Air Pressure Constantly Changing

M

mitch_04

Learnin'
I'm struggling a little here. I have digital gauges on my spray guns, and set my pressure before I start spraying. During the spraying, my pressure drops and messes with my coat. I currently have a 60 gallon 5 HP compressor with 2 inline Aquacheck filters and Milton coalescent filters. I am not regulated at the wall currently, straight compressor pressure. I had previously been regulated in a different building, left it at 130 PSI, and had the same issue.

Any help?
 
try putting the regulator on the wall and run the hose straight to the gun to see if it changes. They all recommend that wall regulator over the gun.
 
You have to have a real regulator to have well regulated air pressure. Most controls at the spray gun are not real regulators, they function like a metered orifice and will deliver different cfm depending in supply pressure. So, as stated above, you need to run the spray gun supply air through hopefully a nice big regulator set for something higher than you spray at, but lower than the compressor will ever sag down to, then you will have constant air pressure that can be fine tuned at the gun with a regular air valve. I'm a little worried that you might be using more than the compressor can deliver.
 
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I don't think you have a big enough compressor, and 60 gallons of air storage isn't a lot especially if the compressor can't keep up. I don't know what gun your using but my old sata 2000 hvlp used around 16 cfm which I doubt very many 5 hp compressors could keep up with. you could ad another tank inline for additional volume which would allow you to spray longer before your pressure dropped. I'm a one man shop and I have 7.5hp compressor on 80 gallon tank with second 80 gallon tank for extra volume. Years ago all I had was 5hp compressor on a 80 gallon tank, it did fine for small collision jobs, but on all overs the compressor couldn't keep up and I would loose pressure before I could get all the way around.
 
If you can have long flash times, adding a large air tank can crutch a too-small compressor, giving you more air for a longer time, but you have to make it up by waiting longer for the pump to repressurize the larger volume.
 
Your wall regulator was probably malfunctioning or set incorrectly. The regulator must be set at a pressure below the compressor cut-in pressure, and the compressor must be able to handle the CFM being used at the time, or pressure fluctuations will occur. For instance, if your cut-in pressure is 100 psi and your cut-out is 125 psi, your regulator should be set no higher than 90 psi. Then you will have 90 psi unless the compressor can't keep up with demand.
 
i run the wall wide reg open and regulate at the gun . test by setting the gun and running wide open until comp kicks in. this will tell you what you have. many 5 hp compressors today are really 3 hp with dual starters.
 
Shine is so right, never go by HP., go by CFM.
If you want to know HP comparisons check the motor plate
for how many amps the motor is rated for, that is the best way to
compare motors, they vary a lot.

I have Eaton 5 HP that puts out a lot more CFM than
my friends 7.5 HP Home Depot compressor.
 
My compressor kicks off around 160 and I believe it was a quality unit, but I don't know the amperage rating offhand. It says the motor has a 30 amp breaker on it in the link I had, 15 cfm @ 175. I just can't imagine that when I have 100 gallons of air storage and I'm painting something that small that it can't keep up, but maybe I'm wrong.

Also, LPH400 gun. I've been meaning to get a DAD-500 for painting, maybe I'll have to push that up the list a little.
 
this is a true 5hp motor . notice the loop on top to lift it with. that is a 7 in pulley . they use to have to stamp SPL for hp ratings now they are stamping 5hp on a 3hp motor. so when you see a motor half the size of your pump dont be fooled into believing it is a 5 hp.
 

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but you'll end up at 20+ using around 11 cfm :)

the problem is not the cfm supplied by the compressor it is the delivery to the gun. small fittings and hose can really kill it. that is the reason behind 100+ at the wall .
 
Frustrating. I'll have to mess with it sometime when I'm not painting, just hook up the gun and spray some air, see what happens. I have 3/4" piping up to my Aquacheck filter, then 3/8" hose from there. Only 2 fittings to pass through.
 
I had forgot about it, but years ago at a shop I worked at we started having pressure fluctuating problems in the booth that we chased for a while, finally ended up putting a new hose in and fixed it. all we could figure was the old hose must of had a bad spot and was trying to collapse inside.
 
You need to step up in the upgrade department. If you want to do anything worth doing and putting all your effort and time into it then upgrade the air compressor. Also it really dosen't matter how big your airline is and how many filters you have in the line you will have issues. Each filter will take away some level of PSI the more you have in line the more you take away. Also you will always have a very good chance of still having crap in your air whether it is water or oil. You must cool the air temp down first and foremost. Either with an aftercooler or refrigerated air dryer or both. Each that can handle the temp, CFM and pressure no ifs and or buts.

I have both an after cooler (with fan) and refrigerated air dryer (Hankison HIT35) along with an in line filter and auto drain for the compressor tank.

The more you have for reserve such as a separate tank will tax the hell out of your compressor making it run far longer then it is designed for causing it to get too hot and pass more oil then it would if you just kept it the way you bought it.

If you don't have the coolers and you run the crap out of your compressor all the filters in line will only do so much because the air is still warm and will condense in the hose as it cools and POW now you have water in your work. Don't think so run it hard and use a blow gun on a panel and see if you can see a moist spot on the panel.
 
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dmattingly said:
I don't think you have a big enough compressor, and 60 gallons of air storage isn't a lot especially if the compressor can't keep up. I don't know what gun your using but my old sata 2000 hvlp used around 16 cfm which I doubt very many 5 hp compressors could keep up with. you could ad another tank inline for additional volume which would allow you to spray longer before your pressure dropped. I'm a one man shop and I have 7.5hp compressor on 80 gallon tank with second 80 gallon tank for extra volume. Years ago all I had was 5hp compressor on a 80 gallon tank, it did fine for small collision jobs, but on all overs the compressor couldn't keep up and I would loose pressure before I could get all the way around.
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A 5hp with 80 gallon tank is fine so long as you have a good compressor like my Champion Advantage series if you have a crapped CH from Tractor supply or Sears Craftsman then yeah you should have saved your money and bought a real compressor. Buy once Cry once.
 
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