means the 3/8" hose

by RAHUL
(DELHI)

hose is 3/8" what meand the 3/8"


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Bill says...

Rahul, please read the pages on this site to do with air hose and air tube, all linked from the site map.

I have taken pains to explain as fully as I can what the dimensions of both mean, on those pages.

Cheers,

Bill

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3/8" NPT couplings to 3/8" rubber air hose

by Robert
(Apopka, Florida)

Hi I recently purchased a sandblasting cabinet and pressure pot. After setting it all up and plumbing in all my air lines I attempted to sandblast an axle. My pressure was great for about oh 3 seconds and then there was substanial drop. I contacted the Company that maunfactured the Cabinet and I was told on two seperate calls that every fitting leading to this cabinet and pressure pot has to be larger than than 1/4". So here is what I have to give you an idea. 80 gallon compressor rated @ 23 CFM @ 90 or 100psi, cant remember which. From the compressor air outlet on the tank is a 3/4" quarter turn valve. This valve shuts off the air supply to the shop line. From the air out side of the valve I reduced it to 1/4" with a 3/4" to 1/4" reducer. Then I put a 1/4" galv. nipple due to the filter/regulator having 1/4" NPT in/out ports and mounted the filter regulator. From the air-out side of the filter I have another 1/4" NPT galv nipple to a female coupling. From there I have a 4' or so piece of 3/8" rubber air line with male connectors on each end that connects to another female coupling on the wall which feeds a 3/4" hard air line. This line dead ends into a 90 degree fitting with another 1/4" npt female coupling. This dead end coupling is where I have my Sandblasting cabinet and pressure pot set up. The total length of line from the compressor to the cabinet is about 20 or so feet. Just to let you know the line Tees off about 3' from the compressor and feeds the inside of my shop which is 16'x 12'. There are 3 stations with hanging coil line inside the shop with 1/4" couplings. And yes some of these cheap couplings do leak air when nothing is connected to them. Now back to the original issue. So to comply with the maufacturers recommendations this is what I was going to do and want to know if I am doing the right thing. I removed the reducer from the 1/4 turn valve and replaced it with a 3/4" - 3/8" reducer with a 3/8 nipple into my new filter that has 1/2" npt inlet and oulet. I used 1/2" to 3/8" reducers on each side of the inlet and outlet to accept the 3/8" nipples. Now I am at the point where I need to get 3/8" couplings. I seen industrial type and mechanic type with MPT and FPT, I do not know the difference between the four. Once I fiqure which type to use and what MPT and FPT mean I plan to put these from the filter outlet to the hardline using a 4' or so 3/8" rubber "whip" hose and then at the end of the line connection for the blasting equipment only. All other conection will be left 1/4" "std" couplings. And I say "std" loosely but hopefully I explaiined it well enough for you to get a mental picture. My thought is that by increasing all the fittings from the 1/4" npt to 3/8"npt that will directly feed the blasting equipment I will be supplying the blasting equipment with the air it needs. Sorry to be so long winded but it can get costly troubleshooting these issues... Thanks alot.

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Bill says...

Robert, excellent description. Thanks.

Visit "Pressure Drop In Compressed Air Systems" linked from the site map page. You need to read this to get a better idea as to how pipe diameter, length and the addition of fittings all combine to reduce effective compressed air flow and pressure at the end.

In supplying equipment from the compressor tank, bigger lines are always best.

After you have read the page of info, if you have a specific question, please just ask.

You might also want to read the pages on couplers, one on connectors and another on fittings, all linked from the site map too.

Cheers,

Bill

Comments for 3/8" NPT couplings to 3/8" rubber air hose

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Nov 14, 2011
NPT size
by: Robert

Hi Bill, thanks for posting my question. First, I wanted to say I read your post on NPT and I had wondered why a fitting was called 1/4" NPT when in fact neither the OD or ID was even close to 1/4". When I measured the ID and found it to be larger than 1/4" I began to wownder if the customer service people I spoke with heard me say 1/4" NPT air couplings/fittings and automatically said "nope, wont work, all fittings have to be greater than 1/4" not knowing that the actual ID of the couplings were greater than 1/4". I guess I will give them a call again and make sure I cover that and get a answer before buying all the 3/8" air coupling/fittings. Even though Im sure the larger volume of air could never hurt, right??

________________

Larger volume never hurts in terms of compressed air supply, and chart showing the actual sizes of NPT is found on this site.


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Downside to too short a discharge hose?

by Chris
(Southern California)

Is there any downside to making the discharge hose very short? I mean about 8 inches total.
I'm combining parts from two compressors and the outlet ends about 8 inches from the check valve.
It's a 2 stage 80 gallon, Manchester tank with Generic compressor.
Thanks
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Bill says...

Hi Chris.

To my mind the discharge hose is the one that runs from the compressor tank to my air tools or air using appliances.

If that is what you are talking about, I'm not quite sure why that would be an issue.

If this isn't it, please provide more details as a comment here.

Thanks,

Bill

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Nov 13, 2011
Thanks
by: Chris

This unit is for a home shop, going to be 80 gallon tank, mostly air tools, some die grinder.
So not high tank use. Going with the 8 inch length with 5/8 copper line.
Thank you for the help.

Nov 07, 2011
common definiton of discharge hose
by: Chris

Still trying to get this to post.
By Discharge hose I mean the hose/tube from the compressor to the check valve.
In this case it is 8 inches or less.
The air from the compressor is about 200 plus F degrees.
Downside?
Do I need to run the hose much longer? Which would necessitate removing the Teflon/braided and putting some copper so I could route it.
Thanks

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There is no downside to running the air from the pump to the tank over a longer hose. Your compressed air will cool in the line. That's fine.

There really isn't a downside to a shorter hose from pump to tank either. They all run too hot to touch, and that's why they are metal or metal braid.

The issue of hot air is that it contains much more water vapor than cool, and that water vapor will condense as it cools. Where, in your system, will that happen?

If your compressor is high demand, and hot air is flowing out into your lines, the water will condense there. If there is sufficient dwell time in the tank the water will condense there.

See all pages on this site relating to compressor water for info on how it's caused, and how to treat it.

It were my compressor, I would not worry about the short discharge hose. If you want to lengthen it with copper, go ahead. I wouldn't bother.


Nov 07, 2011
common definiton of discharge hose
by: Chris

The discharge hose is the hose between the compressor and tank.
The one from the compressor discharge to the check valve, into the tank.
Only thing I've ever seen it called.

I'm concerned about length because it is very hot in use. I've seen them routed through water tanks, etc.
On this compressor there is going to be only 8 inches between the outlet from the compressor and the check valve.

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Compressor lets all air out at once?

by Glen
(Cynthiana, Ky)

My compressor builds up air and holds it in the tank. When I hook up a tool or air chuch all the pressure comes out of the tank at once. What is going on?

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Bill says...

Good question, Glen.

Please give me more details.

From what I read, your compressor builds pressure normally, the air stays in the tank until you connect an air line to the discharge coupler, is that right?

When you do connect the air line, where is the air coming out of?

Cheers,

Bill

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Level of compressor noise - how to resolve

by Michael
(Kent, UK)


I have ABAC 3HP 50 litre tank air compressor. The level of noise is pretty high.

Could you please advice how insulate compressor to reduce level of noise dramatically.

Compressor installed in the garage with neighbours property above of my garage.

Or what kind of quiet compressor would you suggest with the same specification.
Thank you
Michael

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Bill says...

Hi Michael.

It seems axiomatic that, the lower the cost of the air compressor, the higher is the sound volume from it as the compressor operates.

On the location page linked from the site map, I have written about isolating the compressor to keep it quiet.

That costs money, of course. Buying a quiet air compressor costs more than a loud one does, as well.

You have to determine what sound proofing level you need for your air compressor based on its location, and compare the cost of that process to simply buying a new air compressor that runs quietly.

As to manufacturers of quiet air compressors, there are many in the world. One that comes to mind is Jun-Air, and I suspect they are available to you near Kent.

Contact them, find out their local distributor, and ask how much a 3 HP compressor of theirs will be. That will give you a benchmark against which you can compare the cost of building soundproofing yourself.

I know which way I would go. :-)

Cheers to you,

Bill

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conversion kit - converting a Freon tank

by Karl Frey
(Melrose, MA, USA)

Many years ago I purchased a kit for converting a Freon tank to an emergency storage tank for tire air. It contained a fitting for filling, one for filling a tire, a gauge and a shut-off valve to keep the air in. Where can I get same.

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Bill says...

Karl, I know of no such kit, though another reader may, and I invite them to post a comment here if they can help.

Pretty much all of the parts you would need to put one together would be available from a good plumbing shop, or better than that, an industrial supplier that sells air cylinders and air valves. These folks often can put together standard air components for you.

The following company could probably help you out, particularly if they were nearby.

Action Automation & Controls, Inc.
10 Larsen Way
PO Box 2540
North Attleboro, MA 02763
Toll Free: 1-800-783-5161
Phone: 508-699-7411
Fax: 508-699-2060

Cheers,

Bill

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