# What kind of pump not limited by atmospheric pressure?

Most pumps like centrifugal pumps are limited by atmospheric pressure. This is because the pump simply create a vacuum where the atmospheric pressure pushes the water into it. Hence there is a limit of 10 meters of waters it can acquire due to gravity.

What kind of pump where it is not limited by atmospheric pressure so it can acquire say 20 meters of water?

If there is none in production. Then theoretical. Like for example in certain explosion, great vacuum is created. This can make it suck more than 10 meters of water, right? Or other techniques not limited by existing technology. I just want to have idea how such pump can operate. I googled but didn't get the answer.

• Mostly people just put the pump down in the fluid and push liquid up rather than sucking it. Oct 9 '20 at 19:50
• Making a vacuum doesn't get past the limit of atmospheric pressure because vacuums exert no force. Oct 9 '20 at 21:39
• You cant create a vacuum of say negative 1 million psi?
– Jtl
Oct 9 '20 at 22:15
• @Jtl Only if your atmospheric pressure is 1 million PSI. Think about it...what provides the actual pushing force? Suction doesn't exist. It's always something pushing. Vacuum pressure is measured relative to the surroundings. That's why a vacuum pump open to the atmosphere is limited to atmospheric pressure. Think of fully evacuated bottle in space, at sea-level, and at the bottom of the ocean. What's the pressure on the bottle in each place? Is it the same in all three places just because the vacuum inside hasn't changed? Oct 9 '20 at 22:24
• The units on the gauge switch from psi to in.Hg (inches of mercury) once the pressure is below atmospheric pressure. A perfect vacuum is -30 inHg which is equal to -14.7 psig (or 0 psia). Oct 10 '20 at 21:22

Piston pumps and reciprocating pumps like concrete pumps have independent cycles of suction and pumping, positively locked off from each other. So the pumping cycle is isolated from atmospheric pressure. And it positively pumps the exact amount every time regardless of the output head.

Search for reciprocating pumps.

• So this can make the pump suck more than 10 meters, like 30 meters or more?
– Jtl
Oct 9 '20 at 22:25
• The OP is asking about suction pumps lifting, for example, water from deep in a well. You reciprocating pump, I suspect, has a head of concrete on the inlet side so it is force fed. Oct 9 '20 at 22:57
• Head of concrete means impeller made of concrete? If you use this on a well..cant it suck 15 meters deep since it is force fed, meaning it can carry 15 meters of water?
– Jtl
Oct 10 '20 at 22:28
• No, no suction pump could do that because the water will start to boil well before that or if it is very could we have a good vacuum machine in our disposal. Oct 11 '20 at 0:15
• @Jtl, it is not clear if you understand the basic problem yet. Can you see that with absolute vacuum on top of a column of water that the only thing pushing the water up the pipe is atmospheric air pressure. At 10 m the force on the bottom of the column of water is equal to atmospheric pressure. Since you can't push any harder then you can't lift any higher. 10 m is the maximum lift you can do with a vacuum on water under atmospheric pressure. Oct 13 '20 at 7:44

An Archimedes screw pump just scoops up the water in a giant, long corkscrew so it doesn't depend on atmospheric pressure. Neither does a belt or chain with a series of scoops on it.

If the water or other liquid is enclosed, instead of sucking with the pump you can use the pump to send gas to pressurize the reservoir which pushes the liquid up another pipe.

• So this can make the pump suck more than 10 meters, like 30 meters or more from the well? Then why dont people use this and instead of the centrifugal pump? And why is the centrifugal pump more popular?
– Jtl
Oct 9 '20 at 22:30
• @Jtl Have you looked up or thought about what an Archimedes screw actually is? It doesn't use a pipe. It is the pipe. An archimedes screw reach down a 30m well would be 30+ meters long. Oct 9 '20 at 22:35

Like for example in certain explosion, great vacuum is created.

A vacuum - even a great one - can only get to 0 bar absolute. The suction can only be the difference between ambient and the vacuum pressure so in the natural world (i.e., on the Earth's surface) that means only 1 bar is available.

From The Far Side by Gary Larson.

This can make it suck more than 10 meters of water, right?

Wrong. The only way an explosion could cause a greater lift by vacuum would be by increasing the pressure pushing the water towards the vacuum.

Or other techniques not limited by existing technology.

It doesn't matter what technology is used. You can't get below zero absolute pressure. That means that you can't lift water by suction past 10 m.

Oddly enough, despite Gary Larson's cartoon, most of nature (the vastness of space) is a vacuum!

Atmospheric pressure makes little difference to so-called hose pumps (positive displacement pressure or PDP pumps.) They can also pump types of material that will trash a centrifugal pump pretty quickly. Have a look at the pumps used in the mining industry. Popular brands are Verder, Watson-Marlowe, etc. Tubes wear out faster than the impeller on a centrifugal pump (rubber instead of steel) so in applications where it is possible to use a centrifugal pump, they will be more popular than hose pumps.