However after wrench tightening the adapter i see some sort of thin metal scrap coming out of the thread. Due to the shape of tapered thread fittings its particularly important that they never be over tig h t ened.
Airline Hydraulics Faq What Is The Tightening Torque Of The
How to tighten npt fittings. How to tighten npt fittings step 1. The same thing applies to plumbing fittings. I have a question for experienced thread fitters. This allows some lee way to get the fitting pointing in the right direction. More than any other fitting they are prone to damage due to over tightening. I usually tighten npt threads by hand as tight as i can then use a wrench to tighten up to 1 or 1 12 turns more.
Do not tighten your fitting past this point. Put on a specific length of thread tape and tighten up the fitting. Thats why tfft rather than torque is recommended for tapered. I have rarely used npt threads i am in a part of europe where parallel fittings are used but now i had to install some 12 npt threaded male adapter to 12 npt female valves. Continue to turn the male pipe fitting in a clockwise direction until you can no longer. Youll develop a feel for it.
The tensile stress created by tightening the fitting beyond hand tight and 1 or 2 more turns will crack the female fittings. At this point you can use a wrench to complete one or two more turns. Damage to the threads or even a cracked port end which can lead to leaks and make re use imp ossible. They should be hand tightened and then another 1 or 2 turns but no more. Insert the male thread into the female fitting. Maybe the solution is to just carry on as you are but keep a 14 npt tap handy when you come to install the valve into the tank.
Tfft assembly turns from finger tight with pipe thread sealant or teflon tape applied. If you remember which way you have to turn the fitting you will avoid a bad seal or plumbing fittings that are potentially stripped. Turn the male pipe thread in a clockwise direction. Once the pieces are together tighten the connection by hand slowly until the fitting will not turn any more. Do not cross the threads at this stage. It is a common mistake that can easily be avoided.
Brass and steel pipe thread npt installation procedure and torque specification table and chart. More turns will put to much pressure on the fitting and may crack it and cause a leak. When you put in a screw turning it to the left loosens the screw and turning it to the right tightens it. How tight do you have to tighten national pipe thread.
Gallery of How To Tighten Npt Fittings
