After posting this article on Slingers I have been contacted by Christopher James, an expert on the topic with an exceptional amount of real world experience.
He has been so kind to share is knowledge on the theme and I am thankful for that. I am sharing it with you in the very comprehensive post below with almost with no edits.
You can reach him via LinkedIn or following one of these links:
(Beginning of guest post)
This video link shows some of the applications of the Slingers working on wind farms.
Slingers are high speed material placing machines. By introducing them to backfill cable trenches most companies can remove one piece of earthmoving equipment, one operator and two or more labourers.
While doing all of this they are able to increase production of over 10 times faster than some operations and while almost reducing waste of the imported material. In the video below these speeds of backfilling are real time speeds. The machine was backfilling cable trenches on a wind farm in NSW, Australia.
Speed is obviously an advantage but it is the ancillary savings like reduced labour and equipment. Also the waste of the imported material is huge with traditional methods. In some cases on large scale wind farms we are able to off-set the cost of a Slinger to just the savings alone…all on one job.
These machines can move up to 3.5 cubic meters per minute. This is in a perfect world and perfect conditions. Generally speaking a good average to work on is 8 to 10 meters per minute on most 400mm wide trenches. As you can probably tell this is huge production compared with some of the old methods.
This wind farm in NSW where we brought this TR-30 Slinger (rubber tracked with cab) they were using a 25 tonne articulated dump truck and a 20 tonne excavator. The excavator would scoop material out of the truck and place into the trench. We were around 15 times faster than this operation with the obvious one less machine and operator.
I have also added the below the link to a video by Buckeye Trenchers working on the cable trenches on wind farms in the USA. We are agents for Buckeye Trenchers and these really are high speed trenching machines. A Bucketwheel trencher is suited to soils or small stoney ground. They are not suited to rock at all. Once you hit rock you have 2 options, either a Chain Trencher or a Rock Wheel trencher. Either way there are options.
A chain trencher is one of the most common trenchers around the world, as seen in the Vermeer video link below. These units can range in trenching widths from 300mm up to over 2 meters wide. Ranging in weight from 20 tonne up to over 200 tonne.
A rock wheel trencher as shown in the video below by Vermeer will generally only go up to 350mm wide trench. Now I have seen up to 450mm wide but not a very common machine.
Next you step up into the “dig, lay, bury” machines.
Rivard make a unit in the attached video. These are great units for single pass operation. From experience though if one link in the chain stops, like the trencher or the cable spooling and so on, everything stops. This can be quite costly.
From my experience having crews working on multiple fronts at once limit your risk and usually allows for a more productive environment. For example a bucketwheel trencher should get around 3 kilometres of trench done in a shift, the same goes for backfilling with a Slinger (depending on many factors).
If you were doing a single pass operation you would not achieve numbers like this.
It really comes down to how much production you really want, or you can achieve.
Each operation has its pluses and minuses, no doubt about it. As I was always taught in pipelines, get the basics right. Get the equipment right. Lower your risk as much as possible and then find minutes to shave off each process. Laying cables is as repetitive as it comes, just like pipelines and it is all about streamlining processes as much as possible to get as efficient as possible.
This is why we have always used trenching machines for pipeline works. They replace many excavators (bucketwheel trencher can replace up to 10 x 25 tonne excavators). Trenchers also make exceptional backfilling material, excavators just cannot do this.
As a general rule (very general as all ground conditions change dramatically) please see the below for trenching equipment production:
- Bucketwheel in good, dry soil ground conditions: 3 kilometers up day digging 400mm wide trench at 1.5 meters deep
- Chain trencher in firm, dry, small stone ground conditions: 800 meters to 1000 meters per day digging 460mm wide and 1.5 meters deep with a 45 tonne class machine
I cannot give production in rock as it is too much of an unknown with the hardness and so on.
I have had 45 tonne class chain trenchers take 3 days to cut 4.5 meters of pink quartz and then dig 600 meters of hard limestone. It is too much of a variant to give some solid figures.
Additional links that you might find useful: