steveinak,
All I use here in the shop is a LocTite product #567. The full LocTite p/n is 56747. It comes in a 1.69 o.z. tube. It is expensive, but lasts a long time. One tube lasts me over a month in a busy production rebuild shop. I have used it in past years on GE Steam turbine lines and in many other critical applications. It is a white thread sealant PST with PTFE. After you apply it, it will take a light "set" after about an hour . There is one application that I use it on regularly. The pipe fitting is only screwed in 2 1/2 turns due to interferring factors that cannot be avoided. It is the ONLY product that I have found that works in this application. As for tape, it is good to have for an emergency. Fittings can "unwind" with the tape due to it being so slick. Also alot of folks will wrap the tape around the end of the fitting to get the best seal. This allows the possibility of some of the tape cutting loose from the joint and getting into the system inside. I was taught to always apply the liquid sealant "2 threads back" from the end of the fitting. Upon installation, the liquid sealant will not enter the system, yet still provide a good seal. I get it at Grainger. Just my 2 cents. Good Luck,
Butch