Tube Fitting

Straight thread type of tube fittingThreaded fittings make a connection by attaching two threaded pieces, one male (where threads project on the outside of the fitting) and the other female (where threads are found inside the fitting). Male threads are inserted into female threads.

Threaded fittings come in two distinct varieties: those with straight or parallel threads, and those with tapered threads. Straight threads are designed to hold a nut onto the body of a tube fitting and rely on supplemental items, including gaskets, O-rings, or metal-to-metal contact to create a leak-tight seal. For this reason, straight threads are typically used in applications where system pressure will not exceed 5000 psi.

In contrast to threaded fittings, compression tube fittings commonly utilize ferrules to create a leak-tight seal. When the fitting's nut is tightened, the ferrule is compressed between the nut and the receiving fitting. As a result of this compression, the ferrule effectively bites into the tube, thus creating a strong grip and a tight seal. The reliability of the tube grip is related to how well the gripping ferrule performs this function. Compression fittings also offer the benefit of being simple to assemble and disassemble.

Medium-pressure mechanical grip fittings—an evolution of two-ferrule compression fittings—also deliver outstanding performance along with enhanced installation efficiency. This design creates a unique dynamic wedge. The dynamic wedge allows for remakeable pullups by torque and provides gaugeability at initial assembly and remake of the tube fitting. The two-ferrule design creates a more robust bite into the tubing, creating a leak-tight gas seal upon initial installation and every remake.

Finally, cone and thread fittings are available in a wide variety of alloys and have several design features that make them suitable for medium- to high-pressure applications. Their reliable performance has made them a standard high-pressure fitting choice in a variety of demanding applications for many years.Cone- and thread-specific tubing, featuring thicker walls and a higher pressure rating, is typically required when cone and thread fittings will be used. A high-performance cone and thread fitting will feature a gland, a collar, a female port, and a weep hole that enables you to detect leaks and verify proper installation.