Rank: Forum user 
|
Hi all,
I am trying to get my head around the guidelines for safe pushing and pulling, am I calculating this correct ?
Cage is 400kg
Starting load movement 20kg (man) (L23)
Keeping load in motion 10kg (man) (L23)
Slope gradient 1 (degree) push force (kg) increase per 100kg = 2 - total = 8kg (L32)
TOTAL 438kg.....
Just another quick question, when completing the RAPP assessment what denotes a high score for a Total RAPP Score, I cant find any guidelines on what the actual final score is, is it good, bad or what?....or am I missing something ?
|
|
|
|
|
|
Rank: Super forum user
|
SPR The soundest way to understand the biomechanics involved in safe manual handling is to appreciate the principles of the variety of sources of forces involved; the calculations follow easily once you understand them and remember that they can be illustrated in three-dimensional models, drawings and equations of calculations. Once you can readily make sense of different ways of illustrating any manual handling situation (including in many sports), you will be able to explain how to compensate for particularly hazardous situions such as cramped space, slippery floor or stair surfaces, weak handles on loads and so on. A good way to get your head around this subject is to read the latest edition of 'Bodyspace' by Stephen Pheasant and Christine Haslegrave, published by CRC Press. It's available on Amazon.
|
|
|
|
|
|
Rank: Super forum user 
|
The whole point of the RAPP tool is to help you focus on the most hazardous tasks, and the most hazardous elements within those. So concentrate on the 'red' scores first and deicde if there's anything reasonably practicable you can do to make them green. The the same for the amber ones. Of course you need to involve those doing the tasks, to stimulate good ideas from them. Once you all agree you've done everything reasonable, then at least those doing the task understand the elements which post the most significant residual risks for them.
|
|
|
|
|
|
Rank: Forum user
|
Taking the previous post one step further - No doubt at some point you will be sense-checking your RAPP findings with the people at risk and it's easier in my experience to relate to them by referring to colours than scores.
|
|
|
|
|
|
Rank: Super forum user 
|
Originally Posted by: SPR  Hi all,
I am trying to get my head around the guidelines for safe pushing and pulling, am I calculating this correct ?
Cage is 400kg
Starting load movement 20kg (man) (L23)
Keeping load in motion 10kg (man) (L23)
Slope gradient 1 (degree) push force (kg) increase per 100kg = 2 - total = 8kg (L32)
TOTAL 438kg.....
Just another quick question, when completing the RAPP assessment what denotes a high score for a Total RAPP Score, I cant find any guidelines on what the actual final score is, is it good, bad or what?....or am I missing something ?
No I don't think so, as once you have started then the load drops. so you either have 400 + 20 + 8 = 428 to start it moving then down to 400 +10 +8 to keep it going
|
|
|
|
|
|
Rank: Forum user
|
438kg; 428kg; 418kg? Regardless of what the "textbook" answer is - will it make any difference to how you manage the risk? As a profession we sometimes try to "scientificify" what we do in order to justify our existence; our salary; or to show how clever we are - I know I have. Better to look at the safety problem; devise a solution; communicate that solution to the workers. Do you think the operative has any interest in how many kg of force it takes to move the cage? Here's what the HSE has to say:
"There is no requirement to give force information to employees. Instead, you should concentrate on reducing risks by providing good trolleys and working conditions and training staff in pushing/pulling techniques." And, the Amber/Medium band for rolling a cage is 250kg - 500kg, so it's a moot point anyway.
|
|
|
|
|
|
Rank: Super forum user
|
I just thought I would answer the question actually asked, what they do with the info is their business. Perhaps they just wanted to understand what the HSE has put in L23, in order to understand the concept.
|
|
|
|
|
|
Rank: Super forum user 
|
Originally Posted by: chris42 Originally Posted by: SPR Hi all,
I am trying to get my head around the guidelines for safe pushing and pulling, am I calculating this correct ?
Cage is 400kg
Starting load movement 20kg (man) (L23)
Keeping load in motion 10kg (man) (L23)
Slope gradient 1 (degree) push force (kg) increase per 100kg = 2 - total = 8kg (L32)
TOTAL 438kg.....
No I don't think so, as once you have started then the load drops. so you either have 400 + 20 + 8 = 428 to start it moving then down to 400 +10 +8 to keep it going
It doesn't take 428kg to start a 400kg cage moving. You don't need to exert more than the weight of the cage to start it moving - if you can exert that much force you could start it moving vertically straight up off the ground. Surely even the much maligned common sense tells you that when something is on a wheeled trolley you don't need to push with more than the total weight to start it moving? Anyway, my reading of L23 is not that it takes 20kg to start a cage moving, it's that a cage which takes 20kg to start moving is on the limit of what is acceptable (subject to various caveats).
That is, the 20kg is not a figure used for working out what force it takes to move a cage, it's a figure that having worked out (or measured) the force it takes to move the cage, you then decide whether that figure (whatever it is) is acceptable.
Or am I looking at the wrong bit of L23? I'm looking at table 1 in paragraph 129.
|
|
|
|
|
|
Rank: Super forum user
|
Yes, I was just trying to make the point that the force required to start something moving then drops once it is in motion (not added to it). I was just trying to keep it simple.
In reality you need to know the coefficient of friction for the wheels on the surface they will be on. This can be affected by the actual materials ie steel wheels on a steel surface will be different to polyurethane wheels on a steel surface. The wheels bearings will make a difference etc. So you have elastic properties of the wheel / surface, friction at the contact points and roughness of surface, bearing type and characteristics.
You would have something along the lines of the following for 400 Kg on a trolley with 4 wheels
Load for each wheel would be 100Kg, say you have found out the coefficient of friction for you wheels on the surface you will be using them and is for the sake of demonstration 0.047 and lets say the wheels are 200mm diameter, so a radius of 100mm (0.1m).
We then get 0.047 x (100kg /0.1m) =47 times that by 4 wheels and you get 188Kg to keep the load moving on the flat. It will take more effort to start it moving in the first place and if going up a slope it will also take more effort as previously noted. Use bigger wheels and this reduces your rolling resistance.
Realistically the best way is not to calculate it, but to try it with a load cell or similar to test actual not theoretical. However, having and understanding of the general idea does not hurt.
And this is still a simplified version.
Chris
|
|
|
|
|
|
Rank: Super forum user 
|
Originally Posted by: chris42 Yes, I was just trying to make the point that the force required to start something moving then drops once it is in motion (not added to it). I was just trying to keep it simple.
In reality you need to know the coefficient of friction for the wheels on the surface they will be on. This can be affected by the actual materials ie steel wheels on a steel surface will be different to polyurethane wheels on a steel surface. The wheels bearings will make a difference etc. So you have elastic properties of the wheel / surface, friction at the contact points and roughness of surface, bearing type and characteristics.
You would have something along the lines of the following for 400 Kg on a trolley with 4 wheels
Load for each wheel would be 100Kg, say you have found out the coefficient of friction for you wheels on the surface you will be using them and is for the sake of demonstration 0.047 and lets say the wheels are 200mm diameter, so a radius of 100mm (0.1m).
We then get 0.047 x (100kg /0.1m) =47 times that by 4 wheels and you get 188Kg to keep the load moving on the flat. It will take more effort to start it moving in the first place and if going up a slope it will also take more effort as previously noted. Use bigger wheels and this reduces your rolling resistance.
Realistically the best way is not to calculate it, but to try it with a load cell or similar to test actual not theoretical. However, having and understanding of the general idea does not hurt.
And this is still a simplified version.
Chris
Or test out how much force it needs and if it is too much for the individual, separate into smaller loads or get help.
No wonder people don't like posting on here, it seems to be about peoples own knowledge and not assisting the person posting.
|
 1 user thanked Invictus for this useful post.
|
|
|
|
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.