometimes we find the support beams DO NOT carry straight down to solid concrete footings and causing excessive vibration to everything in the area.
I actually got this senario on a PM but, was unable to reply due to wrong email address or whatever, so I will try to address here generically. ■