Environmental, Health And Safety
Occupational Safety & Health
Why the capacity of wire rope slings decreases when the angle decreases. Example - At the angle of 60 degree it lifts more weight where as at 30 degree its lifting capacity reduces. Why?
Please help me & specify the technical reasons.
27th June 2012 From India, Bhubaneswar
From the question I take it that you are not from safety, you are not aware of any crane rigging, types of slings, hitches, mechanical handling and so on. However I definitely appreciate your attitude in seeking knowledge and I am always happy to help. My only problem is I do not like to spoon feed. Those who are really interested in learning from me like my attitude because my way of teaching makes them competent in the profession.
On to your query:
Please honestly do the exercise in steps 1 to 4 mentioned below and post your experience.
1. Take a bucket full of water keeping hand close to the body. In this case the angle between 0 and 1 is too small and you could probably lift it easily.
2. Move the water bucket away from your body to position 2 increasing the angle between the body and bucket.. Now, check -how you feel about the weight?
3. Move the bucket away from body to position 3 further increasing the angle. Check again how you feel about the weight?
4. Again move the bucket further away from body and keep it almost to horizontal position.
In all the positions though the volume and actual weight of water remained the same do you feel the load differently?
There are different types of slings; not only wire rope sling. With not only wire rope slings but with every other type of slings the effect of sling angle is the same.
There is a simple formula to calculate the stress on slings at different angles.
I will wait for your post on the result of the above experiment to give you a clear explanation.
30th June 2012 From India, Kollam
Thanks for your reply. whatever You have explained is absolutely correct. I highly appriciate your example.
But What are the factors I mean the technical reasons behind this. Though I know the formula to calculate the capacity of wire rope slings at different angles.
so far your given example is concerned, In step 1 it is easier and at step 4 it is difficult. Everybody knows it.
My question was what are the technical reasons come into force.
1st July 2012 From India, Bhubaneswar
You have the formula for calculating capacity of wire rope slings at different angles. You want to know the technical reason!
1. Consider that you are using two slings in vertical position to lift a load. In this case there is only a vertical component. There is no horizontal component. The load on the slings is exactly the same as your load weight.
2. Now consider to flatten out the slings. This time both slings may be at the same angle or different angles depending up on the CG of the load.
In this case the vertical component remains the same, but a horizontal component is added. The load in the sling is the sum of the vertical and horizontal components. As the slings flatten the horizontal component increases, the angle between the sling and the horizontal plane decreases so the load in the slings increase.
It is a function of trigonometry.
I am leaving the load factor, included angle etc. since you already have the formula.
You have the formula for wire rope slings. What about other types of slings? Will there be any difference?
3rd July 2012 From India, Kollam
Thanks for the great inputs from your side again...
To continue the discussion at the point where you stop with a question, whether there will be different formula for different slings... Yes, it is there... I do have a presentation on Rigging which included these different formula... I am attaching the same for your perusal and the benefit of all other members those who not having this...
Please guide further for learning more on the topic...
5th July 2012 From India
Thanks and Regards,
5th July 2012 From India, Mumbai
As per my observation from this forum, we have found two Gem of Persons in Safety professionals as you all knowing inspite of my eagerly express my views as member of this forum they are truely GEM of this Forum for helping all needy persons concerned to safety they are.................1) Mr. Kesav Pillai sir.
2) Mr. Dipil Kumar sir.
Really we safety professionals are fortunate to get this Great persons as you know in this world lot of Selfishness prevailling!! such in such situation also these two persons helped by sharing & helping by needful safety information to all this forum members.
I pray to Almighty God behalf of this forum bless with his mercy always.
Thanks for all sharing their views.
With Respectful Regards.
Valli basha Sab.
5th July 2012 From India, Hubli
Thanks to explain the matter in so admirable way .....
Further sir i like to share with you that I am working in a State Level University. Our University is under process to get ISO 9001:2008.
I feel very good to work for & think that it will definitely improve the style of working & uniformity in all aspects. It's giving chance to work other than routine things & gives scope for creativity. I am also very curious about the results of the whole exercise.
Sir, in govt. organization it is very hard to get speedy work from subordinates.
Will you guide me on issue, how to prepare minds of class III & IV peoples to contribute & implementation of the same as well as raise speed & spirit of working?
5th July 2012 From India, Nasik
I am not deserving for this much appreciation words from your side... Surely Mr. Kesava Pillai is deserving for the same... Please don't embrace me with this much kind words... I am assuring you to give my best to this forum as this forum helps me a lot to improve my personal and professional life...
6th July 2012 From India
Hope you have studied the ppt before posting. I wonder how you could post it to prove that there are different formulas applicable to different types of slings!
(The title of the ppt is Safety in Rigging and Erection Operations. I find there is no mention of any erection related points though unrelated topics like allowable noise level, Gas cylinders safety -10 commandments , specification of welding glass, causes of backfire, nozzle data, proper method of lifting method-manual are included. ) I am sure it is the creation of not a knowledgeable person in the field.
From the ppt it is clear that there are chain slings and web slings too. However I am not able to make out any different formulas applicable to different types of slings.
Now what is the formula applicable from the ppt? What you derive from the one formula in the ppt?
How will you interpret it and prove the main point?
Rigging is a specialization. It is often part of erection. In erection rigging is not always employed.
Safety officer need not be a rigger. However it is always recommended to understand at least fundamentals on this subject to effectively monitor the site. Now let us start to learn by getting simple answers for the following questions:
What is rigging?
How do Riggers move heavy loads?
What are the responsibilities of riggers?
What are the job site considerations?
Slinger, signallar and Banksman- responsibilities?
After getting the answers from interested ones if any we will go further.
9th July 2012 From India, Kollam
Nice to see your regular participation on our thread whenever you participate on our forum we learn some new things. Let's go to the topic.,,
What is rigging?
The process of lifting and moving heavy loads with ropes, chains, and mechanical devices
Rigging describes the task of lifting & hoisting, positioning, moving & transporting heavy loads. This includes the use of Cranes, Load Movers and Heavy Haul Trucking.
Rigging - It is the handling or load or loads. It includes the maneuvering, shifting, lifting and fastening of loads in accordance to procedures and safe practices.
How do riggers move heavy load?
A rigger needs to have technical skills in order to move heavy loads safely and efficiently. Riggers use such gear as high capacity jacks to lift the load off the ground, similar to a car jack lifting a vehicle. The load is then placed on dollies and pulled with a pulling vehicle - such as a forklift - out of the building. Outside, the load is lifted onto a flatbed truck with a crane and transported to another location where the process starts in reverse.
What are the responsibilities of rigger?
Inspecting objects to be moved, to estimate their size, shape and weight and decide on the type of equipment necessary
Erecting a temporary jib or derrick, and install cables, pulleys, booms, braces and other tackle
Attaching hooks, slings, chains and cables to lift loads safely
Erecting cranes and mobile crane booms, increasing the height of tower cranes by bolting component parts in place and rigging cables
Erecting structural steel for buildings and precast-concrete panels used on facades of buildings
Inspecting, maintaining and repairing equipment
Ensuring that work safety requirements are met at all times
Splice ropes and cables to make slings and tackle
Erect precast-concrete panels used on facades of buildings
In general, the rigger does the majority of work required outside of the truck cab. The rigger is in effect, a second set of eyes for the driver. The tasks are labor intensive.
Operate a tag line when positioning loads
Reports directly to the driver while in the field.
What are the job site considerations?
Handling, setting and erection of materials and equipment are a hazardous occupation. Each operation presents its own peculiar problems and no two jobs are alike. With proper consideration taken, each job can be performed free of bodily harm to the employee and without damage to the equipment and/or property. The person authorized and qualified to do rigging must always pay close attention to details.ne careless moment or act can result in serious injury or death and tremendous property damage. Proper rigging is an art and should never be left to the inexperienced. If you dont know how to-do it properly, then dont attempt it. Persons performing rigging tasks usually already have four strikes against them when they start.
Unfavorable Job conditions.
Job Schedule to meet.
Need to meet all legal requirements using proper standard signals etc.,,
In our workplace we are using slinger and signaller as a same person he holds the below responsibilities while performing the job;
Conform with manufacturers requirements as per technical data, other types of information source and relevant regulations and legislation
Interpret and extract information on all relevant documentation
Undertake all pre-use checks on non-specialist lifting accessories and identify non-serviceable items
Explain procedures for placing non-serviceable items out-of-service
Identify centers of gravity and estimate weights of loads
Prepare and ready the area of operation
Choose the relevant lifting accessory for a given load
Explain action required for hazards, underground and overhead services
Secure various types of load to a lifting hook using the relevant lifting accessory and procedures
Ensure load balance, security and integrity
Direct and guide the movement of loads to different types of location
Accurately place loads
Arrange, use and comply with communication procedures
Maintain safe working situations
Responsibilities of Banks man;
A banks man is the individual in charge of crane operations within a site. Because cranes may not always have great visibility of the loading area, the banks man comes in handy in the management of such activities. The banks man is also known as the reversing assistant in many civil engineering circles.
His responsibility includes;
Monitoring of Loading Areas
Loading and Unloading etc..,,
Awaiting for your comments.
10th July 2012 From United States, Fpo
This was one of the presentations in my Data Collection. I have only looked for the different formula given for calculations, frankly not studied the entire presentation before uploading. I have uploaded the presentation by thinking that it may help others. From your reply it came to know that it is not such a great presentation.
When comes to SWL of wire ropes, commonly using formula is 8x Dia in mm square... This is the only formula which coming to my mind when think about SWL of Wire Rope Slings. As we using all the slings in which SWL is embossed not yet gone in depth to think about it.
In the attached presentation Slide No: 8 Formula for calculating SWP. Its not clear to me, also the graph. Can you help me to understand this slide?
Other queries put up by you Raghu already given detailed inputs... Please let us know more in detail from your side...
11th July 2012 From India
OSHAS is really important which needs HIRA (Hazards identification and risk assessment), which gives you a path to break all the necessary working activity to break up in micro activity and analyze them with the risk parameter and if any severe fault in process is there then how to mitigate or remove the factors...
12th July 2012 From India, Bangalore