Re: Vibrating Screen Housing Design
M12 bolts seem quite light for a 16'x5' screen - why M16 on one side and M12 on the other - would it not make more sense in making both sides M16.
I have never seen a screen with different size bolts for the bearing block mounts. But maybe that is normal on some - I have just never seen it.
Were the dynamic and static loads calculated for the size of bolt required?
Are the bolts breaking in shear or tension?
Are the bolt being torqued correctly? Dry torque vs lubed torque are different. ■
Gary Blenkhorn
President - Bulk Handlng Technology Inc.
Email: garyblenkhorn@gmail.com
Linkedin Profile: http://www.linkedin.com/in/gary-blenkhorn-6286954b
Offering Conveyor Design Services, Conveyor Transfer Design Services and SolidWorks Design Services for equipment layouts.
Re: Vibrating Screen Housing Design
Dear Gary,
The bolt sizes have not been calculated scientifically.
We have been manufacturing 10'x4' two bearing vibrating screen over the years. The 16'x5' design is an extrapolation of the 10'x4' design - the no. of M12 bolts have been increased from 8 in 10'x4' to 10 in 16'x5'.
The bolts are breaking in shear - and not in tension - furthermore - the diameter of the holes drilled for the M12 bolts increase in size
Also, the side wall hole for the bearing housing increases in diameter. It seems as though the bearing housing is rubbing against the side wall hole - as the housing portion that comes in contact with the side wall shows a dent.
We had initially diagnosed the problem as a manufacturing defect - clearance b/w the bearing housing and the side wall - and had taken special care in ensuring a tight fit
As the problem has recurred - leads us into thinking that the problem lies elsewhere.
Inadequacy of the bolts is a possibility - Could there be anything else that could be going wrong??
Thanks and Regards,
Keshav ■
Re: Vibrating Screen Housing Design
From the proportions shown on the drawing the sideframes seem terribly thin local to the well designed shaft assembly. Excessive wall flexure could induce bolt failure before there is some crack development in the region. Is there any cracking starting? ■
Re: Vibrating Screen Housing Design
The bolts shearing indicates improperly sized bolts to me. Higher tensile bolts will not correct this as that only increases the tension or torquing ability.
Only larger diameter can prevent shear.
I would have a metallurgist do a profession failure analysis on the bolts and on the unit. He can tell you what is teh cause.
Why is the bearing block flange on the outside on the drive side and on the inside on the off drive side? Can that be playing a factor causing imbalance? ■
Gary Blenkhorn
President - Bulk Handlng Technology Inc.
Email: garyblenkhorn@gmail.com
Linkedin Profile: http://www.linkedin.com/in/gary-blenkhorn-6286954b
Offering Conveyor Design Services, Conveyor Transfer Design Services and SolidWorks Design Services for equipment layouts.
Re: Vibrating Screen Housing Design
The walls are not cracking as yet - however the m/c has only recently been commissioned.
Wall Flexure could also be a possibility- But the other housing is working perfectly fine.
Larger dia bolts would resist shear - but what might be causing the shear to be transmitted to the housing bolts. (Or is it normal for Housing Bolts to be encountering such shear??)
M12 Bolts are shearing off in 50 Hrs - Suppose I increase the bolt dia to M16 - Would the bolts still shear off (This time maybe in 100 hrs instead of 50??) ■
Snapping Bearing Hsg Bolts
Well........this situation can happen for a number of reasons:
1. If sideplate holes are not matched layed out and drilled, a slight misalignment can indeed cause bolts to BREAK under vibration. A built in twist so to speak.
2. If bearing housing bolts are NOT properly, evenly torqued to their proper value, they can back off or move ever so slightly, unnoticeable by eye but, WILL BREAK if not adequately torqued. Any movement of the bearing hsg whatsoever will cause the bolts to SNAP and BREAK, pick a word.
3. The design of the SHAFT ASSEMBLY cross tube especially when we get wider, longer and heavier is wild critical to keep this assembly absolutely TRUE end to end. A small deviation here, will easily cause hsg bolts to BREAK off. How are the bearing housings attached to the shaft tube ends? This is typically where misalignment can and will happen if NOT VERY CAREFUL with assembly of that component.
4. Hole size in the sideplates and the bearing housings must be CRITICAL tight tolerance to ensure NON MOVEMENT. In the good old days these parts were REAM FIT HOLES, so hardware was DRIVEN THRU THE HOLE, the hardware was NATIONAL FINE THREADS to make sure of absolute tightness, so NOT MOVEMENT..between the parts bolted together.
5. Lots of vibrating screen companies, actually incorporate a REINFORCING, KEEPER PLATE on inside of the sideplate, tight to the bearing housing outer edge, to make doubly sure the brg hsg DOES NOT CREEP, MOVE AT ALL.
6. You may need to STRESS RELIEVE the shaft assembly ....... as it MAY have a undiscernable TWIST in it, that may need to be relaxed by HEAT treatment or special gun.
7. HOW thick are your sideplates now? that size of screener should have 1/4" or 5/16" or even 3/8" thick mild steel A36 plate typically. When you said, DENT, that we do not like to hear on vibrating screen sideplates.....NOT GOOD.
Some points, I have learned over lots of years. ■
Re: Vibrating Screen Housing Design
Dear Mr.Keshav,
I could not see the link or any attached file. If you could attach any photos, we may understand the problem better.
Regards, ■
Anything New On This Front?
Can u update us on your file please. ■
Re: Vibrating Screen Housing Design
Mr.Keshav
You have movement on non drive and of the mechanism and that is the most probable reason that the bolts fail in shear - please email pictures of the side plate and housing after failure.
There is also a chance that flexing of the side plates contributed to the problem.
Your housing looks a bit small with bolts too close to the plate edge.
Any chance to get a better view of the plate and mechanism connection?
Regards
Ziggy Gregory
ziggy.gregory@vibfem.com.au ■
Vibrating Screen Housing Design
Dear all,
We have recently developed a 16' x 5' vibrating screen.
The screen suffers from a recurring problem.
Kindly click on the link to view the dwg. of the shaft assembly.
The M12 bolts break after 50-60 hrs. of operation.
We have taken the following measures to ensure the problem does no re-occour:-
1. Used High Tensile M12 Bolts with Nylock Nut
2. Ensured that there is minimal clearance b/w housing and side wall
3. Ensured that there is minimal clearance b/e housing and ring
4. Additionally - Staggered welded the ring on the side wall
5. Reduced the counter wt.
However, the problem continues.
The interesting thing is that the drive side housing bolts remain intact.
I would be really thankful and greatful for your insights into this problem
Thanks and Regards,
Keshav ■