NPT (National Pipe Thread) and MPT (Male Pipe Thread) are not exactly the same, but they are closely related. NPT is a standard thread used in the United States for pipes and fittings. It is a tapered thread, meaning that the diameter of the thread decreases gradually along its length. MPT, on the other hand, specifically refers to the male version of the NPT thread.
In the NPT system, the external threads on a male fitting are tapered, allowing them to create a tight seal when joined with the internal threads of a female fitting. This taper helps to prevent leakage by effectively sealing the connection. The NPT thread angle is 60 degrees, and it is commonly used for applications involving water, gas, and other fluids.
MPT, as the name suggests, refers to the male version of the NPT thread. It is used on the external part of a fitting or pipe and is designed to be joined with a female NPT thread. The female NPT thread has internal tapered threads that match the external tapered threads of the MPT, creating a secure and leak-free connection.
It is worth noting that NPT threads have a slight taper, which means that a thread sealant must be used to achieve a proper seal. This sealant, such as Teflon tape or pipe dope, fills in the gaps between the threads, preventing any leaks. Without a sealant, the tapered threads may not create a tight enough seal, leading to leakage.
In contrast, there is also NPTF (National Pipe Thread Fuel), which is a modified version of NPT. NPTF has a truncated thread profile, which means that it does not have the same taper as NPT. Instead, it has a flat crest and a controlled root radius. This design allows for a mechanical seal without the need for a thread sealant. NPTF threads are commonly used in applications where a leak-free connection is critical, such as hydraulic systems.
To summarize, NPT and MPT are related but not identical. NPT refers to the standard tapered pipe thread used in the United States, while MPT specifically refers to the male version of the NPT thread. NPT threads require a thread sealant to achieve a leak-free seal, while NPTF threads have a modified design that allows for a mechanical seal without the need for a sealant.