Bucket Elevator Problem
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
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?
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
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 ........
bucket elevator suppliers ???
guy's maintaining bucket elevators on plants ???
Originally Posted by DRKREDDY
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
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.
Please find the link for Bucket e;elevator operating vidio file
Originally Posted by lzaharis
I was thinking it was swinging "in and out", not "side to side".
Haven't seen that before.
Originally Posted by designer
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.
Originally Posted by lzaharis
Once again forwarding the link for your view
Originally Posted by 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
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