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.

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.

Pipe Koncentrik

Koncentrik® unions’ four-piece assembly consist of a threaded piece, tailpiece, union nut, and PTFE seal. Metal-to-metal contact between mating taper angles in the union is reinforced by a fully confined PTFE seal to form a leak-proof joint. The PTFE seal is preinstalled in a precision-machined groove in the male cone shaped tailpiece prior to shipment. The PTFE 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.

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  • MAWP: Up to 10, 000 psig (689 bar)*
  • Temperature Range: -100 to 450°F
  • Body Material:  316/316L Stainless Steel, Alloy 400.
  • End Connection
    • Sizes:  1/8 to 2 in.
    • Adapter types:  NPT, SAE, pipe socket weld, tube socket weld, pipe butt weld, tube butt weld.

*Pressure ratings are based on using Schedule 40 pipe.

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.

Feature Koncentrik® Unions, Pipe Fittings & Adapters
PressuresVery high to 10,000 psi
TemperaturePTFE: -100° to 450°F
Vibration Resistance

Very good

Materials Available316/316L stainless
Alloy 405 
Size Available (tubing OD)

 1/8 – 2 in.


Seal ReliabilityVery good
PTFE seal reinforced by metal-to-metal seal
Medium tolerance to surface imperfections
Medium tolerance to assembly variation like under-torquing
Thread & Port PreparationVaries. Connects to tubing, pipe & port connections.
Ease of AssemblyMedium. Flats from Finger-Tight method utilized.
Ease of MaintenanceVery 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