What does "safe" mean to you?
What does "safe" mean to you?
(OP)
As engineers, it is expected that we hold paramount the safety of the general public. Everyone has heard the expression "safety first."
One definition for "safe" (Webster's) is "free from harm or risk." I would argue that no product or process whatsoever is completely free from harm or risk.
So how do we really decide if a product or process is safe? Obviously, at some point, you have to accept some level of risk. How do we decide what level of risk is acceptable?
With some products or processes, there are codes or standards that must be met for safety, which can make our jobs easier. But did you ever stop to think where those codes and standards came from? Who developed them and what was their reasoning? More importantly, do you agree with their reasoning?
Anyway, before I ramble too much (maybe it's too late), I'd be interested to hear (read) peoples' thoughts on this.
Haf
One definition for "safe" (Webster's) is "free from harm or risk." I would argue that no product or process whatsoever is completely free from harm or risk.
So how do we really decide if a product or process is safe? Obviously, at some point, you have to accept some level of risk. How do we decide what level of risk is acceptable?
With some products or processes, there are codes or standards that must be met for safety, which can make our jobs easier. But did you ever stop to think where those codes and standards came from? Who developed them and what was their reasoning? More importantly, do you agree with their reasoning?
Anyway, before I ramble too much (maybe it's too late), I'd be interested to hear (read) peoples' thoughts on this.
Haf





RE: What does "safe" mean to you?
In other cases, such as the Space Shuttle, there was a calculated and acceptable level of risk.
In yet other cases, such as when we speed or do something stupid on the freeway, no consideration is taken for level of risk, even though we may consciously be aware of the risk.
In yet other cases, such as when we wake up, we simply ignore the risk and the possibility of risk altogether.
TTFN
RE: What does "safe" mean to you?
RE: What does "safe" mean to you?
The shuttles appeared to be one case of use outside of the established performance envelope (launch in conditions too cold for the O-rings seals), and a case of reality proving that "theory" is exactly that. Theory: Foam impact should not cause damage. Modified Theory: Foam impact might cause damage. Reality: Self explanatory.
Note that these are my opinions only. For any design, there is a need to accomodate an expected performance envelope. With in this realm, we are bound ethically. Use or misuse outside of this envelope is beyond the control of designers and engineers.
Regards,
RE: What does "safe" mean to you?
The O ring problem ,as Feynman showed, was that the system was routinely being stressed beyond its design limits.
I don't think anyone has really demonstrated what happened with the foam, yet, to the same sort of standard.
Cheers
Greg Locock
RE: What does "safe" mean to you?
I think your post implies the engineer knows the risks associated with the product or process. There is a clear responsibility for the people who use the product or are employed to operate the process are advised of the risks.
There are plenty of court cases that determined this did not happen. That's not answering your question, but ensuring people know the risks is part of the equation?
J.
RE: What does "safe" mean to you?
I believe a good example of this is the OHSA in Ontario. The approach is taken that an operator will at some point go out of their way to do something that will injure themself. The safety of a machine being operated is approached from this standpoint and every effort is made to ensure that it is impossible for the operator to injure themself on the equipment even if they are trying to injure themself.
ie. guarding must go low enough and light curtains mounted low enough that an operator cannot reach under them and touch moving equipment. The opposite is true as well.
In our manufacturing environment if I say "well it looks safe enough..." I know more work needs to be done.
In terms of the general public I believe the term is called due diligence. As an Engineer you are responsible for assuming that an item will be pushed beyond its design limits by the general public in its normal application. You are expected to design for this (translate as factor of safety).
For unusual applications not forseen by the Engineer you sometimes must demonstrate that it should have been obvious that the item would fail in this application (translate as the guy was an idiot for trying that and should have consulted an Engineer).
The second item rarely occurs but there have been two cases in which it was required to demonstrate that the individual should have known to consult with an Engineer.
All cases are relevant to Ontario Law and may not be the same where you live.
So safe to me means Darwin is spinning in his grave.
RE: What does "safe" mean to you?
Do you design a $100,000 Pinto that's absolutely safe and too expensive for your "general public" to buy?
It's nice to think that engineering is clear cut, but it's not. You have a certain price range that you KNOW your customer is willing to pay. You then fit all the required features into the design and find that it's double the price and you still haven't gotten it perfectly safe.
Perfect safety is a myth and to buy into that notion and ultimately deny your customers a useful product because you want to design for the 10th sigma is a disservices to the public.
The bottom line is that the public makes and allows some level of risk and couples that with a firm belief that it won't happen to them. Otherwise, you'd never get out of bed.
Don't want to start a flame war, but consider that MILLIONS of Americans still smoke, even though the occurence and mortality rate from cancer is absurdly high. Clearly, the smoking public makes a trade between cost and benefit as well.
TTFN
RE: What does "safe" mean to you?
This is quite an interesting case to me, when I am thinking about system design. How do you design a practical system that quite simply cannot be allowed to fail?
Cheers
Greg Locock
RE: What does "safe" mean to you?
1) complying with minimum design loads and criteria, as dtermined by long term observation and experience.
2) including some redundancy in the design can increase the degree of "safeness" but is often not a quantifiable change.
3) something is "safe" if it conforms to generally accepted practice which assumes a certain (again not quantifiable) amount of risk that has been determined as acceptable.
4) if I design a device and include a manual of operation, it is "safe" if operated within those boundaries. I have communicated clearly what those boudaries are.
5) My designs are not made in a vacuum, but with input from our procurement, fabrication, installation, sales and legal departments. Everyone contributes and has veto power. Engineering has the last veto for anything not cosmetic.
6) If design guidelines are not available then full-scale testing is often the only way to know.
7) I'm sorry - life is risky!!
PS - I think Greg is referring to the Human Driver.
RE: What does "safe" mean to you?
If it were a purely mechanical system, you cuold certainly overdesign by what you consider to be an adequate margin. Electronics are often dealt with through redundancy.
But, in the end, your system would neither be practical nor simple.
From a statistical perspective, the concept of "not" or "impossible" is anathema. Consider the humble bolt. How would you keep in from failing and under what set of conditions? You'd probably wind up with a bolt that's 3 times the size and weight that you'd otherwise use.
TTFN
RE: What does "safe" mean to you?
Cheers
Greg Locock
RE: What does "safe" mean to you?
TTFN
RE: What does "safe" mean to you?
Edward L. Klein
Pipe Stress Engineer
Houston, Texas
All opinions expressed here are my own and not my company's.
RE: What does "safe" mean to you?
FIT FOR PURPOSE
RE: What does "safe" mean to you?
The original Shuttle SRBs would be "fit" for their purpose of launching the Shuttle, but they were clearly unsafe in certain conditions.
TTFN
RE: What does "safe" mean to you?
Don't get me wrong, I beleive that we need product liability laws etc. to protect the general public because our profession does have it's bad apples. But, when we see hair dryers with the instruction "Do not use while asleep", or "Do not use in the bathtub or shower" don't you just wonder a bit if we are not somehow short circuiting evolution? The woman who spilt hot coffee on her lap while going through the drive through and then sued McDonalds, her lawyer and the judge who let such a judgement out the door, absolved us from having to be responsible for own unwise actions. They and others opened a Pandora's box that we will never get closed. Common sense has escaped us and will not be easily regained. The points made here about over designing and redundancy are good ones. However, do any of us think that such measures can protect us from lawsuits in today's world? I remember in college hearing a professor say "the problem with trying to make something fool-proof is that the world is always busy inventing a better fool". Good words to live by on this issue I think. To my mind, the real problem is that Americans, as appears to be our nature, have taken a good concept and pursued it to the bitter end. Will we ever learn?
RE: What does "safe" mean to you?
Common sense, likewise, should be applied to designers and suppliers. Up until recently, most cars did not have cupholders as a built-in feature. When I was in college and driving home on Coke and No-Doze, I didn't have a cup holder and holding the can between my legs was a normal occurrence. Even ignoring that aspect, a car is a moving vehicle, subject to sudden or unintended movements, and allowances should be made for a higher probability of spillage. Even ignoring that aspect, it was shown that the McDonald's coffee was kept at so high a temperature than even a normal spillage would have potentially caused severe burns.
McDonalds was clearly negligent in providing coffee that did not need to be that hot, particularly in the drive-through.
The jury award is a separate issue.
TTFN
RE: What does "safe" mean to you?
RE: What does "safe" mean to you?
In good, dry conditions, with light traffic, in a sound vehicle, 90 mph on an interstate is less dangerous than 35 mph.
RE: What does "safe" mean to you?
Risk is defined as the probability of an event multiplied by the consequences of that event, so something that will happen once a century but kill loads of people is the same risk as soemthing that happens daily and causes a minor injury each time, and both must be dealt with.
So, for the Safety Cases I compile before each well we drill, we'll look at all the things that could go wrong and then do a cost benefit anaylsis: we calculate the likelyhood of an event and the consequences of that event (using a number of criteria: material damage, damage to reputation, environmental damage and value of loss of life & limb using actuarial tables). Then we work out he cost of reduing those risks. Usually it's just a matter of emphasising something in the procedures or changing how we're going to do something, but for example, I have proposed to the UK authorities ommitting a downhole safety valve on a certain type of well as the risk of a blowout was smaller than the cost of installing and maintaining that valve, and the proposal was accepted.
The problem the general public have with this approach is two fold:
1. they don't like the idea of there being any risk at all. They perceive this approach as "well only one person per year will die so it's ok".
2. The public gernally underestimate risk in situations they are used to (crossing the road, or driving in their cars for eaxmple) but overestimate the risk in situations they are unaccustomed to (flying....)
The SAfety Case system is gernally 'better' than the regulations type safety system, as it forces teh designer to think about what they are designing rather than simply looking up a regulation and making sure they've ticked the box. Sadly, like most improvements in safety engineering, the goal setting system is usually only adopted after a disaster: Piper Alpha in the UK, the Alexander Kielland in Norway and the Ocean Ranger in Canada....
RE: What does "safe" mean to you?
The calculation went wrong when the punitive damages were set so high, precisely BECAUSE a cost benefit calculation had been used!
Cheers
Greg Locock
RE: What does "safe" mean to you?
Also, we use other criteria beyond simple finacial cost to mearsure the effects of risk when doing our risk assessment- loss of reputation for example.
RE: What does "safe" mean to you?
The case of the Pinto is an interesting one.
The Pinto cost benefit analysis had two main flaws:
(a) It was woefully inadequate, and
(b) The assumptions were badly wrong.
Cost benefit analysis is a useful tool for determining acceptable risk, but it is precisely that. As with most tools, the quality of the output is directly related to the quality of the input. As drillernic points out, it is just one tool. There are other risk assessments that could and should have applied in this case, not least common sense.
In what sense is addition of a part costing a few dollars not practical?
If there was any justification for that decision whatsoever, it would be that we have to take into account the context and date of that decision. However, times have moved on. Product recalls happen on a wide range of products, and safety is very much of the forefront of most (I would hope all) engineer's minds. Such analyses are now relatively commonplace for assessing risks in a wide variety of applications. I hope that it's not being seriously suggested that the same conclusion on the Pinto would be reached today.
RE: What does "safe" mean to you?
Number of crashes * damages per crash vs number of cars sold * cost per car of fixes
only has four variables.
As I said, my understanding is that the "damages per crash" estimate was wrong, and the reason it was wrong was that the juries were annoyed/horrified that anybody could be so cold blooded. The actual figures are pretty revealing. In practice 27 people died, and 2 million vehicles were sold before the changes were introduced. At the usual 2004 rate of 4 million $ per person, that's about $54 per vehicle in current $. The cost save was $11 in 1974 dollars, which sounds about right.
According to this presentation
www.nottingham.ac.uk/scheme/admissions/ currentstudents/Lecture%207%20-%20Economics.ppt
the actual calculation used 180 deaths+180 serious injuries +2100 cars, at $200000 $67000 and $700 respectively, and sales of 12.5 million vehicles, with a fix cost of $11 each.
So, as I said, the error was in the punitive damages, because of the cover-up, not the analysis. Where do you disagree?
Yet, oddly, this type of calculation is used all the time. Incidentally, do you buy the exact same tyre for your car that it originally had? and do you always specify the top of the range safety features when you buy your car? If not, you have just made a cost benefit decision, with, I would argue, even less information.
http://walterolson.com/articles/gmtrucks.html for a non hysterical account.
Cheers
Greg Locock
RE: What does "safe" mean to you?
I haven't got the inclination to research further, the lawyer in the newspaper article is probably a good jumping off point for further research.
Cheers
Greg Locock
RE: What does "safe" mean to you?
I am not sure that I believe either the 27 nor the 900, but suspect the truth is somewhere in between. I tend to believe neither journalists nor lawyers, when it comes to 'facts', but that's another thread.
My comment on the inadequacy comes not from the complexity of the calculation, but rather that it appears to have been taken in isolation from anything else.
I do agree that there is a difference in the general public's perception of risk between 5 fatalities per year from 2 million units, and a risk of 1 fatality per 400,000 years from 1 unit. A cost of $11 per unit in one to reduce the risk, equates to a cost of $22million per unit in the other. The vast majority of people would pay $11 to save their (or a loved one's) life, few could afford $22million. Whether you would pay $11 to save a totally unknown person's life would be down to the ethics of the individual. Some will pay $11, some $1, some $111, while others will pay nothing at all. When you see the effects of failure to pay the $11, that person becomes (apparently) known, and this will sway many people, but if it's hidden - who knows? (Incidentally, that's why so many people chose to vote for political parties who promise to cut taxes - they don't necessarily see the effect of that policy.)
RE: What does "safe" mean to you?
I'm sure similar criteria exist for consumer products.
RE: What does "safe" mean to you?
RE: What does "safe" mean to you?
Can you imagine being tackled by a 300-lb lineman running at full bore without padding and living to talk about it?
The issue is that once the equipment is sold as protection, it should do its job. If it doesn't, the manufacturer should be liable.
TTFN
RE: What does "safe" mean to you?
RE: What does "safe" mean to you?
Regards
Andy
RE: What does "safe" mean to you?
As with many systems, particularly, the Shuttle, bad practices that result in no immediate ill effects wind up becoming the norm.
Lest you think that you are immune from that, I'll remind everyone that there are those that seriously think that they can drive as well as anyone after a night of heavy drinking. There are those who think nothing of driving at 100 mph down the freeway or even down a large street.
TTFN
RE: What does "safe" mean to you?
It could also show that analysis was needed in another area entirely!
Jay Maechtlen
RE: What does "safe" mean to you?
Nowadays safety has become almost as important as production, and the various attached complex theories (models, mathematical techniques, etc.), and applied practices, have transformed it into a real scientific field of study.
It is now a discipline capable to anticipate and identify hazards and quantify risks, in order to enable taking decisions and steps towards forestalling accidents and their consequent damage in its various forms.
Could that be considered a reasonable definition ?
RE: What does "safe" mean to you?
http://assist.daps.dla.mil/quicksearch/
Good luck,
-MC