how to choose suitable marine valve ?
General knowledge of valves from marineusedgood Co.,Ltd
Valves can generally be divided into: national standard valves, American standard valves, German standard valves and Japanese standard valves according to national standards. The body material and internal parts are usually cast iron, cast steel, and stainless steel, but the different standards in different countries are the difference between the production standard and the pressure level.
American Standard Valves are valves designed, manufactured, produced and tested to US standards. German standard valves are valves designed, manufactured, produced and tested in accordance with German standards. So on and so forth.
American standard pressure grades range from 125LB to 2500LB (or 200PSI to 6000PSI), standard primary API, ANSI. The so-called API, ANSI valve is also the American standard valve. German valve pressure is usually PN10 to PN320, using DIN standards. If flanged valves are used, the corresponding flange standards are also used. The world's major valve standards are also American Standards Petroleum Association standards, American national standards ANSI, German standard DIN, Japanese standard JIS, national standard GB, European standard EN, British standard BS.
The difference is: 1 flange standard is different 2. structure length is different 3. The detection standard is different.
Because most of the medium used for marine valves contains seawater, seawater is corrosive to ordinary metals. If ordinary metal valves are used, it is easy to be turbid and suitable for valve damage. The ship usually sails at sea for a month or two. If it is damaged while the pipeline is damaged, serious consequences may occur. Therefore, the marine valve must be made of bronze or stainless steel 316L.
If the gate valve is used, the body can be sprayed with cast iron brakes. The valve stem can be used with 20Cr13 to meet the requirements of use. The valve plate is made of stainless steel. For seawater medium, when the medium flow rate is <15m/s, the valve body material can be used 304/31. When the flow rate is >1.5rnfs, the valve plate uses bronze or duplex stainless steel. The hard and soft seal is selected according to whether there is any particulate matter in the medium. If there is solid particles that can damage the glue, the hard seal is selected. The sealing surface valve plate is made of the body material or surfacing. Other metals (small rust steel, hard alloy), the valve body can be welded with stainless steel or hard alloy.
It is more common to use the butterfly valve for seawater, as long as the material of the butterfly valve is made of aluminum bronze.