Define "HVLP"

[Edward Oleen]

Thanks a lot, guys.

My daughter saw the post and bought me a Senco PC0968, which I can't possibly trade in, now can I?

If the purple HF gun works, well... I'll try it. What do I have to lose, aside from a few bucks and some varnish? I'd be spraying my ol'dependable: AquaZar Water-based Polyurethane, or at least try it...

[Tom M King]

Look at how much air you need to move (cfm's) for any particular gun. I doubt that little compressor will move enough air. I don't see why you couldn't return it.

[Curt Harms]

2.2 CFM @ 90 PSI is gonna be on the small side, I'm afraid. I tried my P-C PSH1 on a similar sized compressor. It would maintain the tank pressure above 60 PSI but did not shut off. If I tried to spray with that compressor for any extended time, I think it would have a short unhappy life. My larger compressor is rated 6.8 CFM @ 90 PSI. That seems adequate. I don't have the HF purple gun so don't know how much air it needs. If you have an HF store nearby you could buy one, take it home, hook it up and try it without putting any fluid in the cup, just squeeze the triggger for air flow. If the compressor isn't happy, you could return it.

[Steve Baumgartner]

Curt raises an important point: most small compressors are rated for 50% or lower duty cycle. If your compressor can't deliver enough air you will burn it out. They don't say so explicitly, but that "50%" usually means that it should not run continuously for longer than the time it takes to refill the tank from empty and then should rest (cool down) for a similar amount of time. In other words, 50% means "run 1 minute then rest 1 minute" not "run 10 minutes then rest 10 minutes"!

[Dave Cullen]

2.2 CFM @ 90 PSI is gonna be on the small side, I'm afraid. I tried my P-C PSH1 on a similar sized compressor. It would maintain the tank pressure above 60 PSI but did not shut off. If I tried to spray with that compressor for any extended time, I think it would have a short unhappy life. My larger compressor is rated 6.8 CFM @ 90 PSI. That seems adequate. I don't have the HF purple gun so don't know how much air it needs. If you have an HF store nearby you could buy one, take it home, hook it up and try it without putting any fluid in the cup, just squeeze the triggger for air flow. If the compressor isn't happy, you could return it.

The HF gun needs 6 CFM @ 40 PSI. That Senco compressor won't do it. With a 2.5 gallon tank you'll only get a few seconds of spraying before the compressor runs out of air.

[John TenEyck]

The HF gun needs 6 CFM @ 40 PSI. That Senco compressor won't do it. With a 2.5 gallon tank you'll only get a few seconds of spraying before the compressor runs out of air.

This is correct. That's a nice little compressor for running nail guns, and even spot spray repairs or something the size of a jewelry box, but it's not up to the task of running a spray gun for a large project. You need something with at least a 25 - 30 gal tank and a compressor large enough to deliver more than 6 CFM at 40 psi. If your spray requirements are modest, meaning you only want to spray once or twice a month or so, HF makes a compressor in that size range that is well regarded for light duty use.

John

[Edward Oleen]

What material do you want to spray? If it's something like shellac, lacquer, or another low viscosity product, the HF purple gun will spray beautifully with a compressor that can output about 6 CFM at 40 psi. All the other data is interesting but irrelevant. You can get a great finish for the princely sum of $29 ($9 if you buy the one on sale w/o the mini regulator, and 20% less than that if you have a coupon). Those purple guns have a 1.4 mm orifice so they can't spray anything very well above 25 seconds through a #4 Ford cup (boring but important data). If you need to spray something with a higher viscosity then you can thin it or get a gun with a larger orifice, or buy a gun with multiple needles and air caps. That's the better option if you want to have one gun that can handle a wide range of products. If that's the case, call Jeff Jewitt at Homestead Finishing. He sells several products at fair prices and can recommend a good setup based on your needs and compressor capability. Me? I have 3 cheap guns that cost about $100 total and have no complaints with the finish quality they lay down. I also have one of the HF purple guns, that I bought as a lark just to see how well it can spray. For shellac it's awesome at about 20 psi inlet pressure, and I'm sure for lacquer, too, I just won't spray it in my basement shop.

If you have a good sized compressor I see no advantage of buying a turbine unit unless portability is important. A conversion gun will cost far less and have an easier time putting down a high end finish.

John

John, are you psychic? I do want to spray polyurethane - water based Aqua Zar, to be exact, and I do want to spray small objects, not an entire room, much less a car or house. I've gotten one of the HF "purple spray guns", and my '0968 makes it spew water no problem, and that small cup empties rather rapidly. And I have no intention of doing my spraying indoors - I'm as fond of my lungs as the next guy - maybe better, since the guy who lives next door to me chain-smokes cigars.

Also, as an aside, or as more-information-you-ever-wanted-to-know, (a) "UGL" stands for "United Gilsonite Laboratories", (b) "Gilsonite" is a roof coating product that UGL no longer manufactures, since it is obsolete, (c) the viscosity of AquaZAR (at least) is reported in "Krebs Units" (KU), (d) there is no known conversion table between KU and seconds, at least known to the "chemist" that I spoke to at UGL - I cheated and called the company, (e) a "Krebs Unit" is a unit of viscosity unique to something known as a "Stormer Viscometer", (f) which is unique to the coatings industry, (g) which industry mainly uses cups with which the eflux time is measured, i.e., a Zahn cup, or a Ford cup, and finally (g) a Ford #4 cup is the most-often used in the paint industry...

SO! - whole new topic... Why does a coatings manufacturer use a measure that nobody else - including their main customers has ever heard of, much less use???

[John TenEyck]

No, not psychic for sure. It's hard to imagine that little compressor with 2.5 CFM at 90 psi can supply the HF gun continuously without the tank pressure falling off. 2.5 psi at 90 psi is around 3.75 psi at 60 psi and that gun could easily consume a lot more than that. But if it works it works, and that's a good thing but still, I wouldn't want to run that little compressor hard for very long. That's not what it was designed to do.

FYI, I spray indoors all the time. I use a temporary spray booth in my basement shop and use the 1200 CFM fan from my dust collector to vent it out a nearby window. I have no over spray nor residual odor after spraying. Of course, I wear a respirator with organics cartridge while spraying, and you should, too, even if you spray in your garage or outdoors. I only spray shellac and waterborne finishes so I'm not concerned with sparks, etc. I can spray year round in a dust free environment. You might want to give that some thought.

Krebs Units sounds very similar to how a Brookfield viscometer works; by measuring the shear resistance of a rotating disk. It's a common method of measuring viscosity for coatings that are applied by brush, doctor blades, any process where a shear element is part of the application process. Why they used that for Aqua Zar is a mystery though. But I did see in their literature that for turbine HVLP application you should thin it 5%. That suggests you should be able to spray it fine with proper thinning. And for about $6 you should buy yourself a plastic #4 Ford cup, so you can measure and adjust the viscosity of products you want to spray. Much better than guessing.

John

[Michael Weber]

With an HVLP turbine, it's more like a vacuum cleaner running in reverse.

Not only more like a vacuum cleaner but exactly like a vacuum cleaner. A vacuum motor is what is inside the box. I built my own turbine years ago from a surplus 3 stage vacuum motor and bought a Graco gun. It works great.

[Bruce Wrenn]

I have owned an Apollo 5000 since 1998. Saved enough finish material to more than pay for gun. I built my own turbine using Ametek Vac motor from Grainger. I also own several of the HF purple guns, which we use spraying rails, and doors. One is loaded with primer, and the other with top coat. It's hard to justify the time and solvent to clean a gun that you only paid $9.99 for, but I do. If looking at the HF purple one, look carefully as there are two types. One includes wrenches and brushes to take apart and clean gun, but both are the same price.

[Bill Neely]

Here's a link to a viscosity chart that included Krebs Units:

http://www.clearcoproducts.com/pdf/l...sion-Chart.pdf