Hydraulic Pipe Fittings

 

This thread type is the most commonly used tapered pipe thread connection found on equipment made in North America.  Additional sealing aids such as PTFE Tape are used with these threads.  This connection is often used on fluid power systems.

 

Pressure Ratings

SAE Dash Size Fittings w/ NPTF Pipe Threads (psi) Fittings w/ NPSM Female Swivel (psi)
-02 5,000 5,000
-04 4,000 5,000
-06 3,000 4,000
-08 3,000 3,500
-12 2,500 2,250
-16 2,000 2,000
-20 1,150 1,625
-24 1,000 1,250
-32 1,000 1,125
 NPTF – Dryseal American Standard Taper Pipe Thread
NPSM – American Standard Straight      Pipe Thread for Mechanical Joints
NPTF Thread Specifications
Thread Size Nominal Size
(in)
Number of Threads per Inch Male Thread O.D.
(in)
-02 1/8 27 13/32
-04 1/4 18 35/64
-06 3/8 18 43/64
-08 1/2 14 27/32
-12 3/4 14 1-1/16
-16 1 11.5 1-5/16
-20 1-1/4 11.5 1-21/32
-24 1-1/2 11.5 1-29/32
-32 2 11.5 2-3/8
-40 2-1/2 8 2-7/8
-48 3 8 3-1/2
-64 4 8 4-1/2

 

  • Thread conforms to ANSI B1.20.3
  • Physically interchangeable with NPT but has modified threads for better pressure tight sealing
  • Tapered thread profile seals by metal to metal interference fit, usually requires sealing compound for pressure tight connections
  • Pitch and diameter are measured in inches
  • Taper angle is 0.75″ per foot or 1° 47′
  • Thread angle is 60º

 

 

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Pipe Fitting Assembly

  1. Inspect port components to ensure that male and female threads are free of nicks, burrs, dirt, etc.
  2. Apply sealant/lubricant to male pipe threads.  Pre-applied Vibraseal is preferred over other sealants.  With any sealant, the first few threads should be left uncovered to avoid system contamination.  If PTFE Tape is used, it should be wrapped 1-1/2 turns in a clockwise direction when viewed from the end.
  3. Screw Fitting into female pipe port to finger tight position.
  4. Wrench tighten fitting to the appropriate TFFT shown in the chart to the right, making sure the tube end of the shaped fitting is aligned to receive incoming tube or hose assembly.
 

Finger Tight Torque Specifications

Pipe Thread Size Turns From Finger Tight (TFFT) 
-02 2.0 – 3.0
-04 2.0 – 3.0
-06 1.5 – 3.0
-08 2.0 – 3.0
-12 2.0 – 3.0
-16 1.5 – 2.5
-20 1.5 – 2.5
-24 1.5 – 2.5
-32 1.5 – 2.5

 

 

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