How to Properly Swage HPLC Fittings

Being able to properly change and connect fittings on an HPLC system is an essential skill for any chromatographer. At some point, you'll need to adjust or tighten a connection within your HPLC setup. While there are various types of HPLC fittings available, each typically consists of a nut and a ferrule. In most cases, ferrules are secured to the tubing through external compression. Depending on the pressure requirements, ferrules may be held in place either by creating friction against the tubing wall or, for high-pressure fittings, by permanently attaching the ferrule through a process known as swaging.

How do you swage a fitting onto a piece of tubing?

Often, when permanently attaching the ferrule to the tubing, the fitting and the tubing used are stainless steel. In the IDEX Fittings 101 Guide, swaging is described in detail, but I’ll summarize here:

1. First, slip the nut over the high pressure tubing that is being connected.
2. Next, you’ll slip the ferrule over the tubing, just below the nut. Ensure the tapered nose of the ferrule is facing away from the nut.
3. Once the nut and ferrule are in place, you can insert the tubing (with the nut and ferrule) into the receiving port until the tubing butts up against the bottom of the port. *
4. Then, with the tubing held in place, fingertighten the nut completely and then wrench-tighten it another ¾ turn to complete the swage (crimping the ferrule onto the tubing).

*Please note that this process works for most ports, however some ports do not have a solid stop for the tubing to rest. In these special cases, ensure that extra tubing remains extended past the ferrule’s nose, but not too far!

You can ensure your swage has been done correctly by loosening the nut and removing the fitting from the port. The ferrule will not come off if it has been swaged tight enough. If the ferrule is still loose, reinsert the fitting and wrench tighten in ¼ turn increments, checking to see if the ferrule has been fixed onto the tubing after each ¼ turn. Additional tightening may be required for UHPLC systems when working at ultra-high pressures.

Why would you want to permanently swage a fitting to a piece of tubing?

A benefit of swaging a fitting to a piece of tubing is that the fitting can withstand higher pressures. With the trend to increase pressures in HPLC, this is extremely valuable. Also, the fitting won’t fall off and get lost if you take the fitting out of the port for any reason. The downside is that you can only use the fitting in the one port you originally swaged to, because fittings can vary slightly, causing leaks, dead volume, or other problems when used in a different port. For other fitting options, check out our Fingertight Fittings or contact our support team for more information.