The most noticeable difference is that stainless-steel fittings are “swaged” onto the tubing. They are tightened with a wrench, and once the nut is firmly secured, the ferrule is permanently attached to the tubing. Although this produces a good seal that withstands high pressures, the ferrules cannot be removed and reused. In order to replace a ferrule or reinstall on new tubing, the entire fitting and small section of tubing must be cut, sacrificing the ferrule, as well as a small length of the tubing. (Typically, the nut can still be reused.
Pre-seated stainless-steel fittings installed on a Restek mixing capillary tubing (cat.# 26533)
The good news is that polymer-based fittings, such as Restek’s Universal 10-32 connectors and hybrid-ferrule EXP fittings, do not require permanent swaging of the tubing; thus, all of the parts can be reused. The EXP fittings are especially useful because they can withstand higher pressures while the ferrules are still reusable to some degree. The number of times an EXP fitting can be reused is directly related to the amount of torque that is applied. The ferrule can be reused many times when the fitting is finger-tightened but it can only be reused a few times if the fitting is wrench tightened for UHPLC. The limitation is due to a certain amount of deformity for the ferrule, not due to swaging.
PEEK finger-tight fittings (cat.# 27710)
