Need a leak-resistant high-pressure connection

Why high-pressure joints leak

Compression and bite-type tube fittings seal by deforming a ferrule onto the tube and seating it into the fitting body. If the tube is too hard, too soft, out of round, scratched or of the wrong wall thickness, the ferrule cannot grip and seal as designed. Mixing nuts, ferrules and bodies from different fitting systems, under- or over-tightening, re-using damaged ferrules and cutting tube at an angle are also frequent causes. In service, vibration, pressure pulsation, thermal cycling and unsupported tube runs fatigue the joint, while incompatible materials can corrode or gall. Threaded pipe joints add further variables, such as thread form, sealant and the number of turns of engagement.

Options to consider

Using one fitting system throughout, with tube that matches its specification, is the foundation. Double-ferrule compression fittings are widely used in instrumentation, while single-ferrule bite-type fittings are common in hydraulic circuits; the choice depends on the application and existing equipment. For higher pressures, appropriately rated fittings with heavier tube walls are needed. Welded joints, flanged connections or face-seal fittings may suit duties with severe vibration or where any leak path must be minimised. Proper tube support, clamping and correct assembly procedure complete the solution.