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Design and Operation - Koncentric Unions


Koncentrik® unions join pipe or tubing. Metal-to-metal contact between mating taper angles in the union is reinforced by a fully confined Teflon seal to form a leak-proof joint.

The Koncentrik® union is a four-piece assembly consisting of a threaded piece, tailpiece, union nut, and Teflon® seal. The Teflon® seal is preinstalled in a precision-machined groove in the male cone shaped tailpiece prior to shipment. The Teflon® seal cushions the metal-to-metal contact of the surfaces and prevents them from becoming galled or scratched. The unions can be taken apart and resealed many times with no damage to the union or loss of sealing effectiveness.

Koncentrik® unions are available with tube & pipe socket and butt weld, female pipe thread, and male o-ring boss port end connections.

Suggested Applications for Koncentrik® Unions

Koncentrik® unions have been used extensively in high pressure ground support missle systems, hydraulic control systems for turbine generators, and in nuclear and conventional power plant applications.

Koncentrik® unions offer all the advantages of flanges without the disadvantages. Like flanges, Koncentrik® unions can hold high pressures and can be repeatedly disassembled and resealed. But, unlike flanges, Koncentrik® unions are light in weight and quick to assemble. Only one nut holds the union together while flanges require several bolts and cumbersome rotational alignment.

Feature Koncentrik® Unions, Pipe Fittings & Adapters
Pressures Very high to 10,000 psi
Temperature PTFE/Teflon®: -100° to 450°F
Vibration Resistance

Very good

Materials Available 316/316L stainless
M405 Monel®
Size Available (tubing OD)

 1/8" – 2"


Seal Reliability Very good
PTFE seal reinforced by metal-to-metal seal
Medium tolerance to surface imperfections
Medium tolerance to assembly variation like under-torquing
Thread & Port Preparation Varies. Connects to tubing, pipe & port connections.
Ease of Assembly Medium. Flats from Finger-Tight method utilized.
Ease of Maintenance Very good. High number of breaks & remakes with Teflon® snap-ring replacement.
Specification Conformance
(design & thread)
ANSI B31.1.0 Power Piping
ANSI B16.11 Forged Steel Fittings Socket Welded & Threaded




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