Air pressure drop

[gtome]

Well...its closing in on a new year, and I didnt think when i took the job i have it would last this long. But...looks like it could go on for a couple more years. So..... I would like to get things a little more professional at the shop im at. One of the first things i would like to address, is the problems I have been having with air. I have no idea what the compressor it, its been outside a long time, and there are no markings on it. That being said, it is huge and providing air has never been a problem. The problem I do have is that the air pressure seems to change a lot, and that really makes painting tough. So what is happening is for instance when i connect my gun, and set it at lets just say 35psi at the gun gauge. When i pull the trigger, the pressure may then read more like 30 psi. Anyone know what would cause this? I was guessing small hose and or fittings.....but I dont really know. The air is piped around via PVC, and appears to be at least 1/2" so the flow to the regulator should be plenty. But after...im not real sure. I know the hose is pretty small. When I had my own shop, I had big lines and fitting3, and never had a problem, but who knows. Anyway....to recap..... It is a massive compressor and tank, 1/2" (at least) PVC piped all around the shop, then to a regulator (Sharpe) then we have a filter that i attach a hose to when I paint that looks like it holds a roll of toilet paper, then the 3/8" (guessing) hose. Also, i have the same pressure drop when i dont have the filter connected....so I dont think it is the problem. What are your thoughts?

[Bob K]

First thing that comes to mind is that you should set your gun pressure with the trigger pulled, and the second thing I see is that it sounds like your wall regulator is set to low. I would think you need more than 45 pounds from the wall regulator. I don’t know that for sure because I don’t use one, I regulate my gun straight off tank pressure which for me is 140.

If you have the wall regulator set for 35 pounds and then put a lot of small diameter hose down stream you may be maxed out at something like 15 or 20 pounds at the business end when you start using air.

Post a picture of the compressor and someone may be able to identify it for you. Handy thing to know if you ever need parts.


Bob K

[gtome]

Will do, but I keep the pressure at about 160psi on the regulator. I just am worried about setting it with the trigger pulled, then when I release and pull it again having a spike. Also if I need to do a part trigger spray at some point in the job, then the pressure is higher.

[Bob K]

I don’t know what you are talking about when you say a part trigger spray. The air is already open and the pressure spike gone by the time the trigger starts pulling the needle open. You can’t do a part trigger spray; unless you use some kind of gun I am not familiar with. The air always comes before the paint otherwise you would get paint dripping out of the tip before air was going to the fan.

Try setting your pressure with the trigger pulled. That is the proper way to do it. Don’t over think it. Just try it. It will work.

Bob K

[Len]

Will do, but I keep the pressure at about 160psi on the regulator. I just am worried about setting it with the trigger pulled, then when I release and pull it again having a spike. Also if I need to do a part trigger spray at some point in the job, then the pressure is higher.

160 PSI in the hose is too high, I'd keep it about 70 or 80 PSI with 50' of hose or less. If you have any questions about setting the pressure at the gun check the Spray Gun Adjustments Video at the top of the General Discussion forum.

[gtome]

Well....part trigger spray i meant that if I only pull the trigger say half way....paint will come out, but not fully, and the pressure is higher than if I pull the trigger all the way. Make sense? And I do set it with the trigger pulled, but when i let off the trigger, the pressure may go up to lets just say 45psi. Then when i pull the trigger again, for a split second, the spray will have that 45psi til it drops to the 30 psi or whatever. Maybe its not a big deal?? Just never had that happen before? Plus it seems like it wont hold that pressure very well. Like if the compressor is pumping up, the pressure wants to increase. I would like it if i could set it and it would stay there.
I will try to drop the hose pressure down and see what that does. Maybe it will be more stable that way.

[Ragdol]

Bob K. is correct in that when you pull the trigger just for air, the air is full on no matter how far you pull back on the paint. The wall reg. should be set at 80# to 85#, pull the trigger and set the reg. on the gun for the pressure your gun requires for atomization. I'm just guessing, but you do have a good regulator on the gun, Sharpe or equivilent. The kind with the lever & guage will give you varying pressure, it only restricts the air, not regulates it. I was told when learning to use HVLP guns that you pull air on for a second to equalize the air pressure before painting. I'm not the world greatest painter, but this works for me, & I get a lot of complements on my paint jobs. Larry

[gtome]

Yeah after watching Lens set up vid....it looks like that is just how the air works? Never noticed that before when i was painting. I also try to only release the trigger enough to stop the flow of paint, but not the air, to keep that spike from happening. Looks like that was a good teaching aid. I will try cranking down the pressure at the regulatore on the next job. And yeah i have 3 gun regulators and they are all Sharpe. Thats all the local place sold. My Sata has a digital gauge too, but from the time i got it the gauge stayed on all the time and the battery runs dead. I cant work without it and im not willing to send it in for repairs. I am going to be ordering a Plus gun from Len, then maybe see about getting the Sata fixed.

[twfsa]

Let us know how you like the Plus!

[Len]

Yeah after watching Lens set up vid....it looks like that is just how the air works? Never noticed that before when i was painting. I also try to only release the trigger enough to stop the flow of paint, but not the air, to keep that spike from happening. Looks like that was a good teaching aid. I will try cranking down the pressure at the regulatore on the next job. And yeah i have 3 gun regulators and they are all Sharpe. Thats all the local place sold. My Sata has a digital gauge too, but from the time i got it the gauge stayed on all the time and the battery runs dead. I cant work without it and im not willing to send it in for repairs. I am going to be ordering a Plus gun from Len, then maybe see about getting the Sata fixed.

If you want a digital gauge that works well you should try the DeVilbiss gauge shown below. It works like other digital gauges but only comes on when you hit the button. I've been using one for about a year and it works great and doesn't cost a fortune.


http://autobodystore.net/Merchant2/graphics/00000001/devhav555.jpg
LINK (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=DEVHAV555&Category_Code=1D)

[gtome]

Haha!! Already been eyeballing that Len. Im gunna need to get my stuff ordered. My detail gun is such crap i can barely use it anymore. Im super tired of cleaning my gun all the time too. I need a cup system. But now after reading about it, I cant decide whether I want the "Plus" gun or to try a Sagola.:goof: