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  #1  
Old 01-28-2021, 01:13 PM
Meat Meat is offline
 
Join Date: Jan 2018
Location: Glendale, AZ
Posts: 23
Default Andair Fuel Valve and Loctite 648. Why?

Hi All,

I've got the standard Andair FS20x2 fuel selector valve on my RV-14. Andair is very specific that the #4 screws used on the fittings are to be secured with Loctite 648. I was unfamiliar with this particular Loctite product and looked it up. Unlike the traditional blue and red Loctite threadlockers, Loctite 648 is a retaining compound for close tolerance cylindrical parts. It doesn't seem appropriate for use a threadlocker.

Does anyone know why this product is recommended for the fuel fitting machine screws vs traditional threadlockers? I've got an email into Andair as well.

Thanks for your time.

Cheers,

Scott
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  #2  
Old 01-28-2021, 01:39 PM
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Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
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Default

Green locktite is sometimes used for weeping rivets.

May have something to do with resistance to fuel?
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Rv-10, N210LM.

Flying as of 12/4/2010

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"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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  #3  
Old 01-28-2021, 02:01 PM
MED MED is offline
 
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I believe it is because it is “permanent.” The alternative offered to the loctite is staking the screws!
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  #4  
Old 01-28-2021, 02:12 PM
Mckay Mckay is offline
 
Join Date: Dec 2019
Location: Prescott, Az
Posts: 43
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Green Loktite is wicking, it will seep into very small clearances.
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  #5  
Old 01-28-2021, 05:23 PM
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9GT 9GT is offline
 
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Location: Southern Michigan
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Default

Andair has been in the business a long time and produces high quality products. Like anything else, you usually can't go wrong when you follow manufacturer's directions and installation specifications.
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  #6  
Old 01-28-2021, 09:20 PM
Meat Meat is offline
 
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Location: Glendale, AZ
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Default Loctite 648

I'm just curious more then anything else. I'm sure there's a good reason why its recommended. Fuel resistance, its ability to weep into tight tolerances, etc.

Can anyone comment on how difficult the -648 makes it to remove the #4 fuel fitting screws if needed?

Cheers,

Scott
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  #7  
Old 01-29-2021, 06:44 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,133
Default Specifications are more than a color.

Loctite is a Henkel Product. They make at least a hundred formulations of "locking" goo. Color is not a good specification, they all have SDS and MDS, by product, for understanding the differences, not to mention application engineers that will help making specific recommendations. A little searching and you can find the application guide for a top level comparison of available products. That is always a good place to start learning and selecting a good, cost effective, locker.

Viscosity, application & operation temperature range, gaps, shear strength, set time, time vs strength, shelf life, and material compatibility are a few parameters that are under consideration for a product selection.

If all else fails, and you are really curious (or need data), you might be amazed that you can get an application engineer on the phone to address your specific questions. Better than a 1000 posts. Waaaay better.
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  #8  
Old 01-29-2021, 06:50 AM
edclee edclee is offline
 
Join Date: Aug 2008
Location: Lancaster, SC
Posts: 211
Default Locktite

Quote:
Originally Posted by Meat View Post
I'm just curious more then anything else. I'm sure there's a good reason why its recommended. Fuel resistance, its ability to weep into tight tolerances, etc.

Can anyone comment on how difficult the -648 makes it to remove the #4 fuel fitting screws if needed?

Cheers,

Scott
Having used #648 to retain a cylindrical fit part on a shaft, I can tell you that you cannot remove that #4 screw unless you heat the joint to around 300F first. Apply heat to the head of the screw and lots of it before even atttempting to unscrew it. The screw itself will shear in torque first even if you could grip the head well enough. That is VERY tough stuff. Unless the assembly can be heated it will not come out. If the entire assembly can be removed and put in a mill, so precise drilling out of the screw can be done it is the only way to remove it. 648 is fuel proof, oil proof.
Ed
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  #9  
Old 01-29-2021, 07:14 AM
lr172 lr172 is offline
 
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red loctite is very strong, so also don't understand the recommendation. I have used loctite sleeve reatainer (numerous different versions) and, at least on tight slip fit and interference fit applications, it starts setting up before the part is fully pressed in. You have to move fast. Not sure this applies to a thread lock application though.
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  #10  
Old 01-29-2021, 08:20 AM
jacoby jacoby is offline
 
Join Date: Jul 2018
Location: WNC
Posts: 311
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Quote:
Originally Posted by lr172 View Post
red loctite is very strong, so also don't understand the recommendation. I have used loctite sleeve reatainer (numerous different versions) and, at least on tight slip fit and interference fit applications, it starts setting up before the part is fully pressed in. You have to move fast. Not sure this applies to a thread lock application though.
Yeah, the green stuff is basically permanent, especially if you're talking about a fuel valve. Nobody is going to heat it up to remove the screws. I've used the green stuff to make fixtures and assemblies that get turned on the lathe. I used it on the aileron bearings to keep them from turning in the wing brackets.

Interestingly, Permatex introduced orange threadlocker this year. It's supposed to be as removable as blue with nearly red locking ability.
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