What is the difference between the NPT threads and NPTF threads?

Thread is an important part of the bimetallic thermometer, it is used with the action of measured medium equipment connection, at the same time in order to ensure the accuracy of measurement, the thread is another important mission must be to keep the connection part of the seal. NPT and NPTF threads is the most commonly used two kinds of American taper pipe threads, because their names are similar, so much so that many points not clear them, today we will say what is the difference between the two threads? We can from two aspects to distinguish the NPT and NPTF threads: 1. Sealing way, NPT for mechanical or low-pressure gas and liquid, requires the use of sealants to ensure that the seal. When strict sealing sealant may be failure due to high temperature and high pressure, then can use NPTF stem seal screw thread. 2. The thread inspection requirements, the NPT thread sealant is used, as long as using a plug gauge L1 rules ( Internal thread) Or L1 ring gauge ( External thread) To check the size, and NPTF threads because of its particularity, need to use thread gage L2 and L3 gauge to test.