I have seen this before and my first thought is that the swing may be as a result of the "polygon" effect of having a sprocket with only 8 teeth. What sort of chain is being used? ■

Dear,

In a bucket dredger, they use a pentagon driving wheel on top of the bucket chain and a hexagon return wheel down below.

Thereby, two swings are introduced at different frequencies, resulting in the prevention of resonance.

Is this an idea to solve the polygon problem?

Have you already asked a consultant?

Have a nice day

Teus ■

Of course you can always try changing the chain speed to get the excitation away from any natural frequency, but this tends to impact on the capacity of the machine if you decrease the speed, or discharge characteristics if you decrease or increase the speed. You've probably only a 15 or 18.5 kW motor so an inverter unit wouldn't be too expensive to "tweak" the speed a bit and see what happens.

There again, you could fit rollers behind the chains at a couple of positions up the legs to limit the in-swing and break up any harmonics.

Or fit new chains with shorter pitches to run smoother and limit the polygon effect.

Or for really smooth running change to a belt with "continuous" overlapping buckets.

That'll do for now.

Any more ideas anyone ........

consultants ???

bucket elevator suppliers ???

guy's maintaining bucket elevators on plants ??? ■

Originally Posted by DRKREDDY

Dear Friends,

Recently we commissioned the coke calcification plant in Kuwait,in our material handling system have had a double strand bucket elevator which specifications are as follows

• Application: CPC Handling
  
  
• Density: 0.8 M3 /Hr
  
  
• Capacity: 75 TPH
  
  
• Normal operating Capacity: 50 TPH
  
  
• Speed : 0.59 Meter/Sec
  
  
• Height: 51.5 Meter C/C
  
  
• Type : Double strand ,slow speed Gravity discharge chain elevator
  
  
• Casing: 760X 1410
  
  
• Head sprocket R4251-8T-796.6 PCD
  
  
• Bottom traction wheel 737 mm OD
  
  
• Bucket 300x228x300

Now let me explain the problem we are facing Please bear with us, if some of the following is already common knowledge to yourselves, as we are not yet sure of your specific familiarity with the designs as they apply to the equipment.

Bucket elevators are unique to the service of Material Handling However In our case right from trail runs we noticed that Chain is getting swing and causing for casing damages due to continues rubbing on to casings especially at 2/3 of height from boot

Swing of chain may have variety of causes. Incorrect specification or poor quality of suppler tolerances, poor alignment practices

We reported the problem to OEM and subsequently studied the same and reverted back with a proposal of Head sprocket assembly replacement and adding of up to 500 kg Counter weight at bottom take-up and thoroughly checked all the key alignment factors found them selves satisfied, but problem not solved.

At this time, OEM and sub contractors (supplied) it must be pointed out that the factors above are divided among several entities for their design, installation and subsequent warranty. No single entity is willing to accept major responsibility for the failures that have occurred, each pointing to the other as the primary culprit. As expected, the issue has become extremely contentious.

We had already extended the casings by 180mm to avoid rubbing action almost 40 meters height, now the elevator is operating with lot of swing ,but continues rubbing was minimized

I hope this information is adequate to advise us for corrective action as well as probable causes for such discrepancy

Request any of viewers could advise me for further action towards resolving the problem and share your experience…

Thanks for your time

Regards

==========================================================

We had the same problem with an elevator used to lift filled liquid soap cases to a

secondary conveyor and then to a palletizer production being what is is the

system was and is under designed etc. for the capacity.

The chains are swaying simply because of the lift and carry action and in adition

to that the chain rollers are exiting/increasing resonance even more due to

simple flexing forward and the weight of the coke in the tub.

The chain movement stops when it goes over the pullies and starts again when

they are clear of them it is less noticable when they are empty as the weight of

the entire empty chain side is held by the weigh of the empty chain and empty

buckets prior to the scooping of the coke in the hopper.



the chain or chains and bucket following the circumference of the bottom drum

and the weight of the coke is dropping agains the bucket and chain and the

stress of the scooping of the coke and eventual freeing itself from the pile frees

the scoop and it bounces a bit forward and back and it continues to bounce until

or if it stops.

=======================================================

adding rollers to create tension is a short term fix as the chain will eventually

screw up and break been there done that using smaller pitch chains will be a

short term solution simpy as the shorter pitch

chain will suffer the same fate as the chain is only supported and held under

tension at two points and only two points the head pulley and the bottom pick up

pulley.

the carrying distance is still the issue and the only probable solution is to install a

full length continous bucket scoop system with new sprokets to reduce the load

on the entire system by spreading the load over the entire diameter of the chain

distributing the load around the entire chain loop with a small scoop laced into

each section of chain.

The chain guage has not been mentioned as of yet I would like to know what it is

if possible with a picture.

It also sounds as if they do not have a roller chain tension gauge as well.

There is no eyeballing a problem like this as roller chain that travels in only one direction must be nearly taunt.

has anyone looked at the drive unit an its chain drive/gear drive etc. to see how much slack is in the drive chain if it has one?

Replacing the chain and scoops is easy as long as it is done from the top with the hood open or by changing each scoop one at a time at the bottom.

changing the drive sprocket will take some work-but if a crane is used to lift the new sproket/drive shaft, bearings and carry chain with buckets attached it can be done with planning rducing down time

I you could post some detailed photos that would good.

As the installer has said sorry its not my problem I would have a consultant company come in and replace the the elevator chain and buckets with a continuos bucket chain system with smaller buckets and stronger chain.

please read below;

I would seriously contact the builder of the bucket elevator at it home head quarters and by correspondence from you ask someone to come see the installation in situ with no gutting it to investigate it as it sounds like the usual oh sure we can do that with this system.......

Bucket elevators have been in use for as long as grain elevators have been in existance so I am almost positive it is an improper application issue and the manufacturer of the grain elevator if known should be contacted about this issue to solve it for you since the installer contractor will not.



lzaharis ■

I was thinking it was swinging "in and out", not "side to side".

Haven't seen that before. ■

Originally Posted by designer

I was thinking it was swinging "in and out", not "side to side".

Haven't seen that before.

============================================================

Greetings and salutations DKReddy,

As mentioned by designer I have had that problem as well, the video is still up loading but-

Any chain that is not nested in a track/channel iron guide for either vertical or horizontal long distances will wander as it has the ability to swivel. it is simply a fact of vertical pull, gravity, and height distance unfortunately.

The side to side sway is caused by the the vertical lifting of the loaded buckets causing the chain to swivel and move in the side to side direction and in and out as well.

If it is standard elevator chain which it looks to be- I need to see better pictures if possible to confirm it.

The standard grain elevator chain is an overlapping link as is used in gutter chains for dairy barns that allow for easy repair and replacement.

I would contact the Sukup elevator company-they are world wide as well

to look and confirm my suspicions. Their machinery moves a lot of different types of materials.

Paying them for an hour of their time is worth the experience they have with elevators. They will solve it then and there with no debate.

==========================================================

Heavy roller chains do not sway like that as the "roller chain sprockets" at the top and bottom keep everything in line with "channel iron' in the frame of the elevator holding the chains in place during the lift phase and return phase to stop any potential movement.

===========================================================

As designer has mentioned a VFD is a quick solution to slow it down as the actual speed also appears to be the huge problem- sorry still waiting on film.

Calcined coke weighs more cubit foot than most grain and that is what you are up against.

==========================================================

lzaharis ■

IMO when selecting a bucket elevator it is an iterative process. You start with your application and make a decision regarding the type of discharge you want.

This could be simple gravity/continuous bucket where the contents of one bucket are tipped over the back of the preceding bucket as indicated in the video. These run slowly minimising product damage and component wear with very abrasive bulk materials. These can be mounted on chains or belts.

It could be positive/perfect discharge where the buckets are mounted on side chains and a snubber/deflector wheel or sprocket is mounted beneath the driving sprocket. This pulls the bucket in toward the centre of the elevator giving more clearance to prevent discharged material from on bucket hitting the back of preceding bucket. Speeds are higher than with continuous buckets.

It could be centrifugal discharge where the bucket contents are discharged as a mass between 0 and 45 degrees from the 12 o'clock position. The buckets may be mounted on chains or belts.

Finally, it could be high speed discharge where the bucket contents start to discharge from the front lip of the bucket before getting to the 12 o'clock position. This is the current standard for handling wheat, barley and other grains and the belts can run say 3.5 m/s. Probably not applicable for your application.

Having established the type of discharge determines the relationship between the sprocket/pulley radius and the chain/belt speed. Then the bucket volume and pitch is established from the required volumetric capacity (m3/hr), and the chain/belt strength is established from the gravimetric capacity (te/hr).

Unless you are making your own components chain and sprockets/wheels are purchased from specialist chain manufacturers and you have to select the most appropriate size.

For smooth running a belt is clearly the best as you could consider it as a chain with minimal pitch. Round link (or ships anchor) chains have relatively short pitches and will run more smoothly than a long pitch plate chain purely due to the polygon effect. What you actually use is a matter of individual choice of the machine supplier.

But with bucket elevators you can't get away from the relationship between chain speed, sprocket radius and type of discharge. As a result there is probably no quick easy fix. To use an Irish expression, "if I wanted to be getting to there I wouldn't be starting from here". ■

Originally Posted by DRKREDDY

Dear designer,

What is the criteria for selecting number of sprocket teeth even number and odd number,in above case as per chain pitch 8 teeth is required but actually 23 teeth is exist .Is the number of teeth will slove this type of problems

===========================================================

Not to butt in on designer-

The size of the elevator drive sprocket teeth need to be "MATCHED EXACTLY" with the bucket carrying chain links size otherwise it will hop and hop and hop and eventually break been there done that they sent us an intermediate conveyor with the wrong size drive sprocket and it screwed up right from the start.

The sprocket diameter size is is simply a design matter for the rated system capacity and THE PROPER CHAIN SIZE.

If the elevator chain is the wrong size pitch you are in big trouble!!!!

I would remove the hood of the elevator to determine if the elevator chain is properly seated in the drive sprocket gear teeth if the elevator chain is not

sitting in the bottom of the sprocket cut for each tooth it is the wrong chain period.

I would also operate the elevator with the hood removed to see how it handles the travel from the top down if it can be observed safely from a distance/if the work platform is big enough to watch it run loaded with coke.

The diameter of the drive sprocket is not an issue as long as it is carrying the size of chain it is supposed have for those cut gear teeth properly.

for some reason the video will not open at yahoo -unsure why -no problem though.

lzaharis ■

I don't have a problem with the video, opens fine ? ■

DRKREDDY

You have mentioned that elevator supplier recommended replacement of Head Sprocket assembly and adding counter-weights. Was that implemented?

More information and details will be required to get to the root of problem.

If the elevator supplier is experienced enough(Having previously supplied such elevators WITH SIMILAR CHAIN AND SPROCKETS ) then it can be a problem of mis-alignment and incorrect installation and should be re-checked from basics.

Baiju Joshi. ■

Originally Posted by DRKREDDY

Dear designer,

What is the criteria for selecting number of sprocket teeth even number and odd number,in above case as per chain pitch 8 teeth is required but actually 23 teeth is exist .Is the number of teeth will slove this type of problems

I didn't understand the above statement.

However having seen the latest video you have a "walking tooth" sprocket. This is where a sprocket is designed with more teeth than necessary at a shorter pitch so that the wear is spread more evenly spread over more teeth. ■

The more I look at the the more I think that the problem is the pitch of the chain (which I make 12"). This is the cause of the problem.

I'd be looking at changing the chain for a shorter pitch even if this is extreme.

For something less extreme I'd try out adding a guiding sprocket set (say 6T) to both the upleg and downleg chains to reduce the resonating chain length and hence increase the natural frequency. Just use some gash flamecut sprockets on a shaft in some equally gash bearings, no need for expensive machined and hardened ones as it's only a test. If it works then get a proper job installed.

Start twisting the OEM's arm to supply you the bits

You must be suffering downtime on your plant aren't you? ■

Originally Posted by DRKREDDY

Mr.Baiju Joshi,

Yes ,Instalation and alignments ensured at several stages by OEM Engineers and Components supplier engineer ,found that every thing is acceptable limits

During studying of problem noticed that sprocket INDEX was not matching due to offset in Sprocket and Shaft assembly flanges,supplier engineer told that this elevator was designed for chain R3251 (Rexnord) but actually supplied is R4251 hence as the chain is to heavy ,thus suggested for add counter weight and added as per recommendation( 500 KG).

Supplier was replaced the the hole Shaft assembly with sprocket segments after ensuring proper index and was installed .

You may notice the videos attached are before replacement of Sprockets and After replacement of sprockets the discrepancy was not reduced

I hope I answered your Questions

Regards

RK

==========================================================

The problem is with the chain and the sprockets period and at least the chain should be replaced with the proper chain size and side plates to carry the buckets.

They owe you that much as it was thier collective mistake at assembly and inspection prior to commisioning the elevator.

The problem will not go away due to the nature of the chain design as a chain like that is ment to roll along the floor which is acting as a guide for carrying/moving a load.

The lifting side of the chain is the chain that needs the most tension requiring enough tension to be nearly taunt on the lifting side and slightly less so on the dumping side of the elevator.

The other problemm is simply the chain travel is not contained at all and should be by channels to guide the chain sets in both directions.

lzaharis ■

Dear Mr.Reddy,

Please excuse me for my wild guess. Suppose, the drive or driven sprocket is not perpendicular to their shaft. May be it could not be visually checked. If it slightly tilted by say one or two degree, will it not oscillate the chain both the sides? I saw the oscillation is uniform. Can it be related with the rotation of the drive or driven sprocket? Having 5 mm deflection at one end may lead to 100 mm defelection at middle, say 25 meters.

Expecting your feedback.

Regards, ■

Originally Posted by lzaharis

==========================================================

The problem is with the chain and the sprockets period and at least the chain should be replaced with the proper chain size and side plates to carry the buckets.

They owe you that much as it was thier collective mistake at assembly and inspection prior to commisioning the elevator.

The problem will not go away due to the nature of the chain design as a chain like that is ment to roll along the floor which is acting as a guide for carrying/moving a load.

The lifting side of the chain is the chain that needs the most tension requiring enough tension to be nearly taunt on the lifting side and slightly less so on the dumping side of the elevator.

The other problemm is simply the chain travel is not contained at all and should be by channels to guide the chain sets in both directions.

lzaharis

Just to take issue with a few points :

The style of chain used is common in bucket elevators (with origins in North America) and has been used for many, many years so I could not accept any suggestion that the chain is NOT suitable for bucket elevators. It's also used in chain conveyors of North American origin.

The chain tensions are determined by the chain weight, bucket weight and the weight of the material being elevated. By using a sprocket on the head shaft extra dead weight at the boot is not necessary to ensure drive as is the case when using smooth head wheels. Any dead weight at the boot is applied equally to the upleg and downleg chains.

As for the necessity for constraining the chains in guides, I have yet to see this on vertical elevators, inclined ones yes.

Bucket elevator manufacturers - any chance of some input to this thread??? ■

I watched the videos and noticed:

1) Only the empty downward chain part swings (in two directions)

2)Using a stopwatch, I measured a swing period of approx 0.24 sec (10 full oscillations in 42 sec)

3)Using the same stopwatch, I measured 50 chain links, touching the sprocket in 26 seconds ( 1.29 links/sec)

4)This behaviour will cause exponential wear on the link pins in time.

Conclusions:

1)Oscillation is caused by system resonance of downward, empty part

The oscillation frequency is approx. 0.24 Hz

2)Excitation frequency is approx 1.29 Hz

3)Excitation frequency / oscillation frequency = 1.29 / 0.24 = approx. 5.4 x

Sprocket excitation is not likely.

How to proceed:

1)Search for other possible excitations of the same frequency or frequencies with an integer ratio to the natural frequency of the chain.

(Monitor e-drive for Amps fluctuations, structural support oscillations certain points, vibrations of surrounding equipment and machinery, etc.)

If an excitation is found, eliminate it.

2)Have the supplier calculate the natural frequency of the chain part.

The formula is f = 1/2L * SQRT(Tension/massperlength) (guitar string, so, maybe not completely correct)

3)If necessary, change the natural frequency by adapting:

a) Tension in chain by adding weight on the lower drum (extra load on bearings)

b) Mass per length (not really an option)

c) Shorten relevant chain length (advised already before) by using one or more guiding sprockets with a shock absorber.

Advise:

Have the supplier hire an experienced and capable consultant with an university degree and a lot of measuring equipment, s.a. accelero-transducers and software to perform Fourrier analysis.

This is the Walhalla of real engineers.

Success

Teus ■

At last, someone has done some measuring

I just wish I could train some of our young engineers to :

1) observe

2) measure what can be measured

3) calculate what can be calculated

4) use 1, 2 & 3 to come to an understanding of the problem and use this to hypothesise a solution.

It may not be the right solution, but at least it has an engineering basis.

I'm not keen on the shock absorber in the first instance. ■

Dear designer,

Young engineers become old engineers and the talented ones will survive as engineers and do by themselves the right things as you describe.

The other ones become managers.

A shock absorber dissipates the vibration energy so nicely and is therefore so efficient.

Have a nice day

teus ■

But if my additional guiding sprockets prevent the vibration starting then there is no vibration energy to absorb.

I don't suppose we'll ever know if shock absorbers are necessary because no one will ever test our ideas. ■

Dear designer,

I do not think that there is one mechanical installation or mechanism that operates without any resonance vibration.

Think about an internal combustion engine at a wide speed range attached to a drive train and driving a vibrating load.

There is always some part, which is in resonance. However, the resulting stresses are kept within limits, because of dampening (what a shock absorber does).

The science of vibration control is highly technical and mathematical.

I witnessed an event in the past, where the designers were of the ignorant type and built a ship with a heavy forecastle with engine room and deckhouse and an aft machinery room with an even bigger deckhouse and in between (the mid section of the ship) a relatively flexible hopper section.

The propulsion was done by 2 triple expansion steam machines (Brouwer type) directly coupled to controllable pitch propellers. (When all machinery was put on reverse, the ship sailed ahead).

The ship behaved as a 2 mass- spring system and went through the water like a dolphin.

(It would have been a perfect icebreaker, hammering the ice with its bow)

I saw some people turning pale when we discovered the mistake during trials at sea.

Later on, an auxiliary gearbox with internal counterweights was installed at the exact phase angle to the crankshafts of the steam machines.

The designers did not follow the first rule, which is to generate as little as possible excitation, keep the natural frequencies away from the excitation frequencies, and let never the ratio become an integer.

Isolating the vibration source from the system was here not an option, because of the size and the necessary alignment between the steam machine and the propeller shaft. Probably, this would have resulted in a moving propulsion unit.

Another event was with 2 paired ball bearings, acting as an axial fixation in a blower.

The paired surfaces of the outer rings welded together.

Looking at the ball bearing configuration, it had a similarity with a railway train axle with 2 wheels, one on each rail track. The wheels have a slope-running surface to centre the train between the tracks. I saw a technical documentary about a train, swinging between the rails and wearing the flanges of the wheels in no time.

In that documentary, the engineers found a resonance problem in the bogie suspension as the cause.

I told the recruited consultant (a real good one) about this documentary and suggested that there could be an axial excitation, causing the rotors with the shaft to go forth and back.

Thereby pushing the balls out of the raceway and generating forces, which increased the diameter of the outer ring of the ball bearing.

Of course, by that time we knew all the masses, measured frequencies and stiffnesses of all components.

The super consultant understood the idea and within 5 minutes, he calculated the natural frequency of the suspected mechanism and that matched the measured problem frequency exactly. (My eyes must have been wide open of surprise that he calculated it so quickly and I forgot to ask how he did that)

The 2 ball bearings were modified to one self aligning spherical bearing and the case was closed.

The axial excitation was a result of moving air masses, which also was reduced in later designs.

With the bucket elevator problem, something similar must have been happened and therefore, the solution must be found in:

quote

1) observe

2) measure what can be measured

3) calculate what can be calculated

4) use 1, 2 & 3 to come to an understanding of the problem and use this to hypothesize a solution.

unquote

have anice day

Teus ■

To Mr. Teus Tuinenburg .

Respected Sir,

When you mention that "Oscillation is caused by system resonances" in point No. 1, I believe that you are referring to Torsional Vibrations at Head Shaft of the Elevator, since chain swings will not cause a 'Side-Ward' movement of the strand as shown in the video.

And Torsional Vibrations are set-up only because of periodic impulses or torque variations which are mostly under control in Bucket Elevator shafts as far as I understand, unless the shaft is "Out-Of-Centre".

In case the elevator under discussion has Head Shaft with 'Out Centres', I believe Torsional Vibration will arise and consequently the Resonance.

If not, which component else can cause Resonance?

Please note, my intention is not to counter your point. Only to learn from a respected senior like you.

Kindly post your reply.

With regards,

Baiju Joshi. ■

Dear Baiju Joshi,

I assume that torsional vibrations are not the cause of the problem.

The problem has a frequency of 0.24 Hz and possible torsional vibration in the drive train must have higher frequencies, even when a very soft coupling is used.

However, your suggestion of the drive is out of line (misalignment) is a very well possible cause.

From the given data calculated:

Pitch diameter drive sprocket = 0.7966 m

Chain velocity = 0.59 m/sec

Rotation/sec= Chain velocity / (3.141593 * pitch diameter)

Rotation/sec= 0.59 / (3.141593 * 0.7966) = 0.24 /sec

A misalignment creates an excitation with a frequency of 0.24 Hz and that equals the problem frequency.

Therefore, a misalignment in the drive must be investigated and the stiffness of the support structure as well.

Good thinking.

Cheers

Teus ■

Originally Posted by Teus Tuinenburg

Dear Baiju Joshi,

I assume that torsional vibrations are not the cause of the problem.

The problem has a frequency of 0.24 Hz and possible torsional vibration in the drive train must have higher frequencies, even when a very soft coupling is used.

However, your suggestion of the drive is out of line (misalignment) is a very well possible cause.

From the given data calculated:

Pitch diameter drive sprocket = 0.7966 m

Chain velocity = 0.59 m/sec

Rotation/sec= Chain velocity / (3.141593 * pitch diameter)

Rotation/sec= 0.59 / (3.141593 * 0.7966) = 0.24 /sec

A misalignment creates an excitation with a frequency of 0.24 Hz and that equals the problem frequency.

Therefore, a misalignment in the drive must be investigated and the stiffness of the support structure as well.

Good thinking.

Cheers

Teus

==========================================================

Do we know how the head sprocket is secured or if it is a single two piece unit sprocket with a locking ring and using wired bolts? perhaps the sprocket is worn on the drive shaft and twisting from the load and worn key if used?

lzaharis ■

So basically it's a new machine.

So there are two sprockets on the headshaft, confirmed by http://video.yahoo.com/watch/5026422/13367106 which also shows the chains are side mounted to the buckets and there is a walking tooth arrangement to maximise sprocket life by engaging the chain with different sprocket teeth

I cannot make out from the video how the sprockets are fixed to the shaft, but they appear to have "bolt on" tooth profiles. They also appear to be running true in the video although a longer shot in one position would have helped.

As regards the drive, the video shows it to be a hollow shaft gearbox mounted on the headshaft extension.

Not wanting to be a bore, but I think 12" is too long for the chain pitch and this is the root cause of the problem. ■

Dear designer,

Congratulations with your 1000 post

Teus ■

I really hadn't noticed ■

Originally Posted by designer

So basically it's a new machine.

So there are two sprockets on the headshaft, confirmed by http://video.yahoo.com/watch/5026422/13367106 which also shows the chains are side mounted to the buckets and there is a walking tooth arrangement to maximise sprocket life by engaging the chain with different sprocket teeth

I cannot make out from the video how the sprockets are fixed to the shaft, but they appear to have "bolt on" tooth profiles. They also appear to be running true in the video although a longer shot in one position would have helped.

As regards the drive, the video shows it to be a hollow shaft gearbox mounted on the headshaft extension.

Not wanting to be a bore, but I think 12" is too long for the chain pitch and this is the root cause of the problem.

========================================================

Congratutalions on you r thousandth post designer,

I agree with you about the 12 inch chain pitch being to long: I would bet a pint of Lowenbrau that they elevato was not test run with coke at the fabrication shop that built it- meaning all parts gathered per order and assembled on site prior to commisioning. ■

[QUOTE=designer

.... I think 12" is too long for the chain pitch and this is the root cause of the problem.[/QUOTE]

Please clarify my doubt.

Can longer pitch chain always create problems?

Thanks & regards, ■

It's an absolute certainty it wasn't fully erected and trial run with material!

Best I could ever manage was head, boot and 10' casing section, and put material in a couple of buckets and see how it discharged.

No. It's not just the pitch, but the effective number of teeth in the sprocket and the consequent polygon effect. See http://video.yahoo.com/watch/2118795/6685243 ■

Originally Posted by sganesh

Please clarify my doubt.

Can longer pitch chain always create problems?

Thanks & regards,

========================================================

The pitch allows for more movement of each link- think of it ths way sganesh- if a bicycle chain and the exact length of bucket elevator chain were held up next to each other and the bicycle chain was shaken a little bit it would only move a small distance but if the same length of elevator chain was shook the same amount the elevator chain would move a greater distanceue to the length of the current elevator chain links. the polygon effect is also in play with the movement as well

leon ■

Originally Posted by DRKREDDY

Dear Friends,

Request any of viewers could advise me for further action towards resolving the problem and share your experience…

Thanks for your time

Regards

DRKREDDY,

Do you intend following up on any of the suggestions made in this quite extensive thread? ■

No feedback to us ■

Originally Posted by designer

.....bump.....

No feedback to us

I wonder if the poster has left the operation-which is the general conclusion louis and I gathered after the gentleman from Australia with the linear wet sand surge pile whom initially started asking for help.

Anyway lets hope for the best that the problems were solved in both cases quickly and easily with our suggestions and questions relating to both issues. I certainly hope I was not becoming a nuisance

leon ■

Originally Posted by lzaharis

I wonder if the poster has left the operation-which is the general conclusion louis and I gathered after the gentleman from Australia with the linear wet sand surge pile whom initially started asking for help.

Anyway lets hope for the best that the problems were solved in both cases quickly and easily with our suggestions and questions relating to both issues. I certainly hope I was not becoming a nuisance

leon

Perhaps the problem has gone away,

Perhaps the OEM has fixed the problem,

Perhaps the problem doesn't prevent the elevator from working

Perhaps the plant isn't working

Perhaps the elevator has been replaced

Perhaps .....

Perhaps .....

Perhaps ..... ■

Dear Sir,

we are one of the leading supplier of chain equipment for bucket elevators and have hundreds of chain bucket elevators ( double strand ) in operation. There are no problem with our systems but of course the elevator and the chain equipment have to be designed correctly. Kindly send me your phone number so that I can get in direct contact with you.

best regards

Gerhard ■

The sprockets do not look hardened to me - typical treatment is flame hardened - 6mm depth in the contact area.

They need to be harder than the chain bushes but too much - as the sprocket section should be the replaceable items.

Seems like your whole elevator is not up to the mark - I would say that the OEM engg who came to site would not know much. They should not have left site unless they gave a prelim. report!!!

I would be wondering now what next is going to be an issue.......?????

Cheers

James ■

Regarding the number of teeth then based on the pitch of the link and the required pitch circle diameter then the correct number of teeth would be eight.

However, with a long pitch chain it is possible to design the sprocket to have a "walking tooth". In such a case the number of teeth is (X*8 -1) where X is an integer. So putting X=3 we get 23 as the number of teeth. For the user the advantage is that the wear caused by the contact of the chain on the sprocket is spread over a greater number of teeth and the effective life of the is extended. For the manufacturer the production casts are a bit greater and he sells less spare sprockets

I hope the explanation is clear as I did have to think hard about how to design such a sprocket the first time I did one.

Looking at the photo's of the sprockets I suspect that either

• An incorrect material has been used
• An incorrect heat treatment has been used

I suggest sending the worn sprocket to an established metallurgical laboratory for an independent examination covering

• Chemical analysis
• Core hardness
• Surface hardness
• comments on what heat treatment, if any, has been carried out.

One final thought on the sprocket, was the profile machined or laser cut? There is a tendency now to use hardplate, laser (or plasma) cut. This is not really a good idea. ■

Originally Posted by DRKREDDY

Dear Friends,

Recently we commissioned the coke calcification plant in Kuwait,in our material handling system have had a double strand bucket elevator which specifications are as follows

• Application: CPC Handling
  
  
• Density: 0.8 M3 /Hr
  
  
• Capacity: 75 TPH
  
  
• Normal operating Capacity: 50 TPH
  
  
• Speed : 0.59 Meter/Sec
  
  
• Height: 51.5 Meter C/C
  
  
• Type : Double strand ,slow speed Gravity discharge chain elevator
  
  
• Casing: 760X 1410
  
  
• Head sprocket R4251-8T-796.6 PCD
  
  
• Bottom traction wheel 737 mm OD
  
  
• Bucket 300x228x300

Now let me explain the problem we are facing Please bear with us, if some of the following is already common knowledge to yourselves, as we are not yet sure of your specific familiarity with the designs as they apply to the equipment.

Bucket elevators are unique to the service of Material Handling However In our case right from trail runs we noticed that Chain is getting swing and causing for casing damages due to continues rubbing on to casings especially at 2/3 of height from boot

Swing of chain may have variety of causes. Incorrect specification or poor quality of suppler tolerances, poor alignment practices

We reported the problem to OEM and subsequently studied the same and reverted back with a proposal of Head sprocket assembly replacement and adding of up to 500 kg Counter weight at bottom take-up and thoroughly checked all the key alignment factors found them selves satisfied, but problem not solved.

At this time, OEM and sub contractors (supplied) it must be pointed out that the factors above are divided among several entities for their design, installation and subsequent warranty. No single entity is willing to accept major responsibility for the failures that have occurred, each pointing to the other as the primary culprit. As expected, the issue has become extremely contentious.

We had already extended the casings by 180mm to avoid rubbing action almost 40 meters height, now the elevator is operating with lot of swing ,but continues rubbing was minimized

I hope this information is adequate to advise us for corrective action as well as probable causes for such discrepancy

Request any of viewers could advise me for further action towards resolving the problem and share your experience…

Thanks for your time

Regards

please upload the files for your use from Tsubaki and Reynod ■

More information for you that will clear things up I think.

Attachments

renold chain (PDF)

selection (PDF)

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