Murphy’s law
Everything that can go wrong will go wrong.
Especially true when we explore the unknown.
Murphy’s law
Always strikes to make the
biggest damage!
Wise people learn from
someone else’s pain.
Painful Examples:
1. Too long.
2. Too late to know.
3. Too short.
4. Too slippery.
5. Too hot.
6. Too cold.
7. Too complicated.
8. Too absent minded.
9. Too tired.
Two mm too long
Two mm too long.
Two mm too long
Normal welding path
Abnormal part
Cracked welding path
Closeup of the cracks
Cost of that negligence
• An expensive gate valve.
• One whole week of effort to find the
problem.
• A lot longer to solve the problem.
• Delayed graduation by 3 month.
More perspective is better.
Small details sometimes count big
Welding bead is likely to cause
reduced ID, but of which tube?
A
C
B
Too late to know
Intricacy of gate valves
“UHV” compatible?
Vapor pressure of the lubricant counts!
Do pay attention to small prints!
Sometimes it counts a lot!
Why you need a RGA
Too late to know (2)
http://www.mcallister.com/gizmos1.html
This differentially-pumped quick door is really handy for
quick access to large systems where the base pressure is
lower than 10 -7 torr and the chamber must be opened
frequently. The differential seal allows pressures in the 10 -10
torr range. It is also available with an integral viewport or
electrical feedthroughs.
Stretching over the limit
A shortcut induced short
Great Economy ?
Vacuum
Chamber
1
Turbo
Vacuum
Chamber
2
Vacuum
Chamber
3
Vacuum
Chamber
4
Turbo
Turbo
Turbo
Backup
Turbo
Station
Will vent when power fails.
Mishap can multiply
Vacuum
Chamber
1
Turbo
Small Leak
Vacuum
Chamber
2
Vacuum
Chamber
3
Vacuum
Chamber
4
Turbo
Turbo
Turbo
Backup
Turbo
Station
Will vent when power fails.
Murphy’s law strikes hard!
Vacuum
Chamber
1
Turbo
Vacuum
Chamber
2
Vacuum
Chamber
3
Vacuum
Chamber
4
Turbo
Turbo
Turbo
The catastrophe happens
where it can cause the most
damage.
Backup
Turbo
Station
Backup
pump
Consequence
1. All chambers vented.
2. One operating chamber subject to
damage of several instruments:
filaments burnt, channeltron damaged,
etc. Takes several weeks to recover.
Too fragile
Broken cooling connector
Improper ways to tightening bolts:
net force times large distance  large strain
Increased possibility of
crack formation at the weld joint.
F
L
Proper ways to tightening bolts:
net torque without net force !
Too slippery
Beware of cooling connections.
Bad pratices cause lots of flood.
Never use teflon tape to compensate for
mismatching hose diameter!
Absolutely bad idea!
The damage could be huge!
Too Slippery
Consequence of flood
1. The connection under pressurized water very slowly slipped and finally
break loose near midnight. The pressurized cooling water squirted
toward a running PC. In particular, onto and destroyed an interface board
of a CCD camera. Unfortunately, the manufacturer of that expensive
CCD had already gone out of business, and no replacement card can be
found. The expensive CCD thus becomes useless.
2. The water accumulate on the lab floor and leaked through the cracks,
“showering” the lab below on 2nd floor and eventually goes down to a lab
in the ground floor. One photocopier in the 2nd floor lab get soaked.
Fortunately, after taking it apart and cleaned everything, it goes back to
work.
Hindsight:
Use only as much cooling as is needed. We now use fishtank
circulator plus a water container. The water pressure is so
much smaller and the total amount of water is limited.
Too hot!
The burnt pump
Is heat from baking the last straw?
Hindsight
• Exactly the same thing happened in Prof. Jim Lin’s lab.
• “Alcatel” has found the problem and issued a recall.
(They used a cheap but unreliable capacitor!)
• “Alcatel Taiwan” has not informed us of the recall.
This is really unwise! The fire could become a major
disaster if not found early. Then they will be
responsible for much bigger loss.
• “Alcatel Taiwan” has provided free repair of the pump.
It is your judgement whether that can repair their
reputation?
Pump make and model: Alcatel: Pascal 2015SD
Prevention ?
IAMS has since bought a far infrared
thermal camera for inspection of the lab
or malfunctioned instrument. It’s quite
some experience to see the world from
a totally different wavelength!
You should ask your lab’s safety
officer to borrow it and record images of
your instrument while it is still normal.
Too bossy
Space Shuttle Challenger.
The weather can’t be too cold at Florida?
If you are not fuuly convinced,
discuss with your boss!
(unless you prefer to get into big trouble).
Two units are too confusing.
Mar’s rover
Team work needs communication.
Always ask questions!
If you have to do it,
you deserve a satisfying answer.
Too absent-minded
Improper installation
viewed from the inside of the chamber
Too tired. The catastrophic end of a turbo.
Be prepared.
• If we run a Turbo pump long enough, it’s
going to crash sooner or later.
• How do we handle such situation?
• Get the research done and graduate
before the turbo quit.
• Leave it to the boss? What about your
boss run out of cash for the next 6-month?
Control the damage!
Contain the butterfly.
Don’t give it a chance to amplify.
假如 項羽 當年渡過烏江?
李清照 《夏日絕句》
生當作人傑，死亦為鬼雄。
至今思項羽，不肯過江東。
Go for it.
Exercise your own Judgment
Resist temptations
Do it right
If you are innovative, you will encounter un-anticipated
surprises. With all the small mishaps, life Goes On!
And I hope you all make big discoveries sooner or later.