Thread sealer & locker? - RC Groups
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Mar 29, 2012, 04:07 PM
Just call me "Mo"
mogogear's Avatar

Thread sealer & locker?

There are many ways to seal various steam components- soft copper and aluminium washers, fiber washers and various Buna or other o-rings etc

So who thinks they have the best solution to sealing threaded things that just screw together( not using a nut and cone). Or what works for you?

What is your favorite product to seal, lock( but removable) in place and or both??

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Mar 29, 2012, 07:57 PM
Deserteagle's Avatar
I used locktite 565 on all of mine. Good stuff
Mar 29, 2012, 09:22 PM
Just call me "Mo"
mogogear's Avatar
That is my vote also- but before I go through everything prior to boiler testing and use Blue loktite, I thought I would canvas the group to see if I was of too narrow a mind

The Paddle tug is going out to sea trials soon!!!
Mar 30, 2012, 03:38 PM
Registered User
-kno3-'s Avatar
Teflon tape for most screw-in fittings that don't need to be often removed, also soft copper washers.
For removable ones, such as water fill plugs, safety valves etc, i prefer fibre washers. Have also used rubber but they tend to get brittle or to let steam out at higher pressures (if theres is room for them to get pushed out).
Mar 30, 2012, 10:55 PM
Registered User
chesguy's Avatar
Agreed on the Teflon tape, kno3, we used this in the lab on gauge fittings or anything with a pipe taper, and never had a problem up to 2000 psi nitrogen. Also water at 400 psi, all at up to 400 deg. F
Last edited by chesguy; Mar 30, 2012 at 11:22 PM. Reason: Added water
Apr 01, 2012, 01:18 AM
Damp and Dizzy member
Brooks's Avatar
I agree with KNO3, Teflon tape works well. When wrapping the male part, I leave the first 1 or 2 threads clear of tape. This reduces the possibility that the female part will cut tiny stringers out of the tape to dangle in the steam flow. These stringers can be flushed along the line, plugging small holes, like those found in the steam chest. Leaving the initial threads clear of tape is a trick taught me by airplane mechanics; they worry about stringers plugging aircraft instruments, not steam, of course.

I've had o-rings on filler plugs blow out under steam pressure if the ring is attempting to seal a pair of flat areas. Cutting a retaining groove in the filler plug is one option to reduce blow-out, if you have a lathe.

Boy, I hate using loctite, unless I can find the green stuff (can't remember the number). It's weak enough to allow removal of screwed fittings w/o heroic efforts. Hardly any hardware store carries it, though.
Apr 01, 2012, 12:37 PM
Just call me "Mo"
mogogear's Avatar
The fittings I am really concerned about are mostly the clack valve as it screws onto the male thread fitting into the boiler bush. and the gauge bolt through the banjo fitting with the 2 alumimnum washers.

Most everything else is nut and cone and I use nothing

Here is a shot of my "piping extravaganza" Thanks for the various suggestions and input
Last edited by mogogear; Apr 01, 2012 at 06:00 PM.
Apr 01, 2012, 01:56 PM
Deserteagle's Avatar
Originally Posted by Brooks

Boy, I hate using loctite, unless I can find the green stuff (can't remember the number). It's weak enough to allow removal of screwed fittings w/o heroic efforts. Hardly any hardware store carries it, though.
The loctite product I recommended isn't like the blue or red locitite, it's like liquid Teflon in a way. You only need a small drop on the threads and seals very well. I've used it on everything from boiler bushings to fittings. Coles and PM research sells it for a reason. Nothing on my setup leaks after running it all the way up to 100 psi. The nice thing about this product is it also easy to take things apart.
Teflon Tape vs. Pipe Thread Compound... - Plumbing Forum

Posted on the Posted by lazypup
"Per ASTM (American Society of Testing & Materials) Standards we must use a thread sealant on all NPT (National Pipe Taper) Threads & fittings. The type of thread sealant is selected for compatibility with the material that the pipe will be conveying. In residential service the use of NPT joints is normally limited to water, natural gas, propane gas, #1 & #2 heating oils and occasionally low pressure steam, refrigerants or high-pressure air in a shop compressor system. TEFLON TAPE:

WHITE-Single density- should only be used on NPT threads up to 3/8 inch.
YELLOW- Double Density- yellow double density is often labeled as "Gas type"
RED-Triple Density: (Note-the container is red but the tape itself appears as a pale pink color). Presently required on all joints ½" diameter or greater.
GREEN- Oil Free PTFE tape- Required for use on all lines conveying oxygen (I.E. –medical oxygen or welding oxygen lines).
COPPER COLOR- contains granules of copper and is to be used as a thread lubricant but is not approved as a thread sealant. (Generally it is used as a thread lubricant on bolts or pipe threads for mechanical applications where no physical seal is required.)
PTFE tape is only approved as a thread seal when applied correctly. To apply you begin at the end of the pipe and wrap the tape under tension in the direction of the thread turns. Each successive layer should overlap the previous layer by ½ to 2/3 and continue wrapping until the entire threaded portion of the pipe is covered. (Minimum of 3 full turns).
When looking for pipe dope in the hardware or home supply store we commonly find two types, a tube of dark gray paste labeled "Pipe dope" and tubes or small bottles of white "Teflon Pipe Dope". When selecting the pipe dope check the fine print very carefully to insure the product is listed as approved for the application you intend to use it for as some of these products have a very limited range of applications. As a rule the Teflon pipe dope will have the broadest range of applications and will normally meet all requirements that would typically be found in a residential environment.

Loctite 565 specs found here,
Apr 01, 2012, 06:05 PM
sunworksco's Avatar
I have used this sealant on boiler fittings/pipe threads for over 30 years, with or without Teflon tape.
Works every time and foolproof with tape combination.

Apr 01, 2012, 07:31 PM
Registered User
catchthis's Avatar
I just heard of a product called monkey spit. You get all three types for $10 and its something like 1.75oz per bottle. Haven't tried it yet but mechanics I know have recommended it.

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