# hydraulic fitting leaks



## nosoot (Sep 4, 2008)

What is the best material to use on hydraulic fittings -NPT -to seal threads against leaks? I have to replace some black iron elbows on a cast iron valve . The return side elbow is leaking and I had used pipe dope. I am going to replace both pressure and return elbows with hydraulic fittings but I was wondering if there is something better than pipe dope. The paperwork that came with the valve said not to use teflon tape for risk of overtightening and cracking the valve.


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## mga (Sep 4, 2008)

i've used teflon tape and liquid pipe dope with no leaks.


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## husky362 (Sep 4, 2008)

*i use teflon tape*

i cant see a few wrap's of teflon damaging the valve 

i could see tightening past the threads causing damage

ive done hundreed's i still get a few leaks


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## husky455rancher (Sep 4, 2008)

teflon it baby!


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## Crofter (Sep 4, 2008)

Teflon tape is slippery and the wedging force from the tapered thread does increase the risk of splitting a cast iron valve body if you horse it up very tight. It also has the tendency to move around if knocked back and forth a bit and start leaking later.

However if a threaded joint leaks after normal tightening, the threads have been deformed and you will have to use either an anaerobic setting dope or something like teflon to seal it up. Engineers often dont want teflon used because it can also get loose into systems and plug up other small orifices.

I think Locktite has something called Pro Dope that is a good anaerobic setting thread sealant. Combined with a light layer of teflon tape it is almost foolproof, and doesnt need to be overtorqued to seal.

Is there any possibility that you are using an NPT fitting into a non tapered ORB opening on the valve body?


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## PA Plumber (Sep 4, 2008)

I am a fan of teflon tape and pipe compound used together and in that order.

Have caught a lot flack over the years, but have fixed oodles of leaking joints that had one or the other. Only two in 15 years that had both.

As mentioned, be careful on wrapping the teflon tape over the end of the male threads. Same with the pipe compound. Could get into the system.

Pipe compound: For high temp and high pressure (10,000 psi to 600 deg F I believe) I really like Gasoila (sp?). Use it on large gas line jobs with no incident.

for Nat gas, copper, plastic, abs, cpvc etc. I use the Hercules brand that is an off blue color. There are no solvents in it and it does really well with plastic.

I have used both of the above brands for years without incident.


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## PA Plumber (Sep 4, 2008)

Another point on the pipe compound; Only apply it to the male threads.


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## nosoot (Sep 4, 2008)

its a Brand Hydraulics AO 755 valve -all the specs read NPT ports. Thanks for the info -I will try to find the thread sealer. I just hope that having tightened a black iron fitting once has not damaged the threads. All of the other connections came out leak free. And of course I did not use any swivels on the side that is leaking so it has to come apart the hard way -piece by piece.


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## SWI Don (Sep 4, 2008)

I used Loctite 545. It is an anaerobic thread sealant and has worked great. I bought this stuff after trying some other non Teflon sealant that was incompatible with the ATF I am using. This stuff works excellent no leaks and no worries about Teflon tape in your system. 

A lot of people use Teflon tape in hydraulic systems but it is bad for spool valves and small orifices that may be in a hydraulic system. This stuff is anaerobic and will not set up unless it is installed in a joint.

Don


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## SWI Don (Sep 4, 2008)

BTW the 545 stuff even works great on black pipe / galvanized pipe that typically have poor quality threads that have no chance of sealing without some type of tape or sealer. Regular hydraulic fittings seem to be forged steel or bar stock and have higher quality threads that may not require a sealant (dryseal) but it is cheap insurance.

Don


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## mga (Sep 5, 2008)

if you are splitting fittings when tightening them, it's not a failure of the pipe dope or sealer.

you're apparently taking life's frustrations out on the fittings!!


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## Rookie1 (Sep 5, 2008)

PA Plumber said:


> I am a fan of teflon tape and pipe compound used together and in that order.
> 
> Have caught a lot flack over the years, but have fixed oodles of leaking joints that had one or the other. Only two in 15 years that had both.
> 
> ...


:agree2: A guy I work with told me to use both and since then I have had no leaks.


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## Rookie1 (Sep 5, 2008)

SWI Don said:


> I used Loctite 545. It is an anaerobic thread sealant and has worked great.
> 
> Don



Do you know what anaerobic means? I learned it in a class given by Permatex salesman. It means it sets up when it is denied air.


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## Swamp Yankee (Sep 5, 2008)

*Do not use teflon tape in a hydraulic system.
*
Call me anything you want, but I designed hydraulic systems for winches and manufacturing facilities for 30 years, not that you need my resume.

The problem with teflon tape is pieces will either break off upon installation or from fatigue being in the oil steam flow. These pieces will eventually end up in a valve spool, pump or cylinder seal area causing at best a damaged seal needing replacement or at worst, a bound component. I've seen this many times. Remember the sliding clearances inside these components is in the order of .001 inches. Yes, the filter will catch some of the contaminates but that's assuming the contaminate makes it to the filter. Reservoirs that were not properly cleaned of metal scale and welding slag are another huge problem that often leads to component failure. Splitters don't use the best stuff out there but the valve, cylinder and pump clearances are still very tight.

There are many excellent sealants out there specifically for hydraulics. Always liked the Loctite stuff as it didn't ooze and leave you with a big sticky mess every time you rubbed up against a fitting.

So all that have never had an issue with teflon tape in hydraulic systems go ahead and tell me I'm full of crap, I'll continue to spend the extra $2.00 for some decent sealent and the peace of mind it buys.

One man's experience.

Take Care


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## mga (Sep 5, 2008)

*Do not use teflon tape in a hydraulic system.*

i have read that many times in hydraulic forums.

i have now used the liquid teflon sealant.


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## kevin j (Sep 5, 2008)

I design big hydraulic systems.

NPT is a PITA, but it is the most common in cheap complenents, so have to deal with it. Most industrial stuff uses o-ring ports, and flare or o-ring face seal connections.
Two biggest problems, are leaks, then overtightening to solve the leak and the tapered thread forces split out housings, ports, etc. etc.

teflon tape is fine IF USED CORRECTLY. Meaning, skip the first two threads, apply winding in the proper direction, only a couple turns, and hold the loose end tight while installing. 

That said, it take some operator skills. Given the unknown variable of operator skills, it is easier and more reliable to use anaerobic paste or liquid loctite type of teflon sealants. More predictable and less chance of error.

With either, the teflon lubricates the threads and a given amount of torque can create far more tightening force than with unlubricated threads. Don't overtighten. There are 'number of turns' charts, but it boils down to mechanic's feel and skill either way. 

kcj


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## ASEMASTER (Sep 5, 2008)

*dope only*

your best to use only the teflon pipe dopes , permatex clames hand tighten and it will hole 10,000 psi. and I've seen it done at a seminar.


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## Rookie1 (Sep 5, 2008)

Swamp Yankee said:


> *Do not use teflon tape in a hydraulic system.
> *
> Call me anything you want, but I designed hydraulic systems for winches and manufacturing facilities for 30 years, not that you need my resume.
> 
> ...



Ill take heed to what you say but I would say people get crazy with the stuff wrapping it too many timees or over the end of pipe. I have taken many truck hyd. systems apart that used tape and havent found any sign of it in there.


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## Crofter (Sep 5, 2008)

There is another problem with teflon tape even if it is applied properly to the male threads only etc., in that when you disassemble a joint that tape debris can fall into the system. It likely is little concern on the simple hydraulics of a splitter but some pilot operated systems and combinations of air over hydraulic or electronic operated valves etc., are very pernicketty and it can jam the works.

Cracked components from tapered pipe threads is quite common as is new fittings with terrible quality threads. Attempting a fit up with them will permanently damage the other threaded part and you have to add some sort of filler then to make a tight joint. A last resort that will seal some very bad threads is "Angel Hair". I kid you not! It is a fine fibreglass stranded Christmas tree decoration that can be wound (clockwise) onto the male thread, then blessed with anaerobic sealant and the joint made up. I actually got sent down town for some angel hair by an old school engineer after a number of other solutions failed.


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## SWI Don (Sep 5, 2008)

Rookie1 said:


> Do you know what anaerobic means? I learned it in a class given by Permatex salesman. It means it sets up when it is denied air.



Yes I did. Most thread lockers, bearing retaining compounds, and some sealants are anaerobic. You just as well wipe any excess of when you are using it as it will never set up.

I had tried some Harvey's non Teflon stuff that I had bought at Menards originally but had to redo all of those joints due to seepage. Even the low pressure joints on the tank dripped. The Loctite stuff sealed everything up tight.

Don


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