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Use of torque seal

SabreFlyr

Well Known Member
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I've made a quick scan of both AC43-13.1B and the Airframe & Powerplant Mechanics Handbook and didn't find an answer to this. Do you apply torque seal to EVERY tongued fastener & fitting including hydraulic fittings and things firewall forward? Just installed my firewall fuel fitting and put torque seal on the nut but was wondering about the flare nuts on the fuel lines. Also installed the brake fluid reservoir and was wondering if torque seal would hold up in the heat of that environment.
 
Torque seal is typically used on anything that you want to be able to determine if it's loosened during subsequent inspections. Yes, it will hold up to the heat of the engine compartment.

When the day comes that you actually have a plane that's just about ready to fly and not just a project you're working on in the garage, torque seal will also help determine if each of those connections is "ready to go" or if it was only snugged up during initial construction.
 
Torque seal is typically used on anything that you want to be able to determine if it's loosened during subsequent inspections.

Actually, torque seal does NOT tell you if something as loosened between inspections. It tells you that you torqued it at some point in the past. Just because the seal is still intact, does not mean that it is still tight!
 
Sorry......

I don't have much faith in torque seal. I have found, on initial inspection, nuts that were torque sealed and NOT tight! And, unfortunately, it's not that rare.
 
I don't have much faith in torque seal. I have found, on initial inspection, nuts that were torque sealed and NOT tight! And, unfortunately, it's not that rare.

Mel, do you think that's a function of nuts being properly torqued and working loose, while the torque seal fails to break, or of builders/mechanics making a procedural error and applying torque seal to fasteners they have not personally verified to have the torque set properly?
 
Mel, do you think that's a function of nuts being properly torqued and working loose, while the torque seal fails to break, or of builders/mechanics making a procedural error and applying torque seal to fasteners they have not personally verified to have the torque set properly?

In my opinion, these situations would be cases of torque seal being applied when the fasteners had not been properly torqued.

Torque seal is a valuable tool when it is used correctly. It needs to be applied as each fastener, hose end, etc., is torqued.

We use it extensively in our RV-12iS production division. At final post production inspection, if torque seal is missing from any torqued connection or fastener, it gets squawked and has to be checked for proper torque with a torque wrench and then torque seal applied before the airplane is signed off. I did quite a few post production final inspections prior to switching to DAR duties (when acting as DAR I can't have any involvement with an aircraft prior to the point of doing the certification inspection), and I would occasionally find torque seal missing but I believe in all cases the connection was fully torqued but torque seal had not been applied.

In my opinion, this is the only purpose of torque seal.... as a visual indicator that something was at some point torqued properly.

It is a great cross check for any home builder, but should be an absolute requirement on any build where multiple people are participating.
It was standard practice for every connection with the TeenFlight build program that I lead, as well as the One Week Wonder build project done during OSH2018.

As Mel has pointed out, for it to have any value it requires proper discipline when being used.

What torque seal should not be relied upon for is as an indicator that a fastener or connection is still at a proper torque value once the airplane is in service. Once that is true, about all it shows you is whether the assembly has been taken apart at any time since the torque seal was applied and even then that is not total proof. I have seen connections with improperly applied torque seal, taken apart and then reassembled with it being very difficult to tell that the torque seal has been disturbed
 
Torque seal is a valuable tool when it is used correctly. It needs to be applied as each fastener, hose end, etc., is torqued.

That's how I do it. I don't apply it unless immediately after setting the torque on a fastener, or checking the torque. As you say, it requires discipline and holding to procedure to have value.
 
Not working loose!.......

Mel, do you think that's a function of nuts being properly torqued and working loose, while the torque seal fails to break, or of builders/mechanics making a procedural error and applying torque seal to fasteners they have not personally verified to have the torque set properly?

Note my emphasis "on initial inspection"! These aircraft have not been flown.
 
I've made a quick scan of both AC43-13.1B and the Airframe & Powerplant Mechanics Handbook and didn't find an answer to this.

And you'll find nothing authoritative here either. Not even a consensus. And installed bolt preload, for which torque is only a proxy, is often lost in service. It does not require rotation of the nut or bolt. The classic example is a clamped joint with paint layers in the stack-up.
 
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Question, when checking torque value on a faster , do most just apply a torque wrench on the fastener and see if it moves or loosen the fastener and re-torque?
It’s my understanding that for proper torque, a fastener should be moving while reaching it’s value. It takes more torque to get a fastener moving than one already moving.
 
Actually, torque seal does NOT tell you if something as loosened between inspections. It tells you that you torqued it at some point in the past. Just because the seal is still intact, does not mean that it is still tight!

What torque seal should not be relied upon for is as an indicator that a fastener or connection is still at a proper torque value once the airplane is in service.

This surprises me but just a little. Is it because of bolt stretch while in service? And, this being the case, it becomes important to know which bolts need to be checked after some time in service.'

Now, such as in the case of my brake fluid reservoir where there are nutplates, would the torque seal be applied where the screw exits the back of the nutplate (not as easy to inspect in this case) or on the bolt head (where I was thinking I would apply it)?
 
Question, when checking torque value on a faster , do most just apply a torque wrench on the fastener and see if it moves or loosen the fastener and re-torque?
It’s my understanding that for proper torque, a fastener should be moving while reaching it’s value. It takes more torque to get a fastener moving than one already moving.

Yes, sliding friction is always less than static friction. I was always taught it was improper to "check" torque, and that to properly do it, the fastener must be first loosened and the torque re-set.

As Dan mentions above, torque is just a surrogate for clamping force, which is applied by the spiral inclined plane of the thread.
 
Torque seal

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Now, such as in the case of my brake fluid reservoir where there are nutplates, would the torque seal be applied where the screw exits the back of the nutplate (not as easy to inspect in this case) or on the bolt head (where I was thinking I would apply it)?

Treat it as an indicator the fastener has been torqued at least once. In the case mentioned, apply it to the bolt head over the edge and on to the brake reservoir. Personally, I remove it if a fastener is loosened then reapply after it's torqued.
 
In the case mentioned, apply it to the bolt head over the edge and on to the brake reservoir. Personally, I remove it if a fastener is loosened then reapply after it's torqued.

Thanks, Larry. That's what I was originally planning.
 
Prop bolts, complete with torque seal on each head. Total thread engagement was 0.172"...three, maybe four threads.

Just another example of why torque seal is useless as an indicator of airworthiness.
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Prop bolts, complete with torque seal on each head. Total thread engagement was 0.172"...three, maybe four threads.

Just another example of why torque seal is useless as an indicator of airworthiness.
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YIKES!! :eek:
 
Note to Self

When I apply torque seal, it's right after I've torqued the fastener, and it lets me know in the future the I tightened the thing, whatever it was. Does not mean it's tight now. When somebody else has applied torque seal, it's mostly just pretty. I don't see it as relieving me of any particular concern or responsibility.
 
Torque seal

The only thing torque seal shows you is that it was applied at some time. I have found torque seal applied to fasteners that were barely finger tight.

Worse yet, if you seal torque seal you just pass over that fastener and will never check to see if it is tight…
 
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