My Yong Heng just took a crap

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randy_68

randy_68

Member
Mar 29, 2018
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Indiana, United States
But I'm pretty sure I caused the problem.

Last week I was filling my tank out in my garage. It was nice weather so I was working outside and every few minutes would go in and check the progress and bleed the moisture. Well I got sidetracked and when I remembered to check my compressor it was at 4800 psi. It was still chugging along and all seemed ok. Tonight I changed oil and started filling my tank and it made a funny sound about 3200 psi then started blowing oil out the breather. I figured it was a piston ring but when I took the head off I found the top of the piston busted around the high pressure stem. 

At least thy he parts are cheap enough.

I'll be keeping a closer eye on it from now on and not get distracted.

1546566024_16425105735c2eb988e8da54.59933975_20190103_203225.jpg

 
Many thanks for sharing your juicy details - all too often we're tempted to tell edited stories of our intentions and not disclose our slip-ups. And while 4800 psi wouldn't see all that much of an issue, my sense is that between gauges that are miscalibrated and may be displaying a number lower than the actual pressure, and operator-induced hard shutdowns (rather than first doing a pressure bleed) can compound weakness in the pistons and valves.

When it's my turn in the hopper for this, I'll be ordering two piston assemblies...

Happy trails, Michael
 
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Just out of curiosity, which version compressor do you use?

The manual model? Or the automatic-shut-down model where you can set your desired stop-psi?

I have the 2nd. I just try not to use the auto-cut-off / shut-down feature, aside from having it set to just over the psi I need, 
and having it there as a last resort - if I forgot to shut the comp of manually in time..

I kept reading more and more people claiming that the auto versions were the cause of the high psi rod / piston top failures..
They were saying that when the pressure switch reached max desired psi, and kicked the compressors off, 
the compressors would experience a 'hard stop', and the high psi in the top head would contribute to it..

** I always start my comp with both bleeder screws open, then snug the left, then the right..
Let the comp run, fill, and when I'm about to shut the switch off, I open the bleeders in reverse..
Right first - purge the line air / moisture, then Left second, purge whatever wants to come out of that side, 
and then I shut the switch off . . . That drops the psi, allowing for a 'soft stop'. IMO, that's better anyways..

I'm not 100% sure, but, on my Auto, I swear that there's a blow-off-valve.. I'll have to take it apart one of these days..
Either it's just there to blow in the event of too much psi, or, it's actually electronic, and will dump psi when the Auto shutoff feature is engaged.

If that's the case, that'd be great!

Sam -
 
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I have the std version. I also open my valves before starting and before shutting down. High pressure is the only thing I see that can cause that problem as it has pushed the high side stem down into the piston. Or a hard stop. Which i did a couple times when i first got it. But I've filled my tank at least 6-8 times maybe more since then. It's all good. Parts are ordered and it will be going again.
 
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I don't think "hard stops" have any effect on the piston and don't see how they could. This particular pump was a little loose and failed from metal fatigue.

It's a good idea to have spare parts on hand since they're really cheap but really slow to get here.

Click to expand...

^this. I'm trying to think of a possible mechanism why stopping the compressor with pressure in it should break it. It isn't a "hard stop," there is no active braking in the motor, it'll just spin down under its own momentum generating no more, and probably less, pressure than it'd have generated otherwise. Obviously failing to understand a problem is different from there not being one, but I've never heard of anything like this before on other compressors. Furthermore the YH has check valves EVERYWHERE, so it isn't even like it should experience some sort of hard run in reverse, as the check valves from each stage will eat and hold the pressure as-necessary.





As far as that piston head fracture being your fault, don't blame yourself. It didn't break when you ran it over-pressure, it broke later at much lower PSI, so clearly it was simply fatiguing over time. Running an extra 6% over pressure I'm sure didn't help it, but nothing properly engineered in this sort of application is given a 6% margin either. It was just a flawed design. Think about it. If your high pressure connectors were rated to just 6% over-pressure people would be getting whipped to death by high pressure hoses when all the time. 



I will say I'm a bit sour on YHs because mine just died for the third, and final, time. It was 6 months old and had seen only light use, NEVER a marathon session filling a big tank, only guns themselves. The first thing that went was the "resettable" fuse. Cheap fuse with burned contacts right from the factory. And being a thermal fuse once the contacts are burned it'll heat that much more the next time. Finally died completely enough to make me troubleshoot and tada. Replaced it, and the compressor worked again.... briefly. Second was the control electronics. They had no vibration mitigation whatsoever. If I were you, I'd either pull that control box off the compressor and put it somewhere separate so it isn't rattled to death, or go in there with some silastic or potting compound and make sure everything on that board isn't going to break off at the solder mounts. A big ass capacitor being shaken violently will fatigue and break its delicate pins. Third and final thing to die is that the second stage wasn't properly aligned with the first stage and so it ate the inside of the second stage cylinder until things didn't work anymore. The compressor didn't even make it to its first oil change, and maybe that is a good thing because in my opinion it wasn't worth the premium full synthetic compressor oil I put in it. 



I'm going to give the AV Nomad II a spin next. At least it is warrantied for a year...... 
 
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I don't think "hard stops" have any effect on the piston and don't see how they could. This particular pump was a little loose and failed from metal fatigue.

It's a g

ood idea to have spare part 

s on hand since they're really cheap but really slow to get here.

Click to expand...

I agree 100% with this post. The "hard stop damages compressors" is a fantasy. Bleeding off pressure before turning it off is thought by some to extend the life of a compressor. A compressor which turns itself off with an auto shutdown gauge is not damaged by this process. In reality cheap chinese compressors are built to minimal structural standards and have short life spans regardless of how they are run. It is advisable to start any high pressure air compressor with the bleed valves open and the tank valve closed in order to prevent the motor from starting under back pressure. It is also advisable to and run all compressors after a fill with the bleed valves open for a minute or more in order to purge any residual moisture out of the compressor.
Click to expand...
 
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Heavy-Impact, STO, and Humdinger,

I also wonder if some of these failures is just due to quality control of some nature..

The one that I have seems to be working great - so far - *finding wood to knock on*

Initially, for the 1st month, I was only using it to fill and/or top off my rifle air tanks, 
but the other day, I got a new carbon fiber 88 cubic foot scba tank, so used it to fill that.

I use Royal Purple 100 to lubricate it, and for the 1st time, I also used ice [frozen 2 ltr bottles]
in the water to help with better cooling..

Anyways, I made that chart documenting my start times, stop times, pressures, and temperatures.
I'll eventually try to figure out how to make a nicer graph for that 
[compared to the blue shop towel, and yellow notes I initially used] =D 

Running the comp for 10 and 15 minute intervals, then taking cool-down-breaks 
between 15 min and 30 min seemed to do the trick for me..

I was able to get the 88 cf tank pumped from 0psi to over 4,500 psi in a 'total' of about 80 minutes.
That was the actual compressor run-time with the comp at efficient / optimal temperatures.

I have a mechanical background, so I made sure to keep an eye on everything during uses, 
as well as listen for any audible changes.. These things sure are loud, but, that was about it.

Nothing out of the norm that would have me worried..

When I initially brought up the whole high pressure in the secondary head / hard-stop thing..
That was something that I was just curious about after watching this video - It should start at 3:00 in:

https://youtu.be/0KvAZBrPmu8?t=180

His piston top looks to be severely domed in - It just didn't give away causing a hole..
He went on to say that he had gotten new parts to rebuild, and the same thing happened again..
Maybe even a 3rd time, I just can't remember w/o watching his video again.. 

I figured I'd listen to him, while browsing the comment section, 
and see what other people had to say regarding their own thoughts and/or experiences..

Design, construction, materials, tolerances, etc will definitely all come into play..

Sam -

 
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You can tell by the shape of the failed area that it comes from the stacked piston rocking in it's bore. The sole purpose of this stacked design is to lower manufacturing cost. An improvement would be to use a hypereutectic piston with a longer skirt so that it can run a tighter piston to cylinder clearance on the first stage. Separate cylinders in a V or horizontally opposed would be much better but they still need good materials and proper machining. Life is a series of compromises. You can have good and cheap... but rarely together.
 
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Will's videos are great and very helpful of him to share his stories as well as lessons learned. My sense is that his problems have been more operator issues. Even after repeated breakdowns and repairs, Will continues to have shutdowns that seize the compressor like this on his latest video at 16:18:







https://youtu.be/kkI1uwA_G4k?t=978







At least with the HY, it's very important to:
1. Bleed
2. Turn off HY
3. Avoid unequal pressure drops between HY and tank (don't disconnect pressurized lines without quick-release couplings with built-in shutoffs)
4. Disconnect tank

Listening to his video, it seems as though he slipped up which caused an auto shutdown before bleeding, willful shutdown and equalization. Worse, he then tried restarting the HY, with the low-tolerance second stage piston being unable to move. I feel that it's often these types of scenarios that lead to broken pistons, damaged check valves, etc. Don't get me wrong, we are all (all too) human and it was very thoughtful of Will to share his human errors. My point is that when we're not extra careful with our YH, be prepared to head for AliExpress and order replacement parts...

Happy Trails, Michael
 
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Listening to his video, it seems as though he slipped up which caused an auto shutdown before bleeding, willful shutdown and equalization. Worse, he then tried restarting the HY, with the low-tolerance second stage piston being unable to move. I feel that it's often these types of scenarios that lead to broken pistons, damaged check valves, etc. Don't get me wrong, we are all (all too) human and it was very thoughtful of Will to share his human errors. My point is that when we're not extra careful with our YH, be prepared to head for AliExpress and order replacement parts...
Happy Trails, Michael
Click to expand...

Trying to start the compressor with pressure on the high side cannot damage the piston. The electric motor simply doesn't have enough torque to start against the load and will melt the varnish off the windings if left on without relieving the pressure. The force exerted on the piston is less than that of it running at high pressure. Design materials and tolerances are 99% of the problem with these units.
 
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my yong heng got a check valve between the high side piston and high side bleeder valve

you can see the check valve when you take off the high side pressure pipe (that goes into the high side bleed-valve-block)

if the compressor is not running, a tank is connected and you open the tank valve, the pressure gauge goes up but no air is going into the high side piston.
 
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