Two basic types of fittings are used for analytical instrumentation: National Pipe Thread (NPT) and compression, both of which are available in stainless steel or brass. Stainless steel is the best choice for fittings that will be routinely loosened and tightened; the threads on brass fittings are more susceptible to damage caused by repeated tightening. Never mix stainless-steel fittings with brass fittings because of the potential for damage to the softer brass by the harder steel. Similarly, stainless-steel fittings generally should be used with stainless-steel tubing; brass fittings with copper tubing. For more on fitting selection, view our blog article.
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