Tying two Yong Hengs together

So I accidently bought two (impatience and internet acting slow caused me to double my purchase) and I kept one to have as a backup just incase.

With that said I think I'd like to tie them together, less stress on the compressors and less fill time with no tax on cooling or anything else except my ears due to noise.



My question is , I'd need some sort of check valves at rhe end of each individual feed from the compressors incase one fails mid fill to keep from "backfilling", sorry for lack of terminology.... does anyone have any suggestions for a "y" or "t" for this application and a good place to source some check valves where I can look at specs to see what fits?



Am I silly for thinking this is a good idea? Open to honesty and constructive criticism...
 
I have thought about doing this also, I have 2 compressors 1 is rebuilt and the other I bought to use while the other one was down. My only thought is you would have to plug them into to separate outlets on 2 different breakers because of how much draw they have on startup. I fill 3 scba tanks in a row and definitely would be nice to cut the time in half.
 
I have thought about doing this also, I have 2 compressors 1 is rebuilt and the other I bought to use while the other one was down. My only thought is you would have to plug them into to separate outlets on 2 different breakers because of how much draw they have on startup. I fill 3 scba tanks in a row and definitely would be nice to cut the time in half.

This is the same reason I'd like to do this.....



What if you started one and then the other? I don't think that would impact in the same way....
 
I have thought about doing this also, I have 2 compressors 1 is rebuilt and the other I bought to use while the other one was down. My only thought is you would have to plug them into to separate outlets on 2 different breakers because of how much draw they have on startup. I fill 3 scba tanks in a row and definitely would be nice to cut the time in half.

This is the same reason I'd like to do this.....



What if you started one and then the other? I don't think that would impact in the same way....

You can't pull 30 amps from a 15 amp breaker. I split my welding circuit by wiring a two gang 120v outlet box to a male plug for my 240v welder extension cord to use both 120v legs. Male foster fittings usually come with a removable check valve so two of those with a check valve and one without in a log style manifold threaded 1/8 bsp should do the trick but I'm not sure that the single micro bore hose feeding your tank can handle that airflow without being a restriction.
 
I have thought about doing this also, I have 2 compressors 1 is rebuilt and the other I bought to use while the other one was down. My only thought is you would have to plug them into to separate outlets on 2 different breakers because of how much draw they have on startup. I fill 3 scba tanks in a row and definitely would be nice to cut the time in half.

This is the same reason I'd like to do this.....



What if you started one and then the other? I don't think that would impact in the same way....

You can't pull 30 amps from a 15 amp breaker. I split my welding circuit by wiring a two gang 120v outlet box to a male plug for my 240v welder extension cord to use both 120v legs. Male foster fittings usually come with a removable check valve so two of those with a check valve and one without in a log style manifold threaded 1/8 bsp should do the trick but I'm not sure that the single micro bore hose feeding your tank can handle that airflow without being a restriction.

Great points all around , the fill line one is something I actually didn't think about at all so thank you
 
These are not positive displacement pumps and as such with all the tolerance stacks if you merely separated the outputs with individual check valves then combined downstream, one unit will be the majority of the work...they will not pump equally into a common vessel.

Why do you say they're not positive displacement when they fit the positive displacement description exactly? They have pistons and force air from a large area to a small one and then out through a valve. Displacement doesn't get much more positive than that so please educate me.
 
I should have said these are not high tolerance compressors. The original goal I believe was to half the fill time by adding a second unit? While you will probably reduce fill times, you may also spend more time repairing compressors. If two is good 3,4 or 5 would be even better. I think perhaps the goal is to make a high end displacement compressor spec out of more low end units bundled together. I don't believe the time and investment will yield desired result; but, that's subjective anyway. 
 
If each pump is behind a check valve as it should be then each pump will contribute the same as if it were the only pump. The pumps are made to work against a head pressure up to 4500psi so nothing else matters. The load on each pump will be the same as working alone but getting the job done in half the time so less energy is converted to heat. This would not be suitable for filling a gun directly because some guns using a fill probe have too much restriction. It will be fine filling a larger tank through a hose with adequate capacity.

The goal is to make the most of what you have. He did not purchase two pumps with this in mind. This is what he ended up with so now he's making the most of it.
 
I should have said these are not high tolerance compressors. The original goal I believe was to half the fill time by adding a second unit? While you will probably reduce fill times, you may also spend more time repairing compressors. If two is good 3,4 or 5 would be even better. I think perhaps the goal is to make a high end displacement compressor spec out of more low end units bundled together. I don't believe the time and investment will yield desired result; but, that's subjective anyway.

We tried this with two 150 psi 600 cfm screw compressors; one does all the work unless you exceed the cfm capacity, then the other kicks in. But one usually did most of the work.
 
You will need either these, or some inline ones. These should duo the trick as it is what I use. 



https://www.amazon.com/gp/product/B08FQ3W79Z/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

or NPT

https://www.amazon.com/gp/product/B08FMWGP8D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1



I set mine up differently than most people would consider. I removed the Blow off valves for my SCBA tanks, replaced them with the Male Foster fittings with the built in check valve. I also removed the fill whips gauges and replaced them with the male foster fittings with check valves. I fill my tanks by daisy chaining them together off one compressor currently. In the market for a Pro fill station.... 



Here is how I fill mine. - Tank one, gets the Compressor connected directly to the foster fitting on the side of the SCBA tank. I put a fill whip in the output connector of that tank, connect that one to the next tank to the foster fitting on the side and keep doing the same setup for all 3 or more tanks. I open up all the valves of the tanks with fill whips and they cascade fill each other. Filtration and moisture traps are used as well as bleeding off the compressor etc.. Plus once I get up to pressure, I take the tanks, Invert them bottle valve down. Let them cool, then give a couple quick valve cracks to remove any moisture. Check pressure, top off once they are all ambient temp. 



What you could do to add something in here to help with the filling. Wether it be you have multiple tanks and daisy chain them together. fill at both ends. Or get a High pressure rated 3 way fitting. 2 male foster with check valve. one with it removed, or 2 male foster with check valve and one female foster coupler depending on your fittings you use to fill. 



When I fill PCP's. I hook each fill whip up to the next fill whip with the male foster fittings. Then I Cascade fill. Crack the lowest pressure tanks valve. Fill the gun to that pressure. Close the valve, onto the next tank that has the next highest pressure, crack valve, fill, repeat. I use 3 tanks, so I do this 3 times. I also use a pressure release valve and check valve at the end to loose as little pressure as possible. That way, the system can stay pressurized all except the last couple inches off the fill whip at the end. Perfect? No. Saves me some time and air in the long run. Yep. I normally end up filling most peoples PCP's when we go shooting. My system allows for others to Connect their tanks in tandem with the rest of the system so we never run out of air. Still;l always start with the lowest pressure tank as first in the system. I could just make a manifold with valves to turn with all the tanks attached to. Cost is a factor. 

Follow me here before all of you start biting my head off about safety, etc. The Blow off disks are rated to 3XX Bar... They hydro test the cylinders at exponentially more than that. The Male Foster fittings with the check valves are rated up to ~5k max fill. Yong Heng and similar aren't rated up to 5k. If you keep an eye on things like you are supposed to. You will never overfill or get in the danger zones of the tanks.


 
I set this up real quick to show my config last night. Forgot to post. This is 2 of the 3 I fill and I do fill them in a tub of water to keep the temps down. Also run the recirculating pump for the compressor in the same water. I left the filtration off for this pic. But I do use it. Didn't feel like setting it all up. Was movie night with my children. 



20220204_191347.1644092291.jpg




If you have 2 fill whips with male foster fittings on the ends that your fill whip attaches to. You could interconnect both fill whips to each other in the case of 2 tanks. Remove the redundant fill whip gauges, replace with the foster fittings with the check valves in them. Fill from the fill whip fittings you just put on now.



Configurations are endless.