We have the same lenght

There is something wrong with your take up system.

We are only guessing from here.

Go and check it out closely.

The fact that your return belt wrapped itself around the drive indicates the symptoms. Now, U need to find the cause.

I am sure that U will find it....

Cheers

James ■

Not unless the engineer did not correctly analyze the installation.

1. Rail contamination

2. Wire rope and sheave contamination

3. No hysteresis alllowance for ropes bending over sheaves.

4. You said nothing about when its slips which would likely be during starting - poor starting selection

5. Rubber lagging glazes over time or losses/wears the grooves

6. Did not account for the extra mass a nd resistance on the return strand during starting ■

One of our carriages got stuck like that

The Crosby rope clamps were not tight enough, and the cwt dropped. When it hit the ground, the box ballooned a bit. This distortion caused it to get stuck in one position in the take-up tower, and as a result, the trolley did not move as it should,

Check everything is free moving including the sheaves.

Regards

LSL Tekpro ■

Dilip:

Clearly, the engineering is wrong. The problem can be caused by more than one attribute.

Your request for details of sheave and rope hysteresis is sobering. All sheave have bearing drag. Some sheaves have significantly higher drag due to the use of bushing type bearings instead of roller bearings.

Look at any wire rope catalog and you will be told to apply a loss value for bending the rope over a sheave. Some rope construction produces larger hysteresis loss. Smaller sheaves create greater hysteresis due to the greater internal friction between wire strands caused by the greater radial force.

Do realize that this forum is for helping understand the nature of problems and not in re-engineering them. ■

I think that U better look again at the HGT device.

We have a tail TU on a long stacker yard belt and it moves a lot under a soft start.

Pls go over your unit carefully!!!

Pls post what U found.

Thanks

James ■

I have seen and corrected many conveyors with horizontal gravity TUP's on sleds that did not work due to poor engineering. This does not mean they cannot be correctly engineered.

The conveyor is a physical device that obeys the laws of physics. You can place the take-up anywhere, horizontal or veritcal and design for it to correctly work.

There are many reasons that can defeat the proper take-up action. All of these are man made whether it be: spillage on the horizontal rails, poor design of width to length ratio of TUP carraige that causes cribbing, improper rail guidance, sheave diameters that are too small for the selected steel rope, harsh acceleration that causes drive slippage where the TUP cannot acccelerate the return strand fast enough to maintain proper slack tension at the drive, et. al.

I have designed with a tail gravityTUP 16 km from the head drive. It worked as designed.

I know of many conveyors over 5 km in length that have tail TUP's that work.

Most downhill conveyors have head TUP's with tail drives that work without incident.

Its all in proper engineering of the system. ■

Has the take-up bottomed out? That is, has it reached the end of its allowed travel?

Joseph A. Dos Santos ■

Dear Shri Dilip,

The earlier respondents have already given useful suggestions. Following is the additional information / suggestions from my side.

1) You are referring to stacker - reclaimer yard conveyor.

2) The take-up pulley has to make some motion during starting. If it is not making any motion implies either take-up device is jammed, or it is making too little movement short of noticeable magnitude. This means counterweight which is imparting tension, is only marginally more than that required for steady state. Thus, conveyor would not be able to accept the full value of starting tension matching to drive force.

3) The conveyor equipped with stacker -reclaimer needs very careful design. It has contradictory needs A) Tension to be low so that belt does not lift up at concave zone of machine B) Tension to be also reasonably high so that it does not slip during starting.

4) The aforesaid contradictory conditions are tackled by balanced decisions, eliminating adverse effect to harmful level. This is made possible by using A) Drive starting factor of very low value (such as enlarged delay fill fluid coupling or three chamber fluid coupling, B) More wrap angle (or dual drive) C) Provision of adequate space at the rear zone of machine so that radius in machine is not very tight, allowing somewhat more counterweight.

5) You have the existing machine and only option is to change the fluid coupling to required type, change the motor if the same is of oversize, increase the counterweight to the acceptable limit.

If the take-up mechanism is not jammed as per your check-up, then your problem requires design analysis of the conveyor and consequent corrective measures. Vijayawada CHP had similar problem (of very low magnitude) and it was corrected very long time back.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

A further note on the troubling return side slack belt at the drive station and non-motion of the tail take-up.

The return strand idler drag, belt alignment drag, together with the acceleration tension requirement may hinder the take-up action and not allow necessary slack side belt tension at the drive.

Check the return strand belt alignment to see if it has areas where it rubs. We have witnessed excessive belt power and shortened coasting times due to belt rubbing. The idler alignment was the culprit. Once correctly aligned, the empty belt power was cut by 50%, the coasting time increased by a like amount. ■

A simple test to prove this point is to exaggerate the return side idler spacing by two pitch, or 3x the normal return spacing. This assumes the idlers can momentarily carry the load without harm.

At both ends of the conveyor, tail and head drive zone, set the return spacing to the same amount that exaggerates the belt sag for the same idler spacing.

This only works at a steady-state operation, and is not dependent on the carry side loading. Maybe just an empty belt will do the trick. The measurement cannot be made with the belt shut down.

Measure the belt sag with a straight edge. Then calculate the amount of belt tension, at both ends, which is required to set the measured sag levels. Check the tension value with the head and tail tension calculations. If this is the problem, I will bet the sag level is much higher, at the head end than the tail end and is at odds with the value expected by the designer. It’s like pushing rope up a hill.

A good sag value maybe 3.0%, at the head end. Assuming the spacing to be 5 meters or 16 ft, would mean the sag is 150 mm or 6 inches at the 3% head end zone return side. What is it at the other end? Submit this to me or to this forum, and you will receive an answer if the return side drag or counterweight action is the problem.

I have made a rough calculation, with the exaggerated spacing, not knowing your details. If the return side drag is not excessive, then the difference in sag between head and tail will be about 15-18% with a good design. If the difference in sag value is excessive and exceeds 25%, then there is trouble with the return idler drag, belt rubbing or other drag-inducing problem. ■

I vote for a strectched belt that needs a section cut out of and resplicing. ■

There are yet more culprits. One briefly noted in my prior posting. The return strand idler seal and bearing drag, belt drag when rubbing belt-to-steel from misalignment, and idler misalignment causing a belt to idler sliding action. These conditions will cause a larger return strand differential belt tension between the head and tail stations. The belt tension differential can be seen by observing the belt sag between idlers.

A simple test to prove this point is to exaggerate the return side idler spacing by two pitch, or 3x the normal return spacing. This assumes the idlers can momentarily carry the load without harm.

At both ends of the conveyor, tail and head drive zone, set the return spacing to the same amount that exaggerates the belt sag for the same idler spacing.

This only works at a steady-state operation, and is not dependent on the carry side loading. Maybe, just an empty belt will do the trick. The measurement cannot be made with the belt shut down.

Measure the belt sag with a straight edge background fudicial measurement system painted on a plywood sheet and use a digital camera to capture the measurable image.

Then calculate the amount of belt tension, at both ends, which is required to equal the measured sag levels. Check the tension value with the head and tail tension calculations. If this is the problem, I will bet the sag level is much higher, at the head end than the tail end and is at odds with the value expected by the designer. It’s like pushing rope up a hill.

A possible sag value maybe 3.0%, at the head end. Assuming the spacing to be 5 meters or 16 ft, would mean the sag is 150 mm or 6 inches at the 3% head end zone return side. What is the comparative sag at the other end? Submit this to me or to this forum, and you will receive an answer if the return side drag or counterweight action is the problem.

I have made a rough calculation, with the exaggerated spacing, not knowing your design and operating details. If the return side drag is not excessive, then the difference in sag between head and tail will be about 15-18% with a good design. If the difference in sag value exceeds 25%, then there is trouble with the return idler drag, belt rubbing or other drag-inducing problem.

At least this will tell you if the problem is in the return strand action or in the take-up system. ■

If you are convinced that the take up is free to move (get a crane and move it) Then either your calculations are wrong or your installation is wrong. Look at the soft start on your drive. If generate so much slack when you start then you are:

1 Starting too fast.

2 Pulling the slack from the curved portion of your stacker

3 Have way to much friction in the return strand

4 Have the skirts way too tight against the belt at the tail loading point. ■

I second that vote. ■