# Tag Info

## Hot answers tagged vacuum-pumps

5

The terms you are looking for are "self priming pump" and/or "run dry pump". Centrifugal self priming pumps require some water to be in them to start, but can pull a vacuum including air. Diaphragm pumps pump air or water very well. They can run dry and are self priming. Some are specifically designed to just pump air. Vane pumps or any other positive ...

4

I did some internet searching and did not find anyone that had done a direct swap out. Granted, probably the majority of these replacements occurred before the existence of the internet ;-). As I am sure you are already aware (but to be thorough), modern diffusion pump designs do use synthetic working fluids. It will probably take some fine tuning of the ...

4

Geissler invented the so-called "liquid piston" pump using mercury for the piston. The basic idea of the design is to entrap some of the air between two volumes of mercury in a pipe, and then force the mercury along the pipe to release the air into the atmosphere. Geissler achieved 0.1 Torr with that design of pump in the 1850s. Sprengel invented an ...

3

The small tube I believe is for the freezer coil, or it could be a capillary tube (thank you Swift). Regardless, simply solder it shut and use the two larger lines for pumping. I would like to note, this style of compressor cycles some of its lubrication through the refrigeration system, so keeping the crankcase full of oil is important since any oil lost ...

3

The device you're looking for is called a vacuum regulator and sits between the vacuum source and the process. This page from Equilibar shows some examples and provides links that explain how they work. You can also use a vacuum breaker, which operates more or less like a pressure relief valve, but a vacuum regulator will offer more precise control. There ...

2

I am not a vacuum expert, but if you look at the technical data for your pump, you'll find this "Leak rate 6x10-3 Pa m³/s". I take this to mean that your 10 liter = 0.01 m$^3$ vessel will leak at a rate of 0.6 Pa/s. That's pretty slow. You'll want a manual venting value.

2

Evacuating 10 psi of pressure from a 500 cu ft chamber in under a second is pretty insane. This is a good calculator, as you will probably need to change your parameters (most likely time) in order to find a suitable pump.

1

I'm not sure what the first paragraph was about (pickup tool?), but if the vacuum reserve is installed like you have drawn it, there will be no appreciable loss of airflow when the solenoid is open. More likely is there will be a slight increase in flow since the line loss of the previous piping will be reduced because it is reduced by a large opening. It's ...

1

I would suggest separate channels to each set of holes with orifice plates to limit the flow to / from each. That way you can control each set individually. The other solution will be to over-specify the flow rate so that the poorest one is sufficient...

1

It will be a next to impossible task to try and analytically predict the number/position/size of the holes in order to have exactly the same flow. Even if you do for a temperature and a set humidity, at different temperatures you might have unacceptable results. If you are really interested in equalising the flows, a better alternative is to use a flow ...

1

What you are seeing in the video is a vacuum generator/vacuum ejector/aspirator. Figure 1: Venturi effect (source: wikipedia) It uses the principle of the Venturi effect. I.e. that for steady, incompressible, inviscid when there is an increase of speed there is a drop in static pressure. This is mathematically expressed as: p_1-p_2 =\frac{\rho}{2} (v_2^2- ...

1

A pilot operated valve (often unfortunately generalized as a "solenoid valve") uses a small control solenoid valve and the pressure differential across the valve to open a diaphragm that allows flow to pass. This is a very common design because it allows for a large flow to be controlled with very little energy. This YouTube video has a good ...

1

eatscrayons suggestion for leak detection is great. However, instead of acetone, I would use isopropyl alcohol (or even better, a helium gas source since He is such a small molecule). It is certainly a small roughing pump so I would not be surprised if you're hitting a floor of 6 Torr. Time to start looking into larger roughing pumps -- those which use oil ...

1

6 Torr isn't too bad really and that vacuum pump looks a bit small and I am guessing is not a high quality unit? Also, as said in the comments, that water valve may be leaking as well as it isn't rated for vacuum but instead for pressure. Regardless, here is a simple leak detecting technique that can be of help. When we have a vacuum problem in the lab we ...

1

So if your fan doesn't produce a minimum of 1m of water (which is about 2.9 inHg), there would be no flow. Afterwards, it depends upon your fan curve. You would find that the system curve would likely equal 2.9 inHg + K*Q^2, where Q is the flowrate and K is a factor that depends upon how you move the flow - note with smooth curves K is small, and with ...

1

I would recommend a slightly less technical approach and use double sided sticky tape. It's wonderful stuff, and you can get what's called removable tape. Probably makes it a bit easier, but you can always use a heat gun /hair dryer to warm the PCB and lift it. It should have enough gooey shear strength to resist the slight lateral milling forces, ...

1

You will likely want more than just a vent valve - to avoid contamination of a vacuum chamber, typically you re-pressurize with an inert gas like nitrogen to avoid sucking condensates and water vapor into the chamber. Every time you add some condensate to the chamber, they'll need to desorb - which is an extremely slow process compared to pumpdown.

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