Apparently an assessment is required.

Based on the information available, in principle, options may include:

1. Manage both the: 2.5 km, and short; conveyors' stopping duration;

Perhaps this is not an option, and/or additional hazard controls [e.g. guards etc] are required.

Although not my preference, subject to the frequency of the event etc, perhaps a "by pass" chute is an option.

2. Manage the "slack side" tension [additional tension, and/or lock in previous average tension],

3. Perhaps a return side brake,

4. Locally reduce the idler spacing.

Regards,

Lyle ■

Originally Posted by VISHWAJIT

Thanks for the reply, Mr. Lyle.

My observations are as follows:

The problem arises when conveyor is running at full speed and pull cord switch is pulled. Now we have the following options:

1. Should we increase the counter weight at take-up? Maybe. Where is the take up?

2. We can provide controlled stopping of the conveyor by VFD even if pull cord is pulled. Not if, as originally stated, there is a power failure.

3. Currently Return idler spacing is 4 meters where 600 mm sag is observed near the tail end area, we can reduce spacing to 2 meters but however we are afraid that by reducing the idler spacing, the extra belt shall approach beyond tail pulley. It seems that any solution is going to be expensive. What is happening to the loaded carrying strand at the tail end? Reducing the idler spacing will only reduce the sag depth: it won't shorten the belt.

What do you think about the above options? Is there any other better solution available.

A sketch will tell a kiloword. ■

We have seen this many times. Bad design. Engineer did not know how to evaluate shock wave dynamics.

Try # 4: One that is a less costly solution. Use a take-up capstan. Best if you do engineering sums to find the best capstan parameters. It has been done many times world wide. There are multiple capstan designs which depends on the TUP design. ■

You cannot have negative tensions in the belt unless the belt is dragging on the ground in the reverse direction to normal belt travel.

You must think through the physics to conclude belt tensions. No such thing as negative tension. ■

Originally Posted by VISHWAJIT

One of our clients has a 2.5 km 3500 TPH capacity Belt conveyor. The conveyor is provided with 2 numbers of 1000 KW VFD motors at head end. The conveyor runs smoothly during startup. When there is power failure, the conveyor stops and instantaneously the belt near the tail end on the return side loosens and sags about 600 mm between return rollers and after 30 seconds or so, it takes the normal shape. I am looking for an appropriate solution as we cannot provide flywheel at the drive as the next conveyor is a very short length conveyor and has very less coasting time.

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Help us to help us help you;

Has anything changed recently or has there been any maintenance done on this flight of belt??

More than a few issues need to be examined;

Is the upper belt sagging when stopped with a fully loaded belt??

what is your troughing idler distance between idlers?

Is the conveyor flight completely horizontal(zero degrees) or is there a slight slope?

Is this system a steel or cable supported conveyor?

What is the spacing for the troughing idlers and return idlers?

What is the Idler diameter for the troughing and return idlers?

Are fluid drive couplers used or are rubber couplers used for electric motor to reduction gear

to final drive?

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Some sag and some slippage can occur on a horizontal flight of belt.

The idlers will roll somewhat unless a head pulley brake is used.

It may be more than likely that a section of belt may need to be cut out and the belt spliced again to remove the sag.

As Mr. Nordell has stated the installation of more idlers is the least costly solution for now until a complete examination of the system by a

qualified person such as Mr. Nordell will find the issues and offer properly engineered and vetted solutions.

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Various options exist to restrict a vertical take up's movement, however given the mentioned test method is apparently not in accordance with any accepted practice that I am aware of, I am going to resist specifying it.

Please for the safety of: yourself, and others; consider obtaining suitable professional advice.

Regards,

Lyle ■

Yet again we are fed the question in stages as perpetual 'yes but' style.

I can only reiterate my earlier offering in a changed tense: a picture could have told a kiloword, and leave it there because in these situations the painting specification or cabling layout might be expected to interfere further down the line. ■