I can tell you with mechanical drives chain and gear drives with rubber couplers and reduction gear boxes that the belts always stopped shortly due weight on the belt and simple friction and loss of drive energy-of course the idiot that left the drive control panel on hand position and walked away after a belt was trained is another story- he was one of the chosen ones.

lzaharis ■

Not disagreeing with you at all, the belts I had to deal with were level and only 450 and 900 tons per hour-except for the incline belt we had which was 21 deg and 450 ton per hour-it had a mechanical brake

Any level belt with tonnage will stop due to the loss of energy to the motor simply from the friction of the idlers and the weight of he ore on the belts

Why are you feeding a smaller belt with that tonnage?, is there a large 15,000 ton hopper hopper prior to the smaller belt you are feeding? if so why did you not mention that part?

If you have a hopper why do you not use a "bindicator" mercury tilt switches?

The control problem is easy to resolve with adequate planning of the timer sequences for start up and shut down we used mechanical timers in our "Hubble" brand control boxes on our 36 inch belts for many years.

For example:

If one of our belts stopped the timer control for the following belt stopped 5-10 seconds after the first belts power was cut with either an emergency stop or a manual command at the old screening plant via the starter switch or circuit breaker.

My first eyebrow raising question would be: are the timers in series or parallel wiring? if you have a flooding problem.

I would look at your timer settings if it were me. do not forget the last belt in the elephant walk needs to be the first one to stop when the first belt cuts out to avoid burying the preceding belt.

As you are burying the tail pulley with 3. 3 tons per second for 11 seconds of ore you have a timer problem/settingsequence that neds correcting/resetting or a hopper for overflow to feed the smaller belt and be sure to install bindicator tilt switches. ■

Your quoted condition calls for 15 tonnes surge storage capacity in the headchute. For limestone that's 10 m^3 and for a typical ore just over 5m^3.

12,000tph is a lot of conveying requiring quite a fancy drive system.

Mechanically;surely there is a brake fitted.

Geometrically; 4.2m/s will produce a discharge trajectory that says you will have a big chute anyway. 12,000tph of ore will involve a belt width of about 2000mm which means the inside chute dimension will be about 2200mm. 5m^3 soon gets lost in a box that size.

We don't know your transfer point layout but there will have to be enough height between the belt lines to accommodate the trajectory. If there isn't; then what's the short belt doing in the first place? (Or should that be last place?)

Draw it up properly & then see what you come up with. ■

If the system was sized properly and the commisioning was done from A to Z there would be no problems and if there were; I for one would have the installer chained to the timer control box until the settings were spot on.

Your dealing with 40 tons of ore in 11 seconds and that is not good.

all the belts need to be the same size unless there is a buffer bin of some size in between. the surge bin we had was 10,000 us tons but sometimes it was not enough due to screening plant problems.

That is why the timer or a timer is so important the first belt feeding the elephant walk needs to shut down at least 30 seconds before the next belt and so on down the line to allow for room on the last belt.

If you have a smaller belt in this installation you will continue to have problems as it will not cope with it - I been wrong before but with tonnages like this its a no win cricket match with wicked googlies or football game with a muddy and bloody pitch. ■

Dear Mr.Mec00063,

Conveyors can be stopped in two ways.

1. Normal shut down , where all the conveyors are emptied and stopped.

2. Unexpected stoppages due to safety switches activated , say pullcord , belt sway switches etc.,

The system need to be thought & designed for stopping by the unexpected stoppage. This may help you to better design the chutes which can take care of the excess materials accumulated during unexpected stoppages. We may need to consider that the load in the chutes should not hamper starting of the conveyors also. ■

12000tph=3.333tps

Stopping time difference =11-2=9s

Uniform deceleration gives an average speed of 0.5xmax speed.

So the figure should be 3.333x9/2=15t.

Draw it up properly & then see what entrained material depth you come up with. Don't forget that the trajectory outreach decreases proportionately with slowdown so you will have a reasonably uniform distribution inside the chute. Your minimum chute length will have to accommodate the throw over the drum diameter drop anyway, even if you do have a bang board.

It's good to be concerned but don't lose sleep over this issue. You won't fill a properly designed chute. ■