how do I get my NPT connections to not leak

[Mace Canute]

This! Some people seem to think the contamination happens when it's assembled with the tape being wrapped over the end of the male fitting but it's far more likely to happen when a bit of tape gets left behind in the female portion of the fitting when it's disassembled and then pushed in when the male fitting is reassembled.

There's some good information about tightening pipe threads in this site:

Pipe Thread Installation Torque Table Chart | Engineers Edge | www.engineersedge.com

Please ignore the information in the link I provided. It's bogus!

 

[Oldpath05]

LOCTITE 545
(Known as Loctite 545 Thread Sealant Hydraulic/Pneumatic Sealant )
High lubricity thread sealant for locking and sealing metal pipes and small fittings with fine threads.
LOCTITEｮ 545 is a pipe thread sealant designed for locking and sealing of metal pipes and fittings. It is specially formulated to offer high lubricity for easy assembly and removal. Recommended for fine threaded fittings as used in hydraulic and pneumatic installations and small fittings in general. Suitable for fittings up to 50 mm in diameter including pneumatic and hydraulic fittings.
Your benefits:
Excellent solvent resistance
ABSSM approved
CFIA approved
Contains no fillers or particles that could contaminate system fluids, foul valves, or clog fine filters and screens

("easy assembly and removal")<<<That's important, but ouch for the price this stuff better work and what about self life, does it go bad in 5 years, Teflon tape can stay on the shelf for 50 years>>> Loctite 54531 545 Pneumatic/Hydraulic Sealant, Size 5 Ml: Amazon.com: Industrial & Scientific

 

[ray66v]

A friend who is a retired pipe fitter, gave me go-no-go thread gauges to test my fittings before use.

As he predicted, they almost always are very marginal, and quite often fail.

The problem is, it's pretty much all junk out there anymore.

 

[downsizingnow48]

I don't know if it goes bad, I buy it in a tiny little bottle and use it up.

 

[CincyFlyer]

It's simple. Don't use NPT for hydraulics.

All well and good, unless you happen to need a hose or fitting on a Sunday.

 

[downsizingnow48]

As far as I know, all quick disconnects are female NPT. That is my only use for NPT in hydraulics.

 

[LD1]

Sometimes just no other choice. Valves, cylinders, QD's, etc as others have mentioned.

Hoses and fittings....no brainier. Design around npsm or jic.

Sometimes valves and.cylinders can be had with sae ORB ports. But not always. Especially if you are a bargain shopper like me.

I wish the industry as a whole would move away from npt. That's about the only way things will change

 

[ericm979]

I bought some of the Loctite 545. I've had bottles of other grades of Loctite for 10 years or more and they still work. Performance may have fallen some but I didn't notice it.

 

[bob 59912]

Parker 1/2" body ISO 5675 Quick Disconnects of the 4200 series come in 3/4"-16 ORB for both the nipples and couplers. The connect under pressure 8200 couplers and the 8010 nipples also come in both 3/4"-16 and 7/8"-14 ORB

 

[Deere Dude]

have a couple bottles of 242 sitting in the toolbox with caps not sealed just sitting on top of container. It has been 14 years already. A little bit goes a log ways.
I do have half a dozen rolls of tape and a bottle of Teflon paste there also. But for the sure to not leak joint I use 242, but will use any of the above except tape in hydraulics.