I just got a my own compressor and planning how I want to setup my fill station and came across some stuff today about thread types when searching for fittings on mcmaster so I wanted to see what kind of fittings/thread types everyone else uses or recommends. most of the high pressure stainless fittings on mcmaster have NPTF threads which are still NPT threads but they are held to a higher tolorence and are for a dryseal fit where normal NPT threads have a little wider tolorence and should be used with teflon tape or similar sealant. the main reason im asking is because im a machinist and plan to make some of my own manifold blocks and parts for my system but it looks like making / inspecting the NPTF threads is going to be a little bit harder but not sure if just regular NPT threads seal well under high pressure with teflon tape.
NPT OR NPTF threads for your high pressure fittings
- Thread starter Gunner52
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Nobody tries to dryseal compressor fittings. Teflon tape with "normal" NPT fittings are the norm.
^that. All fittings on my setup are standard NPT (taped).
+1 for standard threads and tape - and you don't even need the tape a lot of the time.
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rcontrera
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I don't think you will find anyone in the compressor biz using NPTF (National Pipe Thread Fuel) connections. They are designed for connections where the fluid being transferred is caustic to pipe sealants.
Oh ... and make sure you use the correct materials when making your manifold blocks. I learned from experience that cheaper is not necessarily what you are shooting for in high pressure air. I bought some from a guy that said they were "just like .... brand only half the price!" The first one cracked while I was installing a fitting and the second one waited until I got to 3800 psi before it blew. Turns out it was made with the wrong grade of material.
Oh ... and make sure you use the correct materials when making your manifold blocks. I learned from experience that cheaper is not necessarily what you are shooting for in high pressure air. I bought some from a guy that said they were "just like .... brand only half the price!" The first one cracked while I was installing a fitting and the second one waited until I got to 3800 psi before it blew. Turns out it was made with the wrong grade of material.
cool thanks that's the answers I was looking for just wanted to make sure i'm doing things right sometimes I get a little carried away and over kill with things. Im thinking of making my manifold out of 316 stainless and plan on making it a bit over kill on all my thicknesses but id rather it be a little big than have it blow up on me plus its not going to matter if its big and or heavy since its going to be bolted to the wall.
Thanks everyone!
Thanks everyone!
rcontrera
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Ah ... stainless is something we don't work with in manifolds anymore. Most of my customers are frugal (my wife calls them cheap). A stainless manifold means stainless fittings or hose ends (at least to us) and those aren't cheap either. So the last stainless manifold I had in stock sat for over three years while I couldn't keep my $85 to $150 brass or aluminum ones in stock! I ended up giving it away with a compressor system.
That's $300 I will never hear the end of! :depressed:
That's $300 I will never hear the end of! :depressed:
Keep in mind that stainless and aluminum are not the best materials if you plan to do anything with oxygen or rich nitrox mixes. Brass is your friend in those cases (you'll alway want to be careful with sealing surfaces and any lubricants as well).
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Except that getting brass 5000 PSI fittings is difficult at least. 5000 PSI stainless is a walk in the park. I use Aluminum manifolds on the boat, they hold 3500 PSI just fine, and nitrox to 36%. I use stainless NPT fittings from hoseandfittings.com, they stock most everything I want in 1/4" for about 1/2 the price of Grainger.
Sure - stainless is absolutely the better choice for very high pressure air and low EAN applications. For my own purposes, the parts of my setup which see pure oxygen never do so any higher than 3500psi and brass is appropriate (there are some fittings I just can't get in brass and so I am careful to clean the stainless bits I can get thoroughly). For 36%, I wouldn't expect you'd need to worry about it. It's all in how and where you're moving what gas. My point wasn't that you can't use aluminum or stainless, just that with oxygen it's not necessarily the best material; sometimes you don't get a choice.
Good tip on the site, I've always bought everything from Grainger and MMC.
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