When selecting a control valve for an application, the. Main valve body, actuator and accessories as ordered, additional equipment as ordered. Valve sizing made easy valve sizing this activity can be defined as picking the right size valve for the job or, in certain instances where a valve size is predestined, the correct trim size. Its the right tool for finding the right product, every time. Pdf the purpose of this paper is to provide an understanding of the key issues. Control valve rangeability normally closed valves control valve model valve rangeability standard operators equivalent diameter ratio of flow max. Control valves are an increasingly vital component of modern manufacturing around the world. An oversized valve operates more frequently at lower openings with increased dead band as result. Valve types and features the three basic functions of valves are. Control valve types in line control valves straight globe valve type 72 straight globe control valves combine the protection of a bellows seal with the controllability and leaktightness of a schuf control valve. Normally, control valve manufacturers publish cv values in 10 percent increments beginning at 10 percent open, so its impossible to know what happens to the cv below that point. Sizing the system control valves to provide desirable operating parameters rank among the most important factors in.
Chapter 4 describes digital valve controllers, analog positioners, boosters, and other control valve accessories. Cv flow specific gravity at flowing temperature pressure drop. Chapter 5 is a comprehensive guide to selecting the best control valve for. Verification of valve specifications and precautions on storage 31. Slightly different forms of the basic equation are used for liquids and gases. Control valves may be broadly classified by their function as onoff type or flow regulating type. For measuring the valve capacity of control valves, the coefficient cv or its metric equivalent kv is adopted. Cv % dba flow rate inlet pressure outlet pressure inlet temperature spec wtspec gravmol wt viscosityspec heats ratio vapor pressure pv required cv travel allowablepredicted spl control valve data sheet project unit p. Cv series profile2 proportional control ball valves. The valve is a controlled device that regulates the flow of a liquid or gas in a system. Sizing a control valve for a steam application can be a complex matter. Pressure drop across control valve the following figure is schematic illustration to show fluid flow at around port and plug of.
Metso control valve sizing coefficients 5 high performance triple eccentric disc valves lansi150 neldisc, high performance triple eccentric disc valve, metal seated. Control valve cv hysys simulation chemical process. The cv series is a high performance, general service control valve designed for high control accuracy, optimized flow characteristics and extended service life. Generally in process dynamic simulation, control valve cv is taken based on datasheet details it is taken for max flow which occures at generally 5075 % of valve openingit varies from valve to valve but most of the time, valve datasheets are not available most of the dynamic simulation. A style of valve trim where the flow passes through a multiple of orifices in parallel or in series. From cv table, cv 365 qa 365 v3 or 632 gpm problem.
Flow diagram for cv calculation of control valve for compressible fluid. Cvvalues presented in these control valve sizing coefficient tables are based on laboratory measurements using room temperature water according to the. There are two basic types of control valves control valve a rotary motion valves having ball, butterfly or plug type closures. Note that an oversized control valve may hurt process variability by putting too much gain in the valve leaving less flexibility for the controller. There are many factors that can be considered when sizing valves for flow control including, temperature, pipe size, viscosity, flashing and cavitation conditions, turbulent flow, twophase flow, and expansion factors to name a few. One of the most significant characteristics of this type of valves is its. The valve flow coefficient cv learning instrumentation. The valve gain is equal to the slope of the flow characteristic and is of primary significance in establishing the compatibility of the plug with the process.
The valve coefficient cv in imperial unit the number of us gallon per minute of water at 60 f that will flow through a valve at specific opening with a pressure drop of 1 psi across the valve. Min flow coefficient cv armstrong c1801 honeywell mp953d mp953f belimo nvf24 m9182a af24sr maximum operating pressure, psig bar in mm psig bar psig bar psig bar psig bar. Fisher hp series control valves are singleport, highpressure, globe or anglestyle valves with metal seats, cage guides, and pushdowntoclose valve plug action. This can apply to the control valve itself relative to the piping. Control valves cv series these control valves feature cast steel bodies with 316 stainless steel trim for use with steam, water, glycol and other chemically compatible fluids. For applications involving extreme environments, especially hostile fluids, or pressure classes greater than ansi 600, specify copesvulcan sdsevere duty control valves. Jun 17, 2009 control valves a control valve is a poweroperated device used to modify the fluid flow rate in a process system. Nov 12, 2017 control valve cv refers to the flow coefficient of the valve. With fast response times and precise movement this actuator is ideal for installations where pneumatic lines are not present or prohibitive. A point of confusion regarding control valve sizing is the difference.
The actuators are controlled by a standard voltage for onoff, modulating, or floating point control which moves the ball valve to the position dictated by the control system. A numerical designation of size which is common to all components in a piping system other. Practical control valve sizing, selection and maintenance iceweb. Red valve is committed to providing the utmost in quality equipment to achieve that goal. In addition to controlling the flow, a control valve may be used to shut off flow.
Fisher control valves, known for performance and reliability the control valve is a critical part of the control loop. This article will describe the control valve sizing procedure with some details of related headings like valve flow terminologies, control valve characteristics, cavitation, flashing, etc. Low recovery and relatively low coefficient of flow cv. P is available to permit the control valve to perform its function. When selecting a control valve for an application, the calculated c v is used to determine the valve size and the trim size that will allow the valve to pass the desired flow rate and provide stable control of the process fluid. Find out about the first principle of sizing control valves to effectively manage pressure and temperature in your steam system. The flow coefficient cv is the standard flow rate which. In deciding the size of the control valve that port size we need to calculate the cv value of the process calculated cv by calculating cv has educated more than 50 years, which is involved in. Flow coefficients c v and formulas for liquids, steam and. When sizing calculating which size valve is needed for your application a control valve specialist needs to calculate the flow coefficient. It is also not uncommon for the inherent characteristic to start deviating from the ideal somewhere below 20 percent open. Control valve cv hysys simulation posted in chemical process simulation. A valve which controls the flow rate or flow direction in a fluid system. This standard and the corresponding measuring standards contain equations used to predict the flow of compressible and incompressible fluids in control valves.
Nxt puts the power of ondemand control valve selection and sizing at your fingertips. Belimo ccv series includes htccv and the 6way characterized control valves all which feature the innovative ball design and are operated by a rotary actuator. When unpacking, check for the following items in the crate. Valtek control valve flow capacity c v is based upon the industry standard, ansiisa s75. The cv series with electric actuator is a robust, user friendly alternative to the pneumatically actuated unit. Properly selected and maintained control valves increase efficiency, safety, profitability, and ecology. Notice while the information in this manual is presented in good faith and believed to be accurate, azbil corporation disclaims any implied warranty of merchantability or fitness for a particular purpose and. A control valve is a power operated device capable of modulating flow at varying degrees. Do not read on if you have a computer fully programmed with ansiisa75. Pdf sizing and selection of control valve for process control loop.
The control valve handbook has been a primary reference since its first printing in 1965. In such a design, a wedge slides cross a general passageway in order to control fluid flow like a sliding gate hence, the name. To select the correct valve to fulfill these functions properly, an outline of the different types of valves and their features is given below. Chapter 5 is a comprehensive guide to selecting the best control valve for an. Chapter 2 develops the vital topic of control valve performance. Becker tball control valve for natural gas applications brochure 5 optimized trim selection high capacity and low noise trim tball series capacity cv ratings valve nominal size cv max nps dn fpcvt0 qtcvt1 qtcvt2 qtcvt3 qtcvt4 2 50 260 3 80 550 4 100 975 590 578 306 300 6 150 2,600 1,398 1,371 687 673. These valves are designed for highpressure applications in process control industries such as power generation, hydrocarbon production, chemical processing, and refining. Cv series electric 2way control valves control valves. Description and principle of operation gsgeneral service valve assemblies feature a straightthrough globe. A control valve performs a special task, controlling the flow of fluids so a process variable such as fluid pressure, fluid level, flow rate or temperature p q cv where can be controlled. Valve basics and sizing information johnson controls.
Red valve red valve control valve data sheet download form. The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds to compensate for the load disturbance and keeps the regulated process variable as close as possible to the desired set point. Pressure profile fluid flowing through a control valve obeys the basic laws of conservation of mass and energy, and the. A valve cv can be described as the number of gallons per minute gpm at 60 o f 15. The formulas provided here are simplified for general use. Control valve sizing for steam systems spirax sarco. P is actually the pressure drop added to the system. Becker tball control valve for natural gas applications. They are used in arduous and lethal services with critical media such as chlorine, phosgene, hydrofluoric acid, nh 3, co 2, urea. This handbook addresses the key points in that process. When sizing a control valve, the most common approach is to calculate the flow coefficient, cv which is a measure of the capacity of the valve body and trim. The valve flow coefficient, cv, is the number of u. A constant cv related to the geometry of a valve, for a given valve travel, that can be used to predict flow rate.
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