Unions - Internal

stainless union
Internal union
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Internal unions have female threads and a fitting detail for zero volume fittings. The nuts have male (external) threads.

Choose 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.

Standard material is 300 series stainless. Also available in Hastelloy C, gold-plated stainless, and titanium versions.

stainless bulkhead union
Internal bulkhead union
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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.

Select a union type below to view product numbers:

Standard unions

Bulkhead unions

Standard internal unions

Fitting size Bore Product No.
1/32" 0.15 mm ZU.5XC
0.25 mm ZU.5
0.50 mm ZU.5L
1/32" ZU.5T
1/16" 0.15 mm ZU1XC
0.25 mm ZU1C
0.50 mm ZU1M
0.75 mm ZU1
1.0 mm ZU1L
1/16" ZU1T
1/8" 0.75 mm ZU2
2.0 mm ZU2L
1/8" ZU2T
1/4" 0.75 mm ZU4*
4.6 mm ZU4L*
1/4" ZU4T*

* Available as a special-order item.

Bulkhead internal 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.

Fitting size Bore Hole Product No.
1/32" 0.15 mm 5/16" ZBU.5XC*
0.25 mm 5/16" ZBU.5
0.50 mm 5/16" ZBU.5L*
1/32" 5/16" ZBU.5T*
1/16" 0.15 mm 5/16" ZBU1XC
0.25 mm 5/16" ZBU1C
0.50 mm 5/16" ZBU1M
0.75 mm 5/16" ZBU1
1.0 mm 5/16" ZBU1L
1/16" 5/16" ZBU1T
1/8" 0.75 mm 7/16" ZBU2
2.0 mm 7/16" ZBU2L
1/8" 7/16" ZBU2T*
1/4" 0.75 mm 5/8" ZBU4*
4.6 mm 5/8" ZBU4L*
1/4" 5/8" ZBU4T*

Available as a special-order item.




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