How to distinguish and select the connection threads of rotary joints

Due to different starting standards for rotary joints, the industry standards for selecting joints were not consistent at the beginning. Of course, due to the gradual standardization of industry equipment, many uncommon thread styles of rotary joints were cleaned.
Threaded connection, flange connection, welding.

Today we will talk about thread connections. So how many types of threads are there? What kind of threads are they? Everyone knows that threads can be divided into two categories: metric threads and imperial threads.
Metric threads are commonly known as domestic threads, which are divided into coarse thread and fine thread. Coarse thread is divided into triangular thread, trapezoidal thread, and square thread. The metric threads used on rotary joints are mostly triangular threads with a tooth profile angle of 60 °.
British threads are also divided into: British threads and American threads. British thread can be divided into taper pipe thread and pipe thread. The tooth profile angle of British thread is 60 ° and 55 °, and the British thread used for rotary joints is mostly British 55 ° thread, rarely using 60 °. Usually only used upon customer request. The British cone tube thread also has 55 ° sealed thread and unsealed thread. The rotary joint uses sealed imperial cone pipe threads. The tooth profile angle of American thread is 60. Generally, it is only used based on imported equipment and customer requirements, mainly depending on which country’s equipment the customer has imported.