Pressure Maintaining Valve Information

[Taso1000]

Hey Mark,

Yeah, I ordered the pmv, 2 couplers, 2 nipples, a tee, a plug, a filter cartridge and two bleed valves with hose barbs.  I compared prices from Nuvair, August Indutries and Northshore Compressor because shipping is kinda high.  I guess I'm spoiled by Amazon Prime 2 day shipping that's no charge.

The two bleed valves I have just have a hole that blows moisture everywhere.  With the barbed bleeds I can capture the moisture and possibly measure it to quantify what I'm removing.

Then I saw Steve Scialli's Daystate compressor review,

and he was bleeding off lots of moisture so I'm glad I'll be able to direct it into a container.

I did fail to notice that the barbed bleeds are 1/8 npt.  I had emailed Nuvair about the working pressure but didn't think to ask about the thread size.  I assumed they were 1/4 npt like my other bleeds.  I'll see if I can find some reducers from Grainger locally. 

I keep adding stuff to the Shoebox and I'm not liking all the weight hanging off the front.  Once I figure out the final setup I may remote mount the filtration with a 6000 psi jic ended hose I have.  We will see.   

Thanks,

Taso

[txrpls]

Taso, Thanks for the info. I ordered mine and should be here next week. I planning on putting on the top of my gold filter. Going to start looking for a tee and valve to mount on the bottom to purge in addition to the one on the AV compressor.

[Taso1000]

Hi All,

I added the new pmv in my loop today.  I still need to pressurize the system and set the pressure point once the thread sealer cures.

By next weekend I should have the pressure point set and hopefully catch some water as I have a cylinder almost at 3000 psi that needs topping up.   

Once my testing is done, pretty soon, I think I will remote mount the pmv and Alpha filter because I don't like how everything is hanging of the original Shoebox outlet.  The new pmv has mounting holes that will be a big help.

Thanks,

Taso

[HuskyDude]

Taso I understand why you need the 1/4"x1/8" bushing....but why do you have all the other fittings!?!
Are you looking for extra water collection space??? Or did I miss something???



Found another site for a PMV or priority valve

1310 Back Pressure Regulator (Non adjustable pre set 1900psi) $67.00

[Taso1000]

Dave,

Yes.  I didn't know how much water would be collected in the first drip leg you marked.  Most of the water will collect here in the first leg. 

I don't expect much, if any to collect in the second drip leg under the Alpha but I did need a bleed there if I wanted to take the Alpha apart to change the molecular sieve cartridge out.

I can always remove couplers and nipples later if I have more than enough capacity.  That's why I intend to capture whatever water collects there.  I don't plan on bleeding every 15 minutes like Steve S. but after the cylinder is topped off.

Yes, it's like the pmv on the output of the Alpha filter is the one that came with the filter.  It is non adjustable and opens around 1700 psi.

The big gold pmv is new and is adjustable. 

Thanks,

Taso

[txrpls]

Tasso,

What is the black thing on the bottom of the alpha.

[Taso1000]

Mark,

The black cylinder is a moisture indicator.

https://www.augustindustries.com/visual-indicator-ind-mois.asp?bc=no

And I have installed the 20 - 40 - 60 relative humidity disk.

https://www.augustindustries.com/moisture-indicator-disk-kit-mois.asp?bc=no

Thanks,

Taso

[txrpls]

Mark,

The black cylinder is a moisture indicator.

https://www.augustindustries.com/visual-indicator-ind-mois.asp?bc=no

And I have installed the 20 - 40 - 60 relative humidity disk.

https://www.augustindustries.com/moisture-indicator-disk-kit-mois.asp?bc=no


Thanks,

Taso

Taso,

Thanks for those links. I think I am going to put an extra gauge I have on the opposite side of the PVM outlet to my fill hose as another verification of correct pressure between all three gauges. Any thoughts on that?

Mark

[Taso1000]

Mark,

It can't hurt.   

I also have the big gauge right at the Shoebox outlet.  I don't know how often these high pressure gauges fail or read wrong.  My firefighter scba tanks have built in gauges in the valves that I double check with too when the Shoebox stops at 4500 psi.  All 3 gauges should agree.   

Taso

[txrpls]

It just dawned on me, but if you never empty your tank, is it not in essence a pmv until you open it?

[Taso1000]

Mark,

Could you elaborate?  I don't understand what you are trying to say.   

You want to separate and remove the condensate before it gets to your tank.  That's what my drip legs are for.  They're water traps that work via gravity. 

If your air is not dry enough water will condense as the tank gets colder and/or has more pressure.  If you warm the tank and or decrease the pressure in the tank any condensate will evaporate into the tank air.

That's why a lot of people think they don't have a problem when they relieve the pressure form their tanks and don't see any water in the tank.  The moisture could have been in liquid form at 1000 or 2000 or 3000 or 4500 psi depending on the moisture content.

I hope that makes sense.

Taso

[txrpls]

I understand what you are saying, and I am installing a PMV on the top and a drip leg on the bottom of my filter. What I am saying in theory is that if I do not lower my tank below 3k psi and I do not open the valve until I hit say 3.3k on the compressor, the tank has by default become a PMV until I open the valve. The only time the PMV will have any real benefit is when I completely drain the tank or go below whatever I set the PMV pressure. Does that make sense?

[Taso1000]

What pressure are you going to set your pmv to?

Taso

[txrpls]

I was thinking 3k

[Taso1000]

I understand what you are saying, and I am installing a PMV on the top and a drip leg on the bottom of my filter. What I am saying in theory is that if I do not lower my tank below 3k psi and I do not open the valve until I hit say 3.3k on the compressor, the tank has by default become a PMV until I open the valve. The only time the PMV will have any real benefit is when I completely drain the tank or go below whatever I set the PMV pressure. Does that make sense?

Yes, but how are you going to remove the water that condensed out in your molecular sieve filter and fill adapter?  Once you open your cylinder you're just going to blow that water into it.  You don't want liquid water coming in contact with molecular sieve as it causes an exothermic reaction and will cause a pressure spike in your system. 

If you put the pmv right after a water trap you can remove the condensed water and everything downstream will see drier air.

My understanding is this, Putting the pmv after the molecular sieve filter exposes the media to moisture unnecessarily.  If you put it before the molecular sieve it will see less moisture.  Molecular sieve is really only beneficial to getting already dry air a little drier.  My reasoning is to not have to regenerate the molecular sieve as often. 

I could leave the 1700 psi pmv after my Alpha filter off, I think.  With the scba tank valve closed, if I were to pressurize the whole system and let the Shoebox shut off at 4500 psi I don't think opening the valve on a 3000 psi cylinder would cause the pressure to drop to a little over 3000 psi.  There may not be the same amount of dwell but the molecular sieve would be in its optimal pressure range.

If I was filling an empty tank then the second 1700 pmv would bring the molecular sieve to the optimal working pressure and I would have more dwell.

The Shoebox flow is so low that dwell may not be a huge issue.  I have the 1700 pmv already.  I don't see any downsides leaving it in place only benefits.  So it's staying in the loop.

Thanks,

Taso

[txrpls]

Yes, but how are you going to remove the water that condensed out in your molecular sieve filter and fill adapter?  Once you open your cylinder you're just going to blow that water into it.  You don't want liquid water coming in contact with molecular sieve as it causes an exothermic reaction and will cause a pressure spike in your system. 

Taso

Not sure I follow your logic. I am not using a shoebox. I am using an AV compressor that already has one filter stage.  After the first couple of blow-offs that is always dry. Now I am going to the bottom of the gold filter which has another drain valve installed. On the top is the PMV. Right now it is set to open at the default of 1800 PSI. The PMV forces the air to dwell in the sieve until it reaches pressure and then onto the closed valve on the tank. The Tank will have about 3000 PSI. My point is that the tank is acting as a PMV before I open it. If I never go below 3000psi I really didn't need the PMV. Now if I empty the tank, I'm good to go for a refill. Picture below

[Taso1000]

Not sure I follow your logic. I am not using a shoebox. I am using an AV compressor that already has one filter stage.  After the first couple of blow-offs that is always dry. Now I am going to the bottom of the gold filter which has another drain valve installed. On the top is the PMV. Right now it is set to open at the default of 1800 PSI. The PMV forces the air to dwell in the sieve until it reaches pressure and then onto the closed valve on the tank. The Tank will have about 3000 PSI. My point is that the tank is acting as a PMV before I open it. If I never go below 3000psi I really didn't need the PMV. Now if I empty the tank, I'm good to go for a refill. Picture below

Mark,

Tell me what you don't follow and I will try to explain, if I can.  You never mentioned you were using an Air Venturi compressor and I have no idea what filtering it is doing.

So I will start at the point in your system beyond your compressor and at your trap, molecular sieve and pmv.  To explain I will use the humidity percentages from the quote in my original post.

At your stated pmv setting of 1800 psi the humidity percentage of the air after the pmv will be slightly below 1%, per my estimate,  taking account that  the molecular sieve removing some moisture and the higher pmv setting above 1455 psi will also squeeze some moisture out.

So now you keep on compressing air to 3000 or 3300 psi before you open you tank valve.  This is your theoretical pmv question.  At any pressure above 1800 psi you will have water condensing out into you fill hose.  From your picture there is no way to remove this condensate.  So it will be pushed into your cylinder right?

Say you don't compress past 1800 psi and you open your 3000 psi cylinder.  Your fill hose pressure will fall to about 2800 psi or less.  That air will be as dry as you've previously made it.  Then when you turn your compressor on and complete the fill you're still filling with ~1% humid air.

If you're fine with that humidity and regenerating your molecular sieve more often then you're golden.

Or you can put the pmv set at 3000 psi before the molecular sieve and have .5% humidity going past the pmv and have the molecular sieve deal with that.  You will then be presenting the molecular sieve with half the humidity than your configuration.  It will definitely produce less than .5% humidity going into your tank and the molecular sieve will last longer before it needs to be regenerated.

I don't know how much humidity molecular sieve absorbs but its a fixed weight.  If you overwhelm it and use it up in 5 minutes what's the point in having it? 

Taso

[txrpls]

I think I may kick it up a bit, but at this point, I think I'm trying to crack a nut with a sledgehammer 

[Taso1000]

Mark,

You're going to be making drier air than the vast majority.  I am testing out ideas in my setup and presenting the results, successes and failures  , in my Shoebox thread.  My ideas and setup have changed many times as I learn more.

I like maximizing the performance of the different components.  No method is more right as long as we recognize that we need to keep water out of out airguns and cylinders.  I am very glad that I have not read or heard about a corrosion failure under normal use. 

Taso

[txrpls]

Mark,

You're going to be making drier air than the vast majority.  I am testing out ideas in my setup and presenting the results, successes and failures  , in my Shoebox thread.  My ideas and setup have changed many times as I learn more.

I like maximizing the performance of the different components.  No method is more right as long as we recognize that we need to keep water out of out airguns and cylinders.  I am very glad that I have not read or heard about a corrosion failure under normal use. 

Taso

I'm thankful that there a people like you that blaze the trail so that I don't have to think so much.  The problem I am thinking on now is the money I wasted on this: https://www.pyramydair.com/product/air-venturi-dry-air-intake-filter-for-air-venturi-4500-psi-compressor?a=7906 If I had read more I would have figured out that this is a total waste of money. Now I am thinking about how to filter the input air without another compressor.