Last night I made a $5,000 mistake.
Do you see the problem?
I disassembled this butterfly valve a month ago for cleaning. Apparently when I put it back together I alligned the indicator perpendicular to the flap when it should have been parallel.
Last night I was doing a vacuum check with the clean chamber:
I set the butterfly valve to what I thought was full open (but was actually full closed!)
Do you know what happens next???
I turn on the vacuum pump. The turbopump goes to full speed.
Now the butterfly valve is actually closed. Which means the vacuum can’t get to the chamber.
Which means the chamber is at atmospheric pressure.
Then I turn the butterfly valve….
TTHHHHHWWWWOOOMMMMMPPPPPPP
Apmospheric air slams into the full speed turbopump, and it makes a bad sound.
Then I smell smoke..
And now the turbopump won’t spin up all. I likely ruined the turbopump’s rotor – the most expensive part of the pump. Likely repair:
Worst case $5,000.
Likely case $3,000.
Best case $1200.
When I opened the valve I instantly knew what was happening, but it was too late.
I can’t believe I broke the pump AGAIN. Really heartbreaking, especially because I knew to avoid this specific condition.
The repair will likely take a month. I’m going to ship the pump out and…
I’ll be traveling in december.
I imagine the cheapest way out is to buy a used turbopump like mine to scavenge it’s rotor. Here it is:
Prometheus Fusion Perfection 
That is so depressing.
Try to take it in stride though.
I have a suggestion. Many years ago I used to work in a semiconductor fab and I ran many pieces of equipment with turbo pumps and cryopumps mainly for interconnect metal deposition. We had a tons of machines with these pumps…
You might think of contacting some companies (Intel, IBM, Motorolla) that have fabs and ask about buying or just donated equipment — maybe getting some as corporate sponsors! Just like the SETI@Home folks did…
Nobody said it would be easy!
I’ve been thinking about corporate sponsors lately. Perhaps the project has enough clout to actually pull that off. Would be great to get an appropriate contact person on the inside.
I imagine most of the parts I get on ebay come from decommissioned silicone foundries.
Mark,
As a fellow fusioneer and someone with experience with turbopumps, I would suggest you looking into some of the $99 turbo pumps on ebay. I haven’t checked but they’d probably even run with your existing controller. The worst case scenario would require you to build a controller circuit, but doing so is quite simple and only costs around 20 dollars. And if you made your own controller, you could even integrate a system to not spin the pump up unless the valve is open, etc etc. Anyways, that’d be a heck ‘offa lot cheaper than getting your pump repaired at the manufacture everytime.
Best of luck,
Chad Ramey
I’ve been following your blog with interest since you first raised funds on Kickstarter. I have another $100 with your name on it here (lucky the Aussie $ is at parity). Are there another 49 donors out there? Chin up, $h1t happens, but every one is a learning opportunity – Written operational procedures/checklists spring to mind…
Hey Oliver I appreciate it!
I think this will result in my learning how to repair turbo-pumps. Forced learning.
The project paypal is famulus.fusion@gmail.com
Hmmm, turbo-pumps self destructing, I have heard that before, lovely noise is it not?
I used to work for Edwards, turbopumps are usually bolted straight onto the vacuum chamber (open bore with no valve) with a pressure interlock in the controller circuit. This stops the pump if the chamber pressure is higher than what the rotor can handle.
Worth considering?
Well, the reason for the butterfly valve is to limit the flow rate of the deuterium leaving the chamber. Some flow rate limiter is needed between the chamber and the pump.
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