Can anyone explain the European standard for cookware lid design requirements?

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Discussion Overview

The discussion revolves around the European standards for cookware lid design requirements, specifically focusing on the force needed to remove the lid from the cookware. Participants explore the implications of the standard's specifications regarding force, weight, and temperature conditions.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks clarification on the meaning of the standard's requirement that the lid must be removable with a force equal to its weight plus 2N.
  • Another participant explains that Newtons (N) is the unit of force and provides a conversion from mass to force using gravitational acceleration.
  • Some participants discuss the implications of the standard, suggesting that the lid's design must account for additional forces such as friction and pressure differences.
  • There is a calculation presented by a participant regarding the force needed to lift a lid weighing 350 grams, leading to further questions about measurement methods.
  • Participants suggest using a force gauge or a fishing scale to measure the force required to lift the lid, with discussions on the accuracy of different measuring devices.
  • One participant mentions the possibility of using a universal testing machine for precise measurements, including temperature control.
  • Another participant humorously notes the equivalence of one Newton to the weight of an average apple.

Areas of Agreement / Disagreement

There is no consensus on the interpretation of the standard or the calculations involved. Multiple viewpoints and methods for measuring the required force are presented, indicating ongoing uncertainty and discussion.

Contextual Notes

Participants express varying levels of understanding regarding the physics involved, and there are unresolved questions about the correct application of the standard and the methods for testing lid design.

Who May Find This Useful

Individuals involved in cookware design, manufacturing, or testing, as well as those interested in European standards for product safety and usability.

coffeekwok
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I need help!...

Hi all, I'm new to this forum. I just joined the forum and I hope that you guys could help me out.

I'm in the trading business of cookware. I'm currently studying the European standards for these items and there's a point in the standard that I don't understand at all.

It says:
The design of the lid shall be such that it shall be possible to remove it from the body using a force equal to the weight of the lid +2N in any position at a temperature of 23C +/=5C.

It may sounds stupid to you but I'm not a scentist and certainly not very good at Maths. I believe that N stands for Newton but I do not have a clue of what it means be "using a force equal to the weight of the lid +2N."

I have a meeting coming up next week and your help would be highly appreciated. Thank you so much for your help!
 
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Newtons (N) is the standard unit of force. When forces are given as weights (pounds is often used in the US), then they mean the force of gravity exerted by something with that weight.

The conversion factor here is g (9.8). So the (mass in kg) x 9.8 = force in Newtons.
So in total, m x 9.8 + 2 Newtons.
Or you could convert the two the other way, and it'd be the equivalent of lifting the lid + 204 grams
 


Thanks Alxm! But sorry may be I'm too stupid, I still don't quite understand... do you mean that the lid of the cookware cannot heavier than 204 gram according to the standard?
 


coffeekwok said:
Thanks Alxm! But sorry may be I'm too stupid, I still don't quite understand... do you mean that the lid of the cookware cannot heavier than 204 gram according to the standard?

Sorry if I was unclear. No I divided the added value (2 Newtons) by 9.8 so I got the force-equivalent weight in kilograms (2/9.8 = 0.204).

So, if you express that additional force of 2N in terms of weight, then the force required to lift the lid needs to be the force equivalent of putting 204 grams of weight on top of the lid. (obviously the force needed to lift the lid has to be _at least_ the weight of the lid. Or it won't lift!)
 


If you want to lift any object with some mass (m), then you need to exert a force equal to it's weight (at the very minimum), which is 9.81 x m Newtons. This is simply a consequence of the laws of physics (you need to act against gravity, so your force must be equal or greater to the force with which the Earth pulls on it to lift it).

However, I suppose that in the case of a lid, you may need extra force. For example, there may be friction; if the metal lid expands due to heat, it might be harder to lift it; when the lid closes off the pan completely, a pressure difference may arise between the air inside and outside the pan which makes it harder to lift, etc.
I suspect that what the standard is saying, is that the lid should be designed such that due to all these possible effects, one shouldn't have to exert an extra force (on top of the force needed to overcome gravity) of more than 2N to lift the lid.

Yet in other words, if your lid weighs 500 grammes on a scale, and you try to pull it of with a force meter while cooking, you should be able to lift the lid with less than (500 x 9,81 + 2) = 4907 N.
 


Thanks CompuChip and Alxm! I'm getting there now.

The weight of the lid is 350gram, so in other words I would assume the calculation would be (350 x 9.81 +2) = 3,435.5N.

My next question would be how could I measure that and how do I know whether the design of the lid is correct or not. Thanks!
 


You want your answer in pounds, I'm sure. You have to lift the weight of the lid itself plus 9 pounds of force or less, that's all.

Since things get stickier or looser depending on temperature, they want this to happen when tested at 73 degrees F.
 


coffeekwok said:
Thanks CompuChip and Alxm! I'm getting there now.

The weight of the lid is 350gram, so in other words I would assume the calculation would be (350 x 9.81 +2) = 3,435.5N.

No, the weight has to be in kilograms, so 0.35*9.81 = 3.43 add 2 to that = 5.43.
Makes more sense doesn't it? If it took 3500 Newtons to lift the lid, 2 N wouldn't make much difference now would it?

My next question would be how could I measure that and how do I know whether the design of the lid is correct or not. Thanks!

Well, you could buy a force gauge. But a cheap one is really just the same thing as a scale, since I just explained how weight in kg relates to forces. So as I said, 2 Newtons is equivalent to the weight of 204 grams. So the total force (in terms of weight) would be 350+204 = 554 grams. So what you can do, is borrow a fishing scale (a good kind, the cheap ones are rubbish), attach the hook to the lid with a string or directly, and check that the scale doesn't go above 554 grams before the lid pops off.
 


Phrak said:
You want your answer in pounds, I'm sure. You have to lift the weight of the lid itself plus 9 pounds of force or less, that's all.
.

How did you arrive at 9 pounds for 2 Newtons?
 
  • #10


I think the best thing for you to do is, find a company nearby that has a universal testing machine; http://en.wikipedia.org/wiki/Universal_Testing_Machine

This machine can measure force and displacement extremely accurately, and if it has a temperature control box installed you can also measure at the temperature required for the standard!
 
  • #11


If you can find a local company who will do the testing it's pretty trivial, assuming they have a set of grips that will fit and a load cell accurate enough to measure that small a force. You might even be able to find a local university where a kind lab manager might do the tests for you on the cheap. And 23 +/- 5C is pretty universal room temperature in most of northern Europe (funnily enough where most of these standards are contributed from, either DIN or BSI!) so you probably won't even need the temperature chamber.
 
  • #12


alxm said:
How did you arrive at 9 pounds for 2 Newtons?

By making an error? I multiplied by 4.5 instead of dividing.

What's the answer in ounces?
 
  • #13


A force of one Newton is about the same as the weight of an average apple.

Spooky.
 
  • #14


Thanks Alxm and all!

I got it ... I think I will get a spring scale to test the lid... I saw one on the web it could measure up to 10N...
 

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