Modern HP air compressors

[Alan]

Everyone of us, who own a PCP airgun, need (or own) an air compressor large enough to at least fill our airguns directly. If not, then this article isn't your cup of tea, albeit, you might learn a few things.

PCP compressors, stout enough to pump over 250 BAR, run the gamut from under $300, to as much as $5,000 dollars. Where in this range you sit, depends on several factors. The point is, no matter which compressor you own (use?), sooner or later some maintenance issue will need to be addressed.

The need could be just a refill or replacement of the some part, fluid, or fitting, all of which comes under the heading of maintenance. Most airgunners are self sufficient, in that they can indeed maintain their mechanical stuff, but this raises the question... What about the electronics?

Compressors like the Omega series do have some electrical parts. These seldom fail, but one that can (and does) are adjustable pressure shutoff gauges. These electro-mechanical devices often fail due to vibration et. al. causes. Thankfully, these parts are typically easy to replaced, but sometimes they're not.

For example, I own two Hill EC-3000 compressors. For those who don't know, the EC-3000 is computer controlled, and uses a strain-gauge device to measure the generated pressure. These devices are more accurate than electro-mechanical gauges, and not prone to fail due to vibration. Nonetheless, the Dowty washers, which seal the strain-gauges in place, may lose their sealing capabilities, and will need to be replaced. What then?

Digressing:

As alluded to above, the EC-3000 is a sophisticated, computer-controlled compressor. Because of this, changing a mechanical connection (a Dowty washer in this case) may cause pressure-setting calibration issues. Field recalibrating the compressor is possible, and really not difficult. Unfortunately, it does require more than basic knowledge of electronics. This is the reason the manufacturer has been reluctant in publishing instructions on how to do the recalibration of the strain-gauge/software subsystem. Can you blame them?

While I'm armed with the correct procedure (and the technical knowledge) to recalibrate the pressure threshold, it took me several tries before I got the exact set point to reoccur consistently. No wonder they're reluctant!

It is my belief, that other manufactures will soon introduce PCP compressors which use similar, computer-controlled, pressure measurement devices. While not all of us will have the necessary knowledge to maintain computer-controlled compressors, we can rejoice in the fact that cost-of-ownership will be more affordable in the future. Let us hope.

[bnowlin]

While I have an AV 4500.  I have found it very easy to work on and maintain.  The only problem was finding parts for it.  Forget about Pyramid Air as it is like pulling hens teeth to get anything from them and when they do have something the price is outrageous and their shipping lacks enthusiasm and the same goes for their support.  I needed a piston for it and forget about PA.  I found a company on Aliexpress that will ship parts in less than a week.  So long story short I am able to maintain the compressor myself.

Why do have to calibrate on yours the shut off gauge or what? Just curious. Is it a digital system?  Sounds like a very good compressor.
Bobn

[Alan]

Yes, it is digital.

The strain gauge is mounted inside of a ceramic disc, with the concave side towards the pressure. It is a standard, readily-available, off-the-shelf part. There is a bias voltage applied across the plane of the resistor, and the output voltage is proportional to the pressure (within a few percent). In my case, the calibration was off, due to a Dowty washer failure. That, and the tightness of the pressure vessel which hold the strain gauge, has an effect on the calibration, obviously.

It is really easy to recalibrate, but you have to get into the guts to do it. That is the rub, so to speak. Seems some folks are really afraid of any electrical voltage. Yet, some of those same folks put diesel fuel in the back of their pellets shot from their break barrels! Go figure!

[bnowlin]

Fantastic.  Not as bad as I thought.  Nice unit what does it fill tanks to?
BTW what do you calibrate with to achieve what is needed

[steveoh]

Great article Alan.

There are some very interesting choices when it comes to keeping our PCPs filled.

I started out with a Hill manual pump. After a year of pumping up my Sumatra I determined I did a lot less shooting than I might because manual pumping isn't much fun at all. These days the frozen shoulders that still plague me will not allow manual pumping without misery.

Then I bought a used SCBA tank that suddenly allowed me the freedom of shooting whenever I desired, and allowed me to buy a Sam Yang 909s. Huzzah! It only required a drive to the next town and a visit to the local fire extinguisher business that had a commercial compressor. $11.00 and change to fill, and I was set, as long as it was Monday-Friday.

After a few times of the owner of the fire extinguisher being too busy to fill my tank or going on vacation or the son overfilling (I was Skeered), I decided I needed my own compressor. By this time I had two Quackenbush airguns and I realized I ran out of air very quickly. Found another 45 minute SCBA tank, and bought an adapter to fill tank and rifles. Found out the threads were way out of spec when the fire extinguisher guy stripped them. Ugh. Bought a new valve and had fire extinguisher place do they initial fill.

I then bought a Yong Heng and filled tanks and rifles for a year before it blew up. I rebuilt the thing, and was quickly back in business. Along the way I did UTG at the Yong Heng spit out an enormous amount of water and the included filter was not at all good about stopping the moisture.

So I added one of the giant gold anodized filters and that helped dramatically. But fill times doubled, and I struggled to keep the temperature down on the compressor.

Then Alan in his infinite good nature and generosity sent me a 12 volt compressor. First one was damaged in transit and after a lot of persuasion by Alan the seller sent a replacement. I use it here and there and it allows remote filling of rifles in a short time. Huzzah. It too suffers from moist air though I've not yet come up with a solution. I only need to have spare filters on hand to swap out after each day of shooting.

Fast forward to the day a giant box arrived on the doorstep. It was Alan's much loved and used Omega Air Charger! Oh the joy! No five gallon buckets of ice water required, no super wet air to filter, a much quieter experience and endless air! I'm a happy camper.

The Omega is slower to fill than the Yong Heng but I'm not in fear for my life when using the Omega. The Yong Heng blew a fitting at 4,000 psi one time and I have been Gun shy since. 

These days we have so many choices with compressors. The folks who shoot big bores on a regular basis need more air, more tanks, and a reliable compressor. The  super experienced big bore folks often have ponied up the money for genuine Diver Compressors such as Bauers with their rather hefty expense.

Something I'd like to see are USA made compressors in the same price range as the Hill. If England can do it then why not USA? We need such a state of the art compressor complete with standardized fittings that are higher psi rated than their Chinese counterparts. It should come with effect air/water separator/ filtration and have best of industry reliability. It should offer 4500-5000 psi fills, and be able to fill 90 minute SCBA tanks in a reasonable amount of time and not overheat. You should be able to set desired pressure and safely be able to walk away.

A feller can dream, right?

[steveoh]

This guy understands.

[Capt45]

Wow!  That is an impressive setup.