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Thread: Need Help With Sealing Compressor Fittings....

  1. #16
    Quote Originally Posted by Mike Cutler View Post
    Derek
    How much to tighten a fitting is kind of subjective. I personally like to leave some "room" to take up the fitting if I need to.
    A high quality, machined, NPT, fitting will probably be about three quarters to one full turn from hand tight. After that you risk stretching threads and then the fitting is toast.
    Mike, had no idea. I thought I had to use much more force to keep it from leaking. Can't tell you how many turns I used, I'm sure it was more than what you advised. I'll be much more aware in the future, if I need to redo any of those joints. That is exactly what I needed to know.

  2. #17
    Join Date
    Nov 2003
    Location
    Central North Carolina
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    1,478
    I used a product called "Leak Lock" when assembling my compressed air system. It's a paste type joint compound that's available at refrigeration supply houses and on line. Even Amazon has it. I've never had it fail me. I also do refrigeration work and most other pipe sealants get eaten by the refrigerants. Leak Lock doesn't. My compressed air system gets turned off when I leave my shop, but never do I bleed off the pressure. I can come back to the shop a week later and still have almost full pressure.

    Charley

  3. #18
    Join Date
    Apr 2012
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    2,423
    Quote Originally Posted by Bill Dufour View Post
    Many of the Chinese made fittings have bad threads. You really should run a tap or die over them to clean them up before use. Sometimes British threads end up on them with no taper.
    Bill D
    This actually happened to me recently with some fittings from the local BORG. Bought half a dozen. Five went on fine, the other seemed seemed like some entirely different thread pitch. To make sure I wasn't losing my mind, I checked the SKU and it was the same as the rest. Go figure.

    Erik
    Felder USA Territory Representative: Central & South Texas

  4. #19
    Join Date
    Apr 2008
    Location
    East Virginia
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    701
    All you need is this:

    Permatex Aviation Form-A-Gasket Sealant #3



    I've never had it not work. With Teflon tape, I've had trouble many times, particularly with Chicom HFT fittings.

  5. #20
    Join Date
    Sep 2009
    Location
    Medina Ohio
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    3,695
    When I was plumbing anhydrous ammonia piping and tanks I used John Crane pipe dope. The pressure is very high like 450 PSI or higher and we had no leaks.

  6. #21
    Quote Originally Posted by Charles Lent View Post
    I used a product called "Leak Lock"...
    This is the best product to use. And avoid cheap fittings.
    "Anything seems possible when you don't know what you're doing."

  7. #22
    If it is a "pipe thread" it is tapered and the purpose of the tape or dope is to lubricate the joint so the metal to metal taper can make the joint. That is from my apprenticeship 50 yrs ago. The same holds true today but there have been many formulations to pipe dope since. My view is that it was a lubricant until the marketing dept got their hands on it. I would not trust a threaded joint that was "sealed." It is best to have a clean thread and you may need a die and thread chaser to clean them up. If you are having difficulty, definitely do it. My compressor will hold air but if I leave the air blower valve on the line, it will leak down over time and the compressor will cycle a few times a day. Soap and water is fine for leak testing of air pressure. I agree that todays fittings and pipe have more issues than long ago, but we had them too. The pipe seems to have hard and soft spots. I installed a tankless water heater for my daughter last weekend and had to do a substantial gas line upgrade. Knowing I had good sharp dies I had a heck of a time not tearing a thread along the way. You may not have pipe dies so if you buy at the depot or such they usually have a threader there. Run the nipples into their die by had to clean them up and get the proper size die for your fittings.

  8. #23
    Quote Originally Posted by Jack Frederick View Post
    If it is a "pipe thread" it is tapered and the purpose of the tape or dope is to lubricate the joint so the metal to metal taper can make the joint. That is from my apprenticeship 50 yrs ago. The same holds true today but there have been many formulations to pipe dope since. My view is that it was a lubricant until the marketing dept got their hands on it. I would not trust a threaded joint that was "sealed." It is best to have a clean thread and you may need a die and thread chaser to clean them up. If you are having difficulty, definitely do it. My compressor will hold air but if I leave the air blower valve on the line, it will leak down over time and the compressor will cycle a few times a day. Soap and water is fine for leak testing of air pressure. I agree that todays fittings and pipe have more issues than long ago, but we had them too. The pipe seems to have hard and soft spots. I installed a tankless water heater for my daughter last weekend and had to do a substantial gas line upgrade. Knowing I had good sharp dies I had a heck of a time not tearing a thread along the way. You may not have pipe dies so if you buy at the depot or such they usually have a threader there. Run the nipples into their die by had to clean them up and get the proper size die for your fittings.
    The problem is that you can't always get the thread to thread seal when pipe fittings have to be at pecise orientations. Sometimes you are a half or quater turn from completely tight. That is where thread sealant comes in. If you use teflon tape and have to back off even a little you have a good chance of a leak. Liquid or paste pipe sealants are much more forgiving.

  9. #24
    One of my uncles was a commercial plumber/gasfitter and many years ago he shared with me his secret to avoid leaks: a product called X-pando:

    https://www.mcmaster.com/x-pando-joint-compounds

    It comes as a gray powder in several different formulations and is mixed with water to the consistency of peanut butter for usage. Slather it onto the male threads and make the connection to 1/2 to 3/4 turn beyond hand tight. The stuff expands as it dries to something like 10,000psi. I have never had a joint leak in the black pipe I use for compressed air in over 30 years.

    Taking it apart can be fun - breaking 1/2" or 3/4" fittings require at least a 24" or 36" pipe wrench. 1" requires a 36" and preheating with a propane torch. Larger than 1" is best attempted with MAPP gas or acetylene and heating cherry red. 2" and above takes two people as well as MAPP. This is some tough stuff.

  10. #25
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    I have what sounds to be a very similar compressor to yours Derek, mine is a Quincy 60 Gal that goes to 175 psi. I used plain old Pipe dope from the hardware store and did not have any leaks. I also used hardware store Brass fittings. I do use Milton QD fittings as I have never had good luck with the cheep Chinese fittings. I can leave my system pressurized and it will not leak down. I will see as much as a 15/20 PSI drop in tank pressure from hot to cold. If I get it hot and let it cool down if will drop from 175 to almost 150 but then it will stay there till the cows come home.

  11. #26
    Andrew, thanks. Not having much of any experience with compressed air fittings, I have to say I'm learning a lot, not the least of which is that fact that I've been over tightening all of my joints. I think that has been the issue more than anything. From this point on, if I get any more leaks, I'll be armed with a good joint sealer and I'll do my best to not over tighten. Thanks all, for your help and knowledge.

  12. #27
    I have to agree with you Lee. This is especially a problem in close qtrs. The normal solution is a larger wrench, a cheater or a union. I have been using the standard yellow Rector-seal ("Seal", perhaps being the operative word) forever, but i picked up a small can of the blue crap last week having forgotten the yellow can at home. Net/net it is what works but every time I have to back off on a fitting it is that one I look at first when charging the system. Sometimes you win

  13. #28
    OK...just found more leaks! They are factory joints, I think or maybe they were done at Lowes, during assembly. Anyways, the leaks are at the mail end of the gage into the pressure switch/manifold and where the safety valve connects. Since I need to angle the gage anyways, is it ok if I put an elbow between the gage and manifold? Also, can that safety valve be switched out for a ball valve or should I just assume the valve itself is good and reseal it?

  14. #29
    Join Date
    Oct 2006
    Location
    Manistique, Michigan
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    1,176
    I use RectorSeal Blue +. I used to use RectorSeal #5. Our piping contractor keeps me up to speed as to what the professionals use. I hire the contractors, so they are good about helping us out in other ways. For those of us in process industries, this sealant is preferred because it works well and can be put into service immediately. Production people are impatient.

    Teflon tape can be an issue. It should not be applied to the first threads at the end because it can break off and be carried down stream. Valves and other control components will end up damaged or jammed by the tape. It is difficult to troubleshoot the problem and identity the troublesome component.
    Rich Aldrich

    65 miles SE of Steve Schlumpf.

    "To a pessimist, the glass is half empty; to an optimist, the glass is half full; to an engineer, the glass is twice as big as it needs to be." Unknown author



  15. #30
    Join Date
    May 2008
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    Peshtigo,WI
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    Quote Originally Posted by Derek Arita View Post
    OK...just found more leaks! They are factory joints, I think or maybe they were done at Lowes, during assembly. Anyways, the leaks are at the mail end of the gage into the pressure switch/manifold and where the safety valve connects. Since I need to angle the gage anyways, is it ok if I put an elbow between the gage and manifold? Also, can that safety valve be switched out for a ball valve or should I just assume the valve itself is good and reseal it?
    You can put an elbow in, as long as it's rated for the pressure.
    DO NOT replace the pressure relief valve with anything but another pressure relief valve of the same rating. Doing so could be a good way to blow something up.
    Confidence: The feeling you experience before you fully understand the situation

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