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rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Thu Apr 15, 2021 6:16 pm Post subject: Plumbing Instruments

Hi Group In process of wiring and plumbing instruments. Question: I have Male Nylon 1/8" NPT hose nipples going into metal female threads on Dynon D10A and Altimeter. Should any thread compound or tape be applied before assembly? Thx. Ron P.

neal.george(at)gmail.com
Guest

Posted: Thu Apr 15, 2021 7:15 pm Post subject: Plumbing Instruments

Ron - 

Run them in dry, no Teflon tape, no goop.

Just snug, no need to pull the threadsâ€¦



Neal George

George Aviation

850-218-2939



On Apr 15, 2021, at 9:16 PM, rparigoris <rparigor(at)hotmail.com> wrote:






Hi Group In process of wiring and plumbing instruments. Question: I have Male Nylon 1/8" NPT hose nipples going into metal female threads on Dynon D10A and Altimeter. Should any thread compound or tape be applied before assembly? Thx. Ron P.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=501400#501400

cluros(at)gmail.com
Guest

Posted: Thu Apr 15, 2021 7:16 pm Post subject: Plumbing Instruments

The better the seal, the easier it is to calibrate and test the system. A bit of teflon tape will make for a much better seal.



On Thu, Apr 15, 2021, 19:20 rparigoris <rparigor(at)hotmail.com (rparigor(at)hotmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>

 

 Hi Group In process of wiring and plumbing instruments. Question: I have Male Nylon 1/8" NPT hose nipples going into metal female threads on Dynon D10A and Altimeter. Should any thread compound or tape be applied before assembly? Thx. Ron P.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=501400#501400

 

 

 

 

 

 

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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Fri Apr 16, 2021 3:28 am Post subject: Re: Plumbing Instruments

I ran into a problem with Nylon fittings about 25 years ago during my very first solo flight of my then recently completed ultralight aircraft.  Most Nylon fittings are injection molded (not machined), leaving a tiny seam at the mold parting line.   During climbout, airspeed read significantly LOW (right at published stall speed) and scared the CRAP out of me.    A few other problems, like motorcycle type windscreen collapsing into my lap didn't help either.



Nylon fittings work well if you recognize that they MAY leak.  Pitot and Static systems must be leak tested before first flight.   EASY!  Insert an altimeter into each system; pump it up to 10,000 feet and witch for a slow decay.  If it has not lost more that 1,000 feet after one minute, you are good to go. 



Yes, Teflon tape on pipe threads will help attain a seal; just make sure that whenever the fitting is removed that you take extra care to remove all traces of tape remnants from the inside of the female threads.  And don't over-tighten fittings as the wedge action of pipe threads may easily split plastic instrument cases.



Jerry King

_________________
Jerry King

rv8iator

Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR

Posted: Fri Apr 16, 2021 5:33 am Post subject: Plumbing Instruments

No tape!Â  Teflon or otherwise.Â  It will extrude out of the threads as tiny slivers and enter the system with less than desirable consequences.Â 



Use a joint compound that is plastc compatible.Â Â 



Loctite thread sealer 5772Â Â orÂ Â Loctite thread sealant with PTFE 1527514



.chris stone

RV-8

On Thu, Apr 15, 2021 at 7:20 PM rparigoris <rparigor(at)hotmail.com (rparigor(at)hotmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>

 

 Hi Group In process of wiring and plumbing instruments. Question: I have Male Nylon 1/8" NPT hose nipples going into metal female threads on Dynon D10A and Altimeter. Should any thread compound or tape be applied before assembly? Thx. Ron P.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=501400#501400

 

 

 

 

 

 

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_________________
C. Stone (RV8iator)

echristley(at)att.net
Guest

Posted: Fri Apr 16, 2021 5:57 am Post subject: Plumbing Instruments

Better yet, use plastic fittings.  They'll deform to seal the mate completely.  It's not like they have to deal with any heat or pressure, or carry any load.

cluros(at)gmail.com
Guest

Posted: Fri Apr 16, 2021 8:26 am Post subject: Plumbing Instruments

The restriction against Teflon tape applies to oil and fuel hoses. It has no bearing on pitot or static connections. There are tens of thousands of amateur built and certified aircraft flying around with Teflon tape on the NPT ends of the fittings without consequence. Note that the tape is onlyÂ useful on the NPT ends, there is no benefit to adding it to the compression end of the fittings.



On Fri, Apr 16, 2021 at 6:40 AM Christopher Cee Stone <rv8iator(at)gmail.com (rv8iator(at)gmail.com)> wrote:



 	  Quote: 	
		  No tape!Â  Teflon or otherwise.Â  It will extrude out of the threads as tiny slivers and enter the system with less than desirable consequences.Â 



Use a joint compound that is plastc compatible.Â Â 



Loctite thread sealer 5772Â Â orÂ Â Loctite thread sealant with PTFE 1527514



.chris stone

RV-8

On Thu, Apr 15, 2021 at 7:20 PM rparigoris <rparigor(at)hotmail.com (rparigor(at)hotmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>

 

 Hi Group In process of wiring and plumbing instruments. Question: I have Male Nylon 1/8" NPT hose nipples going into metal female threads on Dynon D10A and Altimeter. Should any thread compound or tape be applied before assembly? Thx. Ron P.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=501400#501400

 

 

 

 

 

 

 ===========

  -

 Electric-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ===========

 WIKI -

 errer" target="_blank">http://wiki.matronics.com

 ===========

 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ===========

cluros(at)gmail.com
Guest

Posted: Fri Apr 16, 2021 8:30 am Post subject: Plumbing Instruments

I believe the original poster said they were using Nylon fittings. While these fittings will seal better than metal ones without tape, they will still seal better with tape.



On Fri, Apr 16, 2021 at 7:05 AM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:



 	  Quote: 	
		  

         Better yet, use plastic fittings.Â  They'll deform to seal the mate completely.Â  It's not like they have to deal with any heat or pressure, or carry any load.

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 17, 2021 6:24 am Post subject: Plumbing Instruments

At 11:26 AM 4/16/2021, you wrote:

  	  Quote: 	
		  The restriction against Teflon tape applies to oil and fuel hoses. It has no bearing on pitot or static connections. There are tens of thousands of amateur built and certified aircraft flying around with Teflon tape on the NPT ends of the fittings without consequence. Note that the tape is onlyÂ useful on the NPT ends, there is no benefit to adding it to the compression end of the fittings. 	


   Cessna Service Manuals circa 1976 called out

   the use of teflon tape on the male fittings

   of the pitot-static plumbing. Modern

   nylon fittings are better fits and advertised

   to seal without the use of tape. In any

   case, a leak check is the controlling condition

   for system integrity.



   Applying tape such that the first two threads

   are left exposed goes to keeping shredded

   teflon from dropping into a system upon

   disassembly. But Nyloseal fittings with

   no tape seems to be the contemporary process

   of choice.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sat Apr 17, 2021 4:08 pm Post subject: Plumbing Instruments

The cleanest approach is the following kit:

https://www.steinair.com/product/pitot-static-tubing-port-kit/

Yes, a little pricey, but you can connect or disconnect the tubing in 

seconds, and as long as your cuts are clean and straight, no leaks.

Quality pipe threads rarely need tape or paste to seal. Cheap pipe 

fittings are all over the map for fit.



On 4/16/2021 10:29 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   At 11:26 AM 4/16/2021, you wrote:

> The restriction against Teflon tape applies to oil and fuel hoses. It 

> has no bearing on pitot or static connections. There are tens of 

> thousands of amateur built and certified aircraft flying around with 

> Teflon tape on the NPT ends of the fittings without consequence. Note 

> that the tape is onlyÂ useful on the NPT ends, there is no benefit to 

> adding it to the compression end of the fittings.

 

    Cessna Service Manuals circa 1976 called out

    the use of teflon tape on the male fittings

    of the pitot-static plumbing. Modern

    nylon fittings are better fits and advertised

    to seal without the use of tape. In any

    case, a leak check is the controlling condition

    for system integrity.

 

    Applying tape such that the first two threads

    are left exposed goes to keeping shredded

    teflon from dropping into a system upon

    disassembly. But Nyloseal fittings with

    no tape seems to be the contemporary process

    of choice.

 

    Bob . . .

 

    Un impeachable logic: George Carlin asked, "If black boxes

    survive crashes, why don't they make the whole airplane

    out of that stuff?"

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sun Apr 18, 2021 5:22 am Post subject: Re: Plumbing Instruments

+1 for the Steinair fittings.  I particularly like the banjo fittings.  Lets you get a real close fit and being able to rotate the fitting is added bonus.

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Tue May 04, 2021 6:47 pm Post subject: Re: Plumbing Instruments

Hi Group After a nice job of plumbing I tried a leak test pulling altimeter to 1,000 from Zero. Leaks about 108 feet per minute. Shoot. Every one of my nothing installed Nylon fittings were leaking. A day job to pull them out (all barb fittings, tubing would need replacing). I tried some thin no stink silicone #3140 while pulling a 1,500 foot vacuum. Worked great. After 5 minutes I dropped pressure to 1,000 for half an hour, then let it go static and cure overnight. The fittings are from McMaster Carr and don't have a seam I can see from molding. I tightened them smartly.  Ron P.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 06, 2021 6:18 pm Post subject: Plumbing Instruments

At 09:47 PM 5/4/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>



 Hi Group After a nice job of plumbing I tried a leak test pulling altimeter to 1,000 from Zero. Leaks about 108 feet per minute. Shoot. Every one of my nothing installed Nylon fittings were leaking. A day job to pull them out (all barb fittings, tubing would need replacing). I tried some thin no stink silicone #3140 while pulling a 1,500 foot vacuum. Worked great. After 5 minutes I dropped pressure to 1,000 for half an hour, then let it go static and cure overnight. The fittings are from McMaster Carr and don't have a seam I can see from molding. I tightened them smartly.  Ron P.

 	


   Good data!



   Did a search of literature and manufactured offerings

   on our favorite plumbing technologies . . . only

   spent a couple hours on it but a simple and time-

   honored understanding of the NTP threaded parts

   was confirmed.



   Making a leak proof joining of parts in fluids

   is not unlike joining conductors of current.

   The term "gas tight' is equally applicable 

   in both instances.



   Studies of threaded fluid fastenings

   reveals a potential for two, spiral leak paths

   where thread tips and roots in the mated joint

   do not come into solid physical contact. 



   99.99+ percent of such joints use

   some form of malleable sealant material

   that exploits the wedging action of a

   tapered thread to compress and extrude

   a sealant into small spiral voids that

   exists between the 'imperfectly' mated

   threads.



   Unlike nuts and bolts with thread engagement

   requirements that speak to strength (screw

   should break before threads strip), tapered

   threads on fluid fittings strive for

   an interference or interruption, fluid-tight

   fit of mated, wedge shaped parts.



   Leak-free pitot static systems assembled

   with 'dry fitted' parts depend on physical

   deformation of the mated parts to achieve

   zero clearance fits of the spiral leak

   paths.



   Here is one of several articles I found

   that discussed technology of tapered threads.



  http://www.aeroelectric.com/articles/Pipe_Threads.pdf



   I did find some claims for plastic parts

   that would achieve gas tightness without

   additional sealants. The quality of such

   joints assumes a knowledge of thread forms

   for BOTH the parts along with confidence

   in the long term dimensional stability

   of the parts (did anyone say 'plastic').



   I found only anecdotal claims of sealant-free

   joining where one or both parts were plastic

   of some variety. One writer said the seal

   was not permanent; leaking developed with

   time in service.



   No doubt there are some plastic parts with

   characteristics that will dry seal on assembly.

   But unless specifically called out by the

   manufacturer and proven in qualification testing,

   the integrity of such joints is problematic.



   If I were assembling my own panel today, I'm

   pretty sure I would find confident comfort

   in application of the technique suggested in

   the 1978 Cessna service manual that calls out

   Teflon tape covering all but the first two

   threads of a male fitting.



   Sometimes the best way to drive a nail is

   with a hammer . . .



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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