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Hydraulic fittings

Discussion in 'Compact Equipment Attachments' started by andrewpond, Mar 3, 2019.

  1. andrewpond

    andrewpond Well-Known Member

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    Hello... as I am typing this unbelievable dumb question...

    I have hydraulic motor bmrs
    http://www.dynamicfc.com/BMRS.html

    Website says npt 1/2" ports. I got hoses made up w 1/2" F Npt fittings... but they simply bottom out and never seat/ seal... what am I missing? The motors brand new and had threaded caps w "o" rings?
    Thxs
     
  2. Welder Dave

    Welder Dave Senior Member

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    Sounds like the motor you have has 0-ring boss fittings. Should be easy to take to the hose place and find the right fittings.
     
  3. Jonas302

    Jonas302 Senior Member

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    My guess is they sent you the pump with 7/8 sae fittings theads are a little bigger and same theads per inch with no taper
     
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  4. willie59

    willie59 Super Moderator

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    Agree with Welder Dave, that motor has SAE o-ring boss ports, those ports are not NPT.
     
  5. TVA

    TVA Senior Member

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    The catalogue says it comes with ORB or NPT ports, if your NPT doesn’t fit then it is ORB.
     
  6. Welder Dave

    Welder Dave Senior Member

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    The ORB fittings are better anyway.
     
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  7. TVA

    TVA Senior Member

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    Hands down!!!
     
  8. willie59

    willie59 Super Moderator

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    IMHO, NPT is for water pipes and air lines, has no place in hydraulics, but that's just me.
     
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  9. TVA

    TVA Senior Member

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    Just was reading thread about You Tube. There’s a channel called SV Seeker, guy building a ship in Tulsa OK, so his fan from Minnesota brought Ridgid thread cutting machine and they started plumbing the whole ships hydraulic system with that! I couldn’t whatch it any further!!! There’s NPTF, but plumb the hydraulic system of the ship with water standard ridgid schedule 80 stainless steel pipe in this day and age - it was beyond the strength of my nervous system!!!
    I guess they didn’t realize what they were getting them selves in to!!!
     
  10. John C.

    John C. Senior Member

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    Pipe thread is still common on low pressure hydraulic systems. In general it can be found on systems operating at less than 2500 psi.
     
  11. TVA

    TVA Senior Member

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    There’s huge difference between regular NPT which used for water supply and Hydrounic heating or CNG systems, and NPTF used in Fluid Power. Regular NPT is way to sloppy and requires some kind of a thread sealant. To assemble system like that with ridgid steel pipe will require many times more work then some other type of hydraulic joints. And if down the road you need to replace section of the piping, it will turn in to nightmare. Best way to do it is cut the section out and weld new one in by “surgical welding” technique. Without messing with threaded joints.
     
  12. John C.

    John C. Senior Member

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    I have a machine apart right now that has all NPT fittings on the control valves with corresponding fittings on hoses and tubing going all the way to the back of the machine. I installed a new valve into the system to enable bi-direction movement on a function and put O ring fittings in the new valve with JIC ends on one end of the connecting hoses and NPT fittings on the other ends. Just because you haven't seen something doesn't mean that it doesn't exist or can't be done.
     
  13. andrewpond

    andrewpond Well-Known Member

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    Thxs Guys. Yep 1/2" ORB.... my confusion was my cross over valve is #8 ORB (metric ?), hadn't thought about ORB SAE and my printed paper work for motor only gave 1/2" NPT as option...

    Thxs again guys
     
  14. andrewpond

    andrewpond Well-Known Member

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    John C. Is ORB and NPTF interchangeable?
     
  15. willie59

    willie59 Super Moderator

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    No
     
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  16. mx727

    mx727 Active Member

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    Not Metric. #8 means 8/16", thus 1/2 inch.
     
  17. John C.

    John C. Senior Member

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    If you have an O ring boss fitting there will be a chamfer in the housing of the motor or pump assembly you are going to use. The catalog shows a NPTF which stands for national pipe thread fuel and it is made to connect with a mating fitting without the use of a sealing agent. There is nearly the same taper in the thread but the threads themselves partially crush along the entire engaged length of the connection to make a seal. I see these fittings all the time in industrial uses at low pressures. Half inch pipe is 14 threads per inch on both types of fittings. As has been stated above, the o ring fittings are far more preferable to use than the pipe threads.

    There is another pipe thread called NPTM which is national pipe thread mechanical. There is a chamfer in the fitting itself which seals against a ball like structure, a 60 degree cone, on the opposing fitting. My book shows it as 14 threads per inch also. It is nearly the same thing as a British Ball nose fitting except the mating surface is a lot smaller. Finally there is a SAE straight thread O ring fitting which can be confusing because in order to keep a 1/2" hole for flow they have to use a 3/4 inch fitting size with 16 threads per inch. So a 1/2 inch NPTF or other fitting would be much smaller than hole it was being screwed into.

    A Parker Hose, Fittings and Equipment catalog will explain all the different fittings and their sizes if you have a dealer near by.
     
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  18. excavator

    excavator Senior Member

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    I have to agree but have always wondered why a portapower that goes to 10,000psi comes with NPT.
     
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