In long-distance pipeline valves, pipeline pneumatic ball valves are mostly used. In the national key pipeline projects, all the block valves of the trunk line are imported large diameter fully welded pneumatic ball valves, and the service life must reach 30 years or more. Split pneumatic ball valve shall be used for block valves below 26in in branch lines and stations. The main characteristics of all welded pneumatic ball valves used in key pipeline projects are as follows:
① High reliability, the valve body has sufficient strength, few leakage parts, and the moving parts are wear-resistant, which can operate normally for a long time under heavy operation.
② Good sealing, no leakage under high pressure and long-term immersion in oil and gas.
③ High switch sensitivity.
④ The resistance is small when oil and gas pass through.
③ Light weight, easy installation.
⑥ Able to work under all-weather conditions.
⑦ It has fire prevention, anti-static and other functions. The development and construction of pipeline pneumatic ball valve has greatly promoted the progress of design, manufacturing and process of pipeline pneumatic ball valve, and put forward higher requirements for pipeline pneumatic ball valve.

6. What is the basic content of measurement? The basic contents of the measurement method of electromagnetic flowmeter are: 1) the purpose of measurement legislation 2) the adjustment range 3) the measurement system unit 4) the management of measurement instruments 5) the measurement supervision 6) the measurement authorization 7) the measurement certification 8) the settlement of measurement disputes