My experience (and analysis) is that the most energy efficient machine for purely elevating bulk material is a bucket elevator.

You refer to the "mechanical counterparts" of the "Pipe Chain Drag Conveyor", can you elaborate what style of machines you are referring to? ■

I have worked in the salt business for over 30 years and would never use a pipe disc conveyor to elevate salt (I am assuming that you are referrring to the type in the attached pic)

It would be a maintenance nightmare to say the least.

Your best and most efficient means of elevating your product would be with a bucket elevator. If moisture is a problem specify the buckets to be made from UHMW plastic Style A digger buckets. Less chance of sticking to plastic than with metal.

Attachments

internal-mechanism (JPG)

■

If you are convinced that this is the way to go then the SS chain is a must as it would lessen some of the problems. All chain components would need to be SS. Standard chain would sease up in no time.

I would also recommend that the pipe be in SS as well.

The biggest problem I see is that as the discs wear the capacity will reduce and efficiency will drop off. So you might want to concider polyurathane discs to minimize wear.

But if it was me I would still use a bucket elevator, much easier to maintain and easier to inspect as well as more efficient.

As far as your existing bucket elevator - if the casing is still in good shape it would be much cheaper to simply replace all the mechanical components and if necessary a new head section.

We just recently changed out a 50 year old 75 TPH bucket elevator that needed a new head section c/w drive, pulley and we also put in a new tail section c/w pulley and take-up, removed and installed a complete new belt and buckets all in 3 - 8 hour shifts.

So downtime was kept to a minumum. ■

I regard ammonium sulphate as corrosive so if you use low alloy steel components expect them to disappear over a period of time

So you would use a high alloy stainless steel. Trouble is, while the low alloy steel would be surface hardened for wear resistance, the normal "stainless" steels aren't surface hardened so you end up gaining corrosion resistance but losing wear resistance

We once supplied a bucket elevator with stainless steel chain to clients specification. It didn't corrode, but wore away quite quickly. They tried case hardened chain which while it corroded a bit had a useful life longer than the stainless steel chain and was cheaper and more readily available than the stainless steel version.

Of course a belt in an elevator doesn't have any corrosion problems, so a belt and bucket elevator with stainless steel buckets would be my choice. You could use plastic buckets, which are all the rage in some industries, but maintaining belt tension is more critical to avoid belt slip due to their light weight.

Oh, and I wouldn't regard a screw conveyor as the counterpart to a "Pipe Chain Drag Conveyor". A chain conveyor/elevator of the en-masse or even drag scraper style, yes. ■

With a belt and bucket elevator the drive between the head drum and the belt is purely friction like with a belt conveyor.

So the tension ration across the head drum is given by

T1/T2 = e^mu * theta

where

T1 is the belt tension on the rising side of the drum

T2 is the belt tension on the descending side of the drum

mu is the coefficient of friction between the belt and drum

theta is the angle of wrap, pi radians (180 degrees)

The lower the weight of the bucket compared with the weight of it's contents, the more critical is the tension, and the more it is essential to do regular maintenance checks. You could always use gravity dead weight tensioning to maintain constant belt tension. ■

Hello,

Earlier participants have already given more specific information. Following is the general information about the equipment conveying bulk material in a enclosed circular or rectangular cross section.

Attached sketch (upper part): German source. Here in view of oval link chain, this type of conveyor can have flow path bends like water pipe (3 dimensional freedom).

Attached sketch (lower part): American source. Equipment known as a ‘Bulk flo conveyor’. Material conveyed in rectangular cross section. In this case the flow path bends can be only in vertical plane which is perpendicular to sprockets shaft (head and tail shafts are parallel and in horizontal plane)

3) Material conveyed in rectangular cross section, UK source, possibly known as a Redler conveyor. Sketch not attached, as I do not have.

Hope the information may be of use. Knowledgeable readers can put more information.

My posting only informs about the available options for the type of conveyor. It does not give any opinion about the suitability of specific equipment (whether regular bucket elevators or as mentioned by me in this reply) for your application.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis is 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

Attachments

tubular and bulk flo chain conveyor_1 page (PDF)

■