> Thank you for a description of a combination locking mechanism that drive=
s
> an electrically conductive member into contact with another electrically
> conductive surface to complete a circuit. The failure of any part of this
> assembly is designed with utmost care and thought to prevent those two
> conductive members from making contact and completing the circuit. Howeve=
r,
> in the event of a catastrophic event occurring, explosion, severe
> deformation or fragmentation of entire assembly, evaporation and ionizati=
on
> of said assembly there is always a possibility, however remote,  that a
> conductive pathway may be made. Testing carried out in laboratory and fie=
ld
> of as many failure modes as possible still does not rule out the one chai=
n
> of events that would cause the safety device to fail safe. How many times
> have I heard the phrase. 'One in a million chance of failure' to be utter=
ed
> after something went wrong. Having done a little risk assessment in the
> past, I have come to realize how we can come to believe that we have
> covered all eventualities only to be reminded of our shortcomings when it
> does not work out that way. I encourage you to look up the inquiry into t=
he
> Piper Alpha oil platform disaster in the North sea back in the 1980's (?)
> At that time, the most safety designed platform built. Killed a lot of
> people, most of them died as aresult of multiple failures of the safety
> systems.
>=20

I use to say - If something can happen, how small the possibility ever is, =
it=20
will. Just give it enough time. If humans are involved in the possibility=20
equation, the possibility is increased substantially.

This is also why I am against nuclear power plants (I used to be pro, in my=
=20
youth). Just look at Harrisburg, Tjernobyl and Fukushima. And when we talk=
=20
about storing the waste, the time is really long...

However, the tricky part is to determine how small possibility of failure i=
s=20
acceptable. Because there will almost always be a possibility of failure. I=
=20
still go outside even though I can get hit by a meteor, I accept this risk.=
 I=20
also drive my car quite often, even though there are humans involved (both=
=20
myself and others), perhaps I shouldn't...

/Ruben

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124
200 39 Malm=F6 Sweden
www.liros.se
Tel +46 40142078
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.