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  #1  
Old 03-24-2021, 11:21 AM
wcalvert's Avatar
wcalvert wcalvert is offline
 
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Question AN vs Industrial MJ fittings

My question is whether an MJ style hydraulic fitting, 37 degree like an AN fitting, may be used in an aviation application. These fittings are available at any hydraulics shop or good auto supplier, and are slightly less expensive than the "aviation" AN fitting.

Some research from Parker

(http://blog.parker.com/an-37-flare-v...the-difference)

revealed the following:

"There are several differences between "comparable" industrial 37 flare (SAE/ISO) and AN 37 flare style fittings.

Some include:

Threads:

AN 37 Flare: Male and female, Class 3A/3B UNJ/UNJF (radiused root threads)
SAE/ISO 37 Flare: Male and female, class 2A/2B, UN/UNF series threads
Reason: Tighter tolerances and better fatigue life for aircraft, aerospace, military applications."

and:

"AN 37 flare and industrial 37 flare fittings function identically. In many cases they appear to be functionally interchangeable, but they are not. What this means is that while the products may look similar, you must not use an industrial 37 flare fitting design as a direct substitution.

Note: Parker Triple-Lok 37 flare fittings (or other TFD products) are not for use in Aerospace, General Aviation, Commercial Aviation or Military Aviation applications."

So the warning is clear that they should not be interchanged, although I am not sure if that only applies to Certified applications or if there is another reason.

The real question is this: How do you know that a fitting is a true AN or an MJ? Most AN fittings are not marked as such.

Anyone have any insight here?
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  #2  
Old 03-24-2021, 12:05 PM
rocketman1988 rocketman1988 is offline
 
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Default Legalese

That sounds like legalese because they don't want the liability of aerospace use...
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  #3  
Old 03-24-2021, 01:03 PM
TS Flightlines TS Flightlines is offline
 
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The flare head specs are the same for both JIC and AN. Major difference is the class 3 thread vs the class 2 for JIC. Tighter tollerances for the AN, but functionality is the same. Materials can vary especially in aluminum fittings.
Look at it like this----the 90* oring boss fittings on some GA fuel pumps from Lycoming are NOT AN, they are industrial JIC. This fitting isnt made in AN, but a AN833-6m with lock nut an o'ring used.

Think about it, if your Caterpilar track hoe or dozer can use JIC---I think your experimental will be just fine.

Tom
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  #4  
Old 03-24-2021, 01:58 PM
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I was thinking the same thing about a tractor application. Most gas powered pumps I've looked at shake like a Lyc on shutdown the whole time. Never seen one break...
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