willie59
Administrator
A common hyd fitting is the inverted flare. My personal opinion, I have no particular fondness for them as compared to JIC or flat face o-ring fittings because all to often I run across an inverted flare connection that has been overtightened. These were on the center swivel of a Case 9050B excavator, and rather large fittings, 1 5/8" wrench size. The hose fitting nut was so tight that it simply loosened the fitting in the swivel body. Grrrrrrr. I knew right then I would have a problem. Sure enough, once I broke the hose fitting nut loose, it got tight screwing off, had to beat on flats of hose fitting nut to get it unscrewed, nearly all the way to the last thread.
Here's what happens, notice the fitting placed on the swing motor, notice how the flare of the sealing surface tapers inward into the fitting, that's what's known as inverted flare. Then notice the taper in the hose fitting that mates with the manifold fitting. What happens when you tighten these fittings too tight, that taper of the hose fittings gets crammed harder and harder into the inverted taper of the manifold fitting. This results in expanding the very end of the manifold fitting making it a slightly larger diameter than it originally was. So a person would fit up this connection, lock it down excessively tight, and in doing so they expand the fitting inside the made connection. When the next fellow comes along to take the connection loose, and the fitting threads are now expanded, it makes that nut so tight on the threads it will screw off hard all the way because it's the very end threads that are expanded. In the case with this particular fitting, it started locking down and began growling from friction. When this happens, you have to take a ball peen hammer and hammer on the flats of the nut to slightly expand the nut, if you don't, you will gall the threads. I can't say what the exact torque procedure is for these fittings, always done it by feel myself, I can only say don't lock them down until the nut will turn no more, then give it an extra 300 pound arse pull for good measure. Bad idea.
Here's what happens, notice the fitting placed on the swing motor, notice how the flare of the sealing surface tapers inward into the fitting, that's what's known as inverted flare. Then notice the taper in the hose fitting that mates with the manifold fitting. What happens when you tighten these fittings too tight, that taper of the hose fittings gets crammed harder and harder into the inverted taper of the manifold fitting. This results in expanding the very end of the manifold fitting making it a slightly larger diameter than it originally was. So a person would fit up this connection, lock it down excessively tight, and in doing so they expand the fitting inside the made connection. When the next fellow comes along to take the connection loose, and the fitting threads are now expanded, it makes that nut so tight on the threads it will screw off hard all the way because it's the very end threads that are expanded. In the case with this particular fitting, it started locking down and began growling from friction. When this happens, you have to take a ball peen hammer and hammer on the flats of the nut to slightly expand the nut, if you don't, you will gall the threads. I can't say what the exact torque procedure is for these fittings, always done it by feel myself, I can only say don't lock them down until the nut will turn no more, then give it an extra 300 pound arse pull for good measure. Bad idea.
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