Sizing NPT fittings enhance Airflow

I m finally pluming my shop for air distribution. This site has a lot of great information and if your book is half as good as the web site, it will be great. (I plan on buying a copy soon). Thank you!

My setup:

I have a big 2-stage 80 gallon, 4hp, 175 PSI, 12.5 CFM compressor. It has a 3/8 outlet port that I expand immediately (after a ball valve) to 1 inch copper pipe that is sloped 1″ to 10′ which rings my shop.
Down T’s to drains at low points. Up T’s reduce the copper size to 1/2 inch and then to a “return bend” (1/2″ u-shaped copper pipe) to down pipes and quick-connects. Then on to various tools for wood and metal work (including milling machines that will use compressed-air vacuum tables for hold-down).
My questions are with respect to the quick connect fittings. The last 2 inches at the end of the copper and another 2 inches entering the tools.

My local hardware store sells “Type M” NPT fittings in 1/4 inch and “Type-T” NPT fittings in 3/8 inch. It is my understanding the type T fittings are Automotive and the Type M are industrial.

Most tools are 1/4 NPT and some of my tools state that quick-connect fittings can reduce air flow. So how do I choose coupling fittings to “standardize” my shop on so as to not starve any of my tools that need the greater air flow.

Bill answers…

Hello Chuck, nice to hear from you. And yes…the ebook is better!

From the sounds of it, you are doing a bang up job in plumbing your compressed air.

You mention that the discharge on your compressor is a 3/8″ outlet port. Is it a 3/8″ coupler…what exactly? To me, there’s your primary restriction.

Even though you increase the pipe size after that 3/8″ outlet with your 1″ air main, essentially what that air main becomes is a sort of compressed air receiver. Though, if any of your applications draws more air than can come out of the 3/8″ discharge from the compressor though, that you have a 1″ main is almost immaterial, except for the additional storage of  pre-compressed air.

Having said that, a 3/8″ compressed air line flows a lot of air, so that may not be a problem.

You write, “My local hardware store sells “Type M” NPT fittings in 1/4 inch and “Type-T” NPT fittings in 3/8 inch. It is my understanding the type T fittings are Automotive and the Type M are industrial.”

Hmmm, I hadn’t heard that before. My understanding is the “M” type connectors fit “M” type couplers, the same with “T” type couplers and connectors, and the “P” type, the Aro type, the Milton type, the Swagelock type etc. etc.

For most of us, if it is an “industrial” versus “automotive” type fitting is less important that “does the connector fit the coupler?”

As to the flow restriction of couplers and connectors, many are “full flow” models, meaning that the inner diameter is the full size of the hose. Therefore, a ¼” hose (with an I.D. of ¼”) will be the same I.D. as that ¼” connector or coupler, and therefore, there should not be a restriction on the flow of air through them.

If in doubt, visit your local industrial supplier that supplies industry with their fittings, cylinders and valves. Ask them for their brand that are full flow, and standardize your shop and fitting kits with this brand. Then you won’t have a problem.

Got a question about compressed air? Just ask.

The difference between a Quilt Block and a 5/3 air valve?

Heck? I don’t have a clue! What’s a quilt block? 

I do know that my wife is into stained glass, and recently she’s added a line of Quilt Blocks to the stained glass work she does.

So, if you don’t mind, if you know someone that’s into quilting, could you send them this post so they can check out Sue’s Stained Glass Quilt Blocks, please?

Thanks, I appreciate it.

Bill

Coalescent Filter for Air Brush Compressor

Hello,

Basically, I have a airbrush compressor setup, built with an old fridge compressor and a modified propane tank. It’s all well and good except for an oil discharge problem.

A coalescent filter should solve that problem, but the only suitable model I found in a nearby shop is noted as “NOT suitable for flows less than 3.5 SCFM”.

I wondered what problems this might pose, since the airbrush barely demands 0,5  SCFM ?

I also wondered if a 0,01 micron filter would be overkill, or if it would be even more suitable with regards to the low air flow ?
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Bill answers…

Hello Pierre-Lucas;

Congrats on building your own air brush compressor. Not something that I’d undertake,  for sure.

You do need a coalescent filter to remove oil if oil is getting into the downstream air flow.

0.01 micron is the norm for coalescent filters that “coalesce” oil through adsorption.

If  Fairchild says their coalescent filter requires more than 3.5 CFM of compressed air flow, then it will not work in your application.

One company that does a good job with air preparation and, in particular, coalescent type filters is Norgren.

I see you are in Montreal. Norgren’s local distributor is Cowper Inc, located in Lachine, and their number is  (514)637-6746. Talk to them about getting the right coalescent filter for your application.

Cheers,

Bill

P.S. have you got a question about using air compressors or compressed air?

Baking Soda Blast…

It’s fairly common knowledge that compressed air is used to “blast” particles at an object to be cleaned.

There’s traditional blast media such a shells, sand, glass, I’ve written about dry ice blasting here, and here’s a new one that’s environmentall y friendly….blasting with backing soda.

Here’s the article.

Two compressors popping breakers…

I HAVE 2 AIR COMPRESSORS AND WHEN I START THEM UP AFTER 10 SECONDS THE CIRCUIT BREAKER KICKS OFF, ONE COMPRESSOR IS 17.8 AMPS, THE OTHER IS A 16 AMP,THEY ARE CONNECTED TO A 20 AMP CIRCUIT BREAKER AND I ONLY TRY TO RUN ONE AT A TIME.THANK YOU

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Bill answers…

I guess the question is, why does the breaker pop…huh? 

The breaker will pop when something in the circuit draws more amperage than the breaker can handle.

If the breaker didn’t pop, the increased amperage draw would create heat somewhere in the circuit, and that heat would ultimately result in a fire. So that the breaker is popping is a good thing.

Seems odd to me that you have the same symptom with two compressors.

If it were just one, I would ask you what components in the circuit are electrically driven, and tell you that one or more of them are failing.  The components could be the pressure switch, or the electrical motor, for sure.

That it’s both would suggest to me that you’ve got some sort of electrical fault in the power delivery system.

If it’s not either of the compressors then it’s got to be something between the panel breaker and the outlet box, or a fault in the outlet box itself.

Are you plugging these compressors into the same outlet?

Try plugging the compressors into a different outlet, preferably one that’s connected to a different breaker. What happens then?

If the new breaker pops too, then it’s got to be a fault on the compressors, so you will have to start examining what electrical component on both compressors has failed, or is in the process of failing.

That the breaker pops after 10 seconds would suggest to me that it’s a motor issue. Again, very odd that the same thing would happen with two different compressors.

As an electric motor runs, it heats up. Maybe it’s developing a short when it’s hot, or the load increases to the point that the amperage draw to run the motor against the increasing load is exceeding the breaker capacity.

One other thing; as the tank pressure builds, the motor has to work harder to drive the compressor head and continue to compress air against the pressure that’s already built in the tank. A weak or failing motor may not be able to continue working efficiently against that load, the motor would slow, and get very hot, to the point that it might shut off on thermal overload or create enough heat to short the motor.

If there any electrical folks out there that would like to add a comment to this, it would be appreciated.

Add a compressor for more air flow?

I’ve written about this subject a few times. Another inquiry has driven me to write more about it.

If you have a compressor that’s unable to deliver the compressed air flow you need at the pressure you want, then adding another small compressor is an alternative to buying a single, new bigger unit.

Here’s more info.

New pages on compressed air couplers and connectors

For those interested, I’ve just posted a couple of pages on compressed air couplers and will be uploading some on compressed air connectors shortly.

This is the page on compressed air couplers.

Tire / compressed air woes

So I get my new to me compressor all rebuilt and working again. I turn it on and let it pressurize to it’s cutoff pressure. I turn the regulator up to about 70 psi, then try to inflate my car tire that is low. I put the tire chuck on the hose, push the chuck onto the tire stem vavle and…nothing! No hiss of air going into the tire or anything. The tire pressure is still low and I can’t figure out why my 25 gallon, 125psi,  7CFM rated compressor can’t inflate a tire to 32 psi?

Any ideas?

Bill answers…

Hi L.

The piece of information that’s missing is…what is the cut-out pressure of your compressor?

Is there not a gage on the tank to show pressure inside it? What does that say?

Obviously, if there’s not high enough pressure in the tank, it can’t blow up a tire to greater pressure.

But I’m going to assume that your pressure in your compressor tank is above the 32 PSI required for your tire.

If you have the pressure in the compressor tank, and since high pressure WILL ALWAYS flow to a low pressure area, your problem must be in the air delivery system.

Toggle the stem tire valve by pushing in the center of it. Does air come out? If it comes out, then it’s a good guess that air can get in.

If the tire valve works then the problem has to be in the valve on your air line (the one that connects to the tire valve), a blockage in the air line itself, a blockage in the connector that inserts into the coupler on the discharge line of the compressor, or the coupler on the compressor itself. It can’t be anything else.

Take a small blunt object and insert it very carefully into the center of the coupler of the air discharge connection on the compressor. Does air escape when you depress the inside center of the coupler? If not, it may be a problem with the “checking mechanism” of this coupler.

If so, then it’s working. If it’s working and the valve on the tire is working, and you’ve got enough pressure in your compressor tank, then the problem has to be in the hose between the two.

Good luck with this. Maybe let us know how it turns out?

Cheers,

Bill

Air / Water Separator for Compressor

I am looking for an air/water seperator for my air compressor. It needs to maintain 120-130psi. I only run 3 main air lines off the compressor. 100gal compressor. can you help me?

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Bill answers…

A few things you should consider.

An air/water separator, also known as an air line filter, doesn’t maintain pressure. It’s purpose is to use cyclonic action and a filter element to strip free water (liquid water) and particulates from the compressed air stream. That’s it.

Most filters will have a delta P (pressure drop) across them of around 5 PSI. So, if you have an upstream pressure of 120 PSI, you’ll get about 115 PSI out the other side of the filter. This is caused by the filter element and filter components restricting the air flow.

As the element gets plugged up, your pressure drop will increase, eventually to the point where you won’t get enough air through the filter to do work.

Some manufacturers of compressed air filters offer an indicator of some sort on their filter housings to show when the element is getting plugged. Having a pressure gage upstream, and another downstream of the air filter would do the same thing…tell you when the pressure drop is increasing, thus indicating that the element is getting plugged.

You indicate that you have a 100 gallon compressor. What you have is a 100 gallon tank. Except for reservoir capacity, the tank size tells me nothing about the compressor. You need to identify the horsepower of the motor. That can be converted (approximately) into CFM, and it’s the CFM number you need to ensure that a new filter has the capacity for your air line.

All of the 3 air lines emanating from your compressor discharge outlet should be supplied through a main compressed air filter. Then, you will want to put another (smaller) air filter at the point of use for each air line. That will strip more free water (it condenses in the air lines) and any additional particulate from the compressed air before it gets to your tools or applications.

While it’s not foolproof, particularly in high demand applications, since most general purpose filters provide around a 25-40 micron element, you can roughly size the filter by getting them with the port size being the same size as the supply line. For example, a 3/4″ pipe air line should be fitted with a 3/4″ NPT ported filter…and so on.

Much more information about air filters is here.

Cheers,

Bill

Why does my compressor keep running?

Boy, I’ve had a significant number of inquiries to the ASK Page of my compressed air information website, asking what might be the cause of their compressor not shutting off.

They know that there is a high pressure cut-off which is supposed to shut off the compressor motor when the pressure in the tank reaches that pressure level. They know there is a problem because their PRV (pressure relief valve) opens and starts to blow down the overpressure in their tank.

Number one: This is a very dangerous situation.

If your compressor’s PRV is blowing, don’t use the compressor until you get it fixed. Heaven forbid that the PRV failed, but if it did, your home compressor has now become very scar with the potential for fatal results.

Number two: If the compressor doesn’t shut off at the high pressure setting, the problem is likely that the pressure switch has failed. Don’t use the compressor until you get this replaced and the compressor shuts off at the right pressure.

Be careful! Overpressurized vessels can rupture with very unhappy results. Get the pressure switch changed out fast.