Re: Lagging With High Powers
Yes, power > 10,000 kW / conveyor. Is it power or belt tension you wish to measure as a barometer? What about temperature conditions, belt width, bottom covers, pulley diameter, type of take-up, ......?
Here are some installations.
Los Pelambres, commissioned 1999, is designed for 10,000 kW on two drive pulleys on two conveyors and 5000 kW on a third. It has a ST-7800 N/mm belt rating. It is been running with rubber lagging.
Collahuasi has 8000 kW on two drive pulleys with ST-6300 N/mm belt rating. A second conveyor has 4000 kW. The rubber lagging is failing from slippage. I attribute the failure to the takeup system that allows the slippage. It has been running since 2003.
Selby, 1983-1985(?), had 10,300 kW on one pulley, belt rating ST-7000 N/mm, with no lagging.
Palabora, 1988, had 7050 kW on two drive pulleys using rubber lagging. The only time the pulley showed slippage is when the lagging grooves wore below a critical depth and then hydroplaning occurred.
There are many conveyors operating above 3000 kW through out the world with ceramic and rubber lagging. Some ceramics have problems with tiles releasing out of the rubber matrix. Some rubber does fail both from bad rubber specs and from bad engineering of the conveyor.
Kennecott 4500 kW - two conveyors - rubber
El Abra 7200 kW; 5400 kW - rubber
Kaltim Prima Coal - 5000 kW? - rubber?
Highland Valley Copper 4500 kW(2) - rubber
Why not share the failure details? ■
Re: Lagging With High Powers
Larry
Thanks for the extensive reply.
Lagging failures are interesting in that a relatively simple product seems to have a great variety of means of failure.
One conveyor carrying steel cord belt seems to scuff the cold vulcanised lagging to bits on a regular basis. I suspect that this may be due to the high torque transitted and the high T2. The high T2 means that the belt relaxes from T1 to T2 in a short arc of travel around the belt, placing a high localised strain in this area.
On another site the customer specifically wanted a very thick lagging and a very deep lagging groove. This resulted in large amounts of strain in the lagging, which led to hysterisis causing the premature failure of the lagging.
Both of these were on drives that were difficult to change out or do on-site lagging replacement.
Your Los Pelambres example I find particulary interesting. I wonder if this and the other examples are hot vulcansied lagging. I'm yet to come across the same sort of issues with hot vulcanising as I've seen with strip lagging. However, given that it is basically the same material it would be surprising if hot vulc' was particulaly better than strip. ■
Re: Lagging With High Powers
Matt,
Lagging rubbers differ and do belt rubbers. Groove designs differ as well. I believe in an earlier response to some posting I noted our FEM of lagging such as Palabora.
Palabora had the conveyor roll backwards downhill to an apparent drive friction coeffient of f< 0.15, after the belt had been washed in the tunnel, started and tripped. Big mess. Since it was my design, I was thorough in investigating. The grooving had worn. FEM showed the collapsed grooves, under ST-6600 N/mm pressure could not trench the water out. The details are a bit more complicated, but you get the idea.
Phelpd Dodge, Morenci Mine had the rubber lagging desroyed from one side of the pulley. This is an ST-5800 N/mm belt driven by 4500 kW downhill. The type of rubber was at fault along with a rain. The logic parked the belt when slip was detected. The belt kept slipping over the drives. The belt reached > 18 m/s before it emptied.
A large Chilean conveyor, with rubber lagging and 8000 kW drive, uphill and downhill, has the lagging being torn of the pulley. Is it the rubber or some other condition that causes the rubber to fail?
My point to these stories is you need to investigate the total system and not just label the concepts as good or bad ( RUBBER, CERAMIC, GROOVES DETAILS, ET AL).
High powered and high tesnion drive lagging undedrgoes a great amount of: stress, heating, deformation, slipping (T1-T2), ...... They require proper engineering along with the rest of the conveyor. ■
Re: Lagging With High Powers
It is difficult to get the message across with all these spelling debacles and sentence structural defects.
I answer some posts with little sleep and don't do the necessary checking. I appologize again for mangling the language.
I beg my friend, the good doctor, invest in a little spell checkerand grammar program. We also see I am not the only one that can get the message twisted and leave the readers perplexed.
Hoping. ■
Re: Lagging With High Powers
Add thoughts:
1. The conveyor design can contribute to lagging failure such as introducing drive slippage using poorly conceived takeup designs or not getting the forces correct
2. Most, if not all, hot vulcanized lagging is superior to cold bonded when measured for overall performance
3. Hot vulcanized lagging must be evaluated for its final form - the autoclave taping distorts the surface dimesions which can lead to belt mal-tracking
4. Product properties such as red muds (iron ore fines, bauxite fines, nickel and brown coal (lignite)) and their influence on the coefficient of friction and material buildup.
5. Item 4 points to load sharing problems as well ■
Re: Lagging With High Powers
Larry
All good points. Thanks for the input. ■
Lagging with high powers
Over the last few years we have seen a number of instalations with high power where the lagging is self destructing in unacceptable time frames.
These are typically on drive pulleys where 3 MW or greater is being driven through them. Steel cord belt is used.
Does anyone know of sites where large amounts of power is successfully being transmitted through pulleys and the type of lagging they are using? ■