Hello,

What happens when the chains are pushed downward?

In that situation the chains need to be heavily weighed to keep them stiff or else you need to consider rigid bars throughout.

At 90^o from tdc or bdc you will have a lateral throw which equals half the stroke. So you need a Scotch Yoke to accommodate the side thrust.

Stamler used to do a rotating chain breaker which was illustrated in Wills 2nd edition. Something similar might help you.

Remember that if you don't break the frozen crust you risk lifting the whole ensiled mass because the downcoming chain will flex.

So you need a reference list for a chain breaker and then another reference list for a bin that will be strong enough. ■

Dear Babak,

we offer a solution with an oscillating beam discharger. See brochure attached and also in our website.

href="http://www.geroldinger.com" target="blank">www.geroldinger.com.

It works with oscillating beams triggering mass-flow in the silo/bunker.

Important is, that your bunker design is laid out for mass-flow. (all particles in movement during discharging). Please check hopper design.

If the outlet section is bigger than critical arching/bridging width you should not have problems with discharge.

what is the required output rate and which dimensions does the bunker have. If you can send me the details, we can work out a proper proposal to you.

Look forward to your reply

Johannes

Attachments

os31_e (PDF)

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What sizes are the primary/secondary crushed ores?

What are the bin capacities/sizes?

Please clarify the permafrost condition in regard to working depth. How do you handle drilling water etc?

Wouldn't a moving bed bunker be a much better alternative? ■

Hello,

I have not dealt with breaking / loosening of bulk material arch formed due to frost. So I do not have specific suggestion. However looking to hanging chain mechanism as shown by you, some points are as below which could be of interest to general readers.

1) As it appears, there is a common shaft at hopper top floor. This shaft has 3 cranks and drive at one end of the shaft.

2) There needs to be 1 eye-bolt, having bearing to fit onto crank portion of the shaft. The eye-bolt eye could be split type. This eye-bolt is like a connecting rod whose one end fits onto the shaft crank and other end suits the attachment to the link chain.

3) The chain will be dragged downward during regular flow out from the hopper or whenever there is empty space at its lower end.

4) There may be some longitudinal shaped counterweight (beam) which will keep the chain tight but will not impose excessive dragging force during regular operation.

5) It could happen that only one chain is stuck-up in the iced portion of arch, but other 2 are free. Therefore, each chain and its crank mechanism should be strong enough to withstand full torque of the drive (stalled, starting etc.).

6) There needs to be some arrangement having compression type load cell below the shaft support points to warn the excessive pull in chain if the iced bulk material block becomes hanging with the chain (formed due to somewhat longer idle time or sudden sharp fall in temperature). If such pull crosses certain limit, it can warn to withdraw up the chains before it becomes too heavy ? And then possibly some manual remedy ? One weak link (point) in suspension unit which is to fail at 50% of chain proof load, to prevent damage to entire suspension unit / system ?

7) As for oscillating beam discharge mechanism, a supplier has already approached you. So you may discuss and know about their system.

Knowledgeable readers are welcome to improve upon above information.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 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 ■

As usual there has been no feedback beyond an assertion that there are permafrost conditions.

Winter has set in so it will be interesting to know the result even if the job is for next spring.

Without knowing the depth of the frozen mass and the bin dimensions it suggests the assumption that the whole ensilement can be solid. In such a scenario the crank will have to lift the entire mass on half the chains. At the other end of the weather scale I saw case, in Zambia, where the bin contents had solidified and the bin panels had been removed to leave the contents hanging some 30m aloft in the rafters. Cameras were sensitve to the point of expulsion in that part of the world so I couldn't provide the evidence. The panel removal made some sense, steel was in short supply, the rafters had held up the choked bin and the TORCO process had been a disaster so they couldn't use the material anyway.

My question is, why bother with a bin when you know it is going to freeze solid? It isn't going anywhere, especially not out of a bin! Why not leave one of the sides open and break the stuff out. Too easy. ■

Hello,

Referring to my earlier reply, I add following information with respect to mechanical arrangement shown in the query.

The arrangement shows one common shaft with 3 cranks. The common shaft is likely to be long (few metres). The manufacturing of such long and strong crank shaft would be difficult task and would be also expensive. Also providing more than 2 plummer blocks would pose alignment and load sharing problem because situation here is different than multi-cylinder IC engine crank shaft where the engine block supporting holes boring / manufacturing is done in single setting in a very precise manner.

The better arrangement is to have 3 independent drive, one for each chain. Each drive arrangement would be similar to drive for reciprocating feeder. This drive will have say approximately 1 m long shaft, 2-plummer blocks spaced at say 650 mm c/c. The circular disc with crank pin is fitted onto one end overhanging portion of shaft. The other end overhanging portion will support the flexible coupling to connect the shaft with the drive gear box output shaft.

Such arrangement will be economical and obviates need for overload sensors, etc. The drive motor stalled condition implies overload and thereby current / overload usual sensor will trip the motor.

Meanwhile earlier reply has useful information that why to bother about the arching issue when material in bin is likely to get frozen.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 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 ■

...sounds like many thread starters are often enough asking the learned amongst us to "Cast Pearls Before Swine".

Roland has often highlighted the dearth of feedback and I sympathise with the proviso that when I spot a baiting situation I do my utmost to lighten the situation.

Often this nips the topic in the bud. I wonder what prompts someone to publish a highly mediocre thread without realising that his, never her (yet), coleagues probably are reading his work alongside the rest of us. But they keep coming back and we shouldn't discourage an amusing scenario.

Back to the topic and Roland is very right in asserting that the chains as a distubance in frozen conditions have as much chance as a snowball in hell. I only just thought of that: but it is appropriate: I think so anyway. ■