Recessed fuel drain install

[GuppyWN]

Changing to recessed fuel drains. Manual says loctite type thread sealant. Anyone use thread tape as well or just the thread sealant?

[Av8r3400]

I never use tape on fuel or hydraulic systems.

[jiott]

No, no tape!

[Delta Whisky]

Not to pile on, but, , , , , , NPT fittings and tape are not a marriage made in heaven - by the very nature of the thread design. Thread sealant is the way to go.

[aviator79]

Never use anything to seal fuel system components that can plug your fuel system.

[airlina]

Years ago, I had a wizzened old A&P tell me to get some stuff called Fuel Lube.I bought a small can of the stuff that will last a lifetime and use it for thread sealant and such. Has out performed anything else I tried and i am sold on it. Its the consistency of peanut butter and never gets hard and is fuel resistant. I checked aircraft spruce by searching for fuel lube but all that came up is a product called "EZ Turn lubricant " which it says is the functional equivalent of Fuel Lube. Bruce N199CL

[896tr]

Sorry to post non aviation related but never use white Teflon "tape" on natural gas or propane fittings either.:eek:

[efwd]

I just bought Fuel Lube. Thought I got it here at the local AS&S. Anyhow, I stated previously on my thread that after my brake line fittings were found to be leaking 5606 hydraulic fluid I got this stuff and it seemed to be working. Not any longer. My brake fittings at all four points on the grove gear leak. The permatex product that was recommended has sealed the fittings where they enter the brake cylinders but neither products has stopped leaking at the aluminum gear. I called Grove. They use Permatex and had no recommendation. My only thought is that I will have to use brand new fittings and try again. I have these tight enough to make me nervous to tighten further. Im hoping that new ones will be a better fit. Any other ideas would be appreciated.

[rv9ralph]

Not to hijack the thread. But what I have used to seal leaky brake fittings on my gear legs was this product.

16423

I also used it to seal the access to the fuel tank on my RV9 project. Follow directions, install and leave for a few days for it to set before you add any fluids.

Ralph

[GuppyWN]

Thanks all. Loctite 565 is the plan but I saw a mention on the super cub forum of adding thread tape. Wanted to see what you thought.

[Floog]

ANY product you use can clog a system if applied wrong. Love that teflon tape!

[jrevens]

ANY product you use can clog a system if applied wrong. Love that teflon tape!

I agree with you, Doug. My favorite thread sealant with metallic tapered pipe threads is the high-temp Loctite, but I have used teflon tape for literally thousands of connections during my career, including aircraft and natural gas. You can read all kinds of silly things on the internet about “regular” teflon tape being unsuitable for natural gas because it will eventually degrade from it. Teflon is teflon for all practical purposes when it comes to thread sealant tape. The only difference between the white and the colored (“for natural gas”) is the color and supposedly the thickness. I say supposedly because I’ve seen & measured the thickness of tape from China (found everywhere now) and have found some very nice thick white and some yellow that was crazy thin, & vice versa. The yellow stuff is supposed to be thicker, which makes it a little more durable when applying and less likely to shred & shed little pieces (which is bad on airplanes, and gas valves & orifices). I always look for a good mil-spec’d tape, preferably made in the USA. If good tape is applied properly it is reliable, and under certain circumstances (like female threads that may be contaminated with oil and difficult to clean for some reason for instance) can be better than any paste sealant. I welcome any disagreement with these statements... I’m not done learning yet.

[Delta Whisky]

It really depends on what material the joint in made of and what thread is involved. If we are talking about NPT threads:


National Pipe Thread (NPT)

This type of thread when mated, may contain slight gaps between the major and minor diameter of the threads. Because of this, a thread seal agent may be required. However, this type of thread is tapered at a rate of 1/16 (3/4"/foot), which often allows a seal to be made without a sealing agent. (https://diy.stackexchange.com/questions/21117/when-should-pipe-dope-vs-thread-tape-be-used#21137)



Note that there is often, by design, a gap between the major and minor diameter of the threads.


And, teflon tape is not designed to be a gap sealer:


Teflon tape:
The purpose of this white, non-sticking tape is to serve as a lubricant when threaded parts of a piping system are being assembled. The inherent slipperiness of the material makes assembly easier.
Strictly speaking, Teflon tape is not a thread sealant (Fig. 1). The tape may have the effect of clogging the thread path, but it does not actually adhere to surfaces as a true sealant should. During installation, the tape must be carefully wrapped in the direction of the threads or it unravels and tears. (https://www.plantengineering.com/single-article/guidelines-for-choosing-a-pipe-thread-sealant/5103ee62235def2053cec5d46dd34156.html)



Now-a-days, there is a third degree of movement available: the anaerobic resin compound/sealer. But, I digress.



The above italicized paragraphs were SELECTIVELY chosen by little ol me because they match reference material I can't locate right now but have been my guiding light (wow, really getting heady now) for a long time. What is interesting, because I couldn't find my old material I went nosing around on the good ol internet and found that you can read gobs (a scientific term) of entries matching whatever you'd like to do and, I discovered, there are now several colors of TFE tape for all kinds of applications. But, be careful, it is the internet and most are not written for vehicles that get very high.



Obviously, if your tape seals the difference between the minor and major diameter differences (if there are any in your parts) then you have a winner. But, it wasn't necessary designed to do that and if the joint has to be opened for any reason in the future, getting the threads cleaned up again for reassembly could be more of an issue if you used tape. This might be an problem if there are tiny orifices downstream of the joint.

[efwd]

You have named my very situation John. My brake line leaks developed on initial install. I think maybe the replacement of the sealant with the new stuff, and its failure, may have been due to my inability to really clean the female threads in the grove gear the second time around since it had hydraulic fluid in
it.

[PapuaPilot]

For all of my fuel fittings I used Fuel Lube; it needs to be applied properly as already stated. I used it for the wing drains that screw into the fiberglass fuel tanks, but you need to be carful not to over tighten these fittings. The Fuel Lube fills the threads on the NPT fittings and doesn't harden.

For the NPT engine fittings I used the Aviation-Form A Gasket on most/all of them. This is a great product and also fills the threads and never hardens.

The problem with using teflon tape is if it gets installed wrong and pieces of it end up in the system. Pieces of teflon tape have been know to get into vacuum pumps (causing them to fail), fuel systems (which ruins pumps, plugs orifices, etc). Be very careful if you use teflon tape, as mentioned it is a lubricant and isn't meant to seal the fittings. I have seen lots of brake bleeders that have leaked past teflon tape on the NPT fitting.

[efwd]

my break bleaders are not leaking.Those are sealed with some kind of red product. It is dry. It appears to be something like the red Loc Tite. I see this same looking stuff on some of my electrical connector hardware. The little screws to close up the connector has red loc tite stuff. A call to Grove certainly didn't help in identifying the product. I notice that my brake fittings don't leak in static condition any more with the fuel lube but when I apply pressure and set the parking brake, that's when it leaks very slowly.

[Delta Whisky]

Well - I'm still looking for the article I "lost" and came across this one: http://www.kitplanes.com/issues/33_5/shop_talk/Best-Practices-Choosing-the-right-sealant_21542-1.html It appears to be available to paid subscribers only but if you aren't one already, I encourage you to join up as this is the best magazine for the homebuilder community (IMMHO). Lots of suggestions and how to's each month.

[efwd]

I subscribe to that Magazine but for some reason Im not able to sign in. I suppose I will just give the author a call today. It just so happens Dave Prizio is my Tech Counselor and DAR.

[GuppyWN]

In case anyone is interested - the recessed drains are WAY better than the old style. Sealed with a permatex thread sealant with no leaks.

These drains work exactly as I’d hoped.

[Rodney]

I'm in the process of making my airplane into a taildragger so I had to order new wheels n brakes from Matco.

They recommend Loctite 567 for all their tapered pipe fittings.

Haven't used it yet, but am getting some on order tonite.

50ml tube was about 20 bucks from Amazon. Will place in my safety deposit box when I'm finished with my gear. LOL. Should be used to it by now. - right???

Rodney

[efwd]

Thanks Rodney. I picked up a couple more fittings to try out. I noticed that on my grove break caliper, Grove uses a fitting that has a Rust colored thread lock or something. The Hydraulic shop near my work couldn't advise as to what it was. They were offering me some Permatex brand thread Lock I assumed, it was the same substance as is stated on the Loc Tite 567 "methacrylate". It was either a Red or a Blue color. I assumed it was a Loc Tite like product. I will try this Loc Tite 567 vs having the unknown rust colored stuff.