Question What do you do when filling an empty tank from a small compressor?

[JohnN]

I have a RIX-SA3 with the pressure valve set to hold backpressure to the filter stack at about 2400 PSI. There are no cascade bottles in my setup.

Question #1:
Should I "feather" the valve to the tank so that the third stage pressure stays >1000 PSI, or is the best
practice just to open the valve up and just let the compressor run?

Question #2:
Since the RIX doesn't use lubrication oil, isn't the filter stack only pulling out trace H20? Given that
what is the preferred packing medium for the filter?


Thanks all!!

 

[rhwestfall]

The BPV will basically do the "feathering".

 

[rhwestfall]

If you don't have a CO concern from outside contributors, you could just go AC and 13x MS...

Because of the age of my previous oiled compressor I always used HOP too and ran a CO detector.

 

[tbone1004]

I have a RIX-SA3 with the pressure valve set to hold backpressure to the filter stack at about 2400 PSI. There are no cascade bottles in my setup.

Question #1:
Should I "feather" the valve to the tank so that the third stage pressure stays >1000 PSI, or is the best
practice just to open the valve up and just let the compressor run?

Question #2:
Since the RIX doesn't use lubrication oil, isn't the filter stack only pulling out trace H20? Given that
what is the preferred packing medium for the filter?


Thanks all!!

I'm not entirely sure what you're asking. You need the PMV to stay where it is to get the water out of the incoming gas, sure it's only taking water and whatever is in the inlet air out vs. oil and other nasties but the water needs to come up.
The way a PMV works is that once the pump side hits in this case 2400psi, then the gas will flow through at whatever flow rate the pump is pushing to maintain 2400psi. Once you exceed PMV pressure then it is just pumping straight through. In this case ~3cfm which in an AL80 is a bit over 100psi/min.

If you are not using a cascade as a buffer, you never want to "feather" the fill valve because you will run the filters up to whatever the compressor pressure cutoff is and then it will stop/start the pump instead of run continuously. Once the pump is on, it needs to stay on without restriction.

Filter media is still going to be fairly normal for the Rix IMO as there is still the potential to suck CO in from ambient air even though it is not generating any from the pump itself. I use the same filters with Rix as I would with an oiled compressor, no downside to having MS,AC, Hopcalite in the system and it makes finding cartridges a bit easier

 

[JohnN]

I'm not entirely sure what you're asking. You need the PMV to stay where it is to get the water out of the incoming gas, sure it's only taking water and whatever is in the inlet air out vs. oil and other nasties but the water needs to come up.
The way a PMV works is that once the pump side hits in this case 2400psi, then the gas will flow through at whatever flow rate the pump is pushing to maintain 2400psi. Once you exceed PMV pressure then it is just pumping straight through. In this case ~3cfm which in an AL80 is a bit over 100psi/min.

If you are not using a cascade as a buffer, you never want to "feather" the fill valve because you will run the filters up to whatever the compressor pressure cutoff is and then it will stop/start the pump instead of run continuously. Once the pump is on, it needs to stay on without restriction.

Filter media is still going to be fairly normal for the Rix IMO as there is still the potential to suck CO in from ambient air even though it is not generating any from the pump itself. I use the same filters with Rix as I would with an oiled compressor, no downside to having MS,AC, Hopcalite in the system and it makes finding cartridges a bit easier

Trying again.

To spitball the problem, if the cylinder is empty and is 15 liters (0.5 ft^3) and at the moment the tank valve is opened the pump will deliver .05 ft^3 @ 3000 psi and I ignore any temperature change, I get 300 psi in the cylinder

My other choice is to reduce the flow of gas into the cylinder to maintain a backpressure of say 1000 psi

What should a poor boy do?

 

[tbone1004]

Trying again.

To spitball the problem, if the cylinder is empty and is 15 liters (0.5 ft^3) and at the moment the tank valve is opened the pump will deliver .05 ft^3 @ 3000 psi and I ignore any temperature change, I get 300 psi in the cylinder

My other choice is to reduce the flow of gas into the cylinder to maintain a backpressure of say 1000 psi

What should a poor boy do?

I'm still not understanding what your problem is and what exactly you are asking.

Where is the 0.05cf @3000psi coming from? Is that the volume in the line between the filter and the end of the fill whip?
What are you concerned about if it does in fact jump up to 300psi when you open the valve?
How are you proposing maintaining a back pressure of 1000psi by restricting the flow? How are you going to measure that and what is the benefit of doing that?

How often is this going to be an issue for you? This should only be an issue after something like hydro/vip or a valve change and I usually recommend using a transfill whip so you can get the initial couple hundred psi into the tank as soon as you are ready to close it up. Pop a few hundred psi in there, purge, repeat a couple of times to get any ambient humidity out, then you can fill as normal.

 

[rjack321]

Assuming your intake isn't in a parking lot...
AC and 13x in the stack
BPV set to 1500ish.

Open the valve and fill.

 

[rhwestfall]

One thing I have noticed is a really hard "rattle/harmonic" if I connect a fully charged fill line (pmv is open like when switching tanks with the compressor running) to the very low pressure/empty tank, and open the fill valve and then the tank valve more than a slight bit. It sounds like it is in the tank valve seat, but is it the resonance of the PMV "dancing with the hp to lp situation as the small amount of volume generated off the compressor is releasing into the large low pressure space of the tank, rapidly cycling the pmv? Maybe he has a concern with that?