mobile cranes

I have never seen a crane without a "LOAD/ANGLE/REACH" Plate attached to it. If it doesn't have one, I would not use that crane.

I use to deliver electrical transformers around the US that weighed from 20 to 250 Tons. I have been in the cabs of hundreds of cranes and they all had this plate along with a certification of the crane, and a log of tests and inspections of the hoisting cables and slings and attachments.

I would not want to be around a crane that did not have these things and I certainly would not pay a crane company who could not produce these items.

Cranes are very helpful things BUT, can be very dangerous.

Your only other two posts deal with homework. Is this part of your homework?

All slings and cranes are rated by the manufacturer. You should be able to contact the manufacturer. Every crane model is different.

Branson

Cranes are governed by OSHA, as are the slings. All equipment of this type are of the construction trade and have markings on them that state the safe working loads or maximum weight allowed, as prescribed by ANSI. If you are working with an unknown you need to know the weekest part of your project and the safe working load limits, i.e. 3:1 or 5:1 ratio of weight distribution

Safe working load can not calculate directly as it involve lot of things to be calculated or known earlier like hoisting/lowering speeds, wind speeds, size of motor/ generator, size of hydraulics etc. In fact crane user is to provide it to crane manufacturer. Structures are also designed keeping in view different parameters like state of loading, coefficient of utilization etc.

For steel wire ropes the braking force and sheeve size is calculated, then through steel wire rope manufacturer table a suitable rope is selected. the formula for calculating braking force is

Zp=Fo/S

Where S= static tensile of steel rope= Qmax./n

Qmax.=lifting capacity, n= number of ropes, Fo= braking force of steel rope

For sheeve Formula is Ds+d = h1.d

d= diameter of rope, Ds= bottom diameter of sheeve , h1= coefficient of depending

In fact its a long debate, for better under standing try to get British standard BS2573 Part1 & 2 OR equivalent in FEM from any crane consultant.

The fact is that I am practising questions for a millwright exam and I ran across some questions like; the load radius of a crane is 25' the tipping axis is7,5 ft.The crane capacity is stated at 45 tones. What is the maximum lifting capacity of this crane? And; what is the safe working load capacity of a double sling if one side is 12 ft one 11 ft. Each is capable of lifting 1500 lb. I am not in school and in all the books I've got don't help much on this problems.

I to am on this site for the same reason. The millwright exam had these questions on it. I have called several crane companies, and they all say a load chart is necessary. So, the question for the most part is unanswerable unless you have more specifics. As for the sling question, don't read into it more than the question. The answer is 3000 Ibs.

Thanks, for your reply, hope that you have pass it

Contact crane companies. Don't over complicate the path to the answer. KISS rule.

Oh, by the way I sit the exam on at the end of next week......

If you have any other Questions let me Know

I've got another one: What is the minimum capacity per roller, when using 4, to move an unbalanced load of 48 tonnes?

I think it is still 12 tons each. But I could be wrong.... Depending on where you are I haven't seen this as a exam question

48 ton always use the the weight

Hey there I am new to the site I to am trying to get my millwright lic. and have wrote the exam with no luck that question about the crane was on mine also and I have no idea how to solve it Crane companies cant answer it either.

if you know any other questions mabye we could figure them out.

After serious research... I can honestly say there is no answer except...Load charts on the crane

I know that there are a lot of tricky questions

O ya, I was thinking, and 180 degrees from the first phase is the option I was thinking of

If I can help, I will. I do have a few, but they may be a little generalized

All slings should be labeled with there load limitations and all cranes with theres. If the sling is unlabeled or unknown throw it out ... if the crane is the same contact the manufacturer for specs on that model. Cranes are not something you can figure with a simple formula ... you have to figure counter weights, type of crane, footing, boom length, wind load. And as far as slings. It depends if its a traditional sling or your choking, dead lift, is it one sling or multiples not to mention angles of the sling or slings the diameter of the shackle. Wire rope, strap or chain. Makeup of the load. Better safe then sorry. The math has been done and tested to the max. Use it don't reinvent the wheel.

Cranes and lifting gear de-rate with cold temperatures, as much as 50%. Careful in cold climates.

Is there any specific standard or guideline for this cold weather de-rating.

i need help also i no it has been a year and by the way crane question is still on exam and still sucks no answer also, 12 tons on balanced or unbaleced skids and 180 degrees to phase 1 what is belt splicing over large pully/ over small pully???

Hi

I contested that Question on the exam. It, in reality is a completely invalid question due to, as others have stated, the mobile has a load plate on the crane. Every crane is indeed different, and individual to the company. I suppose this is due to the combination and uses of different components, each with their own rating.