That's an interesting idea. Do you have any stastics?
Even so, I might have to try it.
Dumah, I would think one would have to wait for the loctite to cure before running fluid through the fitting. Not sure about the pipe dope, but it's not an issue with the tape. I do know the pipe dope sets fairly hard, so I'd be careful on what I used it for.
No stats but I worked in the hydronics industry for years as a manufacturers rep and sold a bunch of different "dopes".
The good pipe fitters, on nearly all the high pressure industrial jobs, and the good residential pipe fitters mostly all used both tape and dope. Over the years I saw thousands of pipe leaks, only a very small percentage, perhaps less than 1% of all the leaks I saw, were with both tape and dope. In many industrial and residential plumbing systems using black pipe the joints self seal when they rust, still a weak spot. In industrial applications for processing where stainless pipe is used they won't self seal.
My brothers boiler has no less than 8-10 joint leaks, only dope was used (Rectorseal). When I installed the boiler in my house I used Real-Tuff and tape. There were no leaks. NPT to NPT fittings do not need a glue as they are tapered threads meant to be held together by friction. If you think boats vibrate you have probably never been to a commercial plant running 200 HP high pressure steam boilers..
The dope/tape only act as a crevice filler and lubricant to get the threads properly mated. During the tightening the tape and dope will fill in any imperfections along the thread path preventing liquids from migrating though the threads.
In an ideal world the threads should self seal, that is the intent, but tap & die machines get dull, tolerances change slightly from manufacturer to manufacturer and people often don't clean the threads before application to remove residual milling crud..
Real-Tuff does not harden, as it is nothing more than specialized PTFE paste. It also has no harsh petrochemicals, like many thread sealants, in it so it's safe for most all plastics & rubbers. I have been using it in marine applications since the mid to late 80's, usually 80% of the time, with teflon tape, with not one leak.
From Hercules Chemical:
"Multi-purpose heavy duty, white, PTFE paste thread sealant for use on Aluminum, Black Iron, Brass, Copper, Glass, Monel, Natural Rubber, Plastic (P.E.,Reinforced), PVC, ABS, CPVC, Stainless Steel, Synthetic Rubber (Butyl, Neoprene).
Contains a unique system of fine grain PTFE particles specifically designed to fill cracks and tiny thread imperfections. Leak free joints can be tested and put into service at once. Real-Tuff holds tight against expansion, contraction and vibration, is non-separating, will not run or drip from joints, contains no lead. Non-hardening lubricating formula permits low torque make-up and easy disassembly without galling or stripping threads. Real-Tuff withstands temperatures from -200°F to +550°F, and provides leak-proof hydraulic
resistance to 12,000 psi. Withstands gas pressure up to 2,600 psi. Real-Tuff is non-flammable and contains no heavy metals or volatile solvents and is applied easily with a natural bristle brush, even at temperatures as low
Real Tuff can be used on lines carrying:
Air Compressed (Gaseous)
Caustic Alkalies (concentrated)
Caustic Alkalies (dilute)
Coal Tar Naptha
Diesel Fuel Oil
Dry Cleaning Fluids
Fatty Acid (liquid)
Liquefied Pet. Gases
Water (cold & hot)