There can be two types of wear in a chute, abrasion wear and impact wear. Abrasion wear ususally occurs when the material slides along the wear liner material and impact abrasion is when the conveyed material strikes the wearliner at oblique angles. One or both types of wear may be present in a chute. Some materials resist impact abrasion, some materials resist sliding abrasion, and some materials resist both very well. In our book Foundations III in chapter 8 there is a complete listing of various types of wearliners. Other considerations are corrosion and temperature. There is a chart form this chapter on page 95 that might help you. ■

Mahmud..

The best liner is the material being handled itself in a dead box.

This will require a lip liner at the edge of the box for which VRN 500 or equivvalent is used for coarse big lumps and ceramics for finer materials,

Elsewhere for lining the chute, the same applies for VRN and Ceramic lining.

Avoid sliding material on liners wherever possible, and never impact of a liner plate.

Also, avoid curved chutes. (They are great in theory, but in practice I have seen them wear out in about half a nano-second if handling anything more abrasive than porridge oats)

Regards

LSL Tekpro ■

Mahmud, I agree with graham but if you are dealing

with chutes-

If you need something quickly go to your steel supplier and ask for "AR plate"

"Attack Resistant Steel Plating",

very strong, easy to use and cut for chutes etc. and a quick fix as it will be easy to bolt into place providing there is enough steel thickness to bolt it to. Use Allen head cap screws on the interior of the chute with blue "Locktite and flat washers for the nuts on the exterior of the chute or nylock nuts-these nuts have nylon inserts to lock the nut to the threads of the bolts. ■

Come-on Graham, A Non-Advocate of Curved Chutes:

Another reminder that curve chutes work extremely well when proper engineering is applied. Case in point: Palabora, there in South Africa, which typically sees 35-50 million tonnes pass through the chute, at 6000 t/h, before local liner replacement is required. Although the conveyor and crusher have been retired for a few years, there are those that know. As you know, the ore is primary crusher copper quartzite. Its hard and sharp with large lumps some > 250mm.

Palabora had a rock-box (RBX) that dropped material successfully onto the belt for 3 years. THe ore could not accelerate immediately causing a large slip length and high impact. Both of these conditions caused the 18mm top cover to be destroyed in 2 plus years. THe curved chute gave the belt a life expectancy of ~30 years. Its now retired after about 9 years of service with little wear.

Another is Los Pelambres, in Chile, transfering primary crushed copper ore (+200mm) at 7800 t/h through three curved chutes with great success. I could name many more now designed by others in hard, sharp and large rock.

There are many virtues of curving the ore flow onto the belt:

1. better central loading with little or no spillage compared to RBX

2. no or little spillage compared with RBX loading on inclines

3. highly reduced noise

4. highly reduced impact idler damage

5. belt life increase due to abrasion by a factor of 3 times

6. belt life increases due to impact by over 10 times

7. reduced dust - now dust-less transfers are recommended

8. and so on totally 20 major design benefits

SInce you know all of this, I must assume this is sport to see if the elders can still recall.

I do admit that some in RSA have made poor attempts to engineer curved chutes that give it a bad image. ■

As far as liner material specifications look to SAG and AG mills. Liner materials are perfected to last for many million tons in very difficult conditions within the mill and feed to the mill. AR plate is not the answer to heavy impact with high abrasion.

Ceramics also can do it, if the flow does not have high impact. ■

Nordell: Do you have a sketch or pic or something to show me the configuration of a curved chute please.

We use typically rock boxes or AR liner plate on feed chutes, etc.

If feeding a 20, 35 or impact idler position of belt conveyor, do we mimick the profile of the trough?

Thanking you in advance, ■

We have many,

Look at our website noted in contact details below. I will also post a number of additional chutes to the already published Palabora (RSA; 6500 t/h, prim crushed copper @ 4.1 m/s) and Los Pelambres (Chile, prim. crushed copper @8700 t/h & 6m/s).

The new posting will include a number of coal, limestone, and prim. crushed iron ore chutes) together with some unusual design requests.

We have also developed interesting:

a) 7.5 m/s transfers,

b) reverb furnace spout with special centering configuration,

c) telescopic ship loader w/ plugged chute forces

d) special circular bifucated loading chutes

e) split stream loading w/ articulation and stream direction change

f) chutes without valley angles for special sticky material

g) bin loading with volume optimizing methods

h) special belt and vibratory feeder analysis and design

George, how do you know the degree of damage you cause with the rockbox? As noted in the Palabora publications, we isolated the damage mechanism for gouging and abraison. Once this was understood, we were able to increase the belt life 10 fold, significantly reduce spillage and rock rollback, improve belt cleaning with the better belt surface condition, improve load centering and belt tracking, and eliminated idler impact damage.

I do not have authorization to publish them. I can discuss them privately. ■

Good morning Larry...

I thought my comments might just get you going!

(All quite deliberate and had the desired effect.)

I do however maintain that if you don't get them right, curved chutes can be a disaster. This is based on my findings in Australia where when curved chutes became the flavour of the month, there were some spectacular failures even on coal.

The curved chutes we did for the three flight Syverfontein 24km overland coal conveying system however, work very nicely and operate at 6m/sec.

Regards

LSL Tekpro ■

Graham, of course you did. You didn't anyone. I know, that you know, that I cannot pass up an opportunity to dialog.

Australia as anywhere - garbage in garbage out. A must is to find the facts that caused the failure. Sometimes its not so easy and you lose on your first impressions and partial knowledge. Sometimes you don't find the second and more comprehensive answer, rhetorically speaking.

I am curious on how you would have handled Palabora's rockbox flaws and saved the day? ■

Jim is right, rubber wears like a pig's snout even on hard rock. I have even used rubber blocks to make small rock boxes and the rubber lasts very well on the edge.

This is one of the reasons why we drive on rubber and not steel tires.

It is not quite as good at shallow slopes however. ■

Dear Mr. Mahmud,

Choice of liner is somewhat intricate subject and often relies on past experience. Liner characteristic is primarily influenced by magnitude of the impact and general abrasion resistance. Suppose you have 300 mm size lump of a particular material falling from 2 m height and alternatively the same material falling from 5 m height can make difference in the selection of liner.

If impact is severe, then work hardening materials like high manganese steel are more suited. If the lump size is very small then liners of more hardness will have a longer life.

There are various types of liners such as rubber liners, UHMW liners, stainless steel liners, to suit depending upon the application. Thick rubber blocks are sometimes used on the impact zones of the chute. They perform silently. UHMW liners have very low friction coefficient and they are good for moderately abrasive material for faster flow or lesser angles of the hopper walls. Their resistance to impact is less. Stainless steel liners are used if material has corrosive effect also or for hygienic applications. In all probabilities, as per my assumption, possibly your query is in context of limestone material. The liner material will depend upon the lump size, chute configuration, magnitude of impact and the price one is prepared to pay. It has been observed by me that many times buyers prefer somewhat thicker and less expensive liner, instead of disproportionately expensive liner. Buyers are also very sensitive to easy availability and easy replacement.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

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