Could have been bad!

[FredG]

I used a 37 degree AN T-fitting with three male ends to join the two fuel lines from the wing tanks to one line that penetrates the firewall to the fuel valve.  Trying to remember if I used one designed for bulkhead (simply because it is longer on one of the legs).  

[Madhatter]

58 minutes ago, FredG said:

I used a 37 degree AN T-fitting with three male ends to join the two fuel lines from the wing tanks to one line that penetrates the firewall to the fuel valve.  Trying to remember if I used one designed for bulkhead (simply because it is longer on one of the legs).  

The reason I asked as in an earlier post the hose from the firewall to the fuel valve must not be higher than the t fitting in the firewall which creates a low spot. I found it to be a challenge. 

[Roger Lee]

Okay you ask for it and here it is. I took the 5/16" hose and installed it on the "Y" fitting. I blinded off the the two "Y" sides with more 5/16" hose and connected my air compressor. So all hose here on all three fittings are the 5/16". Even though this hose is only rated to 50 psi it was tested it at 100 psi. There are two pictures to verify this test. This should put a dampener on all the hearsay about 5/16" hose coming off especially since it isn't under pressure and is just a hollow tube supply line. Never just listen to Joe Blow next door do your own research and testing. Even Rotax experts and Service Centers can be wrong.

p.s.

My wife the executive producer and photographer is a witness. LOL

So if a hose comes off blame the installer not the the hose.

I hate to say it, but I ...........   

[Roger Lee]

9 hours ago, Tom Baker said:

This is with 7.5mm hose. 8 pounds of pulling force. the fitting is sliding in the hose, but slowly. In my opinion, the hose is sealed on the fitting.

IMG_2119.MOV

If 8 pounds of pull moves that hose then it's not clamped properly. I had about 20-30 lbs of pull on my bench.

So I will go out again and pull that 5'16" to destruction or move my entire bench before it comes off. 

All our hoses are clamped so testing one that isn't clamped is not relevant. You must test things the way they are installed. So wiggling an un-clamped hose is not relevant because we don't use it that way. That's like saying your gun is malfunctioning and won't shoot after you put a spent round in it vs a live round.

Next video coming soon.  

[Tom Baker]

10 hours ago, Roger Lee said:

If 8 pounds of pull moves that hose then it's not clamped properly.

That was unclamped. The point was the hose has resistance on the sealing ramp of the fitting. The 5/16" hose does not.

[Tom Baker]

This is the 5/16" hose filled with fuel, and you can see it leaking out between the hose and the fitting. The 7.5mm hose does not leak like this. Roger you can say it is not clamped, but you should not be relying on the clamp to make the seal. The hose should seal without the clamp, and that is the issue I have with the 5/16" hose, it doesn't seal on the fitting like it should.

[Roger Lee]

There's not a fuel hose in the CT that doesn't have a clamp. Any hose on the CT or other aircraft can leak without a clamp if it is designated to have one or the Mfg wouldn't have put it there. Plus most hose can be pulled off if you do not have the clamp in place that was designed to be there.

If what you say is true, "The hose should seal without the clamp, and that is the issue I have with the 5/16" hose, it doesn't seal on the fitting like it should."  Then why put clamps on the 7.5mm at all?

Like I said you can't run a test of the way it was designed to be installed when you alter the way it was designed to be installed. It becomes irrelevant because it is NEVER used without a clamp.

My 100 psi test proves without a shadow of a doubt that when the hose is INSTALLED as it was designed to be installed it is a solid installation and WILL NOT leak. I've proved that too over 20 years and hundreds of installations.

If this was an issue on this fitting then a few hundred CT's would be leaking all over the US.

I've had three Rotax experts call me and ask why you are doing it that way (no clamp) when it isn't installed that way.

I'm not seeing the reasoning to this if you test something that isn't installed the way it is one the plane / engine? 

 

[Anticept]

I doubt the ASTM spec says that this is allowable for clamps to seal instead of the barbs or beads, and demonstrations and anecdotal evidence don't make it OK if the spec says it isn't, full stop. I would be hard pressed to believe ASTM would go against decades of industry standard. But it also wouldn't be the first time I have been shocked by LSA stuff.

Manufacturers make errors too. Unfortunately I can't look up the spec without paying a lot of money and this isn't that worth it to me when I can just go with something that doesn't require me to perform clamping rituals in the hope it doesn't leak when I test it or start leaking in flight from vibrations (had that happen too, it didn't piss all over the place, but it did make a fuel smell).

[Tom Baker]

14 minutes ago, Roger Lee said:

If what you say is true, "The hose should seal without the clamp, and that is the issue I have with the 5/16" hose, it doesn't seal on the fitting like it should."  Then why put clamps on the 7.5mm at all?

Because the purpose of the clamp is to prevent the hose from sliding off the fitting.

16 minutes ago, Roger Lee said:

My 100 psi test proves without a shadow of a doubt that when the hose is INSTALLED as it was designed to be installed it is a solid installation and WILL NOT leak. I've proved that too over 20 years and hundreds of installations.

I have never said that you couldn't make the 5/16" hose seal with a clamp, only that you shouldn't have to rely on the clamp to make the seal, that's not how the design is intended to work. Just because you have been doing that way for 20 years doesn't make it right.

 

38 minutes ago, Roger Lee said:

I'm not seeing the reasoning to this if you test something that isn't installed the way it is one the plane / engine?

The purpose is to show that the hose does not properly fit the fitting. I have attached a description of how this type of fitting should work.

Sealing for single 'smooth' ramp single flute barbs takes place along both the increasing diameter ramp surface and at the peak of the single flute. That type of fitting often has an area for an external clamp. And the instructions for those fittings will offer something like "Do not place clamp on top of the barb."

The clamp does not contribute to the seal. And if the clamp is tightened to the point of displacing hose material, or placed too close to the flute, the design performance of the fitting seal is compromised.
 

And more,

The hose fitting makes a seal with internal pressure against the hose ID, not from external clamping force.

If there is a leak at the fitting, some compromise at the internal pressure point is the cause.

It is, that is, assuming no leaks caused by over pressurization, chemical incompatibility, mechanical strain on the hose, corrosion of the fitting, external damage to the hose, exceeding the design service live of the hose or the one-time-use restriction.

If the internal pressure point is leaking, and not caused from one of the above, the remaining causes are limited.

Either the band is in the wrong location relative to the pressure point, or the band is too tight.

External clamping force isn't creating the seal, and increasing the external clamping force does not repair the source of the leak.

Though the fitting seal against the hose ID may be otherwise compromised, enough clamping force can create a temporary seal elsewhere. And too much clamping force, or the band in the wrong location, creates it's own leak.

Over tightening a clamp is understandable. It is the same ahh . . . 'intuitiveness' . . . that over tightens a bolt.

[Roger Lee]

You're getting off track. You need to put a clamp on the "Y" fitting and install it properly and do your wiggle test and do a leak test. You're branching out off topic. It's only about the 5/16" hose on that "Y" fitting. Clamp it like it is designed to be when it is in use and do your own pressure test. You are altering and testing something that we don't do and this is you're testing hose that isn't clamped. I just did 100 psi test so I know it works.

You can't buy a new set of tires and drive home and then later on call the tire folks and say their tires are defective and you want to return them. They ask how are they defective and you say I let all the air out of them and drove down the Hwy and they all torn apart and came off the wheel. They must defective. 

Put the clamp on and test it as it was designed. Any other test like wiggling is irrelevant because we do not use it that way.

"Though the fitting seal against the hose ID may be otherwise compromised, enough clamping force can create a temporary seal elsewhere. And too much clamping force, or the band in the wrong location, creates it's own leak."

Possibly, but it's irrelevant in this case. 

"Over tightening a clamp is understandable." 

It isn't and that only means you installed the clamp wrong.

"External clamping force isn't creating the seal, and increasing the external clamping force does not repair the source of the leak."

Yes it does. Take the hose clamps off the fuel pump hose and run the engine and let's see if it leaks especially on the pressure side. Plus no clamps and that hose comes off easier than the hose on the "Y".. Take the clamps off the fuel site tubes and on the fuel outlet fitting at the fuel bulkhead and tell me the clamp doesn't keep them from leaking.

Take the fuel pump off and put two pieces of your MM hose on the fittings and now sling it around and let me know if the pump fly's off.

You're presenting arguments here that do not pertain to this one "Y" fitting and the other straight fitting of the same size. The test you're performing aren't relevant because we don't use fuel hose without clamps. Most likely all our fuel hoses would ooze, leak or just come off if they aren't clamped.

You have to compare and test apples to apples. Get rid of the grapefruit.

[Roger Lee]

If science, real installation testing above its normal function and 15 years of doing it this way with no issues that shows it works doesn't tell it all then we we're at a impasse. 

[Tom Baker]

1 hour ago, Tom Baker said:

The hose fitting makes a seal with internal pressure against the hose ID, not from external clamping force.

Roger, you are picking bits and pieces, but you seem to have missed this. It says it all.

 

[Tom Baker]

Roger, can you cite one valid reason for not using the correct size fuel line as called out in the parts catalog and maintenance manual?

[Madhatter]

You guys.need to get a room

[FlyingMonkey]

On 4/18/2023 at 2:00 PM, Anticept said:

The reason I side with Tom is that I am looking to replace the tee in mine. I am having leaking issues unless I clamp it down real tight. I am using the 5/16ths hose. It's too loose on the fitting. Yes I tried new hose.

I just haven't found a tee that I really like, though the 4504 tee is looking attractive. I might just say screw it, bite the bullet, and build one using AN840s and a female tee.

If you call Steve at Aircraft Specialty he can set you up.  He just did all AN fittings with teflon/stainless braid/integrated firesleeve for all my fuel/oil lines.  He probably has all the data from my setup and can sell you what you need, including the lines & fittings behind the panel and through the firewall.

Hit me up if you have any questions on how mine is configured.