In the handbook, on the table for torque for AN Flared fittings, the values for Steel fittings is higher than for alum fittings (in some cases dramatically higher). Is this just because the steel can support the higher loads on the threads, or is there a reason why the steel fittings NEED a higher torque to seal reliably?
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why higher torque for steel fittings
- Thread starter prkaye
- Start date
ahhh... that is a good explanation!
Still... regardin the mixed case (alum and steel fitting together), I'm not sure what value to use. On the one hand, if I use the higher value I risk stripping the threads on the alum side, but if I use the lower value it might not seal properly...
Surely this is a question almost everybody comes across...
Still... regardin the mixed case (alum and steel fitting together), I'm not sure what value to use. On the one hand, if I use the higher value I risk stripping the threads on the alum side, but if I use the lower value it might not seal properly...
Surely this is a question almost everybody comes across...
Lycosaurus
Well Known Member
My guess is to use the lower value, as the aluminum fitting will comply to the steel fitting.
az_gila
Well Known Member
Checking AC43-13....
...and looking at Table 9-2.
The torque data for the AN-818 nut is based on the tube material, not the material that the nut is made from.
As a previous poster said, this makes sense since the steel tubing will need more force to seal the flare correctly.
It also turns Lycosaurus' guess into correct data...
Again, AC43-13 (aka the "bible") is a good source of info. I don't know which "handbook" you refer to.
...and looking at Table 9-2.
The torque data for the AN-818 nut is based on the tube material, not the material that the nut is made from.
As a previous poster said, this makes sense since the steel tubing will need more force to seal the flare correctly.
It also turns Lycosaurus' guess into correct data...
Again, AC43-13 (aka the "bible") is a good source of info. I don't know which "handbook" you refer to.
IowaRV9Dreamer
Well Known Member
It is my understanding that you use the low torque for aluminum TUBE, even with steel FITTINGS. I'd be afraid to use such high torque on the soft AL tube, becuase I think it would overly crush the flare.
I'm not sure what torque to use on something like the aeroquip 90 degree fitting into the fuel pump... probably high since it is steel and there is no soft tube involved.
I'm not sure what torque to use on something like the aeroquip 90 degree fitting into the fuel pump... probably high since it is steel and there is no soft tube involved.
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az_gila
Well Known Member
az_gila
Well Known Member
Does this handbook....
...differentiate based on tubing material, or is it vague/non-commital?
If documents vary, then the FAA prefers it's own AC documents...
Since the AC 43-13 is on line and free, it makes it a good reference.
Link here to contents
The section in question is here at page 21.
And just to make sure we are talking about the same item being torqued, this is the AN 818 nut...
...differentiate based on tubing material, or is it vague/non-commital?
If documents vary, then the FAA prefers it's own AC documents...
Since the AC 43-13 is on line and free, it makes it a good reference.
Link here to contents
The section in question is here at page 21.
And just to make sure we are talking about the same item being torqued, this is the AN 818 nut...
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IowaRV9Dreamer
Well Known Member
oops
Thanks Gil - I was thinking "low torque" but typed "high torque"..... must be getting old....
Thanks Gil - I was thinking "low torque" but typed "high torque"..... must be getting old....
az_gila
Well Known Member
A bad assumption...
... looking at Vans picture -
- it's a blue anodised aluminum fitting.
However, the previous discussion was for metal flared tubing. I expect torque values to be different for the machined ends of hose fitting.
I believe they seal by having a fractional difference in angles.
... looking at Vans picture -
- it's a blue anodised aluminum fitting.
However, the previous discussion was for metal flared tubing. I expect torque values to be different for the machined ends of hose fitting.
I believe they seal by having a fractional difference in angles.
