Check valve...?

[The Z'eer]

I’m still struggling to see the need for check valves. The air isn’t going to leak out of the other compressor, which is what they seem to suggest. The regulator on a compressor doesn’t contain any check valve, that’s between the pump and receiver.

You can of course fit them if you want, and it will work - but it’s an added complication & expense - with both linked together just via plain pipework the system will work just fine, wherever you put your regulator.

Ok, so the factory fitted check valve prevents air from the receiver making its way back into the pump. If I don’t use an additional check valve after the receiver, when both compressors are operating simultaneously air can back flow into that receiver.

If I use a ball valve, to close off the receiver then air can’t travel from that compressor to feed the airline.

 

[bricol]

I don't have check valves in my system when I link all mine together - but I can see it would help keep the supplied air pressure as high as possible for as long as possible.

 

[The Z'eer]

I don't have check valves in my system when I link all mine together - but I can see it would help keep the supplied air pressure as high as possible for as long as possible.

Indeed, that’s my thinking too. Another explanation for the usage of check valves...

Connecting 2 Air Compressors Together | Fix My Compressor

While a single air compressor may not offer enough flow to supply a higher demand air tool and another single air compressor can have the same problem with that same air tool, if you connect two air compressors into one line to the air tool, you may have enough airflow from the two to use that...

fix-my-compressor.com

 

[daleyd]

Indeed, that’s my thinking too. Another explanation for the usage of check valves...

Connecting 2 Air Compressors Together | Fix My Compressor

While a single air compressor may not offer enough flow to supply a higher demand air tool and another single air compressor can have the same problem with that same air tool, if you connect two air compressors into one line to the air tool, you may have enough airflow from the two to use that...

fix-my-compressor.com

I think their theory is way off, but let us know how you get on

 

[The Z'eer]

I think their theory is way off, but let us know how you get on

I certainly will, it appears purchasing the secondary compressor isn’t possible at present. Seeming stocks are depleted of Wolf 90 ltr

I think the theory is sound, it makes sense in that air is forced to the tool rather than refilling the other receiver.

 

[daleyd]

I certainly will, it appears purchasing the secondary compressor isn’t possible at present. Seeming stocks are depleted of Wolf 90 ltr

I think the theory is sound, it makes sense in that air is forced to the tool rather than refilling the other receiver.

In practice both tanks will empty at the same rate, the difference you will see will be negligible at best - plus by adding the valves your introducing a further restriction in the line (a check valve will have some resistance to flow, albeit slight)

The design you have I would have thought would switch between the 2 valves as the tanks empty . 1 drops in pressure, the other tank then becomes the higher pressure, then the other and so on until the pumps kick in.

 

[The Z'eer]

In practice both tanks will empty at the same rate, the difference you will see will be negligible at best - plus by adding the valves your introducing a further restriction in the line (a check valve will have some resistance to flow, albeit slight)

The design you have I would have thought would switch between the 2 valves as the tanks empty . 1 drops in pressure, the other tank then becomes the higher pressure, then the other and so on until the pumps kick in.

Agreed, both receivers should discharge at an equal rate, however it’s possible that upon beginning work that one receiver may have more volume than the other, and thus a pressure difference. Depends on whether I’ve discharged both before before work commences.

Although if both receivers are fully charged, yes the difference in performance could be negligible despite employing check valves in the system, this remains to be seen.

 

[the snooper]

I dont see the point in putting in the check valve, the pressure won't equalise in both tanks so you'll have 2 different pressures feeding into your airlines, a simple ball valve would have done to isolate the machine your not using, as for both machines running you just need to adjust one pressure switch to cut in at a much lower pressure

 

[the snooper]

and you can just fit a ball valve . that thats all i have

That's all I've done in the past, adding in valves is just overthinking it

 

[the snooper]

Agreed, both receivers should discharge at an equal rate, however it’s possible that upon beginning work that one receiver may have more volume than the other, and thus a pressure difference. Depends on whether I’ve discharged both before before work commences.

Although if both receivers are fully charged, yes the difference in performance could be negligible despite employing check valves in the system, this remains to be seen.

They won't discharge at the same rate if they're at different pressures

 

[Chris Snow]

With check valves whichever is at the highest pressure will supply the tool.

With or without check valves one compressor may never run unless you exceed the flow one can produce. This may or may not be desirable.

 

[brightspark]

if both are coupled at tank pressure pump either 120 psi 150 then regulated pressure of one tank to tools works well with ball valve in between

 

[The Z'eer]

I dont see the point in putting in the check valve, the pressure won't equalise in both tanks so you'll have 2 different pressures feeding into your airlines, a simple ball valve would have done to isolate the machine your not using, as for both machines running you just need to adjust one pressure switch to cut in at a much lower pressure

I wouldn’t want for one compressor to cut in much lower than the other, a sustained similar output is preferable.

 

[The Z'eer]

if both are coupled at tank pressure pump either 120 psi 150 then regulated pressure of one tank to tools works well with ball valve in between

I will use a ball valve in the system too. This way I can make use of the 90 ltr receiver when secondary compressor isn’t in use, if required.

 

[Turbo]

I used to run 2x25l direct drive compressors in tandem. The output of each one was direct from the bung in the end of the tank via a rubber flex hose to a 47kg propane cylinder. Both feeds were direct to the propane tank, no NRV, just a pcl coupling on each hose so I could remove the compressor for servicing.

I had my regulator on the output of the propane tank. Most of the time I ran only one compressor, it ran until it filled its own tank, the other compressor tank plus the propane tank. That was more than able to supply air for most things, including my nut gun.

If I was doing something needing more air over a longer period like spray painting I switched on the other compressor and both units would happily run in tandem, switching on & off as needed. I ran this setup for over 10 years until I bought a big 3hp belt drive compressor & never had any problems.

I wouldn’t want for one compressor to cut in much lower than the other, a sustained similar output is preferable.

You need to set the pressure switch on one compressor 5 psi higher than the other, otherwise both will be trying to start at the same time & might draw more current than your supply can handle!

 

[The Z'eer]

I used to run 2x25l direct drive compressors in tandem. The output of each one was direct from the bung in the end of the tank via a rubber flex hose to a 47kg propane cylinder. Both feeds were direct to the propane tank, no NRV, just a pcl coupling on each hose so I could remove the compressor for servicing.

I had my regulator on the output of the propane tank. Most of the time I ran only one compressor, it ran until it filled its own tank, the other compressor tank plus the propane tank. That was more than able to supply air for most things, including my nut gun.

If I was doing something needing more air over a longer period like spray painting I switched on the other compressor and both units would happily run in tandem, switching on & off as needed. I ran this setup for over 10 years until I bought a big 3hp belt drive compressor & never had any problems.



You need to set the pressure switch on one compressor 5 psi higher than the other, otherwise both will be trying to start at the same time & might draw more current than your supply can handle!

Thanks for the info Yeah, I thought the difference for the pressure switch might be around that.

I should see a combined figure of 28 CFM from the two compressors to supply gun and mask. The requirements for mask appear to be a max of 10 CFM at circa 72 PSI. To be safe the requirements for a smaller HVLP gun should be around no more than 15 CFM