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Differences between a diaphragm and a dual-piston compressor?

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  • Member since
    January 2005
  • From: Washington
Differences between a diaphragm and a dual-piston compressor?
Posted by uproar on Friday, February 15, 2008 9:59 PM

Greetings,

What are the functional differences, advantages/disadvantages, etc., between a dual-piston compressor (such as the Iwata Power Jet) and a diaphragm-type compressor? 

Thanks!

 

  • Member since
    August 2005
  • From: Sydney, Australia
Posted by Phil_H on Friday, February 15, 2008 10:19 PM

A dual-piston design is less prone to pulsation in the airflow and can provide a higher, more consitent output pressure compared to a diaphragm type.

You will get pulsation in the airflow of a diaphragm compressor because by its very nature, (for want of better terms) there is a "compression" (up) stroke and a "return" (down) stroke. The diaphragm must return to its starting position and while this happens, it's not pumping air.

In a dual piston system, one piston is "compressing" while the other is "returning", so it is able to maintain a consistent output

Due to the flexible nature of a diaphragm, it can have a lower maximum output pressure (though it's still sufficient for most airbrushing purposes). 

In extreme cases, excessive backpressure in a diaphragm compressor can rupture the diaphragm. (hence the need for a "bleeder" valve in a diaphragm compressor).

  • Member since
    January 2005
  • From: Washington
Posted by uproar on Saturday, February 16, 2008 8:40 AM
Thank you!  I've been pondering getting a nice Iwata Power Jet compressor for some time to replace my Paasche D500 (diaphragm) compressor, but have been put off by the expense.  Perhaps it may be worth it....however, I'm going to need to spend more time than I have lately building to make such an expense worthwhile.  Are the Dual-Piston compressors any quieter?
  • Member since
    May 2005
  • From: Left forever
Posted by Bgrigg on Saturday, February 16, 2008 9:00 AM

Diaphragm and dual piston compressors are "about" the same noise level. As there are two pistons that have to stop and reverse direction, they do tend to be a little bit noisier. If you want quiet there are no inexpensive solutions.

A true "silent" compressor is pretty expensive and uses a screw for compression. They are the same type of compressors found in refrigeraters and make a similar amount of noise.

Even quieter is CO2. If you have the ability to transport a tank safely, that is. Around my parts a CO2 system costs about $150 to set up. The benefit is the CO2 is completely dry, no need for a moisture trap, and is completely silent except for the hiss of the escaping gas. One caveat is CO2 is poisonous and should only be used in a well ventilated room. 

My inexpensive solution to noise is to use a tanked "garage" style compressor. It is kept outside in a ventilated box for protection and I run a hose through the wall to the spray booth. From where I sit and spray I can only hear a distant noise from the compressor, and then only when it is refilling the tank. 

So long folks!

  • Member since
    April 2003
  • From: Hayward, CA
Posted by MikeV on Sunday, February 17, 2008 1:28 AM
 Bgrigg wrote:

A true "silent" compressor is pretty expensive and uses a screw for compression. They are the same type of compressors found in refrigeraters and make a similar amount of noise.

Bill,

Silent compressors are not screw compressors, they are piston driven with cast iron heads and oil lubrication to make them quiet. Wink [;)]

Wisdom is the right use of knowledge. To know is not to be wise. Many men know a great deal, and are all the greater fools for it. There is no fool so great a fool as a knowing fool. But to know how to use knowledge is to have wisdom. " Charles Spurgeon
  • Member since
    May 2005
  • From: Left forever
Posted by Bgrigg on Monday, February 18, 2008 8:12 PM

That all depends on how silent, Mike.

Silentaire for example can be piston or screw, oil or oiless. Depends on how much you want to spend!

Most of the ones advertised as "silent" are anything but. Those kinds tend to be piston. "Super-Silent" like the Silentaire Eco-20 is the same kind of compressor you'll find in your fridge and are much quieter.

So long folks!

  • Member since
    April 2003
  • From: Hayward, CA
Posted by MikeV on Tuesday, February 19, 2008 12:20 AM
 Bgrigg wrote:

That all depends on how silent, Mike.

Silentaire for example can be piston or screw, oil or oiless. Depends on how much you want to spend!

Most of the ones advertised as "silent" are anything but. Those kinds tend to be piston. "Super-Silent" like the Silentaire Eco-20 is the same kind of compressor you'll find in your fridge and are much quieter.

Bill,

Are you saying the "Super Silent compressors are screw driven?

A refrigerator compressor is piston driven I believe.   

I have A Jun-Air and a Badger Million air and both are about as loud as a refrigerator (roughly 30 dB) and both are piston driven.

Even Airbrushtalk.com has an article about Silentaire compressors and the article states:

All silent compressors are piston-driven and oil-filled, which reduces friction in the motor.

Maybe there are silent screw driven compressors but they are not the ones you find from Silentaire, Jun-Air, and other well-known airbrush compressors.

Look here for a view of the inside of a Jun-Air compressor:

http://www.jun-air.com/graphics/pdf/data_sheets/3motor.pdf 

Wisdom is the right use of knowledge. To know is not to be wise. Many men know a great deal, and are all the greater fools for it. There is no fool so great a fool as a knowing fool. But to know how to use knowledge is to have wisdom. " Charles Spurgeon
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