My research machine exploded - back to the drawing board

[dullard]

For my PhD I'm designing a small machine that uses pressurized gas (4 atm). I've finished most of the design except the proper material to make it out of. The machine owner said he liked polyurethane and had extra sitting around that I could use. I recently built another revision. Well its been running quite well for the last few weeks. I needed to switch gas supply lines today and when I connected it back up, I turned up the pressure another 25% to test for leaks. On the plus side, there were no leaks. However, my machine exploded instead. 3 screws and polyurethane glue weren't enough to hold the extra pressure. My ears are still ringing from the noise.

I can easilly rebuild - it will just take a day or two and none of the expensive equipment was damaged. Good thing I found this, since it forces me to find a better material; we can't risk hurting anyone with explosions.

Just thought someone might think my experience was interesting.

 

[Electric Amish]

It would be more interesting if you told us what the machine does.

amish

 

[GoodRevrnd]

So what is its purpose...? Or is that a trade secret.

 

[amnesiac]

Originally posted by: Electric Amish
It would be more interesting if you told us what the machine does.

amish

He told you. It uses pressurized gas.

 

[GoodRevrnd]

Originally posted by: amnesiac 2.0

Originally posted by: Electric Amish
It would be more interesting if you told us what the machine does.

amish

He told you. It uses pressurized gas.

Well my digestive track uses pressurized gas as well, but that doesn't make it interesting.

 

[dullard]

Sorry I didn't think about tell you its use. It is a rapid PCR thermocycler. It duplicates DNA. If you have a university library around, you can read an article recently published about my work:

"Rapid Amplifcation of Bacillus anthracis DNA" Genetic Engineering News, Vol. 22, No. 11, June 1, 2002.

The reason to amplify DNA is to have larger quantities for testing purposes. Suppose you found an unknown white powder and were worried about its potential dangers. A PCR machine can amplify small quantities (theoretically as small as 1 piece of DNA) to detectable quantities. In that article it discusses how currently available PCR machines take 2 hours to amplify DNA - although it has been reduced as low as 30 minutes in some cases. Thus the sample is sent to a lab, waits its turn in line with the other white powders, takes 2 hours to amplify, then you know if it is Anthrax. Currently this process means it usually takes 2-3 days to know if the powder is Anthrax. That article discusses how our machine amplified and detected Anthrax in as little as 2 minutes, 45 seconds. (USAMRIID sent us only pieces of Anthrax DNA for testing - don't think we had access to live bacterium). With a portable 3 minute machine - people have a much better chance of survival - they don't need to wait days to know if they have been exposed to dangerous bacteria.

However its main use will be in doctor's offices. No more waiting 2-3 days to know if you have meningitis, strep throat, etc... You can be told while you are still in the office.

 

[Bignate603]

The company I work at works with alot of high-pressure/vacuum things. We usually work in aluminum with rubber O-rings. The only thing is it's much harder to machine. We always send out stuff to be made, it's too hard to mill anything of a decent size on the machining tools in our shop. What's the dimensions and how complex is the shape?

 

[Bignate603]

oh and one more thing, how tight do the tolerances need to be? The tighter the tolerances the more it costs if you get it machined.

 

[SubZeroX]

dullard,

what makes your PCR machine better or more special than other PCR machines? You said it was "rapid." Does that mean your PCR machine can finish a reaction faster than a regular machine? Typically when I do a PCR it takes 3 hours or so, so it's a long time. If you have found a way to get it done faster that's great.

 

[dullard]

Bignate603, the main requirements (which I knew from the beginning aren't fully handled my polyurethane) are:
1) Withstand 6 atm (100% higher than what it will likely see in practice)
2) Withstand 150°C temperatures
3) Lightweight to be portable and so it doesn't absorb too much energy
4) Low thermal conductivity
5) Able to be easilly machined or molded
6) Able to keep threads

We will probably switch to thin metal with thick insulation - but we just haven't gotten that far yet.

 

[dullard]

Originally posted by: SubZeroX
dullard,

what makes your PCR machine better or more special than other PCR machines? You said it was "rapid." Does that mean your PCR machine can finish a reaction faster than a regular machine? Typically when I do a PCR it takes 3 hours or so, so it's a long time. If you have found a way to get it done faster that's great.

There are two main advantages:
1) High speed. 400 base pair amplifications take roughly 4 minutes. 2000 base pair amplifications take roughly 10 minutes.
2) Less time spent at high and low temperatures means the enzyme holds up better - meaning we probably can amplify much longer DNA fragments than typical machines.

I've got to go now, I'll answer any more questions tomorrow.

 

[J3anyus]

Cool. I did a big DNA project back from November to March, did some PCR. PCR took me about 4-6 hours, so being able to do it in only a few minutes would be awesome. Good luck with your machine.