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Practical Technology of Control Valve

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    Control Valve Brief

    The control valve is a key element in the process control loops, the main function of a control valve is to keep some important process parameters within a required operating range, such as inlet/outlet pressure, flow rate, temperature, or level, etc.

    As a final control element to modulating gas, air, steam, water, or other fluid, the control valve will compensate for the load disturbance and maintain the regulated process variable as close as possible to the desired set point.  

    So it is really important to learn terminology, application, technology, and all information of control valves, no matter you are an engineering, sales, end-user, or instrument expert. THINKTANK engineer department made their professional effort and rich experience in the process industry to ensure the right technical information is shared. 

    Material Selection Factors

    The following are list the general materials used for the control valve body. We will consider about 3 main factors that will affect valve materials selected for control valves. Properties, pressure, and temperature. Let’s discuss carefully one by one. 

    Properties Effects

    Mechanical and Physical Properties

    The most responsible valve manufacturers will provide the material mill test certificate for customers, which includes yield strength, hardness, and toughness data in mechanical and physical properties part.

    Wear Properties

    Erosive wear is caused by high-velocity fluid impingement or erosive particles if flow medium.

    Corrosion Properties

    Corrosion properties definitely is an import index for control valves, and how to select the right material resistance to corrosion from the environment or medium fluid is always the main priority for engineers.

    Pressure Effects

    During the harsh conditions, we apparent will face cavitation, flashing, or erosion problems for control valves. A liquid generates cavitation or flash damage for control valves often caused by upstream pressure and differential pressure. A high differential pressure affects the high velocity of flow like steam, or entrained solids which caused the potential for erosion, and the corrosion caused by the passive layer of steel is washed away from the high velocity. 

    Temperature Effects

    Temperature is a critical matter for yield strength under the same pressure. A high temperature of medium will highly reduce the yield strength of the control valve. 

    If the working temperatures exceed the limit temperature of a material, a phenomenon called “creep” will be caused. 

    What is the creep phenomenon for valves?

    A simple phenomenon to show creep deformation, we see that many ball valve seat ring PTFE has creep deformation because it exceeds the limit pressure of the material, and after the temperature is back normal, the sealing can not tight off anymore. Same as control valves, when a high temperature affects the valve body and trim material into creep phenomenon,  and even after temperature and pressure are removed, the steel material still can not goes back to its original dimension. 

    Pressure - Temperature Curve

    temperature and pressure curve
    Temperature-Pressure Curve 150LB
    temperature and pressure curve 300lb
    Temperature-Pressure Curve 300LB

    Common Material for Control Valve

    Here are the control valve material considerations for customers, engineering, or end-users reference. We should pay more attention to our existing applications, selection, and sizing based on our professional knowledge of the industry field.

    Cast Material and its Correspond Service Condition

    Name
    Material Grade
    Service Condition
    High-temperature Carbon Steel
    ASTM A216 Grade WCB
    Non-corrosive fluids such as water, oil, and gases at temperatures range -20°F (-30°C) and +800°F (+425°C)
    Low-temperature Carbon Steel
    ASTM A352 Grade LCB
    Low temperature to -50°F (-46°C). Use excluded above +650°F (+340°C).
    Low-temperature Carbon Steel
    ASTM A352 Grade LC1
    Low temperature to -75°F (-59°C). Use excluded above +650°F (+340°C).
    Low-temperature Carbon Steel
    ASTM A352 Grade LC2
    Low temperature to -100°F (-73°C). Use excluded above +650°F (+340°C).
    3.1/2% Nickel Steel
    ASTM A352 Grade LC3
    Low temperature to -150°F (-101°C). Use excluded above +650°F (+340°C).
    1.1/4% Chrome 1/2% Moly Steel
    ASTM A217 Grade WC6
    Non-corrosive fluids such as water, oil, and gases at temperatures range -20°F (-30°C) and +1100°F (+593°C).
    2.1/4% Chrome
    ASTM A217 Grade C9
    Non-corrosive fluids such as water, oil, and gases at temperatures range -20°F (-30°C) and +1100°F (+593°C).
    5% Chrome 1/2% Moly
    ASTM A217 Grade C5
    Mild corrosive or erosive applications and non-corrosive applications at temperatures between -20°F (-30°C) and +1200°F (+649°C).
    9%Chrome
    1% Moly
    ASTM A217 Grade C12
    Mild corrosive or erosive applications and non-corrosive applications at temperatures between -20°F (-30°C) and +1200°F (+649°C).
    12% Chrome Steel
    ASTM A487 Grade CA6NM
    Corrosive application at temperatures between -20°F (-30°C) and +900°F (+482°C).
    12% Chrome
    ASTM A217 Grade CA15
    Corrosive application at temperatures up to +1300°F (+704°C)
    Stainless steel 316
    ASTM A351 Grade CF8M
    Corrosive or either extremely low or high-temperature non-corrosive services between -450°F (-268°C) and +1200°F (+649°C). Above +800°F (+425°C) specify carbon content of 0.04% or greater.
    Stainless steel 347
    ASTM 351 Grade CF8C
    Mainly for high temperature, corrosive applications between -450°F (-268°C) and +1200°F (+649°C). Above +1000°F (+540°C) specify carbon content of 0.04% or greater.
    Stainless steel 304
    ASTM A351 Grade CF8
    Corrosive or extremely high temperatures non-corrosive services between -450°F (-268°C) and +1200°F (+649°C). Above +800°F (+425°C) specify carbon content of 0.04% or greater.
    Stainless steel 304L
    ASTM A351 Grade CF3
    Corrosive or non-corrosive services to +800F (+425°C).
    Stainless steel 316L
    ASTM A351 Grade CF3M
    Corrosive or non-corrosive services to +800F (+425°C).
    Alloy-20
    ASTM A351 Grade CN7M
    Good resistance to hot sulfuric acid to +800F (+425°C).
    Monel
    ASTM 743 Grade M3-35-1
    Weldable grade. Good resistance to corrosion by all common organic acids and saltwater. Also highly resistant to most alkaline solutions to +750°F (+400°C).
    Hastelloy B
    ASTM A743 Grade N-12M
    Well suited for handling hydrofluoric acid at all concentrations and temperatures. Good resistance to sulphuric and phosphoric acids to +1200°F (+649°C).
    Hastelloy C
    ASTM A743 Grade CW-12M
    Good resistance to span oxidation conditions. Good properties at high temperatures. Good resistance to sulphuric and phosphoric acids to +1200°F (+649°C).
    Inconel
    ASTM A743 Grade CY-40
    Very good for high-temperature service. Good resistance to spangly corrosive media and atmosphere to +800°F (+425°C).
    Bronze
    ASTM B62
    Water, oil, or gas: up to 400°F. Excellent for brine and seawater service.
     

    The Priority Selection of Erosion Resistance Material For Control Valves (Degraded Performance)

    • Ceramic
    • Chrome & Tungsten Carbide
    • Alloy 6 Hard Facing
    • Inconel
    • 416 SS
    • 17-4 PH
    • K Monel
    • 316 SS
    • Hastelloy B & C
    • Monel
    • Alloy 20
    • Bronze

    The Temperature Limit For Body Material of Control Valves

    • Cast Iron: -28 ~ 210°C
    • Ductile Iron: -28 ~ 340°C
    • Carbon Steel (WCB): -28 ~ 425°C
    • Carbon Steel (LCB): -45 ~ 340°C
    • CrMo (WC6): -28 ~ 537°C
    • CrMo (WC9): -28 ~ 565°C
    • CrMo (C5, C12): -28 ~ 648°C
    • 304SS, 316 SS: -253 ~ 815°C
    • Alloy 20: -45 ~ 148°C
    • Aluminum: -198 ~ 204°C
    • Bronze: -198 ~ 287°C
    • Inconel: -198 ~ 648°C
    • Monel: -198 ~ 480°C
    • Hastelloy C: -198 ~ 537°C
    • Titanium: ~ 350°C

    Alloy Elements

    The corrosion resistance, hardness, and toughness of the material are improved by adding alloying elements to the base steel.

    Seat Leakage For Control Valve

    Here is the standard of control valve seat leakage refers to standard ANSI/FCI 70-2-2006 superseding ANSI B16.104.

    Leakage
    Class
    Designation
    Maximum Leakage
    Allowable
    Test MediumTest PressureTesting Procedures Required for Establishing Rating
    CLASS INo test required provided user and supplier so agree
    CLASS II0.5% of rated capacityAir or water at 50-125 F (10-52C)45-60 psig or max. operating differential whichever is lowerPressure applied to valve inlet with outlet open to atmosphere or connected to a low head loss measuring device full normal closing thrust provided by actuator.
    CLASS III0.1% of rated capacityAir or water at 50-125 F (10-52C)45-60 psig or max. operating differential whichever is lowerPressure applied to valve inlet with outlet open to atmosphere or connected to a low head loss measuring device full normal closing thrust provided by actuator.
    CLASS IV0.01% of rated capacityAir or water at 50-125 F (10-52C)45-60 psig or max. operating differential whichever is lowerPressure applied to valve inlet with outlet open to atmosphere or connected to a low head loss measuring device full normal closing thrust provided by actuator.
    CLASS V0.0005 ml per minute of water per inch of port diameter per psi differentialWater at 50-125F (10-52C)Max service pressure drop across valve plug, not to exceed ANSI body rating.Pressure applied to valve inlet after filling entire body cavity and connected piping with water and stroking valve plug closed. Use net specified max actuator thrust, but no more, even if available during test. Allow time for leakage flow to stabilize.
    CLASS VINot to exceed amounts shown in the following table based on port diameter.Air or nitrogen at 50-125 F (10-52C)50 psig or max rated differential pressure across valve plug whichever is lower.Actuator should be adjusted to operating conditions specified with full normal closing thrust applied to valve plug seat. Allow time for leakage flow to stabilize and use suitable measuring device.
    NOMINAL PORT DIAMETER (INCHES)NOMINAL PORT DIAMETER (MILLIMETERS)LEAK RATE (ML PER MINUTE)LEAK RATE (BUBBLES / MINUTE*)
    3760.96
    41021.711
    6152427
    82036.7545
    10254963
    1230511.581

    Body, Trim Material Considerations For Control Valve

    Generally, we will consider selecting the suitable material for the control valve body and trim from 4 factors.

    1. Strength
    2. Special Performance Require
    3. Treating or Coated
    4. Cost

    Here we will list the typical materials for globe type, butterfly type, ball type of control valve. 

    Valve TypeMaterial TypeBody MaterialTrim Material Stem MaterialSeat Material
    Ball TypeCarbon SteelASTM A352 gr. LCC, A216 WCB, A216 WCC316 SS316 SS316 SS
    Stainless Steel316 SS316 SS316 SS316 SS
    Incoloy or InconelUNS N08825 or A350 LF2, A216 WCB with UNS N06625 OverlayUNS N06625UNS N07718UNS N06625
    BronzeBRONZE (UNS C95800)BRONZE (UNS C95800)BRONZE (UNS C95800)BRONZE (UNS C95800)
    Duplex & Super DuplexASTM A890 GR. 4A  (UNS J92205) (Duplex~22% Cr), ASTM A182 GR. F53 (UNS S32750) or F55 (UNS S32760) (Super Duplex~25% Cr)ASTM A182 F51, F53, F55ASTM A276 UNS S31803, S32750, S32760ASTM A182 F51, F53, F55
    6 Moly SSUNS S31254 (6 Moly Stainless Steel)UNS S31254UNS S31254UNS S31254
    Butterfly TypeCast Iron, Carbon Steel, Stainless Steel, Hastelloy, Brass, Nickel Alloys Steel, Titanium Alloys, Nickel Aluminum Bronze, Duplex SteelCast Iron, Carbon Steel, Stainless Steel, Hastelloy, Brass, Nickel Alloys Steel, Titanium Alloys, Nickel Aluminum Bronze, Duplex SteelStainless Steel, Inconel, MonelSoft Seat: PTFE, RTFE, EPDM, Buna-N, Viton, Neoprene
    Metal Seat: Inconel, Stainless Steel
    Globe TypeCarbon Steel, Stainless Steel, Hastelloy, Brass, Nickel Alloys Steel, Titanium Alloys, Nickel Aluminum Bronze, Duplex Steel316SS, 416SS, 17-4PHStainless Steel, Inconel, MonelSoft Seat: PTFE, RTFE, Viton
    Metal Seat: Inconel, Stainless Steel

    Contact Us

    Should you have any questions or requirements about control valves, self-operated pressure regulators, high-performance butterfly valves, or other industrial valves, please feel free to contact us for further communication. 

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