Material of the instrument control valve
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The materials of the valve core and valve stem in the middle valve body of the instrument control valve are SST; what are SEL materials?
SST is stainless steel; SEL is unknown
SST refers to full surfacing with Stellite alloy, while ST refers to surface surfacing with Stellite alloy; both are used to increase the strength of valve components. SEL is a grading standard; for example, in large hydroelectric equipment, the steel plate thickness is 350 mm, and steel plates of grade SEL072Ⅰ are required.
SST refers to full surfacing with Stellite alloy, while ST refers to surface surfacing with Stellite alloy; both are used to increase the strength of valve components. SEL is a grading standard; for example, in large hydroelectric equipment, the steel plate thickness is 350 mm, and steel plates of grade SEL072Ⅰ are required.
SST cannot be simply understood as stainless steel; 304 and 316 are also types of stainless steel. ST or SST involves welding a layer of cemented carbide onto a base material of 304 or 316. Additionally, the valve stem and diaphragm actuator rod of the control valve are not made of ST or SST; only the valve core, seat, and sleeve are made from these materials. Generally, valve stems and actuator rods are made of duplex steel with good tensile and yield strengths: 17-4PH. The push rods in the cylinders are also made of 17-4PH, but there are also cases where wear-resistant high-manganese steel is required. For example, in the case of Oubit orbital ball valves, if the purchaser has no special requirements, the standard components used at the time of manufacture are made of high-manganese steel. In China, when it comes to the selection of materials for control valves, manufacturers are actually trying to reduce costs; they use ordinary stainless steel whenever possible, unless the purchaser has expertise in this area or the construction personnel assigned by the purchaser are knowledgeable in this field. Since we are engaged in valve repair, we fix hundreds or even thousands of various types of control valves and process valves both domestically and internationally each year. There are countless failures caused by material issues, and actually we welcome this, as it is beneficial for our repair industry. Hehe.