Top 10 Causes for Valve Replacement in Power Generation

Here is what you should know about control valves: Criteria for Valve Selection: 1.When the pressure drop is very high or there is the risk of accumulation of solids, or the fluid velocity is extreme an angle valve is used. Just remember using angle type poses some ramifications. 2. Characterized ball valve is used when the fluid tends to crystallize or where a high Cv is required. Should they be used for as tight shut-off valve, the maximum pipe sizing should be 4 inch. 3. Butterfly valves are used for services with large flow rate and low pressure drop (less than 5 bar). They can be used as tight shut-off valve when the pipe diameter is more than 4 inch. High duty butterfly or triple offset butterfly are commonly used types. 4. Single-seated globe valves is the standard type in sizes bellow 8 inch in non-severe services where the shutoff pressure and pressure drop can be handled. Cage guided globe valve shall be used for more rough services, balanced trim can be used for bigger sizes. Criteria for Material Selection 1.Cast Carbon Steel, A216 Gr WCB/WCC or forged carbon steel, A105 is used in non-corrosive service from -28C to 427C. Low temperature carbon steel, A352 Gr LCB/LCC can be used down to -46C (stainless steel may be considered as an alternative) 2.Alloy Steel, A217 Gr WC1, WC6, WC9 is used for temperatures above 427C. WC9 may also be used for flashing services. 3.Stainless Steel, A351 CF8 is used in flashing services, corrosive service and for temperatures below -28C. Criteria for Selection of Valve Characteristics A unique and simple procedure for valve characteristic determination for almost all Chemical Plants. 1. Use Equal Percentage if the valve functions as FV or TV 2. Use Linear if the valve functions as PV or LV 3. Use Linear if there is Split Range Control Note: Due to process demands, above rules might not apply to some situations Examples: Ex. 1 : A condensate with pressure drop of 40 bar across valve in flashing state requires a flow control valve to regulate the flow Valve Type : Angle /Trim Type : EQ%/ Material : A217 WC9 Ex. 2 : Natural Gas with pressure drop of 2 bar across valve requires a pressure control valve to regulate the pressure. Valve Type : Globe / Trim Type : Linear / Material : A216 WCB Ex. 3 : A unit shut-down valve shall be installed with adjacent piping size of 3 inch for an application in which we have water + dissolved CO2. Valve Type : Ball Valve / Trim Type : Quick Opening / Material : A351 CF8 If you are seeking for an amazing course to show you the design criteria for different equipment, Process Plant Design course is highly recommended! If you want to know more about this course and how it could benefit your career, here is the link: https://lnkd.in/gYWRzWAe

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