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Lines & Fittings from Air Compressor


golem's Avatar
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10-16-10, 02:40 PM   #1  
Lines & Fittings from Air Compressor

Getting a bit frustrated in the course of tweaking my home compressors output. The fittings out of the compressor are 1/4" NPT which allows me to choose an assortment of pipe fittings up to (and through) my filter, regulator, oiler and shut-off valve that have an actual I.D. of 3/8". What seems to be defeatist is every 3/8" hose I find comes fitted with 1/4" ends that have a nice I.D of 3/8" at the threaded portion but just inside of that is a stepped down restriction of 1/4" or 17/64". Granted, this is not as restrictive as if using a full length 1/4" hose but it still is imposing an appreciable loss in CFM.

It's never been a concern of mine before as compressors at work were always commercial sized and plumbed with the ability to deliver more than enough punch but my home compressor is considerably meeker and I'd like to optimize as much as possible. Goodyear hoses have been my choice for many years but I'm open to suggestions as to a brand providing free breathing. Maybe even insight on replacement hose fittings that are nonrestrictive. I'd like to stick with 3/8" hose and not migrate to 1/2" if at all possible.

Thanks!

 
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10-16-10, 03:14 PM   #2  
I've always just gone up a fitting size. If you think about it no matter what you do a 3/8" fitting still needs room for the threads and body of the fitting leaving you with something much less than 3/8". There are some high flow aerospace fittings available but the cost is crazy. I've always found that it is just cheaper and easier to upsize the fittings.

 
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10-16-10, 04:06 PM   #3  
Posted By: Pilot Dane If you think about it no matter what you do a 3/8" fitting still needs room for the threads and body of the fitting leaving you with something much less than 3/8".
Thanks for the reply!

I whole heartedly understand your line of thinking but we may be mixing NPT sizing with SAE. A 1/4" NPT fitting actually has an O.D. over 1/2" (.540"). All my 1/4" NPT brass piping has an I.D. of 3/8" (or nearly so). I'm just befuddled as to why they sell 3/8" hose and find the need to restrict it on both ends down to as little a 1/4" I.D.. Take a close look at your 3/8" air hose factory ends, most likely it will be 1/4" NPT ends and sized as described above, looks great until you inspect closely a bit further inside the fitting. If not restricted, please do give me the model number of that hose!

 
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10-16-10, 07:52 PM   #4  
I've switched over to flexeel hoses about 10 years ago. I have makita hoses that are just rotting away in my garage on a shelf.


Last edited by cheese; 10-16-10 at 09:47 PM.
 
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10-16-10, 09:50 PM   #5  
I think the problem is the hose barb that has to fit inside the smaller diameter hose that is on the inside of the air hose. The hose is thick, with 2 walls and a braid between them. Then the barb has to fit inside that and still have enough metal to be strong. Every one I've seen is like this.


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10-18-10, 10:22 AM   #6  
Thanks for the replies guys!

Doing a bit more research I am finding a few references to "full flow" fittings, connectors, and hose assemblies. The drawbacks to these seem to be a definite lack of retailers carrying the items and the fact that all the "full flow" factory assembled hoses appear to be of the coiled type.

I probably am making a mountain out of a mole hill in regards to this subject. It just peaked my interest when I saw the CFM drop graphs -- @ 90PSI/15CFM & 20ft length a 1/4" hose loses about 20PSI while the 3/8" is less than 3PSI. Since I'd like to stretch my hose lengths from 35ft to 50ft.-75ft. (on occasion) I'm doing my best to curb the "nearly" inevitable compressor upgrade.

Regarding Flexeel hoses -- Do they truly remain flexible between 25-55 degrees? Is the overall flexibility on par with rubber? They also seem to be very thin walled considering the O.D., I like that as long as they hold up to the typical abuse a shop hose sees.

Cheers!

 
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