Hydraulic Fittings Won't Seal

[huffman102833]

Not a thread expert but there is the pipe threads and there is another thread that will screw together with it but they are NOT compatible. Under load they can leak and even blow apart. If you are paying attention very carefully and try wiggling the two fittings you should pick up on more movement than is normal. I have run into this with two different hyd cylinders due to just assuming same threads on all hyd cylinders and they are NOT. When both of mine failed it was a major failure (in regardless to how major the oil leaked) with little notice. I do not think the sealant is your issue but the fittings are not the same thread type.

After more reading and speaking with Marc, the issue is that the hose has NPS ends and the fittings are NPT. The threads are the same but NPT is tapered and seals at the thread, while NPS is straight and seals at the seat. I know many folks have suggested that NPS to NPT will still work with proper sealant, but I decided to purchase NPS fittings just to be safe. The pic helped me better under stand the problem.

 

[/pine]

Not a thread expert but there is the pipe threads and there is another thread that will screw together with it but they are NOT compatible. Under load they can leak and even blow apart. If you are paying attention very carefully and try wiggling the two fittings you should pick up on more movement than is normal. I have run into this with two different hyd cylinders due to just assuming same threads on all hyd cylinders and they are NOT. When both of mine failed it was a major failure (in regardless to how major the oil leaked) with little notice. I do not think the sealant is your issue but the fittings are not the same thread type.

Happy to hear the issue is solved...Sorry for the confusion...I think most of us were going by the description of the hose stating it was "MNTP 1/2 In. x 24 In. Long Hydraulic Hose, Swivel End

Kudos to kthompson for the heads up and Marc at DHH...

 

[bigdeano]

Well, that's very strange. I've never seen a hose with straight pipe threads, didn't know they made them. The picture of the hose looks like they're tapered, but it's hard to see. Do you have some calipers you could put on the threads to see if they're tapered or not? In any case the swivel female fitting would fix the leak.