Unions - External

stainless external union
External union
close move

External unions have male threads, requiring a nut with female threads. Standard material is 300 series stainless. Also available in Hastelloy C and gold-plated stainless versions.

Select the union with the bore that matches the ID of the tubing. If the IDs are different, choose the union with a bore which matches the smaller tube bore. (A through-type union is illustrated at right.)

stainless bulkhead external union
External bulkhead union
close move

Bulkhead versions are designed to be mounted through an instrument panel or on a bracket. The fitting body is undercut so that it bites into the panel when the mounting nut is tightened, eliminating the need for a lock washer.

Note: Because 1/16" external fittings have very thin, easily distorted walls, they are not as durable as 1/16" internal fittings. We recommend the use of external/internal unions when connecting to an installed external nut.

Standard External Unions

Tubing OD Bore Product No.
1/8" 1.00 mm EU2
2.0 mm EU2L
1/8" EU2T
1/4" 2.0 mm EU4
4.6 mm EU4L
1/4" EU4T

Bulkhead External Unions

The "Hole" heading in the table below refers to the size of the hole required for mounting the union through a bulkhead or panel.

Tubing OD Bore Hole Product No.
1/8" 2.0 mm 5/16" EBU2L
1/8" 5/16" EBU2T
1/4" 2.0 mm 7/16" EBU4
4.6 mm 7/16" EBU4L
1/4" 7/16" EBU4T




With a bulkhead union, an O-ring can be installed between the body and the panel to allow operation in purged environments.