Pressure Pot-Priming the spray gun

[wptski]

Yes, the compressor will cycle. Air pressure drops in the pot as the fluid is displaced. The Jc-10 will cycle every 4 minutes or so on my 2.5 gallon pot.

No check valve on the inlet of my pot.

Tom

Do others have the same results?  Where's the air going?

 

[tjbnwi]

Yes, the compressor will cycle. Air pressure drops in the pot as the fluid is displaced. The Jc-10 will cycle every 4 minutes or so on my 2.5 gallon pot.

No check valve on the inlet of my pot.

Tom

Do others have the same results?  Where's the air going?

The fluid is not compressible. Air pressure is pounds per square inch. When the fluid leaves the pot the air volume of the pot increases. This increase in volume decreases the pressure in the pot. Compressor comes on the adjust for the decrease in pressure. Easily seen on the pressure gauges.

Ultimately until the pot is empty, the air goes no where.

Tom

 

[wptski]

The fluid is not compressible. Air pressure is pounds per square inch. When the fluid leaves the pot the air volume of the pot increases. This increase in volume decreases the pressure in the pot. Compressor comes on the adjust for the decrease in pressure. Easily seen on the pressure gauges.

Ultimately until the pot is empty, the air goes no where.

Tom

Yes, I know but your JC 10 has a 2.5 gallon tank as your pot does when empty so am I missing something here?  How many times do you have to fill that 2.5 gallon pot if the air goes nowhere?

 

[tiralie]

Do others have the same results?

Yes, exactly. I don't have a check valve on my tank but I do have a safety valve as probably Tom's does too.

Where's the air going?

The pressure drops in the tank as the paint is sprayed. When the pressure drops enough, the compressor comes on and re establishes the pressure.
Tim

 

[tjbnwi]

The fluid is not compressible. Air pressure is pounds per square inch. When the fluid leaves the pot the air volume of the pot increases. This increase in volume decreases the pressure in the pot. Compressor comes on the adjust for the decrease in pressure. Easily seen on the pressure gauges.

Ultimately until the pot is empty, the air goes no where.

Tom

Yes, I know but your JC 10 has a 2.5 gallon tank as your pot does when empty so am I missing something here?  How many times do you have to fill that 2.5 gallon pot if the air goes nowhere?

The air volume of a 2.5 gallon pot with 2.5 gallons of fluid in it is not 2.5 gallons of air space. As the fluid leaves the pot the air volume increases. It's not a matter of the air going anywhere, its a matter of additional air needed to fill the increase of  space.

As the space increases, the pressure drops, the compressor comes on to adjust for the pressure loss.

If the pot was connected to my 40 gallon shop compressor, I doubt the compressor would ever turn on.

Tom

 

[tjbnwi]

Do others have the same results?

Yes, exactly. I don't have a check valve on my tank but I do have a safety valve as probably Tom's does too.

Where's the air going?

The pressure drops in the tank as the paint is sprayed. When the pressure drops enough, the compressor comes on and re establishes the pressure.
Tim

Yes, there is a pop off valve on my pressure pot.

Tom

 

[wptski]

The air volume of a 2.5 gallon pot with 2.5 gallons of fluid in it is not 2.5 gallons of air space. As the fluid leaves the pot the air volume increases. It's not a matter of the air going anywhere, its a matter of additional air needed to fill the increase of  space.

As the space increases, the pressure drops, the compressor comes on to adjust for the pressure loss.

If the pot was connected to my 40 gallon shop compressor, I doubt the compressor would ever turn on.

If you put 2 gallons of material in your 2.5 gallon pot that leaves .5 gallons of space that your compressor needs to fill, correct?  As your material is used up air needs to be added, correct?  If your compressor has a 2.5 gallon storage tank the same size as your pot why would it need to run at all providing that it was full when starting off?

At what pressure does your compressor cycle ON/OFF at? 

 

[tjbnwi]

The air volume of a 2.5 gallon pot with 2.5 gallons of fluid in it is not 2.5 gallons of air space. As the fluid leaves the pot the air volume increases. It's not a matter of the air going anywhere, its a matter of additional air needed to fill the increase of  space.

As the space increases, the pressure drops, the compressor comes on to adjust for the pressure loss.

If the pot was connected to my 40 gallon shop compressor, I doubt the compressor would ever turn on.

If you put 2 gallons of material in your 2.5 gallon pot that leaves .5 gallons of space that your compressor needs to fill, correct?  As your material is used up air needs to be added, correct?  If your compressor has a 2.5 gallon storage tank the same size as your pot why would it need to run at all providing that it was full when starting off?

At what pressure does your compressor cycle ON/OFF at?

Liquid and gas volumes are not proportional.

95-115 I believe.

Tom

 

[wptski]

Liquid and gas volumes are not proportional.

95-115 I believe.

Not concerned if liquid to gas are proportional as it's 2.5 gallons of air to 2.5 gallons of air space.

Even if the compressor's tank was at the low end at 95psi it should be able to fill the pot at 10psi or whatever.

 

[tjbnwi]

Liquid and gas volumes are not proportional.

95-115 I believe.

Not concerned if liquid to gas are proportional as it's 2.5 gallons of air to 2.5 gallons of air space.

Even if the compressor's tank was at the low end at 95psi it should be able to fill the pot at 10psi or whatever.

Not true.

The only direct conversion I could find was for Nitrogen, the ratio is 750 to 1, for every one liquid nitrogen volume lost it takes 750 gas nitrogen to fill the void. (our atmosphere is 80% nitrogen).

Again, it's not 2.5 gallons of air space once you place 2.5 gallons of something else in it. 2 objects cannot occupy the same space as the same time. It's the change in volume that causes the compressor to cycle.

The tank on my welder has 1200 cubic feet of argon/Co 2 in it according to the gauge. I know the tank is not 1200 cubic feet in size.

Tom

 

[wptski]

Not true.

The only direct conversion I could find was for Nitrogen, the ratio is 750 to 1, for every one liquid nitrogen volume lost it takes 750 gas nitrogen to fill the void. (our atmosphere is 80% nitrogen).

Again, it's not 2.5 gallons of air space once you place 2.5 gallons of something else in it. 2 objects cannot occupy the same space as the same time. It's the change in volume that causes the compressor to cycle.

The tank on my welder has 1200 cubic feet of argon/Co 2 in it according to the gauge. I know the tank is not 1200 cubic feet in size.

I have a 40CF tank of nitrogen for my A/C hobby.

Forget about the liquid.  You have an empty 2.5 gallon pressure pot, connect your filled 2.5 gallon compressor to it which is turned OFF and try to set the pot's regulator for say 15psi.  Your saying that you can't get 15psi in the pot's tank unless the compressor is turned ON?  This would be the maximum demand placed on your compressor.

 

[tjbnwi]

You'll get the 15 psi, but the compressor will turn on. Pressure and volume are two different things.

Tom

 

[wptski]

You'll get the 15 psi, but the compressor will turn on. Pressure and volume are two different things.

Tom

Yes, they are increasing pressure allows more volume stored into the same physical space.

Using  Boyle's Law:

2.5 gallon tank
.33CF@atmosphere
.55CF@10psi
.65CF@15psi
1.2CF@40psi
2.3CF@90psi

Your JC-10 shouldn't have any problems filling your empty pressure pot without even being turned ON.

 

[tjbnwi]

You'll get the 15 psi, but the compressor will turn on. Pressure and volume are two different things.

Tom

Yes, they are increasing pressure allows more volume stored into the same physical space.

Using  Boyle's Law:

2.5 gallon tank
.33CF@atmosphere
.55CF@10psi
.65CF@15psi
1.2CF@40psi
2.3CF@90psi

Your JC-10 shouldn't have any problems filling your empty pressure pot without even being turned ON.

The question that started the discussion is will the compressor turn on---my answer was yes. Next question was will it the compressor come on while spraying---my answer was about every 4 minutes.

Boyle's Law you posted proves this out. You are missing one key thing about this entire topic and the equipment. This will occur in some way across some variable of time depending on the tank volume of the compressor on every compressor I have seen, serviced and know of. Someday you'll have that epiphany, followed by a forehead slap.
=em-upload_owner

As you can see, I made sure the air hose was connected while the compressor was filling. By connecting the hose from the start it added a slight additional volume to the compressor and did not take away from the volume if I connected it after the compressor had shut off. I made sure the fluid hose valve was closed to not affect/increase the volume of the tank.

You will see the fluid line being purged, and the volume of fluid (in this case water, about 1 US gallon) that was displaced from the tank before the compressor turned back on. The gun is a T-70 with an 0.8mm nozzle/needle set and air cap, this is the smallest set available for the gun. I had finished spraying a piece earlier so the gun is set where it was when I sprayed the piece.

Again, I don't edit my videos you see this in real time as it happened.

My Jc10 is set 125 psi off (factory is 115 I believe)--95 psi on.

If the pot was full of fluid the compressor would not have turned on initially, but soon after beginning spraying.

Tom

 

[Scott B.]

Who needs a drink?

 

[tjbnwi]

Who needs a drink?

What ya servin'?

Tom

 

[rst]

I've been fixing things, from paint to automatic door systems and sensors since 1971.  I had really high SATs but had no real plan (YAH!) so did not do college...besides I was a hippie wannbe.  Went to work in custom kitchen factory immediately after high school, farmed and raised stock-pigs until I realized that framing was a really expensive hobby.  Sorry...I digress.  Engineers and people that get caught up in numbers and "what should be" drive those of us that "doit, tryit, fixit".  It doesn't matter if the numbers don't add up in the real world...the only thing that matters is: does it do the job and is it efficient!!  Sorry about the high horse but people that live behind their computers and calculators drive me crazy. 

 

[rst]

Knob Creek?  [tongue]

 

[Scott B.]

I think its good to try to understand how tools work, even have a basic understanding of the engineering intent.

Trying to predict, define or describe performance based on specs is a bit of shell game, which if taken too far can turn into paralysis by analysis.

Its best to keep it simple and practical. Experiment and find what works for you and the work you do.

I have seen a lot of the work that Tom B and Tim R do and it is always very high level. I don't think I could achieve the same results with their products and processes sometimes, but I usually feel like I could with my own. And in the meantime, it is fun to learn from each other. Thats the spirit of the forum.

 

[wptski]

The question that started the discussion is will the compressor turn on---my answer was yes. Next question was will it the compressor come on while spraying---my answer was about every 4 minutes.

Boyle's Law you posted proves this out. You are missing one key thing about this entire topic and the equipment. This will occur in some way across some variable of time depending on the tank volume of the compressor on every compressor I have seen, serviced and know of. Someday you'll have that epiphany, followed by a forehead slap.

As you can see, I made sure the air hose was connected while the compressor was filling. By connecting the hose from the start it added a slight additional volume to the compressor and did not take away from the volume if I connected it after the compressor had shut off. I made sure the fluid hose valve was closed to not affect/increase the volume of the tank.

You will see the fluid line being purged, and the volume of fluid (in this case water, about 1 US gallon) that was displaced from the tank before the compressor turned back on. The gun is a T-70 with an 0.8mm nozzle/needle set and air cap, this is the smallest set available for the gun. I had finished spraying a piece earlier so the gun is set where it was when I sprayed the piece.

Again, I don't edit my videos you see this in real time as it happened.

My Jc10 is set 125 psi off (factory is 115 I believe)--95 psi on.

If the pot was full of fluid the compressor would not have turned on initially, but soon after beginning spraying.

Tom

Thanks for extra time spent to clean your spray gun and that RolAir is sure quiet too!

I did forget to include the air line in and the material line coming out.  If 15' each way that only adds maybe .1CF to the mix.  If I would have tried tried this myself, I would have turned the compressor OFF after the first cycle.  I never denied that it may cycle at least once. If I ever get into a pressure setup with a compressor I will try that for sure although most are 3 gallons or more from what I've seen

Thanks again for taking the time to make a video. ;D