Hydoon in the design process often encountered different marked pipe threads, pt, npt, and rc, sometimes confused by these code names, but also easy to get mistaken, and even mismatched phenomenon, until today to really figure out the meaning of these code names.
Mechanical Finance will introduce you in stages, today's introduction of NPT, NPSC and NPTF.
American pipe threads are mainly 60 ° tooth type, there are many types, we do not introduce them one by one, only introduce the most common npt, nptf and npsc
Drawings in the United States often see markups similar to npt 3/8.
Where npt is a kind of national (american) pipe thread, npt represents the taper thread, represents the English tape pipe thread for general purpose, which belongs to the American standard 60 degree cone pipe thread, taper is 1:16, is a sealing pipe thread, the use of this connection without the need to increase sealing measures.
Among them, 3/8 does not mean that the diameter of the thread is 3/8 inch, but a size code, but also to find the standard to know the size of the large diameter, the size of the small diameter, but this does not affect the engineer's drawing, as long as the hydraulic pipeline or joint drawings are marked 3/8, the manufacturer will produce according to the standard.
Sometimes there are also numerical suffixes, such as 3/8-18, 18 represents the number of teeth within an inch, which can not be marked.
Sometimes you'll see the trailing letter lh, which represents a left-handed thread, left-hand. The unmarked default is a right-handed thread.
The external cone thread can be combined with the inner cone thread and has a sealing effect, but there is also a sealing straight thread in the American standard, that is, npsc, which is the abbreviation of the national pipe strain connection, a pipe joint straight pipe thread for connection. In practice, this internal thread can be used with the joint of the external taper thread.
So, there are two fits, the outer cone - the inner cone, the outer cone - the inner straight.
Both mating forms are inherently sealed, while allowing the addition of sealing material to the thread, and in practice, filling is added to seal, such as sealant.
Then say, nptf, nptf is the code name of dry seal straight pipe internal thread, where f should mean fine.
The tooth shape accuracy of the nptf dry sealing pipe thread is higher than that of the npt thread, and it does not use any filler when screwing, and completely relies on the thread itself to form a seal, and there is no sealing medium between the threads. The dry seal pipe thread regulation has a relatively strict tolerance, which is a precision type thread and can be used in medium and high pressure systems.
In practice, nptf and npt are used together. The nptf male thread can be screwed into the npt female thread, but this is not worth the loss, the sealing performance is consistent with the npt, and the sealant needs to be added.
American pipe threads will introduce these, tomorrow we will introduce the imperial pipe snail