Biggest on the planet

[digger doug]

From Page 94 above:
" the power the motors generated was conducted to grid resistors, where the energy was dissipated as heat"

That was similar to the ex-Navy diesel-electric derrick I deckhanded on. There were big cabinets in the house with those resistors. When you operated a control and tried to feather it, it dumped current into the grids.

I have seen pix of ones running the excess up to a catenary.

 

[Hank R]

I was sure I had more pictures but a couple of moves and a change of camp cook (wife) who know where they are sorry guys.

 

[Nige]

I have seen pix of ones running the excess up to a catenary.

Are you thinking of trolley assist.?
That is a system generally only used to assist climbing out of the pit rather than as a way of feeding back power into the system when descending. Mainly because of the cost of the overhead line installation and the inefficency of converting 2600V DC or thereabouts on the truck back to 33Kv AC of the incoming supply.

There are a number of trolley assist system operating in Africa. AFAIK in addition to Lumwana they are at Kansanshi. (copper), Sishen (iron ore), & Rossing (uranium) among others.They are also used at a couple of Boliden properties in Scandinavia and First Quantum's copper operation in Panama.

Apologies for the fact it's a Siemens pulbicity video but it's the best one I could find to illustrate how a trolley-assist system works. Only the first couple of minutes of the video deal with the trolley system.

 

[digger doug]

I just saw some pix showing the overhead caternary system 35 years ago, was told the trucks going down (and using dynamic braking) were feeding to the system, and the trucks going up were drawing from it.

You've got the real news on this Nige, and I appreciate getting the facts straight.

 

[Truck Shop]

The Caternary system was used in several situations. This hi jacks the thread-but Milwaukee RR used
caternary way back. Where there were ruling grades they would build transformer/storage buildings
on both sides of the grade. A train going up used the power generated by the one that just came down.
And Milwaukee RR still went broke.

 

[Nige]

I just saw some pix showing the overhead caternary system 35 years ago, was told the trucks going down (and using dynamic braking) were feeding to the system, and the trucks going up were drawing from it.

There may well have been systems like that back in the day but I can honestly say I never saw once personally. As I said above the main drawback would be the capital cost of setting up a second trolley line for trucks descending into the pit would effectively double the capital cost of the system. This, coupled with the inefficiency of the energy transfer from DC back to AC in order to return the power generated by the descending trucks retarding to the power grid, kind of makes the idea a non-starter for financial reasons.

Operating cost-wise trolley works really well in countries that have an abundance of cheap power, usually those countries with a well-devloped hydro-electric system. In other words electricity has to be much cheaper than diesel.

Another thing that the proponents of trolley-assist conveniently forget are the grading requirements of the haul road under the trolley line. It has to be almost perfectly smooth and graded to within an inch of its life so that the overhead catenary is no less than Y and no more than X metres above the road surface. It can't have any soft spots, dips or humps because those can potentially cause the truck pantograph to separate from the catenary and if that happens the truck loses the trolley-assist. Not good when you are climbing a 10% ramp fully loaded with the diesel engine at idling speed.......!! From an operational standpoint the requirements to maintain the road under the trolley line is a full-fledged nightmare.

The other downside of trolley-assist is that once it has been installed the mine is pretty well stuck with that road alignment for all haul traffic coming out of the pit until the system is eventually decommissioned, because moving the installation would probably cost more than installing a new system in another location in the mine. Not ideal if the pit in your mine is dynamic and constantly expanding, or changes in profile majorly year on year.

To give you some idea on the cost, here a some numbers sucked from a 2019 report regarding the capital cost of a trolley-assist system for an existing diesel-electric truck fleet that would require a sub-station every 850 metres (935 yards) of trolley line.
Trolley Line installation (structures, cabling, etc) per 850m - $2.3m
Substation (ea) - $2.8m
Pantograph & controls/truck - $350,000
So based on those numbers to construct a 2.55km trolley line (3 units) for a 30-truck fleet would set the mine back $16.3m in infrastructure and $10.5m to modify their truck fleet - $26.8m in total.

 

[Nige]

Continuing with Truck Shop's railway theme. While looking for information regarding the trolley system at Sishen iron ore mine I came across this video.

 

[digger doug]

Nige,
I thought that CAT mining trucks were only mechanical drive (as opposed to the electric wheels on Wabco, unit rig, etc.)
Did they use the catenary system for assist ?

 

[digger doug]

Looks like the Ozzies broke that record:
The Longest Train in the World. BHP Iron Ore set the longest train… | by Daniel Ganninger | Knowledge Stew | Medium

However, your video shows individual engineers in each engine to control the power, a hard thing to do.
IIRC the BHP run uses Locotrol.

 

[aongheas.macask]

Continuing with Truck Shop's railway theme. While looking for information regarding the trolley system at Sishen iron ore mine I came across this video.

HI Nige,
I worked on rigs in Saldanha shipyard a few years ago and seen those trains on a regular basis, didn't know they were record breakers.

 

[Nige]

Nige,
I thought that CAT mining trucks were only mechanical drive (as opposed to the electric wheels on Wabco, unit rig, etc.)
Did they use the catenary system for assist ?

Cat was late-ish getting into the electric-drive truck market, close to 15 years ago. Up until that point their mining haul trucks were all mechanical drive. It seemed as though they were fighting shy of going to electric drive while DC drives were the only option.
Now their mechanical-drive mining truck line (789, 793, & 797) is complemented by an even bigger electric-drive model line (794, 795, 796, & 798). All the electric drive models are designed to be built (or retrofitted) with pantographs to work under a trolley line. This option was only introduced 2 years ago in 2020. The electrical system for the trolley is usually produced by a partner. I'm not sure who Cat are partnered with but both Komatsu & Hitachi are in bed with Seimens, for Liebherr it is ABB.
I don't know how sales of mechanical drive mining trucks today compare to those for electric drive.

 

[Hank R]

In summer of 2013 I went back to Sparwood 33-19 Still looks good.

 

[Hank R]

Not my picture sent to me by a friend.

 

[Nige]

It's amazing the work-arounds that came to the earthmoving market before large off-highway tyre technology improved, which generally co-incided with the advent of radials.

 

[Hank R]

I am amazed at how well everything was built or over built before computers, Just good men designed and used their brains. And it worked ...

 

[digger doug]

It's amazing the work-arounds that came to the earthmoving market before large off-highway tyre technology improved, which generally co-incided with the advent of radials.

IIRC the 300 ton truck design was held up for a short period of time, not having a tire able to handle loads, and still be able to ship it to the mine.

IIRC there was talk of sending the mold to the mine, to vulcanize them on site.
I think Michelin came thru with a "normal" tire, and work continued on.

 

[Nige]

IIRC the 300 ton truck design was held up for a short period of time, not having a tire able to handle loads....

That’s why the first attempts were all for a 3-axle truck rather than the “normal” 2-axle style. Reliable and large enough tyres to design the trucks with 2 axles were simply not available.

Even in smaller sizes such as 27.00R49 (Cat 777 size) there were major tread separation issues with the first radial tyres that became available, and that was back in the late 1970’s.