Why do people put a Pirani between the turbo and the roughing pump? A Pirani after your Turbo (Between turbo and roughing pump) sees a spike in pressure as your turbo is spooling up, and should maintain a pressure higher than your evacuation pressure. By nature of the turbo, it's constantly compressing molecules from the evacuation port into your foreline where you have a Pirani that's just seeing that compression. It's not actually reading anything... Like, I'd get it if you have a system that is meant to switch between two chambers like an LPC that has a dewar + gas system that need to be evacuated independently. But in this application, it seems like you're just oil contaminating a vacuum component by putting it in the path of oil diffusion?
I'm sorry, I'm not sure what you're talking about, every pirani in this system is "before" the turbo. One is at the inlet, across from the BA gauge. The second is essentially in the "vacuum chamber" (the evac port) of the system, it's there because the evac port can be isolated and it's important to ensure that the evac port is roughed down before opening it to the turbo again. Are you commenting about my TC on the roughing line? That's just a cheap refrigeration TC that I stuck in there for diagnostic purposes. I wanted a second opinion during shutdown to see where a loss of vacuum was occurring. Even so, it's pretty far from the roughing pump, after a trap, and it's nice to have some warning if there's a problem in the foreline and the backing pressure is rising (before the turbo starts to bog down) And what do you mean about a pirani "seeing" the compression? Your roughing pressure is your roughing pressure. Sure, the turbo is moving gas molecules into the foreline, but the roughing pump should be pulling them out of there asap. My foreline pressure continues to drop as the turbo spools up. Turbos are not good at compression (even one with a drag stage, like this, which is pretty happy at large gradients) which is why it's important to monitor the foreline and keep the pressure at the right level. Too high and the turbo burns up, too low and you boil the oil out of the bearings.
@@SignalDitch I'm sorry, I'm not sure what you're talking about, every pirani in this system is "before" the turbo. One is at the inlet, across from the BA gauge. The second is essentially in the "vacuum chamber" (the evac port) of the system, it's there because the evac port can be isolated and it's important to ensure that the evac port is roughed down before opening it to the turbo again. *That makes sense. Pretty standard Turbo protection. I'm used to MRI systems (Pumping down the outter Vacuum Space), and our test Cylinders that we test Cryocoolers in). We generally just have one Combination gauge that can go from atmospheric to 1x10^-9 Mbar)* Are you commenting about my TC on the roughing line? That's just a cheap refrigeration TC that I stuck in there for diagnostic purposes. I wanted a second opinion during shutdown to see where a loss of vacuum was occurring. Even so, it's pretty far from the roughing pump, after a trap, and it's nice to have some warning if there's a problem in the foreline and the backing pressure is rising (before the turbo starts to bog down) *I was, that looked like a Pirani (**7:30**, that device just to the right), but that makes sense. Thanks for the input. One thing I don't particularly love about the bellowed hoses is that they seem to trap a lot of gas. No matter how small of a run I use, if I switch to a straight stainless steel pipe (Not practical in 99% of applications), there is less pressure rise when the system it turned off. (I put an isolation valve just after the trap on the roughing pump to ensure rise in pressure was not cause by back streaming of oil.)* And what do you mean about a pirani "seeing" the compression? Your roughing pressure is your roughing pressure. Sure, the turbo is moving gas molecules into the foreline, but the roughing pump should be pulling them out of there asap. My foreline pressure continues to drop as the turbo spools up. Turbos are not good at compression (even one with a drag stage, like this, which is pretty happy at large gradients) which is why it's important to monitor the foreline and keep the pressure at the right level. Too high and the turbo burns up, too low and you boil the oil out of the bearings. *So, in multiple setups, including a one with a scroll pump that is meant evacuate a Helium Vessel (By itself), and then also be able to switch over via a valve to utilize a turbo to pump down a Dewar (The others are just Vane Pumps with a turbo). For one example, we have a Leybold TOPS361. They put combo gauges (One is low vac, and the system will swap over to a PM gauge at high vac) between the roughing pump, and the exhaust on the turbo. I also put a Cold Cathode gauge (Infinicon Blazers) on the inlet of the turbo.* *Immediately, the Pirani on the exhaust starts ticking up as the turbo spools. Additionally, the penning on the exhaust never gets below 5x-4 despite the CC on the inlet being in the 6x-7 range.* *However, I trust/appreciate your knowledge and I think further investigation into what I am seeing is required. Mind you - this TOPS is from the 80's and was sitting in a warehouse and our parts guy wanted to throw it away before someone stopped him and sent it to me to look it. It was missing some pieces, and also had a few used and new Pirani and Penning gauges (These were used to pump down old Opart Magnets), so it's entirely possible my gauges are... Field seasoned.*
While the video processes up to HD, let me pin a comment about a few things I didn't mention in the video: 1) The defect on the old mechanical pump is probably just a shaft seal. This is easy enough to fix and I'll get around to it before too long. I just couldn't pass up the opportunity to collect a second Welch 1402 2) I didn't get into detail about the controller firmware, but if anyone is interested then I'll put it on Github. It needs a little cleanup. 3) The diagram doesn't show the turbo vent port, but I intend to add another valve there with a pinhole so that the controller can stop the turbo more effectively. 4) The vacuum gauge controller (VG Electronics IGC-27) tends to output a small negative voltage on the analog line when the gauges are bottomed out. I ended up dealing with this by just building diodes into my patch cables. 5) There is a pressure transducer on the pneumatic line for the valves, but I need to do some work on the pneumatics anyway to replace the air-drying and coalescing filters. In the future, thr controller will be aware of the pneumatic system pressure. Until then, all valves fail safe anyway so its probably okay if the controller loses valve control and doesnt realize it. 6) You may notice we dont reach UHV in this video, i think we top out at 1e-5 mbar. This is because the system has not been properly cleaned or baked out and was also recently vented to atm. Here in VA were sitting at >60% humidity so its basically full of water. Ideally, in the future, the top end of the system would only ever be purged with dry nitrogen. By the way, I wrote an article on DIY Diodes for the next issue of Make: Magazine (Make: #86) so keep an eye out for that!
Do you have a BOM, sketchy or otherwise, on the components used in the build? Looking for a good head start on the valving, in particular, since your turbopump, roughing pump, ion sensor, and other components are easy to identify already.
Nice build, looks great! I'm trying to figure out physical controller at the moment for similar setup...may try tablet + TouchOSC/Lemur for primary controller with graphs and maybe a small midi controller for any desired physical/tactile switches but will see. Great to see your continued progress!
That Oil mist eliminator is disigned to sit vertically straight above the pump so that oil it collects can slowly drain back into the pump. where you hacve it now is likely to result in it slowly filling and eventually leaking oil.
Very cool setup! The more flashing lights, the better - equipment always works better with them 😂😂 I have to say though that starting to quote Kaczynski rankled a bit - why put that in?
It was a joke about how it looked like I was making a pipe bomb. I think it goes without saying, but I'm happy to say it anyway: I think the Unabomber was a piece of shit. His manifesto is superficially appealing to green anarchist types, but his views were fundamentally regressive, anti-left, racist, and sexist.
If I wasn't before I'm now completely hooked. The idea of me listening to music on tubes I made is otherworldly to me. I am going to have to start gathering my own vacuum Tube creation equipment. Where to begin......
Nice work. Love the disclaimer before someone dense decided you were building something else. Looking forward to watching your progress. You said Schottky diode, think you meant zener, no biggie
You're totally right! I had Schottky on the brain because that's what I put in line to block the negative voltage (due to the low forward voltage drop)
Is there some kind of filter in line with the evacuation port to catch glass going into the turbo should anything break? The rig looks awesome by the way.
Thanks! Yes, there are two screens between the port and the turbo. One is built into the ISO-K centering ring on the turbo, and the other is built into the KF16 centering right between the compression fitting and the tee. I've said before that if you're choosing what size debris can get into your turbo, then you're already in trouble, but it doesn't hurt to try. During high risk operations like tip-off, I'll shut the turbo isolation valves, but that leaves plenty of time during bake-out, etc. for something to go wrong. Good question.
Excellent build , thanks for sharing, (waiting for new videos)
Why do people put a Pirani between the turbo and the roughing pump?
A Pirani after your Turbo (Between turbo and roughing pump) sees a spike in pressure as your turbo is spooling up, and should maintain a pressure higher than your evacuation pressure. By nature of the turbo, it's constantly compressing molecules from the evacuation port into your foreline where you have a Pirani that's just seeing that compression. It's not actually reading anything...
Like, I'd get it if you have a system that is meant to switch between two chambers like an LPC that has a dewar + gas system that need to be evacuated independently. But in this application, it seems like you're just oil contaminating a vacuum component by putting it in the path of oil diffusion?
I'm sorry, I'm not sure what you're talking about, every pirani in this system is "before" the turbo. One is at the inlet, across from the BA gauge. The second is essentially in the "vacuum chamber" (the evac port) of the system, it's there because the evac port can be isolated and it's important to ensure that the evac port is roughed down before opening it to the turbo again.
Are you commenting about my TC on the roughing line? That's just a cheap refrigeration TC that I stuck in there for diagnostic purposes. I wanted a second opinion during shutdown to see where a loss of vacuum was occurring. Even so, it's pretty far from the roughing pump, after a trap, and it's nice to have some warning if there's a problem in the foreline and the backing pressure is rising (before the turbo starts to bog down)
And what do you mean about a pirani "seeing" the compression? Your roughing pressure is your roughing pressure. Sure, the turbo is moving gas molecules into the foreline, but the roughing pump should be pulling them out of there asap. My foreline pressure continues to drop as the turbo spools up. Turbos are not good at compression (even one with a drag stage, like this, which is pretty happy at large gradients) which is why it's important to monitor the foreline and keep the pressure at the right level. Too high and the turbo burns up, too low and you boil the oil out of the bearings.
@@SignalDitch
I'm sorry, I'm not sure what you're talking about, every pirani in this system is "before" the turbo. One is at the inlet, across from the BA gauge. The second is essentially in the "vacuum chamber" (the evac port) of the system, it's there because the evac port can be isolated and it's important to ensure that the evac port is roughed down before opening it to the turbo again.
*That makes sense. Pretty standard Turbo protection. I'm used to MRI systems (Pumping down the outter Vacuum Space), and our test Cylinders that we test Cryocoolers in). We generally just have one Combination gauge that can go from atmospheric to 1x10^-9 Mbar)*
Are you commenting about my TC on the roughing line? That's just a cheap refrigeration TC that I stuck in there for diagnostic purposes. I wanted a second opinion during shutdown to see where a loss of vacuum was occurring. Even so, it's pretty far from the roughing pump, after a trap, and it's nice to have some warning if there's a problem in the foreline and the backing pressure is rising (before the turbo starts to bog down)
*I was, that looked like a Pirani (**7:30**, that device just to the right), but that makes sense. Thanks for the input. One thing I don't particularly love about the bellowed hoses is that they seem to trap a lot of gas. No matter how small of a run I use, if I switch to a straight stainless steel pipe (Not practical in 99% of applications), there is less pressure rise when the system it turned off. (I put an isolation valve just after the trap on the roughing pump to ensure rise in pressure was not cause by back streaming of oil.)*
And what do you mean about a pirani "seeing" the compression? Your roughing pressure is your roughing pressure. Sure, the turbo is moving gas molecules into the foreline, but the roughing pump should be pulling them out of there asap. My foreline pressure continues to drop as the turbo spools up. Turbos are not good at compression (even one with a drag stage, like this, which is pretty happy at large gradients) which is why it's important to monitor the foreline and keep the pressure at the right level. Too high and the turbo burns up, too low and you boil the oil out of the bearings.
*So, in multiple setups, including a one with a scroll pump that is meant evacuate a Helium Vessel (By itself), and then also be able to switch over via a valve to utilize a turbo to pump down a Dewar (The others are just Vane Pumps with a turbo). For one example, we have a Leybold TOPS361. They put combo gauges (One is low vac, and the system will swap over to a PM gauge at high vac) between the roughing pump, and the exhaust on the turbo. I also put a Cold Cathode gauge (Infinicon Blazers) on the inlet of the turbo.*
*Immediately, the Pirani on the exhaust starts ticking up as the turbo spools. Additionally, the penning on the exhaust never gets below 5x-4 despite the CC on the inlet being in the 6x-7 range.*
*However, I trust/appreciate your knowledge and I think further investigation into what I am seeing is required. Mind you - this TOPS is from the 80's and was sitting in a warehouse and our parts guy wanted to throw it away before someone stopped him and sent it to me to look it. It was missing some pieces, and also had a few used and new Pirani and Penning gauges (These were used to pump down old Opart Magnets), so it's entirely possible my gauges are... Field seasoned.*
So excited to see a new video from you! Beautiful build! Keep up the great work!
While the video processes up to HD, let me pin a comment about a few things I didn't mention in the video:
1) The defect on the old mechanical pump is probably just a shaft seal. This is easy enough to fix and I'll get around to it before too long. I just couldn't pass up the opportunity to collect a second Welch 1402
2) I didn't get into detail about the controller firmware, but if anyone is interested then I'll put it on Github. It needs a little cleanup.
3) The diagram doesn't show the turbo vent port, but I intend to add another valve there with a pinhole so that the controller can stop the turbo more effectively.
4) The vacuum gauge controller (VG Electronics IGC-27) tends to output a small negative voltage on the analog line when the gauges are bottomed out. I ended up dealing with this by just building diodes into my patch cables.
5) There is a pressure transducer on the pneumatic line for the valves, but I need to do some work on the pneumatics anyway to replace the air-drying and coalescing filters. In the future, thr controller will be aware of the pneumatic system pressure. Until then, all valves fail safe anyway so its probably okay if the controller loses valve control and doesnt realize it.
6) You may notice we dont reach UHV in this video, i think we top out at 1e-5 mbar. This is because the system has not been properly cleaned or baked out and was also recently vented to atm. Here in VA were sitting at >60% humidity so its basically full of water. Ideally, in the future, the top end of the system would only ever be purged with dry nitrogen.
By the way, I wrote an article on DIY Diodes for the next issue of Make: Magazine (Make: #86) so keep an eye out for that!
Do you have a BOM, sketchy or otherwise, on the components used in the build? Looking for a good head start on the valving, in particular, since your turbopump, roughing pump, ion sensor, and other components are easy to identify already.
Nice build, looks great! I'm trying to figure out physical controller at the moment for similar setup...may try tablet + TouchOSC/Lemur for primary controller with graphs and maybe a small midi controller for any desired physical/tactile switches but will see. Great to see your continued progress!
That Oil mist eliminator is disigned to sit vertically straight above the pump so that oil it collects can slowly drain back into the pump. where you hacve it now is likely to result in it slowly filling and eventually leaking oil.
You're completely right, I don't know why that didn't occur to me. I'll need to get more fittings, but I'll amend that soon.
can I get a pic of the DIM Rail with the power supplies and pneumatics?
Very cool setup! The more flashing lights, the better - equipment always works better with them 😂😂 I have to say though that starting to quote Kaczynski rankled a bit - why put that in?
It was a joke about how it looked like I was making a pipe bomb. I think it goes without saying, but I'm happy to say it anyway: I think the Unabomber was a piece of shit. His manifesto is superficially appealing to green anarchist types, but his views were fundamentally regressive, anti-left, racist, and sexist.
If I wasn't before I'm now completely hooked. The idea of me listening to music on tubes I made is otherworldly to me. I am going to have to start gathering my own vacuum Tube creation equipment. Where to begin......
Awesome thank you for sharing
10:34 there is a pipe bomb in your mailbox
Nice work. Love the disclaimer before someone dense decided you were building something else. Looking forward to watching your progress. You said Schottky diode, think you meant zener, no biggie
You're totally right! I had Schottky on the brain because that's what I put in line to block the negative voltage (due to the low forward voltage drop)
Nice control panel... looks like it cost megabucks. ;) Also loving the Dymo labels for that authentic 1970s DIY look.
Amazing work!
It's such a well thought out system, I love it!
Front panel looks great!
been excited for the next video in this series and this didnt disappoint!
Nice to see more people using DJ lighting switches and dynamo labels for switching on gear. The custom 19” panel came out really well.
That ADJ power strip is very underrated. I love it.
Is there some kind of filter in line with the evacuation port to catch glass going into the turbo should anything break? The rig looks awesome by the way.
Thanks! Yes, there are two screens between the port and the turbo. One is built into the ISO-K centering ring on the turbo, and the other is built into the KF16 centering right between the compression fitting and the tee.
I've said before that if you're choosing what size debris can get into your turbo, then you're already in trouble, but it doesn't hurt to try.
During high risk operations like tip-off, I'll shut the turbo isolation valves, but that leaves plenty of time during bake-out, etc. for something to go wrong. Good question.