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Practical Technology of Control Valve

Meta Description: Unravel the complexities of control valve types with this in-depth guide, offering insights into their applications, advantages, and selection criteria for various industries. There are two categories of control valves, linear motion and rotary motion control valves.

Main Components of Control Valves

Before diving into the types of control valves, let’s explore the essential components of globe type control valves:

  1. Valve Body: The primary structure that houses the internal components and provides a connection to the piping system.
  2. Valve Trim: The internal components responsible for modulating the flow, including the plug, stem, and seat.
  3. Actuator: The device that provides the force to open, close, or position the valve trim as needed.
  4. Positioner: A control device that adjusts the valve’s actuator position based on a control signal.

These valves regulate flow by moving a closure element in a linear motion. Common linear motion valves include:

  • Globe Valves: Widely used for their precise throttling capabilities, globe valves feature a plug that moves in and out of a seat to control flow.
  • Diaphragm Valves: Featuring a flexible diaphragm that moves up and down, these valves are ideal for handling corrosive, erosive, or abrasive fluids.
  • Pinch Valves: With a pinchable elastomer sleeve, pinch valves are suitable for handling slurries, granular materials, and fibrous suspensions.
pressure control valves manufacturer in china thinktank
pneumatic globe type control valves for steam system

Rotary motion valves modulate flow by rotating a closure element within the valve body. Common rotary motion valves are:

  • Ball Valves: Known for their quick shutoff capabilities, ball valves have a spherical closure element with a flow passage that aligns with the pipeline when open.
  • Butterfly Valves: Featuring a disc that rotates within the flow stream, butterfly valves are lightweight, compact, and suitable for large-diameter pipelines.
  • Plug Valves: These valves use a cylindrical or tapered plug with a flow passage that aligns with the pipeline when open, providing excellent shutoff capabilities.

Meta Description: Dive into this comprehensive guide to understand everything about control valve applications, their functions, types, industries, and more.

 

Introduction

Control valves play a crucial role in regulating the flow, pressure, and temperature of liquids and gases in various industries. With a wide range of applications, control valves are an essential component in many industrial processes. This article aims to cover everything you need to know about control valve applications, helping you understand their function, types, industries they serve, and much more. Whether you are a student, engineer, or a curious individual, this guide provides the knowledge you need to appreciate the significance of control valves in our modern world.

Functions and Types of Control Valves

The Role of Control Valves in Industrial Processes

Control valves serve several critical functions in industrial processes, including:

  • Regulating flow: Adjusting the flow of fluids to maintain a steady rate or maintain specific conditions in a system.
  • Pressure control: Managing the pressure within a system to prevent damage or maintain optimal operating conditions.
  • Temperature control: Adjusting the flow of fluids to regulate the temperature within a system or process.

Understanding the different types of control valves is essential to their applications. Some popular control valve types include:

  1. Globe valves: Ideal for precise flow control, these valves use a movable disk-type element and stationary ring seat for regulating flow.
  2. Butterfly valves: These valves feature a rotating disk within a pipe to control the flow of fluids, offering a compact design and lower costs.
  3. Ball valves: Known for their durability and high flow capacity, ball valves use a spherical closure element that rotates to control fluid flow.
  4. Diaphragm valves: Suitable for handling corrosive or abrasive materials, diaphragm valves utilize a flexible diaphragm to separate the flow stream from the closure element.

Control valve applications span across numerous industries, including:

  • Oil and gas: Controlling flow rates, pressure, and temperature in pipelines, refining processes, and chemical injection systems.
  • Chemical processing: Regulating the flow of corrosive, abrasive, or high-temperature fluids in chemical reactions and processes.
  • Power generation: Ensuring the smooth operation of power plants by controlling steam, water, and gas flow in boilers and turbines.
  • Water and wastewater treatment: Managing flow and pressure in pumping stations, distribution networks, and treatment processes.

Specific Control Valve Applications

Control Circulating System
Continuous Circulating System

While control valves serve multiple industries, some unique applications include:

  • Food and beverage processing: Ensuring hygienic conditions and maintaining product quality by controlling flow and temperature during processing.
  • Pharmaceutical manufacturing: Precise control of fluid flow, pressure, and temperature in drug synthesis, mixing, and packaging processes.
  • Pulp and paper manufacturing: Regulating flow, pressure, and temperature in various stages of pulp and paper production.

Choosing the Right Control Valve

When selecting a control valve, consider the following factors:

  1. Flow requirements: Evaluate the flow characteristics needed for the specific application.
  2. Flow Characteristics: Consider the fluid’s properties, such as viscosity, pressure, and temperature, to select a valve that can handle the specific conditions.
  3. Valve size: Choose a valve size that matches the pipeline size and meets the required flow capacity.
  4. Actuator type: Decide between manual, electric, pneumatic, or hydraulic actuation based on the system requirements and available resources. Select an actuator that provides adequate force and meets the desired control requirements.
  5. Material compatibility: Ensure the valve materials are compatible with the fluid being handled to avoid corrosion or other damage.
  6. Regulatory requirements: Adhere to industry-specific regulations and standards to ensure safe and efficient operation.
  7. Noise and vibration: Option for a valve design that minimizes noise and vibration for a safer, more reliable operation.

Maintaining Control Valves for Optimal Performance

Proper maintenance of control valves is crucial for ensuring their longevity and efficient operation. Here are some maintenance tips:

  • Regular inspections: Periodically inspect control valves for signs of wear, corrosion, or damage. This will help you identify potential issues before they become critical.
  • Lubrication: Keep moving parts lubricated to reduce friction and prevent wear.
  • Cleaning: Remove dirt, debris, and other contaminants to ensure smooth valve operation and minimize the risk of blockages.
  • Seal replacement: Replace worn or damaged seals to prevent leaks and maintain optimal performance.
  • Calibration: Regularly calibrate control valves to ensure accurate and consistent operation.
  • Documentation: Keep detailed records of maintenance activities, including dates, procedures, and any issues encountered. This will help you track the valve’s performance and plan for future maintenance.

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.

Yield Strength is an important property of steel. It is defined as the stress at which 0.2% of the material has been permanently deformed. The higher the yield strength of the steel, the higher the resistance to permanent deformation.

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.

The principal harder in steel is carbon. The more carbon that is added (up to 1.2%), the harder it gets.

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. 

The order is just the beginning of the service. We treat every customer seriously and sincerely, try our best to meet the customer’s customized requirements, and provide customers with cost-effective valves as much as possible. Maintaining the interests of our customers is the foundation of our development.