The tensions will vary along the length of the conveyor at rest. Many factors will influence the tensions along the conveyor, load at the time, location of the load, tramped material at the tail pulley (this can create very dangerous tensions - people have been killed trying to clear a jamb not knowing what these tension can do). The CWT will create tensions as well but they will not be equal along the conveyor. The weight of the belt itself will create tensions. ■

Dear Mr.Himanshu,

The tension will be highest at the discharge point at height ( where drive is also usually located ) and lowest at the tail pulley. As Mr.Gary has explained, people should be always very cautious before carrying out the jobs at site.

Dear experts :

If a belt is not working since years, will it be possible that the joint will fail, because of this tension ? ( assume that the joint is in the high tension zone ).

Regards, ■

Originally Posted by sganesh

......

Dear experts :

If a belt is not working since years, will it be possible that the joint will fail, because of this tension ? ( assume that the joint is in the high tension zone ).

Regards,

Many makers suggest 10-12 years maximum life for a belt due to the ozone attack and solar radiation. It is quite likely that a belt left standing for a long enough period might snap on start up if the standing time has infringed the environmental schedule. This is of course regardless of the loading regime. I imagine the 12 year life might be extended where the belts are suitably covered. This is a very nice built-in fall-back situation for consultants etc.

We sometimes hear of claims that belt have lasted over 20 years. Such claims make no mention of mechanical equipment damage caused by metal to metal contact between the steel chords and rollers, drums and cleaners. ■

Hello,

If residual friction is ignored after stoppage, then belt tension calculation during stand still condition is simple as below:

1) For horizontal conveyor, it will be same as belt tension at gravity take-up.

2) For inclined conveyor, the anchor tension will be at gravity take-up, and from there one has to calculate belt tension towards up and down side (with respect to take-up pulley), accounting the gravity effect on belt or belt plus material, as applicable.

If one wants to calculate belt tension including residual frictional resistance; then its calculation becomes subjective, because direction / magnitude of friction resistance is likely to be different immediately after stoppage, and subsequently after sufficient time duration. Such calculations are not of practical utility (component selection, sizing, etc.), and hence one does not give much thought to it.

Regarding conveyor with winch take-up, the belt tension during empty and stand still condition has practical use for deciding the magnitude of winch take-up tension setting, but here situation is easy / simple because direction as well as magnitude of frictional resistance is easily calculated in accordance with whether winch is used for moving take-up pulley in or out.

All the aforesaid information is to be considered as basic hints only, for calculation of such tension by concerned designer.

Ishwar G. Mulani

Author of Book: Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book: Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Take the steady-state tension at an arbitrary point, then algebraically add or subtract the deceleration of the prior masses and the mass up to the point of interest using Newton's Force = Mass x Acceleration Time (Deceleration Time or drift Time). Deceleration will be a negative force (tension), unless there are downhill sections (flights). This is the rigid body principle only. Not true for real life. However, this is a matter of degree (acceptable error) of mass and time.

Be careful, you can end up with negative tensions, which in real life are not possible = need for dynamic analysis. ■

I forgot to give the basic assumption of the prior post tension calculation when the conveyor is at rest, assumes the belt has been running at a nominated speed (Steady-State) ( not at installation), and is derived from the "Steady-State" running condition. It is the belt speed before either cutting power or powering down from motor or brakes. You need to solve the time it takes to stop (not regenerative).

This also assumes a simple head or tail drive. You need to know the condition of the counterweight system and drive mass, and the drive mass belt line amplification due to the gear-reducer.

Sorry to get you confused by my muddling through the answer. ■