Piston suction pump versus external gear pump as vacuum pump

[johnthekid]

What do you think? Have you thought about the pressures on each side? And have you thought about how it will be built to withstand those pressures and what it takes to seal the joints?

We will need to weld any openings if the container is a steel container. Is there a shape that is more appropriate than cube?

 

[Averagesupernova]

I'll ask it again:

Have you thought about the pressures on each side?

 

[jrmichler]

The best vacuum pump depends on your needs. You need to specify two things - the amount of vacuum and the flow rate before we can give you useful advice.

Amount of vacuum could be, for example: 1 inch of water, 20 inches of mercury, 10 torr, 1 torr, 1 millitorr, or other. You need to specify the amount, and know why you want that much vacuum. You need to know how much vacuum you need because higher vacuums cost more.

Flow rate: When evacuating a vessel, this could be as simple as specifying that you want to reach that vacuum in 1 second, 1 minute, 1 hour, or 1 day. You need to specify the volume subject to the vacuum, and the time to get to that vacuum. You need know what flow rate you need because higher flow rates cost more.

We need real numbers to help you with your vacuum pump. And real numbers to help you with your vacuum vessel.

 

[Averagesupernova]

If you are just comparing pumps to see which can achieve the highest vacuum I don't see why you even need a vacuum vessel. A hose with a gauge on the end will suffice. This whole thing stinks of you trying to hide what you are doing. Now the question is what is it that you are really doing that is against forum rules so you need to hide it? Or are you simply that uninformed so you do not realize what you do and do not need for this?

 

[Baluncore]

Even if both are designed as simple as possible? Now I'm curious about the Torr range that a piston pump with pressure operated check valves and an external gear pump can produce.

The piston pump valve requires a pressure difference to lift it. That pressure drop reduces the depth of the vacuum that can be pulled.

Vane and gear pumps do not have valves. The ports open and close based on the position of the vane, or the gear tooth.

 

[johnthekid]

The best vacuum pump depends on your needs. You need to specify two things - the amount of vacuum and the flow rate before we can give you useful advice.

Amount of vacuum could be, for example: 1 inch of water, 20 inches of mercury, 10 torr, 1 torr, 1 millitorr, or other. You need to specify the amount, and know why you want that much vacuum. You need to know how much vacuum you need because higher vacuums cost more.

Flow rate: When evacuating a vessel, this could be as simple as specifying that you want to reach that vacuum in 1 second, 1 minute, 1 hour, or 1 day. You need to specify the volume subject to the vacuum, and the time to get to that vacuum. You need know what flow rate you need because higher flow rates cost more.

We need real numbers to help you with your vacuum pump. And real numbers to help you with your vacuum vessel.

Around 1 Torr I think is enough. Anything above 1 Torr we need more cost. Is fast evacuation or higher flow rate equals to better vacuum pump? What I'm trying to do is just fun experiment.

 

[johnthekid]

I'll ask it again:

If you are just comparing pumps to see which can achieve the highest vacuum I don't see why you even need a vacuum vessel. A hose with a gauge on the end will suffice. This whole thing stinks of you trying to hide what you are doing. Now the question is what is it that you are really doing that is against forum rules so you need to hide it? Or are you simply that uninformed so you do not realize what you do and do not need for this?

I don't have enough experience to understand the details so please tell me more. Sorry, hiding what? Yes, if without using a vacuum vessel means cost saving, we don't have to use sophisticated setup like requiring vacuum vessels, etc.

 

[johnthekid]

The piston pump valve requires a pressure difference to lift it. That pressure drop reduces the depth of the vacuum that can be pulled.

Vane and gear pumps do not have valves. The ports open and close based on the position of the vane, or the gear tooth.

Gotcha. Thank you so much.

 

[johnthekid]

The piston pump valve requires a pressure difference to lift it. That pressure drop reduces the depth of the vacuum that can be pulled.

Vane and gear pumps do not have valves. The ports open and close based on the position of the vane, or the gear tooth.

Where can I get more understandings regarding the comparison between different types of vacuum pumps in their effectiveness in generating lower pressure vacuum especially when used independently on their own?

 

[Baluncore]

Where can I get more understandings regarding the comparison between different types of vacuum pumps in their effectiveness in generating lower pressure vacuum, especially when used independently on their own?

It takes time, you cannot get that understanding quickly. Start by following every relevant link on Wikipedia and look at the references given there. Let the information and ideas soak into your brain, then organise them over time, into reliable concepts.

For each project, write a technical specification, so you know precisely what is required. Then look for reliable solutions, at the lowest cost. Keep working in that field for 10 years.

It takes time to assemble and understand the deeper concepts. It takes engineering to analyse how and why pumps do, or don't work, and their limitations. Study engineering.

Search libraries such as:
https://z-library.sk/s/vacuum pumps
https://z-library.sk/s/vacuum systems

 

[johnthekid]

It takes time, you cannot get that understanding quickly. Start by following every relevant link on Wikipedia and look at the references given there. Let the information and ideas soak into your brain, then organise them over time, into reliable concepts.

For each project, write a technical specification, so you know precisely what is required. Then look for reliable solutions, at the lowest cost. Keep working in that field for 10 years.

It takes time to assemble and understand the deeper concepts. It takes engineering to analyse how and why pumps do, or don't work, and their limitations. Study engineering.

Search libraries such as:
https://z-library.sk/s/vacuum pumps
https://z-library.sk/s/vacuum systems

Cheers

 

[johnthekid]

Hi. If we look at these data sheets of external gear pumps, it said the inlet pressure is 0.7 bar absolute for the Hyva external gear pump and 0.3 bar relative for the Duplomatic external gear pump. Sorry for my ignorance, but are those the vacuum pressure that external gear pumps can achieve?

 

[Baluncore]

Those pumps are expected to be flooded with hydraulic oil, without any air present. I expect those figures are the inlet pressure at which vacuum cavitation, may begin to take place. Cavitation could damage to the internal surfaces.

 

[jrmichler]

Quote from Section 6 in the Duplomatic PDF: – It is necessary to vent the air from the delivery connection before operating it the first time. Another quote from Section 6: The minimum suction pressure allowed is -0,3 bar relative. The maximum vacuum on the suction side is 0.3 bar of vacuum. But only with the pump full of oil.

From the Hyva PDF: Inlet pressure range suction side 0.7 to 3 bar absolute. One bar is approximately one atmosphere, so 0.7 bar absolute is 0.3 bar of vacuum. That is with the pump full of oil. Without oil, that pump would not pull a vacuum and would tear itself apart inside.

 

[johnthekid]

Those pumps are expected to be flooded with hydraulic oil, without any air present. I expect those figures are the inlet pressure at which vacuum cavitation, may begin to take place. Cavitation could damage to the internal surfaces.

Quote from Section 6 in the Duplomatic PDF: – It is necessary to vent the air from the delivery connection before operating it the first time. Another quote from Section 6: The minimum suction pressure allowed is -0,3 bar relative. The maximum vacuum on the suction side is 0.3 bar of vacuum. But only with the pump full of oil.

From the Hyva PDF: Inlet pressure range suction side 0.7 to 3 bar absolute. One bar is approximately one atmosphere, so 0.7 bar absolute is 0.3 bar of vacuum. That is with the pump full of oil. Without oil, that pump would not pull a vacuum and would tear itself apart inside.

Thank you so much. The datasheet below at page 16 it said for some external gear pumps the inlet pressure is 0 bar bis/up to 15 bar while for others it is -0.4 bar (-0.6 bar) bis/up to 1 bar. I believe 0 bar represents the normal atmospheric pressure, because as we can see some have negative value inlet pressure. Is that correct?

 

[Baluncore]

Hey guys, which one creates the higher vacuum (lower pressure vacuum)? A piston suction pump (that kind of looks like a syringe) or an external gear pump design (that used two external gears)? IMO I think it is the former but I want more explanations.

Neither makes a better, lower pressure, vacuum pump. They both fail, but in different ways. The piston pump needs valves that prevent it pulling a deep vacuum. The external gear pump needs thick oil to seal the gear to case clearance, which makes it inefficient, while the meshed teeth cannot fully close, which limits the expansion ratio, and so the depth of vacuum.

You need to consider a "single stage, oil sealed, rotary vane, vacuum pump". Those will extract a higher volume per revolution than a gear pump, while the centrifugal vanes will seal with a lighter oil, making it more efficient, with a higher expansion ratio.

External gear pumps have been discounted by the rest of the world as vacuum pumps, in favour of vane pumps. The decision is a slam-dunk.

 

[johnthekid]

Neither makes a better, lower pressure, vacuum pump. They both fail, but in different ways. The piston pump needs valves that prevent it pulling a deep vacuum. The external gear pump needs thick oil to seal the gear to case clearance, which makes it inefficient, while the meshed teeth cannot fully close, which limits the expansion ratio, and so the depth of vacuum.

You need to consider a "single stage, oil sealed, rotary vane, vacuum pump". Those will extract a higher volume per revolution than a gear pump, while the centrifugal vanes will seal with a lighter oil, making it more efficient, with a higher expansion ratio.

External gear pumps have been discounted by the rest of the world as vacuum pumps, in favour of vane pumps. The decision is a slam-dunk.

You're absolutely right, just saw the data sheets and several vacuum range data for different types of vacuum pumps. There are almost none gear-based vacuum pumps (including external gear pumps) out there while reciprocating piston vacuum pumps are very rarely used nowadays. Most people used a combination of rotary vane pumps and turbomolecular pumps if not cryogenic pumps and ion pumps. Regarding my previous post about Beinlich external gear pump, does 0 bar represent normal atmospheric pressure?

 

[Baluncore]

Regarding my previous post about Beinlich external gear pump, does 0 bar represent normal atmospheric pressure?

That is a 20-page technical document. Please give the page number and identify the figure or table that refers to zero bar.

 

[johnthekid]

That is a 20-page technical document. Please give the page number and identify the figure or table that refers to zero bar.

 

[johnthekid]

Sorry, it is on page 16.

 

[Baluncore]

The file attached to post #45, appears to be different to the one you are looking at. It has a different page 16.

 

[johnthekid]

The file attached to post #45, appears to be different to the one you are looking at. It has a different page 16.

Oh sorry I posted the wrong PDF. Here is the PDF that I supposed to upload. It is on the pg. 16.

 

[Baluncore]

Oh sorry I posted the wrong PDF. Here is the PDF that I supposed to upload. It is on the pg. 16.

Since some of the inlet pressures are negative, the pressures must be referenced to atmospheric pressure = 0 bar, with a vacuum = -1.0 bar.

 

[johnthekid]

Since some of the inlet pressures are negative, the pressures must be referenced to atmospheric pressure = 0 bar, with a vacuum = -1.0 bar.

Thank you so much.