What are O Ring Boss (ORB) fittings and how to they relate to standard AN fittings.

 

These are some ORB to AN adapters:
http://www.goodvibesracing.com/orb_fittings.htm
And this is a close up of one where you can see the o-ring straight thread side and the 37° AN flare on the other side:
http://www.goodvibesracing.com/Produ...s/E-815-12.JPG

This shows more ORB to 37° degree flare adapters with the 45°/90° angle adapters having separate nuts/washers above the o-ring so the fitting can be positioned in whatever orientation needed and the nut is tightened down on the o-ring to provide the seal and lock it in place:
http://www.livermoreperformance.com/xrp_orb.html
A pipe thread connection depends on the threads to seal and an angled fitting may not end up in the correct orientation after it's fully tightened.

Not all 37° flare fittings are created equal which is why there are AN and JIC designations. This is the difference between AN and JIC fittings:
http://www.mechanicsupport.com/articleStronger.html
And of course SAE 45° flare fittings are completely incompatible with any 37° flare fittings.

Here is a list/description of the different thread classes referenced in the above link:
http://www.sizes.com/tools/bolts_inch_threadFit.htm
Obviously, not all threads are created equal...not many people know there are different size threads for the same size bolt/nut.

You can also go from ORB to other thread types, even ORB to ORB:
http://www.discounthydraulichose.com...Ring_s/222.htm
We usually refer to ORB fittings as straight thread fittings...much easier to say.

AN fitting sizes are stated using "-" (dash) numbers like -8 AN fitting. The number refers to the OD of the associated tubing used with the fitting in 16ths of an inch so a -8 AN fitting is for 1/2" tubing.

Happy reading!

 

Great post.

I see that an ORB fitting can be very useful if not required to allow for the fitting orientation to be controlled since the ORB locking nut allows the fitting to be rotated to while still providing a seal. Something that cant happen with a standard AN fitting.

What are the other plus sides of ORB over AN?

 

Oops, I forgot to "connect" the ORB and AN fittings together. (Sorry, couldn't resist.)

ORB fittings relate to AN fittings as a means to provide a way to adapt hoses/tubing with AN connections to the main components at either end. For example in my boat, I have a fuel manifold with four shut off valves (two for each engine) between my fuel tank and my engines. I use hoses with AN fittings on each end between the fuel tank and fuel manifold, fuel manifold to fuel filter/water separator, fuel filter/water separator to fuel pump, and fuel pump to carburetor. The fuel tank, fuel manifold, fuel filter/water separator, and fuel pump all have female pipe thread connections so I use NPT to AN adapters. The carburetors have straight thread (ORB) connections so I have ORB to AN adapters there. Could you imagine the cost of machining male or female AN connections in the fuel tank, fuel manifold, fuel filter/water separator, fuel pump and carburetor. Now imagine what would happen if the 37° flare where the seal occurs were to get damaged...might as well throw it away and get another fuel tank, fuel manifold, fuel filter/water separator, fuel pump or carburetor (really just the fuel bowl). Now imagine a hydraulic manifold that costs $30,000 to replace...we have some on our US Navy ships and I've replaced them before but not due to the connection failing. That becomes a very expensive proposition so it's better to machine a straight thread/ORB or NPT connection into the main components and use an ORB to AN or NPT to AN adapter to make the connection. And there you have the relationship of ORB fittings to AN fittings.

PS Since the nut turns on the hose/tubing of an AN fitting, they can be oriented in any direction too. A pipe thread connection is the one that can't be oriented in whatever direction needed, you're at the mercy of where it stops although you can fudge a lot of times to get what you need. It's just not a desirable way to do business.