By donating you support this blog and my wishlist

Saturday, December 25, 2010

Silent air compressor

For a long time I have wanted to have pressurised air available, especially for glass bead blasting of machined parts. The main reason I haven't just bought an air compressor is that they are loud as a jet engine, usually in the order of 85-95 dB and that just doesn't cut it in an apartment complex.

About a year ago I stumbled upon articles in the internet of how to use a freezer or fridge compressor to produce compressed air silently. The only drawback is low air output volume, but my need is occasional and very little, so this fits for me.

A week ago I was able to obtain a working compressor out of an old freezer. This was an old ZEM compressor with 110 W of power and it runs from 230 VAC 50 Hz supply. The best thing is that it was from a freezer, as these are usually more powerful than compressors from fridges. The compressor had its original oil still in it, so I poured it in to a junk oil container and replaced it with a regular oil meant for automatic transmissions. The only requirements are low viscosity and that the oil is of mineral variety.

These freezer compressors are able to produce enormous pressures and also vacuums, so care must be taken that the system is able to withstand the pressure. This usually means a pressure switch that cuts of the compressor when the pressure reaches a set upper limit and starts the compressor when the pressure drops below a set lower limit. Also an overpressure valve is needed, as it vents if the pressure switch doesn't switch off the compressor.

To have a big supply of air for some time the compressor needs a pressure tank after it. This can be an old carbon dioxide extinguisher bottle or gas bottle that is rated for the intended pressure. There is also a need for the pressure switch, pressure regulator, connectors, piping, oil/water catcher and air drier. If you have to buy everything as new, the total will cost probably around 100-200 EUR plus all the work needed to assemble everything.

This is the reason I thought of buying a brand new compressor unit and just replacing the compressor unit with the freezer compressor. So I spent 89 EUR to buy a Herkules brand compressor from Bauhaus, as it was the cheapest I found that had a 24 liter pressure tank. The original compressor unit fills the tank in about 2 minutes from 0 to 10 bar, but produces an ear breaking noise of 97 dB at the same time. Not good.

So I started disassembling the unit to get the original compressor out and to take measurements of the pipe size used so I can make or buy a proper sized fitting between the pressure container and my freezer compressor. It was quite easy to just unscrew the plastic cover to reveal the compressor unit, but the Abiko connectors to the power switch didn't want to come off so they got a quick treatment from pliers.

After removing everything not needed, I was left with a tank, a one way valve, a pressure switch, overpressure vent and pressure gauge with an adjustment valve. The output is a 1/4" female quick connector and the input to the tank is from the end of the one way valve that has G 3/8" male thread.


The freezer compressor had a 1/4" OD copper tube as its output, so I bought a hose connector that had a 1/4" hole through it. From this I hacksawed the hose connection part off and after cleaning everything, I soldered this to the compressor output tube. To the one way valve I rolled few turns of PTFE tape and screwed on a G 3/8" -> 10 mm hose connector. This way I can attach the compressor to the tank with a small length of hose and avoid induced vibrations to the tank and also avoid messing with rigid tubing and bending.

The pressure switch was factory set to have 10 bar upper limit and 8 bar lower limit. I plugged the modded compressor to the wall for a quick test and started a timer to see how long it takes to fill the 24 liter tank from 0 to 10 bar. The pressure rise was slow but steady and finally after 24 minutes the pressure switch turned the compressor off. This means that the compressor can provide about 10 litres per minute. The 0-5 bar rise time was exactly 10 minutes.

I was a little bit doubtful if the freezer compressor could start against pressure, so I blead the tank slowly until I heard the pressure switch click on at the 8 bar marker. The compressor immediately started to purr and building more pressure to the tank. I timed how long it took to see how much the air output volume would change from the first run as this was against pressure. It took 4 minutes 50 seconds until the compressor shut off, so against pressure the compressor can provide about 9.93 litres per minute, which doesn't differ from the 0-10 bar rise time.

The compressor temperature climbed to quite warm during the half hour test, meaning I could not keep my hand on it for long. I'm quite sure my air need is so small that this will not be a problem as I can switch the compressor off when I have pressure in the tank, but I could add a small 230 VAC fan to blow cooling air over it.

Of course mounting the freezer compressor meant that I had to fabricate some sort of plate that attaches to the tank mounting holes and that has mounting holes for the freezer compressor. I used a proper sized piece of aluminum plate that I countoured with a CNC mill and drilled and threaded for M6 screws. I used the freezer compressors own rubber feets to isolate vibrations from the unit to the rest of the system. In the rear end I also installed a small water separator unit that is screwed to the plate and inside the plate is an 8 mm passage for the air. On the back side there is one electrical connection to the pressure switch, which is wired in series with the fridge compressor and shuts it off when there is 10 bar in the tank.

So how silent is my silent compressor? Well, I can just hear it running, sounds like a fridge humming its things. Yep, beats the so called "silent" compressors they advertise in hardware stores with about 68-70 dB sound output.

Added 06.01.2011: I bought a small Simota brand air filter that had a connection for a 9 mm diameter tube. This was probably meant for some RC car or something, but works wonders in this application and totally eliminates the small intake sound of the compressor.

I also had an idea for a decal to replace the original "Herkules" tape and so I used 5 minutes with KolourPaint and printed off a nice new decal and attached it (poorly) with a piece of tape meant for covering books. The word "Perkules" is a kind of twist from a Finnish curse word "perkele" and the original brand "Herkules". The word below it is my own drunk misspelling of the word "kompressori", which is Finnish for a compressor.

88 comments:

  1. Any that use an oil-lubed pump are repairable. But then you have to keep up with the proper maintenance schedule, make sure the oil doesn’t affect your paint sprayer, etc.
    One other upside of oil-lubed compressors is that they’re generally quieter.
    compressed air equipment

    ReplyDelete
  2. Very informative article. What did you use to measure the sound level?

    ReplyDelete
  3. Blue filter you bought is for "huohotin" in Finnish, i think its breather in english.

    ReplyDelete
  4. Nice work:-) I have just the same compressor and also put a silent one from refrigerator on it. The only difference is that I put filter on external valve just on air exit so the clean air can go directly into my airbrush.

    ReplyDelete
  5. Silent air compressors is largely proprietary knowledge, so the manufacturers do not usually advertise precisely how the noise reduction is accomplished in order to discourage copycats.

    ReplyDelete
  6. This comment has been removed by the author.

    ReplyDelete
  7. sir excellent idea can u just sent me the construction and working of this on my email id akshaychwl2@gmail.com

    ReplyDelete
  8. Thanks for sharing. Looking forward for more like this. Also don't forget to see this Air Compressor Accessories

    ReplyDelete
  9. does this compressor originally shut it's motor off and on what pressure.

    ReplyDelete
  10. I have modified several fridge compressors into silent air compressors. I made a couple of videos to help ppl make their own. Hope you like them. If you have any questions feel free to ask them in comments section.
    http://www.youtube.com/watch?v=k08kYVoXZrQ
    http://www.youtube.com/watch?v=5LvTdvyIFyg
    http://www.youtube.com/watch?v=ge8hZFC4lR0

    ReplyDelete
  11. I have a new air compressor in Toronto. I just got it, but don't know how to install it. Any tips? http://www.comtract.ca

    ReplyDelete
  12. I know some great information about silent or freezer compressors from here. It's such a very nice and useful for me. Such type of silent compressors are really a great for industrial works.

    Belt driven air compressors

    ReplyDelete
  13. This usually means a pressure switch that cuts of the compressor when the pressure reaches a set upper limit and starts the compressor when the pressure drops below a set lower limit.  Kompressor Druckluft

    ReplyDelete
  14. Thanks for providing Vial Washer Plant at a really good price point!
    Air Compressor
    Single Stage Air Compressor

    ReplyDelete
  15. Nice post. I have fully read the post. Thanks for sharing it. air tools.

    ReplyDelete
  16. It was smart to get the compressor from the freezer. They usually are stronger than the ones in a fridge. Do you know what make and model it is? Have you already tried hooking it up?

    Elisa Jed | http://dynamicaircompressor.ca/services.html

    ReplyDelete
  17. One of my friends is getting an air compressor for their little garage. They're more hobbyists than anything, but they're getting a professional grade compressor. They're going to be turning out some truly quality pieces before long. Thiago | http://dynamicaircompressor.ca/parts.html

    ReplyDelete
  18. i have read many blogs about air compressor and i can say that this post is great. thank you for sharing this information, no need to research the information because it's all located here.

    ReplyDelete
  19. Great article about air compressors did you know affordable air compressors here in australia

    ReplyDelete
  20. I am impressed. I don't think Ive met anyone who knows as much about this subject as you do. You are truly well informed and very intelligent. You wrote something that people could understand and made the subject intriguing for everyone. Really, great blog you have got here. Refrigerated Air Dryer || Gold star series || Refrigerated Air Dryer in Thane

    ReplyDelete
  21. Very efficiently written information. It will be beneficial to anybody who utilizes it, including me. Keep up the good work. For sure i will check out more posts. This site seems to get a good amount of visitors. Heatless Air dryer || Micro filters || Moisture Separator

    ReplyDelete
  22. I am very happy to read this. This is the kind of manual that needs to be given and not the random misinformation that's at the other blogs. Appreciate your sharing this best posting. Auto Drain Valve || Water Chiller India || Water Chiller Manufacturers

    ReplyDelete
  23. Small air compressors can include everything from small tire inflators to the more powerful 2 gallon models. While the size may dramatically vary, small air compressors are always portable. This makes them ideal for small work spaces, home use, and for taking to remote locations. http://www.compressorguide.com can give us information of different types of compressor.

    ReplyDelete
  24. Thanks guys for sharing such brilliant post with all of us, surely nobody can defeat this. dc electric motor

    ReplyDelete
  25. Very efficiently written information. It will be beneficial to anybody who utilizes it, including me. Keep up the good work. For sure i will check out more posts. This site seems to get a good amount of visitors. Click here

    ReplyDelete
  26. This comment has been removed by the author.

    ReplyDelete
  27. Hi,
    I see that you have taken a great observation about air compressor! You have also marked original brand! I have recently observed a blog that also inflects awesome information about air compressor - http://www.aircompressorreviews68.com/

    ReplyDelete
  28. I am going to new air compressor. This compressor is very noise, my wife angry about this. I want to buy compressor vary less than 60db. Do you have a lot of experience, give me your opinions?

    ReplyDelete
  29. That post was so helpful. I had no idea what brads were until you clarified. I would love to get one, but am wondering how loud it is. I live in a condo on the top floor so my neighbors may not appreciate my DIYing. Where do you typically do your projects?

    ReplyDelete
  30. Perfectly fitted filter elements for air compressor specially Atlas Copco, Ingersoll Rand, SullAir, CompAir, Hitachi, Boge etc. Order your element today from www.windkraftparts.com

    ReplyDelete

  31. Great article with excellent idea! I appreciate your post. I like ur blog nd thank u..!!!!

    Compress Part

    ReplyDelete
  32. I am going to new air compressor. This compressor is very noise, my wife angry about this. I want to buy compressor vary less than 60db. Do you have a lot of experience, give me your opinions?

    ReplyDelete
  33. Before I read this article, I was a novice when it comes to air compressors but now I know exactly what to look for. Very helpful article even for a novice like me.

    ReplyDelete
  34. ou need to know what you're going to use an air compressor for. If you're not really going to do anything professional out of it, might as well go for piston compressors. These types are the smaller ones and care generally sold for home use. But if you are going to need it for some heavy-duty, industrial work, you need to get the rotary compressors since these are larger and can power more tools.
    Air Machines

    ReplyDelete
  35. I am going to new air compressor. This compressor is very noise, my wife angry about this. I want to buy compressor vary less than 60db. Do you have a lot of experience, give me your opinions?

    ReplyDelete
  36. n order to buy a product it is essential to get detailed information about it so that an investment tends to become profitable. Without any prior knowledge it seems that effectiveness and usefulness of a product is somewhat contained

    ReplyDelete
  37. Oil greased compressors tend to run additional quietly; they are doing, however, need oil changes, operation on a flat, level surface, and will unharness AN oil mist into the air that is extremely ill-suited for applications like painting. though several craftsmen favor to use oil-lubed compressors as a result of they have a tendency to last longer and run quieter (as with the other type) they will not be sensible for a few applications.

    ReplyDelete

  38. Well I think I have found the information I have been searching for air compressor. I must thank you for writing this post.

    best air compressor
    Choosing the best portable air compressor

    ReplyDelete
  39. Wonderful article. Thanks for taking the time to discuss this. Your blog provided us valuable information to work on. I like the valuable information you provide in your articles.

    ReplyDelete
  40. I really like great customer service. I needed two parts not available locally. Found the parts on Sunbeltpartswarehouse.com. Filled out the order form, called their customer service line before placing the order. The rep was able to pull up my order and get them shipped today. No problem, friendly and efficient. Link to SunBelt Small engine Air Filters
    Small Engine Air Filters

    ReplyDelete
  41. Hi could you tell me how u wired the compressor to the pressure switch as I have got the same compressor tank?

    ReplyDelete
  42. Hi could you tell me how u wired the compressor to the pressure switch as I have got the same compressor tank?

    ReplyDelete
  43. Hello there,
    We do custom built super silent air compressors of your choice.
    Any color, any size/capacity etc.

    Contact us at lpm at execs dot com
    lpm@execs.com
    Here are some examples for you...

    http://postimg.org/image/4sxbadloh/
    http://postimg.org/image/quabm3vgh/
    http://postimg.org/image/6gxffb9xd/
    http://postimg.org/image/q51n3z7k1/

    ReplyDelete
  44. Thank you for the great articles. You did a great job putting them together.
    Compressor Oil Services Australia

    ReplyDelete
  45. I really appreciate your work and very amazing and important information about the Best Tank Fill Combo for PCP Airguns which have share in this blog.
    Best Tank Fill Combo for PCP Airguns

    ReplyDelete
  46. As compressed air specialists, Cooper Freer provides high quality air compressor, tools and accessories in Nottingham, Derby, UK, Milton Keynes, Kettering, Coventry, and Lincoln. We completely understand the needs of our customers and provide them reliable and energy efficient equipment.

    ReplyDelete
  47. Our best air compressor for commercial garage working purpose is famous for long lasting performance and long durability. We can use this compressors to do any job easily and perfectly.

    ReplyDelete
  48. What an awesome post, I just read it from start to end. Learned something new after a long time .

    Best Air Compressor


    ReplyDelete
  49. Cooper Freer specializes in air compressor service, installation, maintenance of air tools and air compressors. Established for over 43 years, Copper Freer is an independent air house with clients as far afield Leicester, Peterborough, Corby, Northampton, Nottingham, Derby, UK, Milton Keynes, Kettering, Coventry, and Lincoln.

    ReplyDelete
  50. Good Post! Get the maximum performance Compact and affordable Air Compressor System for your Nissan from 4x4parts.com

    ReplyDelete
  51. Awesome blog thanks for taking the time to write such good information.
    Heating and Cooling Mississauga

    ReplyDelete
  52. Best Air Compressor
    http://www.bestcompressorreviews.com/
    We are providing easy usable best portable air compressor for your helping and any emergency our products help to fight your problem only at bestcompressorreviews.com

    ReplyDelete
  53. What an awesome post, I just read it from start to end. Learned something new after a long time
    best air compressor

    ReplyDelete
  54. At what speed (RPM) of compressor did you achieve this "The 0-5 bar rise time was exactly 10 minutes"

    ReplyDelete
  55. First I have to say thank you for this blog. Because here I find the best compressor in cheapest price. If I get some compressor reviews, then it will be great.

    ReplyDelete
  56. It is a useful post. Also don't forget to see this compressors in erode

    ReplyDelete
  57. Nice post and good information about produce compressed air silently.I read it from start to end it is interesting .

    ReplyDelete
  58. Your blog has given me that thing which I never expect to get from all over the websites. Nice post guys!


    ReplyDelete
  59. This information was very helpful for me. Very nice blog having lot information about Thanks for sharing this post.

    ReplyDelete
  60. Thank you for sharing. This article is very helpful and informative. We need more article like this. Cheers!

    Water Blaster

    ReplyDelete
  61. Thanks for the wonderful blog post. Such a helpful article. It will be really help to so many people who are lokking fo the details of air pump. Keep it brother.

    Aquarium filter and air pump combo

    ReplyDelete
  62. You have defined the history of the air compressor very efficiently 2 in 1 car jumper with air compressor reviews

    ReplyDelete
  63. Silent Air compressor are Dead Trigger 2 MOD APK1.3.3 Unlimited Money and Gold the best and even now we have hungry shark world mod apk ios portable ones which don't even make a single sound racing game download

    ReplyDelete
  64. Air purifier, a basic necessity among every household should be purchased with great knowledge. Today they are using latest technologies for more effective cleaning of air. While purchasing a purifier, one should consider the above mentioned factors apart from cost to live a healthy life. Best air purifier under 20k online India

    ReplyDelete
  65. I am really happy with your blog because your article is very unique and powerful for new reader.
    Silent Compressor

    ReplyDelete
  66. afterour small air conditioner died because of lack of cooling gas I disassembled the big plastic box and found a 900watt compressor AND a nice ventilator to keep it cool - so I will be looking for a pressure vessel of sorts and the necessary armatures (gauges and pressure switch)too.

    ReplyDelete
  67. I just want to give an enormous thumbs up for the great info you’ve here on this post. This post has many information about the air compressors. I can be coming again to your blog for extra soon.

    ReplyDelete
  68. Such great information about air compressors. We are also providing the best Air Compressor Kenya.

    ReplyDelete
  69. Really Good Blog! I appreciate your hard work and research. Thanks for giving useful information about AC Compressor.

    ReplyDelete
  70. when you have dumps with the pin, that means you virtually have the real-life access of the physical credit card. That’s exciting, right? buy cc online shop
    ++ Visit our shop dumps to see all the dumps track 1 and 2 with Pin ++

    ReplyDelete
  71. Parameters
    Model: FB204
    Type: Explosion proof electric torque pump
    Application: Used for hydraulic torque wrench
    Stage: 2 stage
    Brand: TorcStark
    Origin: Made in China
    Warranty: One year
    Packing: Wooden box
    Delivery time: within 15 days : Anti Explosion Torque Pump

    ReplyDelete
  72. They are people with lives before and after their competitive years. They will tell you about their special moments, and there are many. gymnastics hall of fame .

    ReplyDelete
  73. This blog is really a great source of information for me.Thank you for sharing such a useful content about Air Compressor Price In Kenya.

    ReplyDelete
  74. Thanks for sharing useful information with us. If you are finding the best air compressor rental solutions Texas. Contact EZ Equipment Rental, we provide air compressor for your need at very nominal price.

    ReplyDelete
  75. This is very nice information, Thank you so much for sharing your knowledge. Screw Air Compressor

    ReplyDelete
  76. Thanks for providing this information about air compressor with us. If you're searching for air compressor & air tools for rental near me in Dallas. Then you've come to the right place, EZ Equipment Rental is a reputable heavy equipment & tool rental company in Dallas, Texas. Here you can find all types of air compressor & air tools to meet your needs.

    ReplyDelete
  77. Thank you for sharing this information with us. If you're looking to air compressor & air tools for rental near me in Dallas, Texas, you've come to the right place. EZ Equipment Rental is a recognized provider of heavy equipment & tool rental.

    ReplyDelete
  78. I accept one of your advertisements made my web program resize, you might well need to put that on your boycott. Halloween Costume

    ReplyDelete