Dipil
Safety Consultant
Kesava Pillai
Occupational Safety & Health
Pon1965
Construction

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Dear all,
How to calculate the crane capacity if we change the number of fall in the crane because no any crane manufacture provide the different load charts Vs fall.
Eg-110 T crane working in our site which is having 6 pully (12 no of fall),Crane having 12 fall when we inspect the crane but now a days we observe crane operator reduce the number of fall upto 4 then how to calculate crane capacity.

Dear Amol

Its not possible that the crane is not having load chart with reduced falls. You have to first of all go through the manuals of the crane and all load chart in details to find out the reduced configuration. If you still fail to find out such a configuration in the manuals, contact the manufacturer.. They will be surely able to give you the load char with reduced falls.

Now another possibility is that the manufacturer not allowing to alter the design configuration and reducing falls. So this operator doing it by his own risk and based on his experience. So first of all you have to cross check either with manual or by contacting the manufacturer how it is been designed.

I believe that the crane you are talking about must be bring in your site by some contractors or your company hired crane from some agency. In such case getting all the papers would be pretty difficult. The crane people must carry only their single configuration load chart. So don't allow to go ahead until and unless they submitted any documented proof saying this reduced fall configuration lift is possible and this is what the safe limit in reduced fall and all.

You may in future ask to bring a crane having Safe load Indicator (SLI) fixed. Nowadays SLIs coming with configuration setting in which you can put the number of falls as well. SLI along with load chart and rigging plan is the best way to ensure whether your lift is safe or not?

Thanks for reply but my doubt is not clear.
No any manufacture provide reduce sling load chart they provide diff load chart when reduce in counter weight because i have 50T to 2000T crane load chart.if you have any load chart with reduce in fall then share with me.
another part is ASLI which is mandatory in crane but the ASLI setting is manual feeding & ASLI not giving the correct SWl capacity whenever we are not feeding the data in ASLI as per the reduce in fall.

when you reduce the falls, the lifting capacity is reduced. Check the Crane load chart. Pon
Friends,

Capacity of a crane remains the same throughout. It is the maximum load that it can lift. However the lift capacity of a crane can be changed with different configuration. . A crane may have different capacity hooks also. Depending up on the load at hand a crane operator changes the configuration including the number of parts of line and the hook.

I am giving you the answer. However if you are not trained in crane operation please do not take a chance. This is a skilled job and let a professional take care of it. However having an understanding on how such jobs are managed will help those in safety too.

Mechanical Advantage:

The mechanical advantage of a machine is the amount by which the machine multiplies the force applied to it in order to lift or move a load. Here the machine is a pulley or a combination of pulleys forming a block and tackle system. The top fixed sheaves on the block have no other function than to change the direction of the rope. The sheave on the travelling block will create a mechanical advantage of 2:1 on each sheave.

Calculating the Mechanical Advantage of a block system:

Count the number of lines supporting the load with the exemption of the lead line when it comes down over the top block. The lead line pulling down is not counted for mechanical advantage. If the lead line comes up to the winch from the travelling block it will be counted as a supporting line and included in the mechanical advantage.

Mechanical advantage for the system:

The amount of wire rope needed for the system is determined by multiplying the number of parts of line by the travel distance of the load, plus enough wire rope to go to the winch and have at least five full wraps on the winch drum.

Block Friction:

When the load moves; part of the lifting force is lost due to friction in the turning of the sheaves, and the wire rope bending over the sheaves. The lead line pull must be increased to make up for this loss.

The relationship between a rope sheave and friction is called efficiency, and is usually expressed in terms of percent. Each type of sheave has a different friction percentage. The extra load added by friction is calculated progressively on line-by-line, sheave-by-sheave basis.

Block friction ratio:

To calculate the number of parts of lines to be used for a given load, or the line pull required or a given load use the table attached. Example is provided with directions.

This table includes ratio charts for fibre rope blocks of 10% friction, wire rope bronze bushed sheaves at 5% friction and wire rope roller bearing sheaves at 3% friction.

Number of parts of line required:

1. Determine the (S.W.L) of the wire rope

Formula: diameter squared X 8 = S.W.L

2. Weight of the load

3. Calculated load/S.W.L.= R (ratio)

4. Ratio chart

5. The number of parts of line is indicated opposite the ratio table.

Parts of line Example:

- Size of the wire rope : 1¼ inches

- Load weight = 75 Tons

- Types of sheaves : Roller bearing

1. S.W.L. of 1¼ inch rope = 1.25X 1.25 X 8 = 12.5 Tons

2. Total weight of load = 75 tons

3. 75Tons/12/5 = 6 (ratio)

4. From the column under roller bearing wire rope 3% we read 6.3 is the next highest number over the calculated answer of 6. The first column gives 8 parts of line.

Crane operator to choose 8 parts of line.

Regards,

Kesava Pillai


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Dear Sir Thanks for the technical explanations and great support to the forum... Dear Amol Please let the forum knows whether your query resolved or not?
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