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Thank God for torque seal

Maxrate

Well Known Member
After helping a friend complete his condition inspection to include replacement of all fluid lines and overhauling the fuel injection system I discovered the throttle cable to fuel injection control arm nut loose. The only thing that raised my awareness was the lack of torque seal applied! We double checked every nut and bolt FWF after finding that little revelation. I think the additional step of adding a swipe of torque seal after final tightening quite possibly saved our bacon. Maybe the AP would have discovered on his final inspection, and maybe not! When multiple guys are working on a project, having a procedure in place of torque sealing after final torquing is vital, imho.
 
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When multiple guys are working on a project, having a procedure in place of torque sealing after final torquing is vital, imho.

You mean like "Physically check all the nuts and bolts"?

Seriously, torque seal only proves somebody put torque seal on it. A wrench proves they are tight. The stuff is akin to sending new guys for a bucket of propwash.
 
I use torque seal religiously after putting a wrench on a nut/bolt. It's important because my annual condition inspections take weeks to complete and, being old, sometimes I forget what I did last week. I change colors every year. This year was blue. Oh, how rude of me. You RV guys won't know what this is. It's called a "Retractable Landing Gear". (The devil made me post that.) ROFL!

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I'm a fan of having a system. Some systems include torque seal, some don't.

My "system" is based around checking torque on one subassembly at a time, beginning at one point, and ending at the far end.

For instance, if checking the FWF fuel system, I'll start at the firewall penetration and sequentially check the torque on every fuel fitting between the firewall and the carburetor on my RV-6.

On controls, I'll start the aileron controls with the nut/bolt between the aileron on one side and the pushrod, then check the other end of the pushrod on the bellcrank, then the other pushrod on the bellcrank, then... ending up all the way on the other side of the airplane, finishing with the nut holding the pushrod to that aileron.

In general, I don't use torque seal.
 
Seriously, torque seal only proves somebody put torque seal on
True Dan. The theory having multiple guys turning wrenches on a project is that if anyone sees the paint, the final torque was applied. We found that there was too many times one guy had to leave and the next morning the other guy picked up where the last text message said to continue. I found that in our case the TS gave a positive indicator of when someone completed a task. BTW we all got the idea from a local repair shop that does everything from 150s to jets. In our case it may have saved the day. Just thought id share. YMMV.
 
Just me

I use torque seal to show the bolt or nut has been torque. But this is only as good as the process. So the torque seal goes on as the bolts are torqued if there is any doubt the bolt/nut was torqued I do it again. So if I see torque strip Then it is torqued. Often times the torque strip comes off, so I retorque before stripping.
 
could not torque seal in some cases be an indicator that rotation has occurred after the seal was applied?
 
Curiousity question, I was taught that the true way to torque a nut is to have the torque reached while the nut is in motion. If you stop to ratchet the wrench and then apply torque and before the nut moves again the wrench clicks then you probably never reach the true torque value on the nut. My question is now at annual time, when you are checking torque do you all loosen all bolts and re-torque or just put a wrench on each nut and apply some torque (hoping not to go over the original torque) to see if they are really loose and are in need of re-torqueing?
 
+1

I use torque seal to show the bolt or nut has been torque. But this is only as good as the process. So the torque seal goes on as the bolts are torqued if there is any doubt the bolt/nut was torqued I do it again. So if I see torque strip Then it is torqued. Often times the torque strip comes off, so I retorque before stripping.

That?s my process, too. Torque seal used this way is a valuable aid to ensure no fastener torque steps were missed.
 
Just me

I was trained by a person who went on the become a formula 1 mechanic. His concern was to not keep tightening the nut every time it was checked. He emphasis to just run to the torque spec and see if the meter clicked. I think if nuts were loosened first than re tighten this would present problems and was not the preferred approach. We just set the torque wrench at the specified value and made sure it clicked, taking care not to keep tightening the nut. If we saw physical movement of the nut, then we alerted the engineers because that means somethings is moving or yielding.
 
Curiousity question, I was taught that the true way to torque a nut is to have the torque reached while the nut is in motion. If you stop to ratchet the wrench and then apply torque and before the nut moves again the wrench clicks then you probably never reach the true torque value on the nut. My question is now at annual time, when you are checking torque do you all loosen all bolts and re-torque or just put a wrench on each nut and apply some torque (hoping not to go over the original torque) to see if they are really loose and are in need of re-torqueing?

Static friction is always higher than dynamic friction, so yes, if you stop rotation when near a torque wrench setting, starting against the static friction may result in less preload than if you had kept moving until reaching the set torque.

As for annuals and inspections, generally there is no need to turn the nut. Just apply enough force to see if it is loose. In the rare cases where bolt preload is really important (very few AN bolt applications are), then yes, loosen before re-torquing.
 
TS is purely a quick visual indicator. It's there to show the nut/bolt/fitting hasn't moved since it was applied. Unless there is a requirement to check the torque it's a look-see and move on!
 
Yes, please only use the torque seal AFTER the nut/fitting has been properly torqued. It appears there my be some misunderstanding out there, as I discovered this summer when I licensed an RV.

As I walked up to the aircraft I saw that all fittings and nuts had torque seal on them, a practice I really like. However, as is my habit, I casually checked a jamnut and it came loose with my fingers, as did a number of others. So now, nothing was trusted, and rightfully so.

Torque seal is to be used as a visual inspection aid, not as a securing product.

Vic
 
As I walked up to the aircraft I saw that all fittings and nuts had torque seal on them, a practice I really like. However, as is my habit, I casually checked a jamnut and it came loose with my fingers, as did a number of others. So now, nothing was trusted, and rightfully so.

Thank you Vic...a fine example of "Torque seal proves nothing".
 
Thank you Vic...a fine example of "Torque seal proves nothing".

Several points to be made here.

1. Torque check indicator is just that; it's a tamper or inspection indicator that the fastener indicated was torqued. There is absolutely a time an a place for torque check and it is not worthless. It has its purpose, which is to indicate the fastener has been torqued and has not been tampered with since then. It definitely has its place in situations such as when working on large projects, say steam generator or condenser heads that have 150-200 1" nuts, with multiple people working the job. The torque indicator then indicates you've torqued that fastener as you're working through the job.
2. It provides a quick indicator for QA inspectors to know that the fastener has been torqued.
3. When the practice of using it is instituted, the torque indicator's absence means the fastener needs to be checked.
4. It does not indicate the torque of the fastener. Again, It does NOT indicate proper torque on the fastener. In fact, the bolt may have stretched causing torque to relax. It is simply a tamper or process indicator.
5. Don't put it across the bolt and down fouling the threads - apply from side of the flat of a fastener down and out on the material being fastened.
6. If you wipe the fastener with denatured alcohol first, the tamper check will not flake off.

If you want to know the torque, remove the torque check, apply a torque wrench - in the tightening direction. Reapply torque check if required.

One piece of advice; If the fastener had a break-away thread lock of some sort, you can break this lock by going above the original torque, which is counter productive. Also, many fasteners are single use - stretching on torque, so DO NOT check in the loosening direction. Most torque wrenches are +/-3%, so do torque checks at 95% of fastener torque in the tightening direction to prevent going above break-away torque.
 
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...nothing was trusted, and rightfully so.
I guess ultimately you are depending upon the integrity of the individual who applied the torque seal. If you have persons who apply torque seal without checking the torque, then that's a separate issue that needs to be addressed. In my case, I am the only one who works on my plane so I hope I can be trusted :D
 
Several points to be made here.

1. Torque check indicator is just that; it's a tamper or inspection indicator that the fastener indicated was torqued.

Except in the case Vic illustrated, they were not torqued. Worse, we have folks who won't check them, because they might need to remove and replace the pretty torque seal.

It has its purpose, which is to indicate the fastener has been torqued and has not been tampered with since then.

Again, well...you know. As for tampering, seriously, in our context?

Also, many fasteners are single use - stretching on torque, so DO NOT check in the loosening direction.

We don't have any stretch bolts on an RV, with the exception of Lycoming connecting rod bolts. AN bolt torque from the standard charts doesn't result in significant preload.
 
Except in the case Vic illustrated, they were not torqued. Worse, we have folks who won't check them, because they might need to remove and replace the pretty torque seal.

You may know that, but I don't have enough information to make that determination. As far I know, someone claimed they were torqued, but operation, vibration or inadequate torque could result in the fastener coming loose. Indicator doesn't prevent loosening of fasteners; which I've already said.

Again, well...you know. As for tampering, seriously, in our context?

Now, that's a reasonable question and the one that should be asked - is it a viable use within "our context"? It is not "worthless stuff", but rather designed for work process and tampering indicator; I do not consider it a viable application for a private airplane. And if that is your point, I agree.

We don't have any stretch bolts on an RV, with the exception of Lycoming connecting rod bolts. AN bolt torque from the standard charts doesn't result in significant preload.

This is a bit of a rabbit trail from the OP's question, but while I'm glad you've defined one stressed fastener in an standard RV, there are others. Such as cylinder hold-down and crank case nuts, as they stretch too and highly recommended for single use only (the reason the nuts are a lower grade than the through bolts as replacing the nuts is less expensive).

I would also add that anytime you torque a fastener above standard torque for the size (see AC 43.13-1b for further guidance), you should consider the fastener (notably it's threading), stressed, stretched, and should be replaced. An example is AN4 bolts being torqued to 100 ft-lbs on brakes, a common item on RV's. The standard threshold torque for an AN4 bolt is 70 ft-lbs; while you can keep reusing the bolt and likely get away with multiple reuses, either it is stretching, or the nut threads are, and will eventually fail; it would certainly never pass Level 1 inspection scrutiny. If you need further proof, take an AN4 bolt, the longer the more evident over distance, and measure it with a caliper, then torque it to 100 ft-lbs through a solid chunk of metal into a grade 8 metal fastener, remove, and measure again. Keep repeating...it gets longer and the threads get more loose each time.

Another example is propeller hub bolts, either fixed or complex; most prop manufacturers specify replacement at removal. Another is engine mount bolts. Both of these examples are exposed to higher stress and are identified for torque above the standard threshold and should be used once. Re-torquing can lead to failure.

And my favorite...self locking nuts...check the torque on these each time you tighten one and note how the drag torque value drops off. Consider how inexpensive they are and how valuable you and your passengers are... then just replace the things.

However, there are many, many applications of stressed fasteners in the world and my comment is aimed at educating in general.
 
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You mean like "Physically check all the nuts and bolts"?

Seriously, torque seal only proves somebody put torque seal on it. A wrench proves they are tight. The stuff is akin to sending new guys for a bucket of propwash.

I am the only person turning nuts and bolts on my project. I don’t apply torque seal until I have verified the torque, and I apply torque seal to every fastener I have verified. This is my system.

Making a blanket statement that the stuff is useless is pointless. Using it in my system saves me lots of pointless labor verifying unmarked fasteners after the fact.

Edited to add: I also like the fact that the indicator is fragile enough to show that a fastener has been rotated or otherwise displaced. Serves as a visual indicator that something is wrong.
 
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You mean like "Physically check all the nuts and bolts"?

Seriously, torque seal only proves somebody put torque seal on it. A wrench proves they are tight. The stuff is akin to sending new guys for a bucket of propwash.

Are you suggesting none of us use torque-seal just because a tiny few of us use it wrong?

If I bought somebody else's project, I would trust but verify - and put a wrench on everything, but that is not the situation that the OP is speaking of.

Torque seal, like anything else, is only as useful as the person using it. But that doesn't mean it is worthless for the vast majority of us that know how to properly use it. Do you re-check every single fastener at the beginning of each work session just to be sure you didn't miss any - how else would you be sure that you didn't? What process did you use to confirm you didn't miss any when building?

When building, and now when re-assembling anything after inspection, my torque-seal lives in the same tray as my torque wrench, and goes on immediately after. I can guarantee there is no torque seal on any fastener on my plane that was not torqued properly at the time the seal was applied.

It's like I tell people who can't believe I fly a homebuilt - I know the guy who built it and I trust him with my life.

Chris
 
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Gonna open up this old thread to chime in: While I agree torque seal doesn't prove the fastener is torqued correctly, if you are diligent about applying it, then you can at least say that lack of torque seal indicates a potentially problematic fastener.

I was just inside the engine compartment today, tidying up some unrelated stuff in advance of first engine start, and happened to glance up and notice a hose fitting without any seal applied. Well, that pretty much caused me to stop what I was doing, pull out a flashlight and have a closer look. In total, I found the following fasteners without torque seal:

  • Prop control oil line (fittings on BOTH ends)
  • Oil lines to and from the cooler
  • Oil line to pressure sender
  • Fuel line connector at the firewall

Checking each of them, lo and behold all but the pressure sender line were hand-tight! That would have been messy and/or dangerous if I did an oil pressure test or fuel pressure test before addressing them. So, I'd say at least lack of seal can be a good indicator of trouble.
 
Gonna open up this old thread to chime in: While I agree torque seal doesn't prove the fastener is torqued correctly, if you are diligent about applying it, then you can at least say that lack of torque seal indicates a potentially problematic fastener.... So, I'd say at least lack of seal can be a good indicator of trouble.

Exactly. Competently used, it's a great way to highlight fasteners that we inadvertently missed during assembly/maintenance. The FAA agrees:

https://publicsafetyaviation.org/images/Press_Release_A/FAA_SAIB_BELL_11217.pdf

https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=529&sID=907&preview=true
 
TS is purely a quick visual indicator. It's there to show the nut/bolt/fitting hasn't moved since it was applied. Unless there is a requirement to check the torque it's a look-see and move on!

In my years in commercial aircraft manufacturing it was always stressed that torque seal (or even inspector's putty) was not intended to show movement. It was strictly a QC tool at the time of torqueing and had no subsequent purpose after final inspection was bought off. In fact it could be argued that as soon as the aircraft leaves the assembly building it could all be removed (not that would ever happen). However I run into a lot of people who think it is used as a way to monitor bolt/nut movement over time. A pre-flight visual QC as it were. Such is not the reason it was originally implemented.
 
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