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Tech Center
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Interchangeability With so many different fittings in HPLC, and so many looking alike, interchangeability can present a real problem. Let's see if we can offer some clarification. Take a zero dead-volume union, male nut, and ferrule from one manufacturer [Figure 1a]. Put the male nut and ferrule on a piece of 1/16" OD stainless steel tubing. Insert the tubing, ferrule, and nut into the ZDV union. Be sure the tubing bottoms out in the union. Swage the ferrule onto the tubing by tightening the male nut finger tight, and then a 3/4 turn with a wrench. Now remove the male nut, ferrule, and tubing from the fitting. Measure the distance from the end of the ferrule to the end of the tubing [Figure 1b]. Let's call this Dimension X. Dimension X varies from one manufacturer to another [Figure 2]. Dimension X can also vary from the same manufacturer due to variation in tolerances. Because of these typical variances seen among the array of manufacturers, we generally recommend new fittings, new ferrules, and new connections each time assemblies are connected, although such care is not necessary in all cases. Here's an example: Valco, Parker, Swagelok®, and Upchurch Scientific® zero dead-volume fittings are interchangeable at the initial assembly and may be interchangeable in subsequent assemblies. However, dimension X is long with a Waters® fitting. If a ferrule has been swaged in a Waters fitting, and you then insert it into an Upchurch fitting, the ferrule will not seat and will leak [Figure 3a]. Dimension X is short with an Upchurch fitting. If the ferrule has been swaged in an Upchurch fitting and you insert it into a Waters fitting, the tubing will not bottom out and you will have a dead volume/mixing chamber [Figure 3b]. Copyright © IDEX Corporation 2008. IDEX Health & Science is a Unit of IDEX® Corporation. | Privacy Policy |