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MG Midget and Sprite General - Air compressor math... any ideas

Hey guys

Ive ordered a new spray texture machine and the minume spec for opperation are 3.0 CFM@ 40 PSI

The air compressor i want to use is rated 3.5 SCFM @ 90 PSI

My intended air compressor goes to 150 psi....

Is that going to work??? Or do i need to dig out the big dog air comprssor...something i really dont want to haul over to the job site

The "S" stands for standard... Wiki makes this term rather complex fairly fast

The guys at sherwin williams couldnt say if the compressor would .work or not but thought it would.... Now that im thinking about it... Im not sure ...I guess i will find out on friday

Whats your thoughts

Prop
Prop and the Blackhole Midget

I think you're comparing apples with pears. Max. pressure is not really relevant, cause what's the time limit to get there?
In you're case you're looking for enough flow at the right pressure, and for 3.0 CFM@ 40 PSI a compressor delivering 3.5 SCFM @ 90 PSI should be more then adequate.

Standard conditions for measuring gasses and flows are to compare media under different conditions. ie. a gas flow @ 40 PSI compared to a gas flow @ 400 PSI. You will have to calculate how much each flow is at standard conditions (1040 Pa air pressure and 21 C temp for instance)
Alex G Matla

Is the compressor 3.5 CFM displacement or fee air delivery?
Dave O'Neill2

Dave, I assumed CFM stands for Cubic Feet per Minute, so free air delivery.
Alex G Matla

Yes thats correct CFM equals Cubic Feet per Minute

The specs i took off the side of my pancake compressor are 150 psi max, 1.5 hp, 6 gallon tank, 3.5 SCFM @ 90 PSI

SO its the 3.5 cfm at 90 psi, that has me thinking im to small ...if i turn the pressure down to 40 psi...im not going to have near the flow of air....if i turn the air pressure down from 90 to 40 psi... Will i still get the 3 CFM

Im thinking if keep the compressor at 90 psi... Im going to be shooting spray texture like a bullet out of a sniper rifle


I really hope im just over thinking this

Prop and the Blackhole Midget

Alex

Yes, I know that CFM is cubic feet/minute, but compressors are often quoted with displacement figures which are not achieveable in the real world. Free air delivery is what the compressor will actually produce, which is normally about 2/3 displacement.
Dave O'Neill2

Well, I think that you should turn the pressure down, that way the compressor will surely deliver what you need. It will pressurize the tank to 90 PSI, you set the regulator at 40PSI and start spraying. When the pressure in the tank drop, the compressor will start and re-pressurize the tank ---> Loop
Alex G Matla

I reckon Dave is correct, we assume about 75% of displacement. Compressors tend to be rated as displacement cfm whereas air tools are rated at actual comsumption. Mind you the rating is usually a cyclic rating and not an instantaneous one! I have always had at least 14 cfm compressor to run a 9cfm air grinder. We have two 18 cfm compressors supplying our air and occasionally both fire up!

Peter
Peter Burgess Tuning

Friends

I appericate the info.... Your talking the same thing im thinking

I think ill pull out the big dog compressor for just incase...it puts out 6 cfm at 50 psi so it will definatly work... But just a pain to haul...of coarse im sure it will snow 3 ft on the day i need it....LOL.

Prop
Prop and the Blackhole Midget

Prop. It doesn't matter what prssure you have, or what you turn it up or down to, CFM and Free Air Delivery (FAD) apply to what the pump will deliver. The small one may do it even though it has a small reciever. Get the compressor pumped up, set the pressure to what the spraytex manufacturer recommends then start spraying. It will work. If the compressor starts to lose ground on the spray gun, just stop for a minute and let it catch up, then off you go again, and so on and so on.

Bernie.
b higginson

Prop,
If you have a 'pancake' type compressor, it will not handle a spray gun well.
There is not enough volume of air for the comp. to keep up w/ the gun.
I've tried many different guns over the years and none work well w/ such a small air tank.
Phil "pull out the big dog, hoo hoo"
Phil Burke

Hey phil,

Thas what i was sorta confused by also ... The compressor i want to use is a pancake compressor... A 6 gallon, but according to the spray text litargure it says a pancake compressor is good enough

Im wonderimg if there is a sub tank in the spray text sysem that stores air and then pulls from the air compressor tank as needed
Anyway... Ill dig out the big dog compressor and have it ready on stand by if i need it.

Prop
Prop and the Blackhole Midget

Prop,
If you think of it this way - your compressor is rated to pump 3.5 CFM. If pumping into a tank this rate of flow will be available up to a tank pressure of 90 PSI. Above a back pressure of 90PSI the rate of delivery will begin to drop below the rated 3.5PSI.

Most air tools require a particular pressure (in PSI) in order to operate. This may be to operate the mechanism - as with an impact driver - or to provide the right spray pattern - as with your Artex sprayer. But as well as the pressure needed., the tool also require the specified volume of air.

If your compressor will pump 3.5CFM at 90 PSI, then it will manage to keep up with the lower demand rating of your sprayer of only 3.0CFM at the lower pressure of 40PSI.
Guy

Prop,

I would try it first. I have a 9 cfm V-twin compressor and a 50lt tank (11 gallons) with a number different tools. Tank pressure max is 110 psi.

It keeps up with my blow gun, almost with an industrial 1/2" impact gun when the nut is really stubborn, otherwise OK, totally with both spray guns (don't have the cfm) and an air saw (4 cfm), but not all with a small air drill that is rated at 4 cfm!!

Richard
Richard Wale

If you're planning to apply textured plaster/ Artex, you don't want a compressor, you want shooting! Foul stuff that should never have been invented!
Matt1275Bucks

Guys

Thank you... Im starting to feel much better about the direction this is going

Guy.... I like your explanation... That really makes scence...ill post.some pics on friday when i fire it up. And get some spraying done... Luckly, i may have landed another job of spraying pop corn right after this job

So looks like the spray texture system will pay for its self fairly fast

Fingers crossed

Prop
Prop and the Blackhole Midget

Ha....check it out...i never thought to try and google the texture system

This is the one im buying...its entry level, but considering how often and the size of work i do when doing knock down...i think its perfect... Easy and small to store, and not much to keep serviced,.and you fot to love the name graco

Prop

http://www.graco.com/Internet/T_PDB.nsf/SearchView/TexSprayRTX650
Prop and the Blackhole Midget

Hmmm,

The specs are a small bit differant but...it appears m still okay and worse case i still got the larger big dog air compressor that will easily provide the air volume and psi needed to do the job with ease


So im guessing on the pancake air compressor i can just turn the pressure down to 40 / 50 psi and still produce the 3.5 cfm of air volume needed to power the spray texture pump...even with the alt spec. Of the graco website

Prop
Prop and the Blackhole Midget

Prop,
Your not, ....
no, surely not, .........
your not going to use it to spray your whole car with truckbed liner !


Actually, it would probably be rather good for spraying underseal, though might give you a few problems with your next Brilliant Hi-White finish customer job ! LOL
Guy

ROFLMAO....HAHAHA

what a great concept... Knock down rhinno bed linner....thats got potential... After its applied... Paint the car in hunting / military camo

Somehow... That has my imagination

Prop and the Blackhole Midget

I just picked up my new spray texture system...oh is it so cool... I hope to be spraying with it in about an hour... Ill post some pics....later on this evening

Lets hope the compressor does its job,ot this day will be a long one

Prop
Prop and the Blackhole Midget

OMG...THAT IS AMAZING !!!!
I did the entire kitchen in under 2 miniutes and im as clean now as i was this morning... Just one hand has got a small amount on it... My clothes anf shoes and hair look like the did this morning


The compressor is almost to powerful...so ill have to turn it way down next time....im guessing by half to 25 psi...or realy thicken my mud up


Any way... Thanks for the hand holding... Ive got plenty of air in the compressor and then some

Ill post some photos tonight...wow it just dawned on me... Im not even tited ... Normally a kitchen this size would have taken an an hour and just killed me phsically lifting a 2 gallon hopper over my head in every screw ball postion

What a great day

Prop
Prop and the Blackhole Midget

"I did the entire kitchen...."

Images of Prop with something like a firemans' hose just pointed in through an open kitchen window.....
Guy

'Did the entire kitchen in under 2 minutes'

But will it take the next 3 days to clean it off the kitchen units/fridge/sink/washing machine/cat etc LOL.

Glad it works Prop - do Not take the head off it !

R.

richard boobier

Hahaha...yeah no kidding

I already know from past experiance to tape and plastic EVERYTHING...other wise you can spend 2 days with a sponge and hot water cleaning

THE thing is so powerful i ended up scrapping off about 1/2 and redoing it. It went on a little to heavy granted it was passiable before... But i got it looking even better now

I wish it would all dry faster so i can prime it tonight before ai leave tonight...still Its just an amazing tool


I found cutting the air pressure to 15 psi...made a huge differance

Prop
Prop and the Blackhole Midget

This thread was discussed between 02/01/2012 and 06/01/2012

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