Valve to fill additional compressed air tank

How much volume do you need? I would think that a basic gas engine powered compressor (with throttle control) mounted on a 3pt skid would be more fuel efficient than running a large tractor at high idle. Since that compressor has a tank, it should retain pressure between uses so the startup fill time would be minimal.

Pete, there are days when we do not need the compressor. I do not want to start it on a timer.

i

Shut off the main valve at the tank when you leave for the day, isolating any leaks in your distribution piping. When you do need air, open the valve and it only needs to fill the relatively small volume of the distribution piping. If your compressor tank and pump leak a lot you need to fix that.

I'd start with a semiautomatic system, separate manual shutoff valves on the inlets to the small and large tanks and a check valve that lets the large tank flow into the small one.

When you turn the compressor on set the valves to fill only the small tank, so you have pressure quickly.

When you know you will need more volume close the intake to the small tank and let the compressor fill the large tank directly. The small tank will supply immediate needs while the large one fills efficiently, without wastefull pressure drops. Once the large one is up the check valve will keep the small tank full if you forget to reopen its intake valve.

If that plan works out you could automate it with a valve operated by the pressure in the small tank. Then a high demand while the large tank is still filling will switch the compressor back to the small tank.

Looking for a good example of a pressure-actuated multiport valve is too tedious on my dial-up. This should get you started.

jsw

If a valve opens and the flow is large enough through the valve then suddenly there will be a pressure drop in the whole system. The drop depends on how much pressure is in the extra tank when the valve opens and how big it is in relation the the regular tank. Eric

If you already have a check valve going into the small tank it doesn't need a shutoff. The check valve will keep air in the small tank when you open the valve to fill the large one. jsw

Right. But I can deal with that. It is not a big factor.

i

40 feet, I believe 10 gauge, 30 amp breaker, 220v i

A more complicated way... :-)

Have a pressure transducer in each tank and a solenoid valve between them. Possibly with the flow control/check valve in line with the solenoid valve.

Transducers ran to a controller and a little software.

For this, assuming the compressor starts at or below 90PSI and Stops at or greater than 125 PSI.

Valve = Primary_Tank_PSI < Secondary_Tank_PSI OR Primary_Tank_PSI > 120 // Valve ON when secondary can help or when primary is near full

Compressor = (Compressor AND Primary_Tank_PSI < 125) OR (NOT Compressor and Primary_Tank_PSI

Roger, this is what I may end up doing, except no software is needed. All that is needed is a compressor pressure switch and a NC relay.

i

Ignoramus31823 fired this volley in news:lbKdnW91O4HcHT7PnZ2dnUVZ snipped-for-privacy@giganews.com:

I still want to know why the check/flow would:

1) Cause the system to take (much) longer to pump up, and 2) "Waste energy".

If you install a check valve/flow-control between the two tanks, so that the reserve tank can only be filled through a small restriction, but can dump instantly, any time its pressure is higher than 'system', then where's the loss?

The small tank will pump up in about the same time as before, with the only 'loss' being the small flow into the larger tank. The big tank comes up to system pressure slowly; and as slowly as you want. Then, if you demand more than the small tank can provide, the reserve will dump _freely_ (without any significant pressure loss - maybe 1/2 psi) back into the system.

This is a pretty common way to provide reserve short-term capacity without increasing pump capacity. ???

So, (I mean it) please describe the problems so I can critique the method myself. I just don't see the losses or problems you describe.

LLoyd

The loss is a consequence of the delta P across the adjustable orifice in the flow-check. But my gut feeling is that, if the system is used and described, the loss will be insignificant compared to the effort and expense required to eliminate it.

If the "loss" that occurs during initial pumping up is small, then the tank is slow to fill, and it means that it will not be filled fast when the system reaches pressure.

i

Ignoramus31823 fired this volley in news:h_Wdnaf37ryWDT7PnZ2dnUVZ snipped-for-privacy@giganews.com:

So? You said you only need it for occasional "high flow" jobs. If you need it to fill faster, install a manual valve to override the restrictor when you absolutely have to, and let the pump work longer in one session. (the total pump time will _always_ be the same per cubic foot of tank capacity, so you save nothing in pump run time, either way. It either runs in 'bursts' until it's filled the big tank, or it runs continuously...total time is the same).

Again... remember that you're only drawing from that big tank when the small one can't provide the flow you need.

LLoyd

Let me revise my comment a little.

You're a math guy. How will the big tank _ever_ fill quickly, and still not prevent you from getting full pressure quickly in the small tank?

Opening a 'pass-over' valve to the big tank once the small one is full won't do it! It'll drop the system down to system peak divided by the ratio of tank volumes the INSTANT you open it (well, within seconds). So the pump will come back on, and now run an intolerable length of time before you have enough pressure to work. You can't have 'quick' and 'full pressure' in the same formula.

Pump capacity is the limit; always. Lloyd

Very simple. The big tank would start to fill only when system pressure is above, say, 120, and stop filling if it drops below, say,

1. A valve and a pressure switch can do that.

Think some more, you will realize that what I want to do is the nicest way of doing it.

i

I have about 1200 lbs of cables. But my problem is that the wire going to the compressor, goes through a 48 year old wire duct. I am afraid of messing with it. I do not even know how I am going to figure it out.

Perhaps I should start with a clean slate, and get a new 50A circuit to the compressor, with a real neutral, etc, through a separate conduit. And then upgrade the compressor from my 10HP QUincy to the

15HP quincy that I bought on auction. My original plan was to sell the 15 HP compressor. But maybe I should keep it and sell the 10HP inspead. i

Ignoramus31823 fired this volley in news:B-SdnQSwK7C6LT7PnZ2dnUVZ snipped-for-privacy@giganews.com:

If your pump cuts in at 90, then all you've done is complicate the system without improving the performance. The INSTANT your system hits 120, it'll dump _all_ your main tank capacity into the reserve until the pressure drops to 90 -- then the electric valve turns off and the pump starts to run again... it will not improve the length of time it takes to get the reserve up to pressure. That's dependent entirely on pump capacity. It matters not how you fill it, it will always take the same length of time.

Your method will NOT improve run time, or the time to reach "usable" air pressure in the main tank, except for a slight (say 10%) time. But it will increase the complexity and maintenance issues over a simpler, purely solution.

Ig... for any given solution that will work, simpler and less expensive is always better.

Lloyd

Ignoramus31823 fired this volley in news:4dCdnab2zO7qLD7PnZ2dnUVZ snipped-for-privacy@giganews.com:

Amen!

Lloyd