Thread tape should always be utilised on NPT threads, however never on the compression fittings themselves. Any tape should be high quality and NOT obtained from the local hardware store. There are thread tapes that are specifically designed for 316ss and other fittings.
There are liquid type sealants available, these should be selected based on their specification and any anti-galling features. These sealants are particularly useful for hydraulic or clean services where small particles of tape could contaminate valves, ports etc.
Making up a Fitting when Utilising Thread Tape
Initially ensure that the hand-tight joint assembly gives 4 to 6 full turns of engagement.
Unscrew the joint, cleaning any dirt on the threads and then apply tape to the male thread. Begin with the first thread in direction of the pitch ensuring the tape is wrapped with a slight overlap.
Check that the tape does not overhang the first thread, as small portions of tape may be cut off and enter the tubing system.
Tension the tape but do not stretch or thin it out.
Cut the tape and draw the free end around the threads tautly.
Rub the tape onto the thread ensuring engagement with it. In the case of stainless steel fittings, apply a second layer of tape.
Re-assemble hand-tight and make wrench tight with REASONABLE FORCE only to achieve another 0.5 to 1.5 turns. Please note excessive force may damage the fitting. Teflon provides lubrication which will aid deformation or collapse of fittings if excessive force is used. Teflon can also exacerbate loosening of slack joints.
When it is necessary to break and remake connections ensure that any old tape residues are removed from the threads.