Why I don’t like to use NPT threads in our hydro carbon systems?

NPT thread is not in my favorite threads due to many reasons. The first reason for disliking NPT thread is that there are too many accidents which are associated with NPT threads. Secondly I have many alternatives available which are safer than using NPT thread. It is very easy to make a mistake when you are using NP thread as it is very similar to ISO 7-1 BSPT which is also known as (tapered thread). Due to difference of angle between NPT and BSPT thread they will going get fit not perfectly sealed due to which high chances of leakage. NPT thread can also be fit with cylindrical thread but yet there will be perfect seal between the thread. To connect NPT male thread with female thread it is important that female thread is also NPT.

There are two kind of thread which are commonly use. One is NPT and the other is NPTF. It’s hard to identify the difference between NPT and NPTF with a naked eye.  For NPT thread to get seal it is important to use tape and paste. Without tape we will face the issue of spiral leak space between the threads when they will be out in the atmosphere.

The angle and the shape of NPTF are same as NPT, the only difference is the root of NPTF thread is higher than NPT thread and in NPTF it is difficult to eliminate and remove leakage space between the spirals. To place the thread according to the standards in a correct manger it is important for us to have a proper gauge. L1 plug is required to check female thread where as L2 plug is required to check male thread. To check minor and major diameters in male thread we need L2 and L3 gauge and both are critical to sealing thread.

  

Most of the valve manufacturers are not aware of thread gauge and what are its applications. They haven’t heard about NSI B 1.20.1 and B 1.20.3; and they don’t care about it as well. Its easy to make a thread on pipe but for perfection you required expertise and that is expensive as well.

Until now we have discuss the technical problems of threading now lets come to the practical side of it. If the male thread and the female thread are not according to the standards than you will not going to know that how many threads have got intersected which mean there is a space between the thread, therefore more chances of leakage. If there will be no standard that you wont be able to know that how many threads there should be on male and female fittings. Which will cause problem in creating the joint. Rolled threading done by PCFSC is according to the standards, not only this but it also enhance the threads inside female fittings. Rolled threading also safe galvanization process on that pipe which help the pipe to prevent from getting rusted