Dear all,
How can we calculate the crane capacity if we change the number of falls in the crane? As no crane manufacturer provides different load charts versus fall.
For example, we have a 110-ton crane working on our site with 6 pulleys (12 falls). During our inspection, the crane was found to have 12 falls. However, recently, we have noticed that the crane operator has reduced the number of falls to 4. How can we calculate the crane capacity in such a scenario?
Thank you.
From India, Mumbai
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6How can we calculate the crane capacity if we change the number of falls in the crane? As no crane manufacturer provides different load charts versus fall.
For example, we have a 110-ton crane working on our site with 6 pulleys (12 falls). During our inspection, the crane was found to have 12 falls. However, recently, we have noticed that the crane operator has reduced the number of falls to 4. How can we calculate the crane capacity in such a scenario?
Thank you.
From India, Mumbai
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Dear Amol,
It's not possible that the crane does not have a load chart with reduced falls. You have to first go through the manuals of the crane and all load charts in detail to find out the reduced configuration. If you still fail to find such a configuration in the manuals, contact the manufacturer. They will surely be able to provide you with the load chart with reduced falls.
Another possibility is that the manufacturer may not allow altering the design configuration and reducing falls. So, this operator is doing it at his own risk based on his experience. Therefore, you must cross-check either with the manual or by contacting the manufacturer to understand how it has been designed.
I believe that the crane you are referring to must have been brought to your site by some contractors or your company may have hired the crane from an agency. In such a case, obtaining all the necessary papers could be quite challenging. The crane operators may only carry their single configuration load chart. Therefore, do not allow them to proceed unless they provide documented proof stating that the reduced fall configuration lift is possible and within safe limits.
In the future, you may request to bring a crane with a Safe Load Indicator (SLI) installed. Nowadays, SLIs come with configuration settings where you can input the number of falls as well. Having an SLI along with the load chart and rigging plan is the best way to ensure the safety of your lift.
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I have corrected the spelling, grammar, and punctuation errors in the text, as well as adjusted the paragraph formatting for better readability. Let me know if you need any further assistance.
From India
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It's not possible that the crane does not have a load chart with reduced falls. You have to first go through the manuals of the crane and all load charts in detail to find out the reduced configuration. If you still fail to find such a configuration in the manuals, contact the manufacturer. They will surely be able to provide you with the load chart with reduced falls.
Another possibility is that the manufacturer may not allow altering the design configuration and reducing falls. So, this operator is doing it at his own risk based on his experience. Therefore, you must cross-check either with the manual or by contacting the manufacturer to understand how it has been designed.
I believe that the crane you are referring to must have been brought to your site by some contractors or your company may have hired the crane from an agency. In such a case, obtaining all the necessary papers could be quite challenging. The crane operators may only carry their single configuration load chart. Therefore, do not allow them to proceed unless they provide documented proof stating that the reduced fall configuration lift is possible and within safe limits.
In the future, you may request to bring a crane with a Safe Load Indicator (SLI) installed. Nowadays, SLIs come with configuration settings where you can input the number of falls as well. Having an SLI along with the load chart and rigging plan is the best way to ensure the safety of your lift.
---
I have corrected the spelling, grammar, and punctuation errors in the text, as well as adjusted the paragraph formatting for better readability. Let me know if you need any further assistance.
From India
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Thank you for your response, but my question is still unclear. No manufacturer provides a reduced sling load chart; they offer a different load chart when the counterweight is reduced. I have load charts ranging from 50T to 2000T for the crane. If you have a load chart that includes reductions in fall, please share it with me.
Another issue is with ASLI, which is mandatory for cranes. However, the ASLI setting requires manual input, and it does not provide the correct SWL capacity when we do not input the data in ASLI according to the reduced fall.
From India, Mumbai
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Another issue is with ASLI, which is mandatory for cranes. However, the ASLI setting requires manual input, and it does not provide the correct SWL capacity when we do not input the data in ASLI according to the reduced fall.
From India, Mumbai
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when you reduce the falls, the lifting capacity is reduced. Check the Crane load chart. Pon
From India, Lucknow
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From India, Lucknow
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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
From India, Kollam
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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
From India, Kollam
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