Sheev,

For circular motion screens the mechanism should be located as near as possible along a vertical line passing through the C of G of the screen.

The result of moving the mechanism horizontally from this line will result in an increased and more vertical motion at the end towards which it his been shifted, and a decreased and flatter motion at the other end. In practice the horizontal location does not have to be exact, but within say 1% of the screen length should be aimed for.

It is usually more difficult to locate the mechanism on the C of G in the vertical axis (especially on 3 deck screens). The result of positioning the mechanism above the C of G will be that the circular vibrating pattern develops into ovals towards the ends of the screen, with the axis pointing downhill at the feed end (speeding material up), and uphill at the discharge end (slowing material down). Locating the mechanism below the C of G will reverse the direction of the axis to point uphill at the feed end and downhill at the discharge. However in terms of screening performance, the vertical location of the mechanism above or below the Cof G (within normal limits) will have little effect. ■

John.........great answer. covers the theory nicely.

sometimes people will install the shaft 12 inches closer to the FEED END of the box VS dead centre.........this is usually done to give the FEED END OF THE MACHINE a little BIGGER CIRCLE to compensate for a LOW ANGLE of INSTALLATION.

This is no problem and done fairly frequently especially on portable screens where the headroom must be kept low for highway travel.

GEORGE BAKER ■

Sheen,

The selection of bearing housing bolts is by general engineering calculations as described in most design textbooks. Also most reputable bolt manufacturers publish informative literature on design of bolted joints.

For such an important connection I would use be using High Strength Structural bolts (Property Class 8.8).

For a bearing housing 22324, my gut feel is that your 16 – M22 bolts (per housing) would be very very conservative, and most likely even 16 – M20 bolts would still be more than adequate. However do the sums to confirm. ■

DID YOU KNOW?

1. SLOPE can range from 10 degree on low side to 35 degrees on high side

2. Foot travel rate: 75ft/min on average at 20 degrees

3. 75% of undersize passes in the first 25% of the screen length

4. Keep BED DEPTH to a MAXIMUM of 4 times the screen cloth opening size. IF It exceeds this, GO TO NEXT LARGER SCREEN DECK SIZE to maintain EFFICIENT SCREENING.......95%

3 times is even more conservative if want to be real safe in your sizing calculations.

REGARDS

George Baker - MODERATOR ■

http://store.aem.org/index.cfm?fusea...ndardsscreens ■

Greetings from the "Frozen Eastern wilderness",

You will save your self a lot of trouble and down time and reduce the tools needed by using "grade 8 "Allen Head" national fine thread capscrews with drilled heads to accept wire to wire pairs of boltheads together and reduce the possibility of loosening bolts-do not hesitate to spec red or blue loctite for the installation on threads. ■

Izaharus: Your comments are very very true in real life. Drilled bolt heads wired together is excellent design safety feature.

Locktite is excellent and recommended use.

FINE THREAD hardware is more expensive but, much better, tighter hardware than COARSE thread. In the good ole days,,,,fine thread and REAM TIGHT HOLES on vibrating screen bodies was the norm.

WHY? WE WANT all the parts to run "together" as one as much as possible.........the more this is true........the less breakage. It is when bolts loosen off, that parts start to CRACK.....etc.

HYGIENE is extremely important when reassembling vibrating screen bearing in the field. We used to carry the BIG BEARINGS inside a green garbage bag until ready to put in the housing. Most people kinda let the AIRBORNE dust get all over the new bearings and suffer early failure because of this.

KEEP shakin out there.................George Baker MODERATOR ■

SHEEV, Bevcon India

Glad we all could help you on this particular item. As always we love to hear back from our forum partners and especially with your kind words of appreciation. Thankyou.

Makes it all more interesting and fun.

Keep Posting............with Best Regards, George Baker ■