Swagelok VCR Fittings and VCO Fittings Explained (2020 update with illustrations + links)
by Katie Reid, on Wed, Nov 20, 2013 @ 15:11 PM
Swagelok VCR fittings offer the high purity of a metal-to-metal seal, providing leak-tight service from vacuum to positive pressure. Both VCR fittings and VCO fittings can be disassembled in line—with no clearance requirements. Get an overview below, then get details here (free download) or learn about installation:
The primary distinguishing feature of VCR fittings and VCO fittings is that they can be disassembled in line, so you can access the system for repair and upgrades without having to remove multiple parts. This illustration shows how little clearance you need on either end to lift it away from its connection points:
Again, the minimal clearance, or "zero clearance", means that unlike pipe, tube, and weld end connections, the VCR and VCO fittings can be disassembled without having to remove multiple parts.
These fittings also feature silver plating on all female threads, which prevents galling and eliminates the need for thread tape, which improves ease of installation. There are also leak test ports on the side of each nut, where the metal faces come into contact and the seal takes place.
Lastly, there is a split-nut available, which further increases the ease of assembly and reassembly.
Thanks to the flat face seal of both the VCR fittings and VCO fittings, you have unlimited make and remake capabilities. All you have to do is replace the gasket on the fitting each time you remake the connection. The gasket is the least expensive piece of the assembly, so replacing this is much more cost effective than replacing the whole assembly. When installing VCR metal gasket fittings, tighten the nut finger tight and then use a wrench to turn the nut 1/8 of a turn.
In high temperature applications, consider VCR fittings over VCO fittings. Their metal gaskets allow for higher temperatures—as high as 1000 °F for a stainless steel gasket.
With VCO assemblies, one option is gland + body + nut, as illustrated below:
With VCR assemblies, choose from female nut + 2 glands + gasket + body (male nut) OR female nut + gland + gasket + body, as illustrated below:
VCR and VCO fittings are popular in hydraulic systems as well as welded and threaded systems. They also provide a great transition from such systems to a tubing system, by using a tube adapter end connection. And thanks to the variety of end connections that are available from Swagelok, there are almost endless combinations available.