Differences Among Several Common Valve Threads such as NPT, PT, G, ZG, RC and M

In the valve field, threaded connection is a common connection method, widely applied in various conventional valves, including threaded ball valves, threaded globe valves, threaded gate valves, threaded pneumatic shut-off valves, threaded pressure reducing valves, threaded regulating valves, threaded plug valves and other equipment. Different types of threads have distinct characteristics and application scenarios. Thus, understanding the differences among various threads is crucial for the correct selection and use of valves. This article will focus on the differences among several common valve threads such as NPT, PT, G, ZG, RC and M.

1. NPT Thread

NPT (National Pipe Thread) is a sealing pipe thread under the American standard and belongs to the 60-degree tapered pipe thread of the American standard. This thread features a relatively large taper and good sealing performance, and is often used in situations with high sealing requirements. NPT threads are divided into two types: NPT and NPSC. The former is a dry-seal type and requires sealing packing to enhance the sealing effect; the latter is a non-sealing type, mainly used in pipeline systems with low pressure.

2.PT Thread

PT (Pipe Thread) is the code for British standard sealing tapered pipe threads, equivalent to the 55-degree pipe threads in China. PT threads are similar to NPT threads, both being tapered pipe threads, but with a slightly smaller taper. PT threads are mostly used in the water and gas pipeline systems of European and Commonwealth countries. They have good sealing performance and are widely applied to the connection of various liquid and gas pipelines.

3. G ThreadThe G thread, also known as the pipe thread, is a type of non-sealing pipe thread. This thread is mainly used for pipeline connections but does not provide a sealing function. The G thread has a thread profile angle of 55 degrees, and both the internal and external threads are cylindrical pipe threads. After being matched, it has no sealing property and only serves as a connection in the pipeline. With the help of a sealing ring, it can be used in low-pressure pipelines under static load. Due to its structural characteristics, the application of G threads in the valve field is relatively limited, mainly used in some occasions with low pressure and no sealing requirements.

4. ZG ThreadThe ZG thread is a tapered pipe thread under the Chinese standard. Its old code is Z, and the new code is ZG. This thread is similar to NPT and PT threads, all belonging to tapered pipe threads with good sealing performance. ZG threads are widely used in various pipeline systems in China, especially in high-temperature and high-pressure pipeline systems in industries such as petroleum, chemical engineering, and electric power.

5. RC ThreadThe RC (Ring Compression) thread is a sealing pipe thread. Its structure is similar to that of the NPT thread, but the sealing method is different. The RC thread adopts a ring compression sealing structure, and the sealing performance is improved by adding a sealing ring at the threaded connection. This thread is mainly used in pipeline systems of high-temperature, high-pressure and corrosive media, with the advantages of reliable sealing performance, strong high-temperature resistance and corrosion resistance.

6. M ThreadThe M thread, that is, the metric thread, is manufactured according to the thread profile, nominal diameter and pitch specified in the national standard. The M thread has a thread angle of 60 degrees and is divided into coarse threads and fine threads. In the valve field, M threads are mainly used for the connection of some small valves or accessories, such as pressure gauges, thermometers, etc. Due to its simple structure and convenient manufacture, M threads are widely used in valve manufacturing and maintenance.