Originally Posted by Roland Heilmann

Dear Mr. Narayanan Nalinakshan,

a more detailed sketch of the TCar together with the designed belt radii (concave / convex) and belt conveyor layout (tension, troughing etc.) would be very helpful.

However, in the transition zone mentioned by you the belt has to leave the troughed state with probably in same time leaving the straight or curved beltline in order to arrive at the discharge point. Due all this the belt undergoes stresses, which will if permitted by little load transfer into strain re deformation where this becomes possible.

I'm sure the dedicated forum specialists on belt behaviour can more deeply analyze this and perhaps hint towards an action / strategy to be adopted.

Imo the belt should not buckle, this impacts severely onto lifecycle. Keep the low load running down.

Regards

R.

Looks like your 5m transition distance is too small and you are buckling the belt center as the edge cords are causing lateral stress that cannot be supported by the belt sectional modulus. Get a manual from competent supply that gives detail of 2000 mm ST3500N/mm and your trough angle and pulley alignment. ■

I think Larry has picked up on the issue as the change of belt carcass to steel cord should have been audited and the correct length and trough profile should be one of the criteria that needed to be addressed. There is a saying in the conveyor industry and I am going through this at this moment where a conveyor is relocated and the specifications in the new conveyor layout were not addressed correctly with horrendous financial consequences. The design engineering firm do not want to know about the deficiencies in their calculations.

My saying:-

One good thought to remember is,

"When any one parameter in a conveyor system is changed, then ALL parameters

need to be re-evaluated so the system will perform to expectations". ■

Originally Posted by tecmate

I think Larry has picked up on the issue as the change of belt carcass to steel cord should have been audited and the correct length and trough profile should be one of the criteria that needed to be addressed. There is a saying in the conveyor industry and I am going through this at this moment where a conveyor is relocated and the specifications in the new conveyor layout were not addressed correctly with horrendous financial consequences. The design engineering firm do not want to know about the deficiencies in their calculations.

My saying:-

One good thought to remember is,

"When any one parameter in a conveyor system is changed, then ALL parameters

need to be re-evaluated so the system will perform to expectations".

As I recall, if the belt alignment (slope) projects to the pulley tangent and its work point (~12 o'clock), the transition distance needs to be about 5 x belt width for 35 degree idlers. It could have a higher multiple, depending on belt modulus. Assuming this is about right you need 10 m of ideal transition length. The buckling sensitivity is inverse to length reduction (i.e. you approach an infinitly high stress as the transition length approaches zero). In other words, you are applying far more than double the lateral stress to induce center buckling than with a belt supplier's recommendation.

I believe you must have asked a belt salesman and not an belt design engineer. ■

Hello,

For identical situation, the steel cord belt requires more transition distance compared to textile fabric belt, because steel cord belt modulus of elasticity is more compared to NN / EP belts.

Also raising the pulley level with respect to the straight line touching the top of middle rollers, tends to reduce the transition distance, for any type of belt.

First option is simply to increase the transition distance by reinstalling the first regular trough idler away from pulley, to increase the transition total distance by say about 20%, and then spread out the transition idlers. Presuming this will not cause spillage problem during time interval when the belt passes the transition zone.

The second option is to raise tripper pulley level, so that prefixed transition distance becomes suitable for steel cord belt also. Assuming 3 equal rollers and 40 degree trough, the recommended value for pulley rise is upto 30% i.e. 0.3 x bf x sin(troughing angle) = 0.3 x 625 x sin40 = 120 mm. One can also take this value upto 50%, but then belt aligning powerful action in trough - flat zone, will become nil resulting into possibility of belt alignment problem. The exact value in this range depends upon belt tension. For this, first try to raise pulley level by 60 mm to 70 mm and then decide further course of action. The pulley level can be raised by welding MS plate packing / adaptor on frame base where plummer blocks are installed. Contact some conveyor designer, if you don’t want to take chance by trials and errors.

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 ■

You should take it seriously. High levels of buckling will cause unwanted and excessive rubber strain between the steel cords. Excessive cyclic strain can lead to rubber weakening and failure, and debonding between steel cord and core gum. ■

Hi

With belt tension , especially tripper close to head end, where tension is maximum, there is requirement of minimum radius for the belt. With tripper pulley position fixed , you may not be getting the required radius profile. Pl check the same and solution may be reducing belt tension , of course ensuring no slippage at pulley-- Such solution are possible at design stage where the drive station is properly designed and laid out.

Regards

Subash

Originally Posted by NarayananNalinakshan

Dear Experts,

Recently one our EP belt was replaced with Steel cord belt.(ST1600,Belt width 2000mm,inclination 12degrees.3500TPH,Speed 3.8mtrs/sec).

The pulleys are lagged and NOT CROWN.

Towards the discharge point prior to the 5mtrs transition point,the centre of the belt bulge upwards at NO-Load.

I have seen this phenomenon on many steel cord belt at stacker tippers and ship loader tippers.

As soon as the belt is loaded,even 20%,the bulging disappears. Is it due to the absence of Weft?.

Belt manufacturers are not able to give a clear answer.

I request for your valued opinion.

With Regards,

NarayananNalinakshan.

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