Seeking help; by the way, let’s discuss the material selection for valve spools and valve seats
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I’m a beginner and would like to ask about the selection of materials for the valve spool and seat in control valves. Generally speaking, it’s directly related to the medium, right? Things like the physical properties of the medium, operating conditions, temperature, etc. Could you please provide more specific details? The reason is as follows: the specification sheets in our company are all copied from those of the design institute; the material specified for the valve core is 316SS + Stellite, while the material for the valve seat follows the standards set by the manufacturer. For a project that is our own, I still used 316SS + Stellite when filling in the details regarding the valve core and valve seat. Currently, 2 suppliers have sent back their information. One of them meets my requirements, while the other specified 316+PTFE in the valve core section, which is different from the 316SS+Stelloy I requested. I hadn’t paid attention to this aspect before; now I’d like to ask everyone how they make their choices. The operating conditions here are DN15 PN50, nitrogen gas, flow rate of 2 Nm3/h, inlet pressure of 0.6 MPa, and outlet pressure of 0.02 MPa.
First of all, it’s a gas, so there’s no risk of corrosion or wear; there’s really no need for Stellite – a PTFE sealing surface is sufficient
Oh, so that means STL has good performance in terms of corrosion resistance and wear resistance, right?
1. Leakage level: lower for hard seals, higher for soft seals. 2. Hard seals are better for long-term use. 3. The cost of hard seals is higher; a comprehensive consideration based on requirements is necessary
316 + PTFE is sufficient. The main factors considered in selecting the material for the internal components of control valves are: resistance to high pressure and high flow rates (due to the reduced diameter of the valve core), tolerance to low temperatures (caused by throttling), resistance to erosion (due to high flow speeds), corrosion resistance (when the medium contains harmful impurities), and the ability to ensure zero leakage when the valve is closed (to guarantee pipeline safety). Therefore, this material meets the specified operating conditions.