word definition question on pump/compressor

[frankiee]

What is the differece between a air compressor and an air pump

Is there a line where a device it to be called a pump, as in a bicycle pump or a compressor as in a air compressor?

Thanks

 

[JLSeagull]

In the analyzer business, what we call a sample pump is a little compressors that draws low pressure sample to an analyzer or send it for disposal. I often use the phrase "sample pump (compressor)" in communications that includes those not associated with process analyzers.

 

[BigInch]

Compressors make fluids (i.e. gases) smaller. In doing so they increase pressure, which can be used as a source of motive power, but that function is really secondary to the function of a compressor. Pumps do not significantly reduce a fluid's volume and their primary function is thus to provide motive power. In the case of a bicycle pump, yes the air volume may be halfed in the process, but the term pump implies that the air is just moved from outside the tire to within, although I do think calling a bicycle pump a "pump" is rather a bit of a misnomer. Its hardly different if at all from filling a bottle with pressurized gas, however if you consider that the inner tube expands in the process, maybe there is not much relative compression actually being accomplished. OK, that's debatable, but it works for me. Unfortunately "laymen" do not always use technical definitions in a precise context and "bicycly pumps" have been around for a long time now, so we're probably stuck with that one. On a similar note, there is not much reason to call a "hot water heater" a "hot water heater", as it obviously heats cold water... a.i.

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[jistre]

I've always considered compressors, fans, and blowers devices that work on compressible fluids and pumps to be devices that work on incompressible fluids. All of these devices are similar in that they put energy into the fluid. What that energy can do to the fluid is where I make my distinction.

The difference to me is really whether or not the fluid the device is putting energy into is compressible or incompressible. With incompressible fluids, the device can generally either change the fluid's pressure or its velocity. With compressible fluids, it can still change pressure and velocity, but work is also done changing the fluid's density.

I have a feeling this is going to be one of those "bolt or screw" types of discussions.

 

[BigInch]

Jistre, I'm pretty sure it will draw at least 50 responses.

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[IRstuff]

tomato or tomato

Much of the distinction come from a historical usage perspective. A typical bicycle pump requires the user to push and pull the handle to compress the air for the tire, hence, it's a pump, because it's like a water pump or oil pump.

A compressor is a standalone thing that has no obvious push-pull behavior, since it's all internally concealed by the housing, hence, it's a compressor.

TTFN

FAQ731-376

 

[Ashereng]

I think for the most part, they are used the same.

Positive Displacement Pumps are always called pumps where we are.

The rest are often interchanged:

Centrifugal pumps are also called compressors.
Screw pumps are also called screw compressors.



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