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Barrie(Badger)Etter  
#1 Posted : 18 October 2019 11:16:53(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Just been asked by my MD, " What is the minimum weight (KG) that will injure a persons foot if not wearing safety shoes?".  The presumption is they are working at a bench and something is knocked off and falls on a foot.

I plucked a random weight of 2Kg but am aware the shape and composition of an object have various factors.  A bag of sugar will hurt but possibly split on impact but a small cast object with electronics inside may cause the injury.

So, I need to know what weight (mass in Kg) falling from an average bench height would cause injury?

Thanks for any assistance in this matter.

hilary  
#2 Posted : 18 October 2019 11:27:22(UTC)
Rank: Super forum user
hilary

How long is a piece of string?  How many times have you been working in the kitchen, dropped a vegetable knife and instinctively jumped so it doesn't land point down in your foot?  Quite sure it doesn't weigh 2 kgs.

thanks 2 users thanked hilary for this useful post.
Barrie(Badger)Etter on 18/10/2019(UTC), Hsquared14 on 22/10/2019(UTC)
CptBeaky  
#3 Posted : 18 October 2019 11:28:06(UTC)
Rank: Forum user
CptBeaky

I am not convinced this has a definite answer. There are so many variables such as:

  1. What footwear are they wearing? open toes, leather, canvas etc
  2. Where abouts on their foot does it land? toes, heel, arch etc.
  3. What shape it the object? Sharp, round etc
  4. How dense is the object? feathers vs metal for example

Without all these factors taken into account there can be no answer. A 250g knife landing on open toes will do a lot more damage than a 5kg pillow landing on someone wearing doc martins.

Basically you would need to look at the realistic worse case scenerio of what could fall of your benches and then compare it to the least protective footwear you are allowed to wear at that bench and then decide. It may be that you don't need safety footwear, just closed toed shoes will suffice.

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Barrie(Badger)Etter on 18/10/2019(UTC)
Natasha.Graham  
#4 Posted : 18 October 2019 11:28:27(UTC)
Rank: Forum user
Natasha.Graham

Depends what's falling from the bench and how high the bench is! The way in which things fall from the bench can differ depending upon the object, which part of the foot they land on and what footwear they're wearing. Also depends on the environment the bench is in?

I would argue that it's not just about what falls from the bench but what can penetrate the sole of the footwear on the ground too?

So I agree with Hilary - not one specific answer! 

thanks 1 user thanked Natasha.Graham for this useful post.
Barrie(Badger)Etter on 18/10/2019(UTC)
Barrie(Badger)Etter  
#5 Posted : 18 October 2019 11:40:02(UTC)
Rank: Super forum user
Barrie(Badger)Etter

I appreciate the string scenario but would appreciate best geuss opinion please.

Presume your average leather shoe at best and open sandle at worse.

Bench heiht around waist height.

CptBeaky  
#6 Posted : 18 October 2019 12:19:03(UTC)
Rank: Forum user
CptBeaky

Sorry, but I wouldn't even know where to start without more infomation. What would you consider an "injury". Some saying "ouch!", a bruise, a fracture? Amputation?

As I said, I really don't think there is a suitable answer for this without a very specfific risk assessment being done. If it helps though I can agree 2kg hitting your foot after falling from a waist high bench would probably hurt! In fact 1kg of metal would probably hurt too.

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Barrie(Badger)Etter on 18/10/2019(UTC)
Ian Bell2  
#7 Posted : 18 October 2019 12:21:24(UTC)
Rank: Super forum user
Ian Bell2

AGree with the previous posts, may variables that might happen.

As guidance, aren't safety boots usually rated at 200 Joules impact energy?

SO using the standard physics equation of Potential Energy = mass x g(9.81) x height then you can estimate the energy at impact and compare to the 200 Joules and hence get a ball park indication of potential for injury.

However, the area of contact will have a bearing, as others have stated - on the area of damage/impact

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Barrie(Badger)Etter on 18/10/2019(UTC)
A Kurdziel  
#8 Posted : 18 October 2019 13:21:41(UTC)
Rank: Super forum user
A Kurdziel

As someone had said this is a how long piece of string type question. The approach is back to front, you have a control (reducing the weight of the item that might fall on a foot) and you are trying to decide what risk it is suitable to manage.

What are you actually going to be working with-you will now, know its weight, shape etc.  You will also know who will be working with it and where.  Then you can decide if the control is sufficient

 

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Barrie(Badger)Etter on 21/10/2019(UTC)
Roundtuit  
#9 Posted : 18 October 2019 16:51:29(UTC)
Rank: Super forum user
Roundtuit

You are being led down a dangerous path - give an answer which is less than any weight which can fall from a bench and the company is justified stating safety footwear is not required.

Injury as stated is not only related to the mass and distance but the form of the load - a dart weighs between 18 to 23 grams but with a sufficiently sharp point will penetrate leather shoes.

Its that cracker question "which weighs more a tonne of lead or a tonne of feathers" we all know which in a choice of the two we may wish to stand under as it falls, or do we? Compact both in to a to a tightly packed mass....

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Barrie(Badger)Etter on 21/10/2019(UTC)
Ian Bell2  
#10 Posted : 18 October 2019 18:11:49(UTC)
Rank: Super forum user
Ian Bell2

..... volume

Brian Hagyard  
#11 Posted : 21 October 2019 07:22:10(UTC)
Rank: Super forum user
Brian Hagyard

EN ISO 20345 requirements -resistant to an impact of 200 Joules

Joules =  Mass(m) x Height(h) x Gravitational Acceleration(g = 9.82m/s).

So if my maths is correct and the bench is 1 m high thats approximatley 20KG - But thats in the lab where they can insure it hits the toecap only and we all know thats unlickly in the real world!

Happy for someone to correct my maths.

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Barrie(Badger)Etter on 21/10/2019(UTC)
Barrie(Badger)Etter  
#12 Posted : 21 October 2019 14:08:56(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Originally Posted by: A Kurdziel Go to Quoted Post

What are you actually going to be working with-you will now, know its weight, shape etc.  You will also know who will be working with it and where.  Then you can decide if the control is sufficient

 

The weighty items which are being built on the benches with noted weights upto 2.25 kg on anverage with some exceptions upto 11kg.  Shapes are hand span in length and half that in width / height boxes with electronics inside or average around 2" dia., approx foot long metal sticks with electronics inside.

Hope this this gives a better picture of what we're dealing with.

Roundtuit  
#13 Posted : 21 October 2019 14:47:25(UTC)
Rank: Super forum user
Roundtuit

Any tail lifts, FLT's, pallet trucks, pallet lifters around these benches? Palletised goods in racks?

The hazard isn't of necessity a vertically falling item.

Barrie(Badger)Etter  
#14 Posted : 21 October 2019 15:39:44(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Originally Posted by: Roundtuit Go to Quoted Post

Any tail lifts, FLT's, pallet trucks, pallet lifters around these benches? Palletised goods in racks?

The hazard isn't of necessity a vertically falling item.

Pallet truck a rarity, almost all goods are man/ lady handled to next port of call (calibration).
hilary  
#15 Posted : 22 October 2019 07:49:11(UTC)
Rank: Super forum user
hilary

Barrie

I just had my screwdriver set out, one with interchangeable heads.  I dropped a set of 10 heads on my toe and it hurt because I'm wearing sandals. 

I thought of you!

Hilary

CptBeaky  
#16 Posted : 22 October 2019 07:54:56(UTC)
Rank: Forum user
CptBeaky

Originally Posted by: Barrie(Badger)Etter Go to Quoted Post

The weighty items which are being built on the benches with noted weights upto 2.25 kg on anverage with some exceptions upto 11kg.  Shapes are hand span in length and half that in width / height boxes with electronics inside or average around 2" dia., approx foot long metal sticks with electronics inside.

Hope this this gives a better picture of what we're dealing with.

I would be enforcing safety toe caps with that work. I wouldn't be too bothered about the mid sole etc.

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Barrie(Badger)Etter on 22/10/2019(UTC)
achrn  
#17 Posted : 22 October 2019 08:53:21(UTC)
Rank: Super forum user
achrn

You could advise the MD that it can only be verified by testing and if he brings his foot to the workshop you'll be happy to drop some weights on it and he can determine the point at which he wants safety shoes.

thanks 6 users thanked achrn for this useful post.
mihai_qa on 22/10/2019(UTC), Barrie(Badger)Etter on 22/10/2019(UTC), Roundtuit on 22/10/2019(UTC), jmaclaughlin on 22/10/2019(UTC), Mark-W on 22/10/2019(UTC), SJP on 23/10/2019(UTC)
Barrie(Badger)Etter  
#18 Posted : 22 October 2019 09:46:58(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Below is a table of equivilent weights dropped from a known height based on CaptBeaky suggestion.  My question is does anyyone know what the Joule impact value of a hammer hitting a nail to drive it into wood is?  This knowledge I can then translate into something the MD can understand.  Apologies if the table doesn't comeout right, looks ok as appied whilst typing.

Joules

Mass - Kg

Gravity

Height in MT

4.41

=

0.5

9.81

0.9

6.62

=

0.75

9.81

0.9

8.83

=

1

9.81

0.9

11.04

=

1.25

9.81

0.9

13.24

=

1.5

9.81

0.9

15.45

=

1.75

9.81

0.9

17.66

=

2

9.81

0.9

19.87

=

2.25

9.81

0.9

22.07

=

2.5

9.81

0.9

24.28

=

2.75

9.81

0.9

26.49

=

3

9.81

0.9

28.69

=

3.25

9.81

0.9

30.90

=

3.5

9.81

0.9

33.11

=

3.75

9.81

0.9

35.32

=

4

9.81

0.9

37.52

=

4.25

9.81

0.9

39.73

=

4.5

9.81

0.9

41.94

=

4.75

9.81

0.9

44.15

=

5

9.81

0.9

46.35

=

5.25

9.81

0.9

48.56

=

5.5

9.81

0.9

50.77

=

5.75

9.81

0.9

52.97

=

6

9.81

0.9

55.18

=

6.25

9.81

0.9

57.39

=

6.5

9.81

0.9

59.60

=

6.75

9.81

0.9

61.80

=

7

9.81

0.9

64.01

=

7.25

9.81

0.9

66.22

=

7.5

9.81

0.9

68.42

=

7.75

9.81

0.9

70.63

=

8

9.81

0.9

72.84

=

8.25

9.81

0.9

75.05

=

8.5

9.81

0.9

77.25

=

8.75

9.81

0.9

79.46

=

9

9.81

0.9  

Edited by user 22 October 2019 09:49:11(UTC)  | Reason: Not specified

Roundtuit  
#19 Posted : 22 October 2019 09:52:27(UTC)
Rank: Super forum user
Roundtuit

Mr Google reckons 100ft/lb is the force of a hammer on a nail so 135 Joules or several expletives

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Barrie(Badger)Etter on 22/10/2019(UTC)
Barrie(Badger)Etter  
#20 Posted : 22 October 2019 10:07:01(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Originally Posted by: Roundtuit Go to Quoted Post

Mr Google reckons 100ft/lb is the force of a hammer on a nail so 135 Joules or several expletives

Thanks, in that case a mass of 15.5 Kg would be an equivilent value.  As stated preveiously, the average mass with the potetial for being dropped is around 2.5 Kg so would equal brusing, hopping around and expletives!

I reckon by tweaking the values icould call that a 1/4 impact value of the hammer and work up from there.  Thanks to everyones input.

Natasha.Graham  
#21 Posted : 22 October 2019 10:11:32(UTC)
Rank: Forum user
Natasha.Graham

I still think that this is a dangerous view to take.  Any object can cause a certain amount of damage if the conditions are right.  I think you're better off trying to convince your MD of that! As someone mentioned in a previous post, if you set a minimum weight in relation to safety footwear and someone gets injured by something falling on their foot which is less that your stated value, then that may open a whole can of worms! 

thanks 4 users thanked Natasha.Graham for this useful post.
Barrie(Badger)Etter on 22/10/2019(UTC), Hsquared14 on 22/10/2019(UTC), hilary on 23/10/2019(UTC), SJP on 23/10/2019(UTC)
chris42  
#22 Posted : 22 October 2019 12:22:37(UTC)
Rank: Super forum user
chris42

A Tube of electronics you say. So a hot soldering iron falling fine tip down weighs ?

Just a thought

Not an unreasonable question you ask. At what point does foot protection kick in (no pun intended), but it has to be looking at worst case scenario and only you know that. Of course, whatever you come up with as a minimum you will be happy to demonstrate with your own foot and so will any powers that be.

Hsquared14  
#23 Posted : 22 October 2019 13:09:05(UTC)
Rank: Super forum user
Hsquared14

I'm not sure that the weight of the object is entirely relevant here.  Which would you prefer fell on your foot - a 2Kg bag of feathers or a 2Kg billet of metal?  You need to consider more than just weight, sharp edges, points, density etc all have a part to play just putting a blanket weight limit on something is not practicable and not indicative of the relative risk of different objects.

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Barrie(Badger)Etter on 22/10/2019(UTC)
hilary  
#24 Posted : 23 October 2019 09:38:50(UTC)
Rank: Super forum user
hilary

Originally Posted by: Barrie(Badger)Etter Go to Quoted Post

Just been asked by my MD, " What is the minimum weight (KG) that will injure a persons foot if not wearing safety shoes?".  The presumption is they are working at a bench and something is knocked off and falls on a foot.

to be completely honest Barrie, if your MD who is legally responsible for people's health, safety and welfare is actually asking this question to get out of buying safety shoes, then you may be in the wrong job.  Just saying ....

thanks 2 users thanked hilary for this useful post.
Barrie(Badger)Etter on 23/10/2019(UTC), SJP on 23/10/2019(UTC)
Barrie(Badger)Etter  
#25 Posted : 23 October 2019 10:25:59(UTC)
Rank: Super forum user
Barrie(Badger)Etter

... to be completely honest Barrie, if your MD who is legally responsible for people's health, safety and welfare is actually asking this question to get out of buying safety shoes, then you may be in the wrong job.  Just saying ....

Hilary, probaly correct!  That said, with only 5 yrs before retiement movement not an option really....
kevkel  
#26 Posted : 23 October 2019 11:50:06(UTC)
Rank: Super forum user
kevkel

Would you not just fit a lip on the bench and stop weights falling in the first place?

Barrie(Badger)Etter  
#27 Posted : 23 October 2019 12:37:56(UTC)
Rank: Super forum user
Barrie(Badger)Etter

Originally Posted by: kevkel Go to Quoted Post

Would you not just fit a lip on the bench and stop weights falling in the first place?

Subject to size of lip would impede product production.  But that would not cater for pick up and accidentally lose grip on an item.
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