Control valves precisely adjust parameters such as flow rate and pressure of fluids within the machines according to commands, serving as critical components to achieving precise control, rapid response, and efficient production for you.
This article will guide you through the specifications and standards of control valves to help you choose the most suitable option.
1. What Is a Control Valve?
A control valve is formed by a valve body, controller, and actuator and it has precise regulation functions of flow, pressure, and direction. It is widely used in chemical, electrical, petroleum, and other industries. If you need to maintain stable system operation under complex conditions, the control valve will play a crucial role in achieving this.
2. Requirements for Control Valves
2.1 Leak-Free
Control valves must possess superior sealing performance to make sure no internal or external leakage occurs during operation.
2.2 Good Stability
Valve bodies and internal components must be made from corrosion-resistant, high-temperature-resistant materials compatible with the medium to bring long-term stable running to your machine.
2.3 Compatibility
Control valves also need to match your required pipe diameters, pressure ratings, and other specifications to keep seamless installation and coordinated operation.
2.4 Rapid Response
It is capable of swiftly executing system commands to reach precise and timely control for you.
3. Control Valve Specifications
3.1 Control Valve Size
The size of a control valve does not refer to the valve’s physical dimensions, instead it represents the pipe specifications it can accommodate.
3.2.1 Nominal Diameter (DN)
Nominal diameter means the standard pipe size in millimeters, denoted as DN. Common ranging from DN10 to DN2000.
For example, butterfly valves are typically available in sizes from DN50 to DN2000, while ball valves usually cover a range of DN15 to DN200 (equivalent to ½ inch to 8 inches).
During your Model Selection, please ensure the valve’s DN matches the pipe’s DN to avoid compromised sealing and flow performance.
3.2.2 Connection End Dimensions
The connection end serves as the interface between valves and pipelines, with the specific dimensions determined by the connection method. Common methods include flange connections, threaded connections, and welding.
For example, if you choose a threaded connection, you must make sure the thread specifications are perfectly matched.
3.2.3Valve Body Dimensions
The length, height, and width of the valve body all affect the installation.
So when designing and selecting models, you need to comprehensively consider these factors in conjunction with the installation distance.
3.2 Performance Parameters of Control Valves
3.2.1 Flow parameters
Flow parameters are the core indicators for determining whether a control valve can meet the requirements of the operating conditions.
3.2.1.1Flow coefficient
The metric unit for the flow coefficient is . And it represents the volume of 20°C water flowing through a control valve at a pressure differential of 0.1 MPa across the valve, measured in typically ranging from 0.5 to 2000。
When you are selecting a valve, first calculate the appropriate Kv based on maximum flow rate, normal flow rate, and the pressure differential across the valve, while allowing a 10–20% margin to prevent prolonged operation of your control valves.
However, some also use to calculate. It is a U.S. unit and shows the flow rate through a control valve at 1 psi and 60°F, measured in .
3.2.1.2 Adjustable ratio (R）
The adjustable ratio is the maximum flow rate that a control valve can regulate divided by the minimum flow rate, also known as the adjustable range, also known as the adjustable range.
The bigger the adjustable ratio, the wider the range you can adjust.
3.2.1.3 Flow Characteristics
Flow characteristics can describe the relationship between flow rate through a control valve and the position of its stem, directly reflecting the correlation between valve opening and flow rate. Common flow characteristics include linear, equal percentage, parabolic, and quick-opening characteristics. And among them, linear and equal percentage characteristics are more common.
3.2.2 Pressure parameters
Pressure will determine the size and type of valve required, and pressure parameters are influenced by temperature and the medium. It is advisable to ensure the valve can handle the system’s pressure conditions.
3.2.2.1 Nominal Pressure(PN)
Nominal pressure is commonly denoted as PN, meaning the maximum working pressure that can be sustained at a specified temperature. Common units include bar and megapascals (MPa). Generally, it refers to the maximum static pressure that the valve body and connecting components can withstand for a long time at 20°C (or 120°C for cast iron).
3.2.2.2 Work Pressure(P)
This is the pressure a valve can sustain stably over extended periods under actual operating conditions,usually denoted by P. It ranges from 60% to 80% of the nominal pressure.
It is essential to make the working pressure remain below the nominal pressure; otherwise, the valve may fail.
Generally, for low-pressure applications, ball valves or butterfly valves are common choices. But if it is applied in high-pressure, ball valves will be more suitable for you.
3.2.3 Temperature
The valve material and sealing components must be compatible with the medium temperature and ambient temperature. If the temperature exceeds the valve’s tolerance range, it may result in seal damage or valve body deformation.
3.2.4 Level of Disclosure
The leakage rate refers to the amount of leakage when the valve is fully closed and is a key indicator to assessing sealing performance.
A lower leakage rating indicates more reliable sealing, but also brings higher costs at the same time. You should select an appropriate leakage rating based on the specific operating conditions.
3.2.5 Control Accuracy Parameters
3.2.5.1 Hysteresis
It is the maximum deviation in valve stem travel between the rising and falling edges of the input signal, primarily caused by friction and mechanical clearance.
An excessive hysteresis may cause your device to become unstable..
3.2.5.2 Dead time
This means the delay time from the command signal change and the valve beginning to operate. The shorter the dead time, the better the control performance of your valve.
3.2.6 Response time
Response time depends on valve type and diameter.
Generally speaking, response time is controlled within 3 to 15 seconds. For example，small-diameter angle-travel valves (like ball valves, butterfly valves) have an opening/closing time ≤3 seconds. Large-diameter high-pressure valves may reach ≤15 seconds due to heavier loads. When designing systems, it is also important to consider whether response speed meets control requirements.
3.2.7 Noise Level
Noise control is particularly important in sensitive applications such as petrochemical and power generation facilities. When it is required, you can choose valves with noise-reducing designs.
4. Control Valve Standards
When referencing control valve standards, you can choose the appropriate standard based on the project location, industry application, and interchangeability requirements.
4.1 International Organization for Standardization (ISO)
It is internationally recognized and commonly used in multinational engineering projects and global supply chain initiatives.
ISO 60534: Covers methods for selecting, evaluating performance, and testing industrial process control valves.
ISO 5752: Primarily addresses straight-through control valves (such as globe valves, globe valves, and single-seat valves), specifying connection dimensions and mounting dimensions to ensure interchangeability among valves from different manufacturers.
4.2 European Standard(EN)
The European Standard System is developed by the European Committee for Standardization (CEN) and is more suitable for use in projects within the European Union and the wider European region.
EN 1349: It is the general standard for industrial control valves in Europe, largely consistent with ISO 60534, convenient for European companies’ participation in international projects.
EN 558: This standard specifies face-to-face and end-to-end dimensions for metal valves (including gate valves, globe valves, check valves, ball valves, and butterfly valves) with flanged, welded, or threaded end connections. It ensures interchangeability between valves from different manufacturers without requiring system modifications.
4.3 American Society of Mechanical Engineers (ASME)
ASME standards primarily cover valve temperature classes, pressure ratings, materials, and valve body design.
Specifically, ASME B16.34 specifies design and manufacturing requirements for metal valves, including control valves with flanged, threaded, and welded ends. It addresses pressure and temperature ratings, valve body wall thickness, and end dimensions.If you need to procure valves for high-pressure, high-temperature applications, you may refer to this standard.
4.4 American Petroleum Institute (API)
API is the primary U.S. organization focused on establishing standards for control valves used in petroleum, natural gas, and related industries.
API 6D: it specifies the structure, material selection, actuator selection, and other requirements for control valves used in petroleum and natural gas applications, keeping stable valve operation under extreme conditions.
API 598: this standard is about factory inspection and testing methods for industrial valves. After purchasing valves, you can request manufacturers to conduct testing according to these standards or add supplementary inspections at the factory.
4.5 Manufacturers Standards Society (MSS)
MSS standards are primarily developed by valve and pipe fitting manufacturers, emphasizing production processes and details. They often serve as supplements to ASME standards.
Among them, MSS SP-86 standardizes metric dimensions for valves, flanges, and pipe fittings, facilitating product selection and interchangeability across different manufacturers.
Conclusion
Control valve’s specifications determine its suitability for your operating conditions, while standards are necessary to ensure interchangeability and reliability across different manufacturers and projects. By understanding key parameters such as flow rate, pressure, and temperature, and applying standards like ISO, EN, ASME, and so on, you can achieve faster selection and design while making sure global compatibility and stability of control valves.
If you want further information about control valve specifications and standards, or seek the most suitable control valve solution for your project, please feel free to contact us at any time. We will provide tailored technical support and services for you.
