Did I make a big mistake? I bought a Yong Heng compressor from China!!

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Hi Mike,
Yes, I did purchase one of those gold tube filters and have plenty of dessicant of various sorts on hand (activated alumina and various forms of silica beads/gels). I also have a Campbell-Hausfield filter system for the inlet. Hopefully the tank comes soon!

I read through your Tuxing thread - the V-twin pump setup with your add-on cooling system is sweet. I have a mind to try and cool that 1st stage outlet tube where all the heat is generated but want to take this data first before considering any mods the YH. It wouldn't be too difficult to braze a copper jacket around that tube and drill a couple of water channels through the copper. But, 320F or even 400F isn't a big deal for 304SS tubing, though it remains to be seen how much higher the temperature goes when doing a real fill (from 3000 to 4500 psi). And taking that heat to dump it into the water just heats up the water to higher temp, so who knows. 

The other thing I want to experiment with once the tank arrives is feeding the inlet of the YH with 110 psi air and basically running it like a booster. Really just for grins because our building at work has 110 psi hospital quality compressed air distribution, so why not. I'm curious how much faster it could fill a tank acting as a booster.

-david
 
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Hi David, thanks much for all the testing, we appreciate it. Once you have the tank, please do similar testing on the tank once you get it to about 3000 psi, and up to 4500 psi. Like I've mentioned, we normally "top off" our tanks with our personal compressors, and don't fill them from zero. I think you'll find that the compressor works a lot harder than it does unloaded, and your temperatures will reflect that. 

If you don't mind me asking, why did you buy the YH with the direct first to second stage setup rather than the YH that has the cyclone separator between the first and second stages? Having the separator makes it easy to add small aluminum heat sinks to the sides of the separator block, to assist in reducing air temperatures. Adding those to the outlet block (if there is room) also helps. I listed a link to those small heat sinks in my downloadable pdf write up on my Tuxing two cylinder forum topic.

Interesting thought about feeding the YH 100 psi air to the first stage. Never considered that, but it does make sense. Let us know how that goes once you do. Thanks again,
Mike
 
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@prfssrlee and @centercut,

Things I have learned about compressors: Some inexpensive 120v compressor motors run great on 220 and visa versa. I own one, a Porter Cable shop compressor. It comes with a 120v cord, also comes with instructions to run it on 220v. The second stage of a compressor gets way hotter than the first stage. The first stage makes more heat volume, but the second stage is where temperature skyrockets. O-rings are not meant to act as piston rings, that is to say, constant high speed mechanical movement at high temperatures. In this type of pump, they are at the very edge of failure. Keeping them cool and not shock loading them is vital. So, starting the pump unloaded is important for both for the motor and O-rings. If there's a way to bypass initial pressure shock, and gradually increase it with a hand valve, it would help both the pump and help with motor startup.

Happy New Year guys!
 
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Thanks Bobad, but what O-rings are you talking about? The YH and Tuxing compressors use metal rings in first stage (3) and semi-metallic rings on second stage (4). Lets let David do further testing to see which stage generates the most heat, I'm not certain and I think perhaps this two stage HPAC reacts differently than a regular shop compressor. Think of it this way. If the first stage goes from one atmosphere to approx. 300 psi (perhaps higher, don't know since there is no gage), it ends up compressing the air approx. 20 times the original pressure (15 psi to 300 psi). Then, the second stage goes from 300 psi to 4500 psi, which sounds like a lot, but is only 15 times compression. As you can see in this example, the first stage is doing more work than the second stage. It would be good to know at close to 4500 psi discharge pressure what the output pressure of the first stage is...
 
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@Centercut- I bought this model basically bc I didn't research things carefully enough beforehand. The longer story is that I am a total airgun newbie and bought my first pcp over BF weekend along with a hand pump. Saw this YH for $178 + free shipping on Walmart and thought "fantastic price, why not?". Figured I could make it work one way or another - or at least learn a lot trying to. I've done a fair amount of UHP and UHV stuff over the years.

Found a couple feet of seamless 316 tubing (1/4" OD, 0.065 wall - rated to 8200 psi @RT) lying around at work and have a drawerful of swagelok fittings, so its worth teeing in a gauge at the 1st stage to see what kind of compression we are getting. Just need to figure out the fittings they are using - probably some sort of metric compression fittings, but I wasn't paying attention before so I'll check when I can get back into work. Then order some adapters and probably build a replacement 1st-2nd stage connector with a gauge teed in and maybe also a cyclone trap as you suggest.

@bobad- thanks for the advice on how best to startup the compression. I agree it would be nice to throttle the startup. Possibly a needle valve on the inlet? You can't really adjust the restrictions through the system, so the only way to cushion the initial pressure shock would be to gradually bleed the inlet. Simple enough to do, though the input hole has some non-standard threads that I have to figure out. I have a 8-turn needle valve that I use for this very purpose on some other stuff that's connected to 1/4" tubing which I can temporarily steal to try it out. Throttling on startup may be even more important when I try boosting the input (but I can do that with the regulator on the CA line).

Really can't use this thing as intended until my tank gets here anyway - so as long as it isn't here, I'll just keep going on this thread.
 
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Sounds great! One thing you might do if you have the capability, and since you have the tubing, is to make a "coil" with 4 or 5 loops to connect between the first and second stage, and after the second stage prior to the outlet valve block. That's the way that big boy (Bauer and Coltri) compressors are set up with cooling coils between stages. I think the AV also has one on the outlet of the second stage and the AC has a minor coil set up on the outlet of each stage. PS., $178 plus free shipping is an awesome price!

I'm very interested in seeing what type of compression the YH is getting from the first stage. I have seen IR scans of the AC compressor, and it certainly shows the first stage being much hotter than the second stage, although the AC runs much cooler than the AV/Tuxing/YH. 

PS., just start it up with the vent valve open, and let it run for a few minutes to warm it up prior to shutting the vent valve and pressurizing the system... Oh, and don't open the tank valve until pressure in your compressor is at or near the tank pressure...
 
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Mike, Yes I thought about making a coil and cooling it as well. I don't have a mandrel and this super thick wall stuff is a pain to bend nicely. For the 1st stage output at relatively low pressures, ugly would work so maybe I'll do that. But then the tubing won't be available for other use by someone else... we'll see.

Doh!!! Your comment about IR scans just reminded me that I have a FLIR B300 thermal imager sitting unused at the moment (the experiment its for is being rebuilt). It has the high-temperature option and is calibrated to +/-2% up to 1200C. I also have carbon black to coat the tubes and make sure they have uniform (high) emissivity. Pretty soon I'm going to have to make this a project for a student. Hmm.
 
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"prfssrlee"Mike, Yes I thought about making a coil and cooling it as well. I don't have a mandrel and this super thick wall stuff is a pain to bend nicely. For the 1st stage output at relatively low pressures, ugly would work so maybe I'll do that. But then the tubing won't be available for other use by someone else... we'll see.
Doh!!! Your comment about IR scans just reminded me that I have a FLIR B300 thermal imager sitting unused at the moment (the experiment its for is being rebuilt). It has the high-temperature option and is calibrated to +/-2% up to 1200C. I also have carbon black to coat the tubes and make sure they have uniform (high) emissivity. Pretty soon I'm going to have to make this a project for a student. Hmm.
Click to expand...
Extra credit.
 
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There seems to be too much emphasis for concern of the head temperature and cooling, than justified. My opinion, after filling my 98 cf tank for 4 months is, that the oil, crank and motor temperature are the weaker link in the chain. While the head temp remains well inside limits, during a 15 minute run time, the crank housing and contents is what concerns me, for an overtemp condition...solution-don't run for more than 15 minutes w/ a 15 minute "cool down" period in between run times. Mines still going strong after 8 tank top offs from 2800 to 4500 psi.
 
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Interesting point of view. Why are you concerned about motor and crank/housing? What I mean is what are your indications that give you concern? Filling from 3000 to 4500 psi on an 88 cubic foot tank only takes 15 to 17 minutes, so unless you are topping off multiple tanks you don’t need that cool down, right? I think the reason I seem concerned about HP cylinder head temperature is in emails with both Tuxing and Yong Heng, both manufacturers stated that they recommend an operating limit of 65 C, and a maximum of 70 C. Not sure where AV came up with 80 C, or 95 C? In any case, it is smart keeping an eye on oil temperature by monitoring degradation. I’ve topped off six tanks in the past month and the Royal Purple Compressor oil still looks pretty good and not black and sludge-y.
 
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@huntjunky- Hi, I can stick one of the thermocouples onto the motor if you want. Easy enough to do. I didn't notice anything in the very short open-air runs I did earlier (of course, that's easy when the motor isn't working against back pressure). Mainly, I just figured it would be useful to characterize the compressor as much as possible just so everyone has the information as a baseline (in case something goes wrong in the future, for example). I enjoy tinkering and don't have my tank yet, so why not. My interest in the head temperature was originally spurred by a comment in another thread asking if anyone noticed that the steel tubes got really hot to the touch. I figured why not quantify "really hot" a bit since I don't have anything better to do with the thing at the moment. Then curiosity got the better of me - it's a bit of a rabbit-hole thing - now I'm curious which stage is doing the most work (ie, has the highest compression ratio) and whether I can do simple things to improve the efficiency. For example, what if there are relatively easy mods to allow for continuous operation instead of pausing every 15 minutes? In order to tackle that question, one needs a baseline characterization.

Is there a thermistor on the motor? I don't know if mine has an overtemp protection circuit on the motor - that's a good question. Characterizing the motor is interesting as well, I agree. For example, how big is the initial current rush and what is the current draw while pumping as a function of output pressure. Maybe I'll get a chance to look at those quantities as well. Honestly, I'm just hoping that this kind of information will be useful to someone in the future when/if their YH breaks down and they want to troubleshoot the problem.

Really not trying to make a big deal of it. It's actually great to hear that you've used yours to refill many times without issue!
 
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Quick update: My Acecare cylinder came yesterday so this weekend I'll finally run a fill from 3000 to 4500 while monitoring the tube temperatures and water temp. Also, I took the motor housing off to make some measurements as someone had asked about earlier. I've attached pics below, but the surge cap is 45 uf rated to 450VAC and the motor coil is 6.7ohms (didn't have an inductance meter, sorry). also, the reset button looks just like a 13A resetable fuse - I couldn't find a thermistor anywhere on the motor. So if I can find another thermocouple meter, i'll stick one on the motor too to check how hot it gets. I also took a closer look at the stainless steel tubes - and they are way overengineered. The larger tube is 8mm OD with a 1.5mm wall thickness. That's rated to 520 bars. The 6mm OD is also 1.5mm wall thickness. It would be rated to 710 bars. Temperature derating is only 10% at 500F, which these tubes never even come close to seeing. That's good! I guess i should expect that, given how many people are out there just using these compressors like tire pumps. But I still get a bit scared every time I watch the needle climb up into these pressure ranges. 

Last, I'll just mention that there are alot of these YH compressors going for about $275 on Walmart right now with free shipping. They are the newer version with the cyclone separator between 1st and 2nd stages (mine does not have this big improvement). And they run at 110V (at least, that's what is on the listing). Here's an example link: https://www.walmart.com/ip/110V-High-Pressure-Air-Pump-Electric-PCP-Air-Compressor-for-Airgun-30MPa/998993293

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Sorry it took a week - but I finally took data in a typical usage scenario on the temperature of the steel tubes in the YH (bc my Acecare cylinder finally arrived).

I started with the 6.8L cylinder at 3500 psi. 1st changed the oil, then ran the YH vented for a minute before closing the vent. I allowed the hose+filters to reach 3500 psi before opening the valve to the tank (thx Centercut for that advice). You can see on the graph where I opened the valve to the tank as the fill rate drops way down. Also, it was so loud that I couldn't hear any small leaks - though clearly there was one the whole time. Why do I say that? As a guess, I tightened down on the fitting that held the burst disc at the very end, and - lo and behold - within 20 seconds the pressure went from 4250 psi to 4600 psi.

So while this whole refill took about 12 minutes, I suspect if I had not had a slow leak in the burst disc fitting, it would have taken far less time. This makes me want to encourage all the YH compressor owners to check their fittings. Once I shoot this tank down to 3200, I'll refill and take the same data (hopefully with a digital pressure transducer next time - it's on order from aliexpress).

I think the data say that there's no need to worry about overheating of the steel tubes, which was the original question. I did put my hand on the motor and the crankcase housing throughout the run - and yes, they do get hot, but clearly not as hot as the steel tubes. The hydraulic oil I'm using (Mag1) has reasonable viscosity in this range of temperatures, so I'm not worried about it. However, I did notice quite a few aluminum shavings in the oil when I changed it. So, while I think the oil won't break down any time soon, I'll probably change it once again after one more fill up just to get the aluminum shavings out of there. 

Finally have a tank I can refill fairly routinely - time to start shooting. Hopefully this data will be helpful to someone in the future when they need to troubleshoot their own compressor.

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