I just had this posed to me by one of my operators: "Excavators should have flat teeth. A shovel style tooth. It helps grade the bottom of the ditch better. A pipe will last longer on a flat bottom ditch. Fuel economy is not effected by sharp or flat or dull teeth." This statement was a little bit contrary to what i felt i had learned over time. Our work is more like mining that pipe laying. We install rural water which is "blow and go" work. We put in 2000' to 3000' feet of pipe in per day. We are full throttle all day. Digging all day. We are also in a lot of prairie so the ground is dry and hard. This is what i though i knew: GET can make a big difference in fuel economy. In hard ground the pointier the tooth the better--faster easier digging. Frost teeth wear out too fast. Super V SYL wear out too fast and are little too blunt for hard ground. Super V SDX have extended life and are a little pointier for easier digging. A sharp tooth on the final pass loosens the earth and helps create a saddle for the pipe to lay in. Please tell me what you know. Help me learn here about GET. When we are on a job i can spend $600 per week per machine on teeth so I am willing to listen if you can save me money.
IMO asuming a baseline rpm that the machine operates at regardless of tooling GETs don't make a difference in fuel economy per hr.... BUT can make a huge difference in lf of pipe in the ground per hr which in accounting/job costing terms I would equate to greater fuel efficiency. Furthermore, if the given machine has different work modes (our Hitachis have Economy/Normal/Kick Ass modes) and the mode of choice for the operator happens to be one that raises engine RMP based on force exerted this could also have an effect on gal/hr as the lower penetration teeth would likely cause the operator to be a bit more agressive with the sticks...I also think though that the best way to leave the bottom of the trench is smoothed/pressed out with the bottom of the bucket, if the pipe layes on a loose material that is capable of additional settlement from the state that it is in when the pipe is layed on it, there is a chance that that settlement may cause an issue in a joint near it. We typically use crushed/washed stone for bedding in our trenches to cradle the pipe while protecting it from settlement.
What type of tooth are you running? For example, "esco super v", "kmax", etc. I have always suggested a twin tiger application for rocky and extremely compacted material.
I am almost sure that i have noticed a 2 gal per hour fuel savings when switching from old teeth to new, but there could have been different conditions involved too. We are mostly using an Esco Super V. I have been running the SDX but i have been told that i should be running a flare by this operator. We are installing 40' pipe lengths. We put the pipe together on the surface and loop it into the trench. We don't take the time for bedding material. This work gets done for under $10/ft. It is blow and go. Thanks for the responses. Keep them coming if you have any more info.
Give your operator a shovel and a spade and then ask him which is easier to dig with and which requires more energy to get the job done? Then take him to a pile of sand and ask him which is more productive to shovel loose material with? Obviously sharp GET will save fuel because the machine can dig faster with less effort, you will probably hear the engine load up as it digs into the ground, when an engine loads up it will use more fuel. Blunt tools will mean the engine loads up more and perhaps for longer. I guess basically you have to keep detailed records of fuel usage, teeth usage, productivity, etc to work out what is best in your situation. However I will say that a good operator will save you the most money and be the most productive, not sure whether flat tooth Fred falls into that category. Things like the angle of the bucket and the depth of the cut are important factors in getting the best out of your machine. Perhaps you could look at mixing up the teeth, having a couple of tiger teeth and a couple of flats?
If you are digging in soft ground, the flat, shovel style will do good. They retain more material in the bucket for a greater fill factor, and in soft ground penetration is not an issue. If you are digging in hard ground, the sharpest teeth that will give a reasonable wear rate are best. Your stated choice sounds right to me. As far as the pipe, if the operator is worried about it, he can heel the bottom flat in one pass with the bottom of the bucket. I would not be worried about it myself. When you backfill, if you get material compacted in around the haunches, that is what gives the pipe its support.
We also find side cutters help the bucket to heap a bit more and get a little more fill. I have asked here before about "how to dig a ditch fast" and that bucket angle statement is pretty important. However the second fastest (ft/day) operator I have ever had work for me dug in a completely unintuitive way. He would jam the bucket teeth on the horizontal into the ditch wall. He would then crowd and curl in a motion like wiggling the bucket until it was full. Most of the other operators use a shaving type method to shave thin layers of the earth into the bucket.
I agree with your method of pipelaying
If the operating cost differential between types of teeth is that critical, the work is being bid too close to cost. But that's the nature of the beast in this line of work.
It isn't necessarily about the bid but more about general economy. Here are some numbers: Set of teeth for 30 ton machine $600 Fuel cost per gallon $4.00 Savings per hour with sharp teeth 2 gallons per hour or $8 per hour Savings per 12 hour shift $96 Set of SDX will last two weeks set of SYL will last one week. Savings of $600 every two weeks or $60 per day Total daily savings $156 Total weekly savings $780 Total monthly savings $3380 Total annual savings $40,560 We can't work all year round so this is a bit of a stretch. Also we work a 12 hour shift but we don't run the machine for 12 hours strait all the time so these numbers are a bit skewed. In the end GET makes a difference. Its not a little item.
Could you post a photo of your current lip/tooth/sidecutter arrangement and maybe also a typical photo of the type of material in which you're digging most of the time ..? Going back to basics the photos will show if your bucket width is correct for the material and type of work you're doing.
Another comment - sharp vs dull teeth will maybe not affect the hourly fuel consumption of the machine enough to measure but it sure as Hell will affect the volume of material you can move in an hour.........
Most of our buckets are smaller. This is a 42". I have posted pictures of this bucket before when the lip tore out. These look like they might be Super V SYL teeth. Sent from my DROID RAZR using Tapatalk 2
Good comment Nige, probably in this case, would be better to work out fuel burn as gal/ material volume?
End of the day the aim is to get the bucket full as soon as possible, the wiggle method works pretty well in softer stuff.
Actually thinking about it with dull teeth the machine is going to spend more time (as a total percentage of the time in seconds taken for a complete bucket cycle) running at full hydraulic stall while filling the bucket therefore the amount of fuel consumed per hour will be slightly more. The really big thing is that you get so much less bucket cycles per hour due to the longer time to fill the bucket, therefore it's your production that you see suffering big time. Maybe what I'm going to put here is complete overkill but you can see the logic of how it was worked, and the best thing is it works for any loading tool, you just have to divide the loading cycle into segments and know what your fuel burn is for each of them. Obviously on big mining tools cost per tonne of material moved is of prime importance, therefore even shaving a couple of cents/ton. Entitled "Bigger Isn't always Better" (referring to using smaller, sharper GET instead of boxing gloves) it goes something like this: - The cost/ton calculation for Production Loading Tools must include all aspects of the machine's design including the impact of GET and bucket design on total performance in cost per ton terms. When looking at loader productivity, the time loading the bucket is the most influential on both productivity and cost per ton. Improving machine productivity has the greatest single impact on reducing cost per ton. Therefore a bucket with better digging and filling capability will produce a lower cost per ton. A bucket with better digging and filling capability will impact cost per ton through more than just production improvements. It will also affect availability, repair cost, fuel cost, and tire cost. During the loading portion of the cycle, all machine systems are at maximum load. Improving the digging and filling capability of the bucket will reduce the duration of the loading time and reduce costs and/or stress in the following machine systems. A.. Engine fuel consumption mainly determined by time spent at or near stall during the loading cycle. B.. Tire wear while operating under load at or near torque converter stall (maximum rimpull). C.. Machine Structure. D.. Hydraulic System Load (hydraulic stall conditions). E.. All Power Train Components. F.. Cooling System (heat dissipation). In designing the bucket and GET package, we must seek to optimise the digging performance, durability of the bucket/GET package, and their consequent impact on machine operating costs.
Wow! Sent from my DROID RAZR using Tapatalk 2
A bit of a War & Peace epic but it is a good illustration of how you can calculate the benefits of "sharpening up the front end" of any loading tool, be it excavator, front shovel, or wheel loader. All you do is first make a cycle time study then plug your numbers into the calculation.
Most people think of it in terms of decreased wear on the bucket and savings on rebuilding cost but I think your analysis helps to add another layer. Sent from my DROID RAZR using Tapatalk 2
Nige I really like how you have broken this down. he only thing I would add it to include in the study the cost of the teeth, and the expected lifetime per set. The sharps dig more, and save fuel, but need changed more often, which adds some service costs, as well as more replacement sets of teeth. I am sure you have factored this in as well, as thorough as you are.
Jerry. 100% correct, however way back when at the time we did this study on 994 Wheel Loaders we had major issues on drive trains, hydraulic cylinders, and structures, so what we were most concerned with was taking stress off the machine by speeding up the time it took to fill the bucket. As you can see from the example we got the bucket filling time down from 11 to 9 seconds by sharpening up the GET and also by removing loads of old 16 grader cutting edges that the customer had welded on as "wear protection". Later the buckets were re-designed by making them narrower by also 2 feet (245" vs 222") but deeper front to back and we got the average bucket fill time down to around 7 seconds in good material. Now 11 seconds to 7 was a huge improvement in taking stress off the machine. Somewhere I do have relative costs of Penetration versus Abrasion GET (there were no ARM coatings available back in those days) in terms of cost per cu.m. moved. I'll have to dig them out. These days we generally use Heavy Duty Penetration GET (another new "invention") with ARM coatings on them. Also with the new style Capsure teeth changing them only requuires a 3/4"-drive breaker bar so we tend to do them at lunch break/shift change time so as to minimize effect on production. No hammers and pin drivers needed these days......
What is ARM coating? Sent from my DROID RAZR using Tapatalk 2
Abrasive Resistant Material. It's a spray-on coating available on a lot of Cat GET. Also on other makes as well. Teeth cost (maybe 30% or so) more but it brings major benefits if you work in abrasive material all the time because it enables you to keep a sharp-profile penetration tip but you get the benefits of an Abrasion tip wear-wise. We use ARM cutting edges and end bits on our dozers as well.
It is good stuff. Basically it is tiny flakes of tungsten carbide imbedded in a special welding flux. It is "welded" or sprayed on, usually in 1" wide strips. As Nige says, you can order tips with it from Cat, and many of the big suppliers of edges can set up a program for you. I had an independant shop that would add it to the edges I supplied. On most items, we did no less than triple the normal life with a good pattern of ARM. Here are a couple of links that explain it well. http://www.atcgroup.com.au/WearProtection/ATCOverlay.aspx http://www.weld.com/index.php/mr-tig/42-tungsten-carbide-hardfacing
Jerry, we see similar - triple the life or better - on dozer edges protected using ARM versus conventional non-ARM edges. On dozers ARM comes at a price premium of about 60% over standard edges but even at that price it still makes good economic sense, and the mechanics especially like it because no-one really enjoys doing a cutting edge & corner bit replacement on something like a 10 or an 11 even if they have all the tools for it. Those edges are finger-trappers ....... We're planning on experimenting with ARM-faced track shoe grousers to see if we can cut down on grouser wear in our really abrasive areas of the mine. Currently they last 400 hours between re-grousering where in our limestone quarry they might well go 1500-2000 hours.
How about on grader blades?
Never tried it. Don't think it's available TBH unless we got an outside company to do the coating for us. Problem is that a grader cutting edge stays in hard contact with the ground all the time the mouldboard is down, therefore the coating would likely wear off faster. Even on dozers there will be times while pushing that the cutting edges are only making the lightest contct with the ground.
I have not done it on grader blades, but would try it as a strip on the front edge. This would be 1" wide and the full width. I have seen that work on dozer and scraper edges. As Nige point out, the blade is in near constant contact with the road, and that is an ideal reason to protect it, in my opinion. Keep your blade tip position constant, and it will hold up. If you vary the tip position, you accelerate the wear. What happens is the trailing portion of the cutting edge will wear thin until the TC portion breaks off. It does so in small areas as it wears thin, leaving ripples in the finished surface. Doing rough grade work or haul roads, it would be fine. Forfinal trim, sometimes it could draw complaints. I have a 613 scraper with TC on the edges and routers. I do not know how many hours are on it, but at least 4 or 5 times the normal life. It is scalloped badly, and some areas the TC is completely gone, leaving a rough surface. Once enough of the TC is gone, the edge will run to nothing quickly, since the portion above the TC strip is wore very thin. I had some on a D-8H once pushing loose gravel in a quarry. The edges and end bits were still full length, but above the strip they were very thin. I moved it to a new job pushing rock, and all the edges broke off the first day. They were worn so thin, they snapped at the bolt holes when a load was applied. Never seen that kind of thing up till then. One of the best places for it was sole plates on the rubber tire dozers. Changing them out is a job no one likes. When they got the first TC, they tripled the life. Then, the next time, since we changed the TC pattern after seeing the failure of the first time, we got up to 5 or 6 times the life. The same on the dozer edges, after we figured out you have to have another strip just before the bolt holes so it does not wear thin and break off. When business gets busy again, I would like to try it on the mouldboard edge of my mass excavation buckets, to prevent scalloping between teeth, as well as along the tops and sides of the shanks, to keep the welds from washing out and dropping the shanks off.
Any thoughts on side cutters for excavators?
That would definitely work IMO. Actually though we are going away from bolt-on sidecutters on our excavators and instead using pinned-on sidebar protectors like a wheel loader. They cover the side plate of the bucket better because they go completely over the side plate rather than just being a half-arrow from one side.
Pictures or links please.