Crane Test weight- 240 tons 2

[arunmrao]

I have a RFQ from a power station for Crane Test Weight 240-260 tons . This weight will be used to calibrate the lifting capacity of new crane purchased from China. The power station does not want to risk lifting the generator before having it calibrated. As it is one time use they want to keep costs at the lowest.

My foundry does not have the capacity to produce a single piece casting of 250 tons.I intend producing 16 numbers of 15 tons casting each. The sub weights of 15 tons will be integrated in a self locking manner for easy assembly and interchangeability.( Please see a representative picture).

Yes, for design and fabrication of structure ,services of a Certified Engineer along with TPA approval is being done.

Seek any advice or comments about any pitfalls in the proposal to handle this project.





"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[zeusfaber]

Best crane test weights I've seen have been large textile bags that you fill with water on site. They're portable, you can add weight progressively, if the crane renders or the wire breaks, the floor takes less of a pounding and you can fine-tune the load you apply (which means you can use the same bags to test another crane with different load requirements).

 

[arunmrao]

I agree about the water bags, but bringing them into Nigeria will be a long process. Hence this simplistic approach of calibrating with a tolerance of +/- 10 tons.



"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[JStephen]

I would think concrete blocks would be cheaper than cast iron. Or possibly fabricate steel boxes and fill with sand.

 

[dhengr]

Arunmrao:
Many foundries and steel mills have ingots of various sizes and shapes, as inventory and in storage for future use in the process of final shaping or remelting for castings and the like. These should be of a fairly std. shape, or shapes and sizes, so you know the approx. size and shape and can design some sort of a holding/lifting structure as is shown in your photo. The point is, your weights don’t have to be some expensive, finely formed or designed shapes. We’ve also used stock steel jumbo column WF sections (W14x500’s, etc.) as test loads. You send eight or ten truck loads of this material out to the crane site, and have weight tickets for each truck load. I don’t know what you mean by calibrate the crane, you are running a certifying (or certified) load test on the crane, its boom and its rigging. And, they usually do this to about 1.25 times the load to be lifted or 1.25 times the crane cap’y. depending upon the customer’s requirements. The crane manufacturer ought to actually provide, or pay for, this certifying test, and they should have the ability to do this testing at their plant, on every crane they build. Alternatively, the PO should spell out who does this.

 

[arunmrao]

Thanks all for your responses and time.

dhengr ,to an extent I have factored some of the pig metal in scrap yard lying for decades. But I plan to melt these into uniform shapes. I have issue of knowing the COG ( center of gravity)before lifting the 240 ton weight.

I am not running a certified load test program. The crane manufacturer is from China, and the power station purchasing department has goofed ( less said the better about bureaucratic decisions). Now,, the Chief Engineer is sweating and trembling to commission the power plant.

I have a crazy idea. Can I invest cement concrete over the sub weights and make a solid block. Of course I will throw a few heavy steel sections all around. Any supporters for this idea?

Thanks once again for your time and suggestions.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[dhengr]

Arunmrao:
Well, the conc. weighs 150lbs./cu.ft. and the steel weighs 490lbs./cu.ft., so you need 3.3 times the volume of conc. vs. stl. The conc. certainly isn’t free, you have to form for it, buy it, place and finish it; then you have a potential disposal problem after the test. 240tons of conc. is about 3200cu.ft. or 119cu.yds. of conc., that’s a 14.75’ cube of conc. With the stl. you have a valuable product which you bring back to your foundry for reuse. Regarding CG’s, make your pigs some std. size, maybe 12”x12” or 16”x16” by 10 or 15’ long, and paint a center line at 5 or 7.5’ for placing at the crane site. You certainly know where the CG is on a 12”x12”x15’ pig, and you know its weight too, and you stack them accordingly on the test structure at the crane test site. It’s like stacking chord wood in a wood bunk, which you can then lift. Of course, someone has to design this lifting system and weight support structure so it can be lifted. It can’t get much easier than that. Your CG calcs. will be within an inch or two and the total load will find its CG when lifted a couple inches. You really only need to lift the load a few inches off the ground to prove the crane cap’y. Of course, they have to arrange the pigs carefully, they can’t just throw them in a pile and lift it. I’ve seen various conc. products used for test weights too, but then they are usually reused for their intended purpose. They are not usually special cast conc. blocks just for the particular test. Someone has to do some availability and cost analysis here. If you have to transport the conc. or stl. a 1000km, in the desert, bags of sand may be pretty practical. But, then someone has to design a fairly elaborate lifting structure to support these non-self-supporting bags of sand.

 

[arunmrao]

Thanks dhengr for your valuable comments. A star comes your way!!

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[chicopee]

Per djengr "The crane manufacturer ought to actually provide, or pay for, this certifying test, and they should have the ability to do this testing at their plant, on every crane they build. Alternatively, the PO should spell out who does this". I agree with that statement and if the Chinese manufacturer is not willing to have this test done and witnessed by an outside third party, then, I would have reservations about Chinese made cranes. You should have bought American made eventho. more expensive but less headaches. At least with American made cranes liability issues would be minimal but with the Chinese, good luck.

 

[MintJulep]

Arun,

I submit for your consideration a simple child's toy.

At the slight cost of needing to have two separate molds you gain a simple interlocking.

 

[fel3]

MintJulep…

It's going to take a whole bunch of Lincoln Logs to make a 260-ton test weight.

Fred

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[TimSchrader2]

hello

240 Tons is alot of concrete. We use concrete poured into boxes made or 1/4 steel with ribs. Then there are holes for tubes which holds them together when the 2 ton blocks stacked. But that is only for about 16 Tons. You could stack steel plates in a similiar way. Not cheap either.

Or if transportation is a big issue you could rig up a 8 part line block and tackle that would reduce your required load to about 240/12=20 tons. 12 to 14 for friction instead of 8. Note this idea would still require a hard point on the ground to hold 240 Ton. So I have retracted/deleted the details of this concept.

 

[IFRs]

Build a steel tank and fill it with water then pick up the tank

 

[itsmoked]

Already been discussed IFR.

I like where Tim's going with this.
Why not just bury, in the sand, a single thing like, oh, a twenty foot shipping container with cable around it. Then try to pull it out of the sand while using a calibrated strain gauge block on the crane. Then you do no environmental damage (wasted concrete) nor waste a bazillion kilocalories melting metal. Instead you use a couple of gallons of diesel for a backhoe or a skip-loader.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[djhurayt]

I agree with IFRs, you are probably only looking at an 18ft cube of water by the time you figure the weight of the steel for the tank. A 20ft cube is just short of 250 tons.

 

[TimSchrader2]

Hello

You could put the water bags in the shipping container if your not sure of the soil mechanics. I thought of a hard point, but was not sure what equipment he has on site. This would require more then one conatainer with reenforcing beams/strongbacks and other structure. The water will take more containers then concrete about 150/62.4=2.4 times more.

 

[IFRs]

Water bags were ruled out earlier. I think waterproofing a shipping container may be more trouble than it is worth. Making a metal bin is a little material and some welding, then vac-boxing or diesel testing the seams. The box proportions can be set by available materials. Putting it in a hole deeper than the box makes getting rid of it easy. There may be value in using calibrated gauges and a 300 ton box so you can use the soil to prevent distortion of the box sides which may lead to failure.

You could fill the shipping container with steel but the COG is needed...

 

[berkshire]

When thinking of shipping containers, has anybody considered that the maximum safe loading of a 40 foot container is about 30 tons?
B.E.

You are judged not by what you know, but by what you can do.

 

[tmschrader]

Hello
Note thst there is s error in the words on the reverse block and tackle idea. It is more different then how we do it in cranes. A hard point would still be required. The structure would need to push against the crane, which may not be feasible.

The water bags was discounted cause they are hard to handle. The reenforced container would contain the water bags. Alot of reenforcement.

 

[JStephen]

With the concrete idea, note that you don't necessarily have to haul them off when done, just discard on site if possible.
The foundry iron is basically scrap when you get done with it, so some value there, but not a huge amount.
Another idea might be to use steel rails, beams, plate, slabs, or other usable steel items and then return them to that service upon completion, rather than scrapping.