Pipe sizes means to determine the exact dimensions. Pipe dimensions depend upon diameters of the pipes and the curve angles.NPT stands for National Pipe seams. NPT is an international standard of pipe fittings just like BSP pipe fittings. NPT seams are actually tapered threads. They are also known as general purpose threads. They are the most commonly used type of seam pipes. NPT threads have an angle of about 60 degrees. They are used for sealing and joining of pipe fittings weather in liquids or low pressure air. Taper threads are deeper at the edges. They are shallower from the end of the pipe.
Pipe is allowed by the taper at the end for screwing inside the fitting till it is forced to do so. Screwed length of the tapered fittings is usually determined by ANSI standards. Wrench is used for tightening the fitting. Some vacant spaces can be left in lines which may ultimately cause leakage problem. These gaps are usually filled by Tube sealants to avoid leakage. NPTF which are dry sealed seams also consist of tapered threads. NPTF threads are used when Tube sealing compounds fails due to high heat and pressure. Lines can be sealed mechanically by efficiently crushing the threads at the time of tightening with a wrench. Hence tubes and fittings can be joined like this without the use of sealants.
When suitable joint compounds or PTFE tape is to be used then NPTF and NPT seamscan be interchanged.FPT or FIP are the terms referring to female NPT seams. MPT or MIP are the terms used for male NPT threads. NPSM stands for national standard free fitting straight mechanical Tube threads. These tube threads are straight and particularly used for joining. Washers and gaskets are used for sealing these kinds of connections.
NPT seams are famous because they can be joined easily without using a sealant. NPTF threads have controlled truncations at the root and crest. seams crests are flattened out until metal and flanks have contact with each other.
Pipe seams usually have very high blow off resistance capability. Creation and maintenance of sealing depends upon many factors. Quality of threads is one of the factors. Quality depends upon form, dimensions and the surface. It is also an important factor to consider that what kind of sealant is used and where the pipe has to be used. Join tightness effects the durability of the fittings.