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NPT thread
NPT thread design rules
NPT (National Pipe Thread) is a standard thread type used in the United States for joining pipes and fittings in various fluid-handling applications. The design rule of NPT threads is crucial for ensuring proper sealing and connection integrity. Here's an introduction to the design rules of NPT threads:
- Tapered Threads: NPT threads are tapered, meaning they have a slight conical shape. The taper rate for all NPT threads is 1 to 16. measured by the change of diameter over distance. This design feature allows for a tight seal as the male and female threads are engaged, creating a wedge-like seal.
- Thread Angle: The thread angle of NPT threads is 60 degrees. This angle facilitates easy assembly and disassembly while maintaining a secure connection.
- Thread Pitch: NPT threads have a specified thread pitch. The number of threads per inch varies depending on the size of the pipe. Common sizes include 1/8", 1/4", 3/8", 1/2", 3/4", 1", 1 1/4", 1 1/2", and 2" with thread pitches ranging from 27 to 8 threads per inch.
- Thread Crest and Root: The crest refers to the top of the thread, while the root is the bottom. In NPT threads, the crest and root are truncated, meaning they are flattened to form a line of contact when the threads are tightened. This helps to create a proper seal.
- Thread Engagement: The recommended engagement of NPT threads is typically around 3 to 4 threads. This ensures a secure connection while still allowing for easy assembly and disassembly.
- Sealing Method: NPT threads rely on the taper and mechanical deformation of the threads to create a seal. Usually, a sealing compound, such as thread tape or pipe dope, is applied to the threads before assembly to further enhance the seal and prevent leakage.
- Thread Inspection: Proper thread inspection is essential to ensure the integrity of NPT connections. Threads should be free from damage, burrs, or irregularities that could affect sealing or engagement.
Understanding and adhering to these design rules is critical for the successful installation and operation of NPT threaded connections, ensuring leak-free and reliable fluid handling systems.
van
Reviewed in the United States on August 3, 2023
Fits good
josh
Reviewed in the United States on April 17, 2022
High quality works good
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