Hydraulic Thread Identification

Various industries use hydraulic-powered machinery, from agriculture to aerospace. These applications require a wide range of hydraulic fittings and adapters with different port types, thread forms, and sealing methods.

Correctly identifying hydraulic threads is crucial to avoid catastrophic consequences. While it may be easy to identify different sealing methods, distinguishing hydraulic threads by appearance can be challenging. It is important to correctly identify hydraulic threads to ensure the selection of the right replacement part during maintenance and repair processes.

Using the wrong type of hydraulic fitting can lead to malfunctions, damage the thread, and compromise the seal reliability and pressure holding capacity. Learn how to correctly identify hydraulic threads to protect your equipment and workers for safe, productive, and profitable operations.

The Most Common Types of Hydraulic Threads

The most common type of quick coupler hydraulic threads include:

• NPT thread– National Pipe Tapered Thread: NPT threads are traditional tapered fittings used in hydraulic and pneumatic systems. They are a metal-to-metal sealing type that requires a pipe sealing like Teflon tape or pipe dope to make a leak-free connection. We do not recommend unmaking this connection, as it will leak upon reconnection.
  ● SAE thread – can be identified by the visible O-ring at the base of the male thread. The SAE thread and the straight JIC 37° Flare are both the same threads, although the ORB seals with an O-ring for a better leak-free connection.
  ● BSPP thread – British Standard Parallel – a straight thread often expressed as a “G” thread that requires a secondary bonded washer or dowty seal to make a leak-free connection.
  ● JIC thread – Joint Industrial Counsel Thread (37° Flare Type) – common in fluid power systems and can withstand higher working pressures. Both male and female fittings have 37° seats with a seal made at the flare of the male coupler and the coned seat of the female. Can be disconnected and reconnected without concern, although are susceptible to cracking when overtightening.
  ● ORFS thread – O-Ring Face Seal – identified with an O-ring against the shoulder of the male on the face of the male thread. The O-ring on the face seals against a flat surface face on the female thread. This is a straight thread type, and the connection can be made and unmade without risk of leakage.

How To Identify Hydraulic Threads

In order to choose the correct type of hydraulic hose fitting for applications, operators must know how to determine the type of quick coupler fitting and match the port connection with that on the hydraulic hose. It is critical to determine the type of fitting design, thread size, and type of seal when installing, repairing, or replacing hydraulic quick couplers.

Operators must:

• Determine the gender of the coupler
• Identify the fitting and thread size
• Match the port connection to the hydraulic hose
• Identify the type of seal