First ever Turbo experience

[Richard Hull]

Still mystified as to the need for the heater at the top of the pump. I have never even connected it. Likewise the external fan? I have run the turbo for up to 1 hour, (longest run in the now aborted fusor V effort), and felt the base of the turbo and it was at ambient??? Why the fan..? Is this for labs and processes where the system is left running 24-7? If so, I will never need the fan or the heater?

Still coming up on the wonderment of the turbo. I am very pleased with it, thus far. I had a moment of fear when the first arcs in fusor V turned the controller off automatically. but the reset button, (standby), always worked and restarted....Whew!!....

Richard Hull

[Andrew Seltzman]

The heater at the top is for baking out the pump when removing water vapor or contaminants if it will be used at UHV vacuum levels.
The fan keeps the motor cool when the heater is on, or when pumping very high gas loads, or gasses with high molecular mass such as argon.

[Richard Hull]

Thanks Andrew! Since I have no current aspirations for UHV, the heater is out and the fan will also not be used, due to the total isolation of the turbo in and out with valves. (Stays at low, "fore line" pressure, few microns)

When I shut down I shut the valve to the chamber, let the turbo wind down. (~10 minutes) This leaves the turbo and fore line at about 3 microns. I then valve off the turbo outlet to the fore line. then within seconds I turn off the mechanical pump and slam off pump's exhaust line with a ball valve, then let the pump up to air and immediately reseal the fore line. Thus, the mechanical pump can't "breathe" in or out. (The exhaust line goes out the back of the building)

When I start up, as I hit the mechanical pump switch, I simultaneously open the exhaust line ball valve. I typically hit 10 microns within 20 seconds on the fore line. I then open the outlet valve of the turbo and the fore line pressure might drop or rise by 2 or 3 microns I immediately open the chamber valve and the pressure on the fore line might rise on the TC gauge to 40 microns but within seconds is back down to 10 microns, due to the small cross volume. I start the turbo immediately and within 60-80 second from starting the mechanical pump, the chamber is sub micron (0.0500 micron on the .1 torr baratron) with the fore line TC gauge zero'd out. In the remaining 3 minutes of spin up the baratron drops the chamber to a rather stable 0.002 micron.

Richard Hull

[Dan Knapp]

Turbo controllers often include signal lines for rotational speed readout (commonly 0-10 VDC) as well as a switchable line for reduced speed or “soft start.” I find it useful to be able to switch to reduced speed and read out the rotational speed (yet another use for the red HF freebie meters).

[Jerry Biehler]

Use the fan, it is still needed without the heater. You can fry the bearings otherwise.

[Peter Schmelcher]

The little turbo pumps can be cycled fast back and forth to atmosphere quickly and you can even get them with aerodynamic breaking vents. When these are used in a production setting that ends up as a lot of mechanical PV compression energy and things get hot, so they fan or water cool them.

[Richard Hull]

Fortunately, at shutdown of a fusor, there is no time critical period for stopping a spinning turbo at 90k rpm. It is a walk away and "pop the tab on a cool one" time. Of course, I could run the fan for grins and googlers.... It don't cost much in 'tricity.

Thanks for the added info on the fan usage in up-down rapid operations where they are used in time critical operations.

Richard Hull

[Jerry Biehler]

Even on stuff where you just leave it on you want a fan.

[Dan Knapp]

I run a Varian TV-301 (300 l/s) turbo full time without a fan. I regularly monitor its temperature with an infrared thermometer, and it usually runs 52 degrees C. They offer an optional fan for this pump "for heavy duty use" whatever that means. My guess is that I would get longer bearing life running at a lower temperature, but the pump has well over six years running time on it and only sings a little.

[Dennis P Brown]

Fans do help extent bearing life on turbos; considering how expensive most turbo's are, a rather good idea to add a fan.

[Richard Hull]

As mine spins up I have to wear hearing protection (very annoying), but once at speed it's Ok. Spin down is equally annoying. Pumps fabulously though.
About 15 seconds into spin-up it passes through some resonant point that sounds nasty and vibratory for about 2-3 seconds and then mellows right out for the rest of the 60-80 second high pitched spin-up.
At no time do I hear contact scrapes or bearing noise. That resonant point sounds wicked, though. Of course it is mounted and bolted directly to a wood table. (sounding board)

Richard Hull

[Jerry Biehler]

I fried the bearings on my TV-301 on my SEM by running it without the fan, wont make that mistake again.

[Dan Knapp]

I suspect that the SEM application would be considered “heavy use” with frequent cycling. I have run these turbos on mass spectrometers under constant vacuum for years before bearing changes were needed. Fusor use might be considered “medium” or “heavy” depending upon how much cycling of pressure one does. A fan is easy enough to install to play it safe. Some older turbos I have used had water cooling, which is more of a pain.

[Richard Hull]

Mine has both water and fan capability, (seen in photos first page) neither of which I will use. I have run the Turbo for three hours straight and the motor bearing base is ambient. That is a very long run. I would call a fusor near a zero use device from my stand point as I tend to run a working fusor like fusor IV about 6-10 times per year with no more than 5 hours run time per operation. For the average turbo in a vacuum system, I would think that is near zero run time.

This is why I used a diff pump since 2004. I just could not justify the cost of a Turbo for such intermittent use.

Richard Hull