Why few compressors work and most dont!

[Chickenthief]

Bear with me on the metrics as it’s easier on the whole world except the US.



If you want to go to 300bar on a 2 piston setup then you need to go 17,3-1 compression ratio on each cylinder as a bare minimum. Square root of 300 is 17,32.

Insidently thats above the ignition threshold of an (old) diesel engine. So compressed air with any oil contaminants will to some degree diesel ie combust just by compression alone. Might not be much but carbon will build up on valves and cause leakages ie backflow. The higher the working pressure the worse the problem! And run for prolonged periods of time undue wear on piston rings and gaskets is inevitable.



Now a ”proper” compressor will have three or four compression stages to avoid this problem. To go 300bar a 3 stage compressor will have to do 6,7 as compression ratio. Thierd root of 300 = 6,67.

Most 3 and 4 stage compressors tend to stick to some 7:1 ratio between cylinders and be done with the dieseling and undue wear as a result of high work load.



It’s not pixie dust, just physics.



300Bar = 4500psi

 

[xindaris]

Nicely explained.

 

[bltefft]

Ain't got a clue as to what chickenthief was talking about, but I 70+ years old and my poor ole brain is 70+ years old, too.

 

[CoyoteGod]

I think for the most part people buy a high pressure compressor expecting it to just fill. Well we all (mostly all) know that you buy one to fill a gun OR fill a bottle. People are breaking their compressors trying to fill bottles over hours and those "less than $1500" compressors just can't do it... for long. My $850 Omega can fill a bottle, but it's made to directly fill a PCP gun, so I use it for that only and I should get a long life out of it with the correct maintenance. 

Buy with your maximum intention in mind. If you want to fill bottles and PCP guns buy to fill bottles first then use to fill guns at your leisure. Just saying. 

 

[dizzums]

cheap compressors like a chun king work just fine .. just have to understand what you got, and that is a design aimed at poorer asian places that simply 'cant' afford high end things .. it takes time to fill a bottle with one and they know better than to beat the crap out of it .. elaborate 'home fixes' to make it better i think are kidding yourself for the most part, but take your time and it works ..'industrial output' and trying to make one fill 5 bottles a week and its not lasting long period lol ...

 

[Long_Gun_Dallas]

Good to have some numbers to pair with what I see first-hand. That said, this is why I do not fill to 300 bar, lol. I tend to stop around 250ish. Using a well aged (and also broken many times) yong heng. Live and learn.... mine still does the trick, though. Just not to 300. Also, don't get any combustion on mine, and have been using proper high pressure comp oil from shell rotella 

For informational purposes, my YH fills a 9 litre (to 250 bar) from 150 in about 10 minutes (stopping after 5 minutes, and resuming again after cooling a bit). Which isnt bad considering most of my guns usually run at ~15fpe, so a 9 litre will last FOREVER. Mine has probably filled and/or topped off that tank close to 30 times, has had some failures, but all have been remedied, and lessons have been learned.

 

[bandg]

My Yong Heng is now almost 3 years old. I have an MCH6 Coltri compressor now but still use the Yong Heng regularly to keep it functional. I have multiple 3600 psi guns and therefore I top off my Great White tank to 4400-4500 regularly and have done so since the Yong Heng was new. I have always used the best HP compressor lube available and have always kept it cool, using ice and an external fan during hot weather. It still works as well as ever and tops off my GW tank in about 11 minutes if I get it down near 3600. The Coltri will do the same job in about half the time for probably 7 times the price but I expect it will outlast me. The Yong Heng compressors can work just fine WHEREVER one is located, but it is nice knowing I have a bulletproof backup. I would buy another Yong Heng in a heartbeat if I were needing a startup compressor and budget was a concern.

 

[Eaglebeak]

It’s not pixie dust, just physics.



It's not pixie dust or physics, it's just jibberish.

 

[triggertreat]

Now please forgive me if my calculator is incorrect. 300 BAR is 4351 PSI. I see 300 BAR stated as 4500 PSI a lot...Not sure why that is. According to my calculations 310.29 BAR equates to 4500 PSI. I could see rounding off 310 BAR and stating as 4500 PSI but 300 BAR is a bit too much rounding off for 4500 PSI. If you have a 300 BAR compressor, I wouldn't recommend trying to push it to 4500 PSI/310 BAR.

 

[Chickenthief]

Now please forgive me if my calculator is incorrect. 300 BAR is 4351 PSI. I see 300 BAR stated as 4500 PSI a lot...Not sure why that is. According to my calculations 310.29 BAR equates to 4500 PSI. I could see rounding off 310 BAR and stating as 4500 PSI but 300 BAR is a bit too much rounding off for 4500 PSI. If you have a 300 BAR compressor, I wouldn't recommend trying to push it to 4500 PSI/310 BAR.

So you really think the remaining 150psi is going to give a difference in wether a compressor works properly or not at highly elevated pressures???

We're talking 300bar~4351.132psi

4500psi~310.264bar

We're in the 3% error range.

In th region of do you give a rats A** whether your F150 goes 100mph or 103mph?

 

[triggertreat]

Now please forgive me if my calculator is incorrect. 300 BAR is 4351 PSI. I see 300 BAR stated as 4500 PSI a lot...Not sure why that is. According to my calculations 310.29 BAR equates to 4500 PSI. I could see rounding off 310 BAR and stating as 4500 PSI but 300 BAR is a bit too much rounding off for 4500 PSI. If you have a 300 BAR compressor, I wouldn't recommend trying to push it to 4500 PSI/310 BAR.

So you really think the remaining 150psi is going to give a difference in wether a compressor works properly or not at highly elevated pressures???

We're talking 300bar~4351.132psi

4500psi~310.264bar

We're in the 3% error range.

In th region of do you give a rats A** whether your F150 goes 100mph or 103mph?

Yes I do. A lot of these compressors are rated at only 300 BAR while others are rated at 310 BAR. Make sure you know what you are buying and talking about first. It’s not pixie dust, just facts.

 

[Chickenthief]

The Coltri MCH6 four stage compressor is sold as 232bar~3364.876psi, 300bar~4351.132psi and again as 330bar~4786.254psi.

Do you really think that they would sell the excact compressor for 3 (way) different pressures if it would'ne be safe?



Bottles are typically proof tested to 1.5 times their working pressure.

So 200bar~2900psi is proofed to 350bar~5076.231psi

232bar~3364.876psi is proofed to 387bar~5612psi

300bar~4351.132psi is proofed to 450bar~6526.698psi



There is no way they're going to go haywire with just 3% filling above stated working pressure.

That's not how it works!

 

[triggertreat]

The Coltri MCH6 four stage compressor is sold as 232bar~3364.876psi, 300bar~4351.132psi and again as 330bar~4786.254psi.

Do you really think that they would sell the excact compressor for 3 (way) different pressures if it would'ne be safe?



Bottles are typically proof tested to 1.5 times their working pressure.

So 200bar~2900psi is proofed to 350bar~5076.231psi

232bar~3364.876psi is proofed to 387bar~5612psi

300bar~4351.132psi is proofed to 450bar~6526.698psi



There is no way they're going to go haywire with just 3% filling above stated working pressure.

That's not how it works!

I have no idea what Coltri is up to or their output rating schemes. My reference to "proper" as you used was to being able to fill a 4500 PSI tank complete to begin with. You referenced only one compressor manufacture with different output rated models. My reference was on any compressor one may select. That's assuming one would want to fill a 4500 PSI bottle to 4500 PSI with a properly rated compressor. I selected a 4500 PSI output rated compressor so I could fill a 4500 PSI bottle to 4500 PSI. Had I selected a 300 BAR/4351 PSI rated compressor, I would have come up short on a full fill. Are you not in agreement with this? This has nothing to do with the bottle. But yes, the bottle should also be rated at 4500 PSI if filling to 4500 PSI.

 

[ctshooter]

This thread was interesting until the pettiness started. 

 

[xindaris]

Ctshooter I hope everyone who posts takes to heart what you just said before their next post.

 

[Scotchmo]

I selected a 4500 PSI output rated compressor so I could fill a 4500 PSI bottle to 4500 PSI. Had I selected a 300 BAR/4351 PSI rated compressor, I would have come up short on a full fill. Are you not in agreement with this? ...

That's the best approach. If that last 150psi is really important, you should invest in a precision/calibrated gauge. Commercial gauges can be +/- 3% in the middle reading and possibly worse than that in the upper and lower readings. You could easily be getting 150psi more or 150psi less than you think.

The consumer grade mini/micro gauges used on PCP airguns/tanks/regulators might be even less accurate than that.

For most of us, 300bar or 4500psi, close enough so that is doesn't really matter.

That said, when I ordered my MCH6, I specified the 330bar (4700psi) relief valve just to make sure I could get 4500psi if I wanted to. Most of the time, I stop around 300bar. The accuracy rating for the 2-1/2" Wika gauge on the MCH6 is +/- 1% in the middle range.

 

[triggertreat]

I was just trying to make a simple point regarding 300 bar rated compressors verses 310 Bar rated compressors, like the YH verses the AV-4500 compressors, for example. That's all., as the OP seemed to have missed. All the OP should have said, in my view, was thanks for the input and acknowledged the differences in compressor output ratings. That did not occur.

My apologies for having had any input in this thread on an open forum to anyone in disagreement with my simple input Feel free to grab up a YH compressor to fill your 4500 PSI tanks with, if you believe they will work fine for you.

I too would like to hear more from the OP regarding his obvious talents with portions of these compressor workings. So, I am done with "the pettiness"...carry on. I am all ears moving forward.

 

[bandg]

"Feel free to grab up a YH compressor to fill your 4500 PSI tanks with, if you believe they will work fine for you."

Thanks. Already done that. For nearly 3 years.

 

[BackStop]

Guess I am lucky... what I have and use quite effectively for pesting is a .177 Benjamin Fortitude Gen2 and a cheap hand pump. I don't try and shoot all the way down to see how far it will go without losing fps. I usually pump up long before it reaches 2500psi. Saves the hand pump from heating up, reduces moisture, IMHO improves consistency even though it is regulated and most of all it saves me from a long pumping session. Never pump more than 30 or 40 pumps. Usually about 20 +/-

To each their own and I understand that some higher caliber guns require are easier to pump up with a compressor because they only provide a few shots before they are depleted.

However, most can be filled with a hand pump easily unless you HAVE to shoot the MAXIMUM amount of shots before refilling. Frankly, I don't understand this obsession with shot count. At least for me, I only shoot when I have a pest target unless I am sighting in a new scope or checking/adjusting zero as needed. Only then do I shoot paper and I don't "plink". Nothing wrong with plinking. I just don't do it.

 

[bandg]

Some shoot as you do. That would probably be fine for them. Many do not shoot that way and a hand pump would be useless for them.