What is a Control Valve? A Comprehensive Guide

Control valves are critical components in various industrial processes. They regulate vital parameters like flow, pressure, temperature, and level, helping industries maintain optimal operations. Whether you’re working in oil and gas, chemical processing, water treatment, or manufacturing, understanding how control valves function can significantly enhance system efficiency, reliability, and safety. This guide will explore what control valves are, their types, working principles, components, and applications in different sectors. Modular design is adopted for the products of TangoValve Group to meet the requirements of specific working conditions, so that the control valve can adapt to the most difficult requirements under the most severe working conditions. In addition, modular design reduces the cost of spare parts, installation, and maintenance, so that the important total cost can be saved.

 

Functions of Control Valves

Control valves are integral components in regulating fluid flow within a system. Their primary function is to manage the flow rate, pressure, temperature, and level of various fluids within industrial applications. Through their ability to adjust the flow dynamically, control valves ensure that systems operate within optimal parameters, enhancing efficiency, safety, and performance.

1. Flow Regulation: One of the key roles of control valves is to modulate the flow of fluid through a pipeline. By adjusting the size of the valve opening, they can either increase or decrease the flow rate, ensuring that the system maintains the required fluid flow according to the operational needs.
2. Pressure Control: Control valves play a crucial role in maintaining pressure within the system. By regulating the flow, these valves prevent pressure from exceeding safe limits, thus avoiding potential damage to equipment or systems. This makes them essential for maintaining pressure stability in industries like chemical processing and power generation.
3. Temperature and Level Control: In addition to flow and pressure control, control valves are used to regulate the temperature and level of liquids and gases within tanks, boilers, and pipelines. They are employed in systems where maintaining specific temperature or level setpoints is critical, such as in HVAC systems, water treatment plants, and refineries.
4. Safety Functionality: Control valves contribute significantly to the safety of industrial processes. In case of emergency conditions like pressure buildup or system failure, control valves can quickly adjust the flow to mitigate potential hazards. This feature is particularly important in chemical, oil and gas, and food processing industries, where safety is paramount.

 

Components of Control Valves

Control valves are critical components in regulating fluid flow within a variety of industrial systems. Their components work in harmony to maintain accurate and efficient control over parameters such as pressure, temperature, and flow rate. The key components of a control valve include the valve body, trim, actuator, positioner, and bonnet.

• Valve Body The valve body is the foundational part of a control valve. It serves as the primary housing for all internal components and provides the necessary structural integrity to handle the pressures and temperatures in the system. The material used for the valve body varies, with common choices including stainless steel, carbon steel, and specialized alloys, depending on the operating environment and type of fluid being controlled. The body directs the fluid flow and plays a significant role in the valve’s overall performance and durability.
• Valve Trim The valve trim consists of the internal components that directly interact with the fluid. This includes the valve plug, stem, seat, and sometimes a cage. The trim’s design ensures that the valve can regulate flow accurately:
  • The valve plug is a cylindrical part that moves within the valve to either block or allow fluid to pass.
  • The stem connects the plug to the actuator and facilitates its movement.
  • The seat provides a sealing surface against the plug to prevent leakage when the valve is closed.
  • A cage may be used in some designs to help guide and stabilize the plug during operation.
• Actuator The actuator is the power source that drives the valve plug, regulating the flow. Actuators can be pneumatic, hydraulic, or electric, and their function is to convert energy from an external source into mechanical motion. Pneumatic actuators are common in many industrial applications due to their reliability, while hydraulic actuators are often used in high-torque or high-pressure situations. Electric actuators are ideal for environments where compressed air is unavailable or when precise control is required.
• Positioner The positioner is a critical component for ensuring that the valve plug reaches and maintains the correct position for optimal control. It monitors the actual position of the valve and compares it to the desired position, sending corrective signals to the actuator to maintain accuracy. This feedback mechanism ensures the valve operates efficiently, reducing the likelihood of errors or deviations in flow control.
• Bonnet The bonnet is an external cover that houses the valve stem and protects the internal components from environmental factors such as dust, moisture, and temperature fluctuations. It also helps to prevent contamination from entering the valve, ensuring reliable performance over time.

 

Working Principle of Control Valves

The working principle of control valves involves several critical steps:

1. Receiving a Control Signal: The process begins when the control valve receives a signal from a control system. This signal indicates the desired operational condition, which may represent a specific pressure, temperature, or flow rate.
2. Actuator Response: The actuator, connected to the control valve, converts the control signal into mechanical motion. Depending on the type of actuator (pneumatic, electric, or hydraulic), the control signal adjusts the actuator’s position by either moving a diaphragm, piston, or motor. This movement drives the valve’s internal components.
3. Valve Stem Movement: The mechanical motion from the actuator is transferred to the valve stem, which in turn moves the valve’s internal component—typically a plug, ball, or disc. This movement can be linear (up and down) or rotary (rotational), depending on the valve type.
4. Flow Area Adjustment: As the valve’s internal component moves, it alters the size of the opening (or orifice) through which the fluid passes. By increasing the opening, the valve allows more fluid to flow, thereby increasing the flow rate. Conversely, decreasing the opening reduces the flow rate, restricting the fluid passage.
5. Flow Modulation: The valve continuously modulates the flow by adjusting its internal components based on the control signal, ensuring that the flow rate aligns with the desired setpoint. This modulation ensures that process conditions, such as pressure or temperature, remain within predefined limits.
6. Feedback Loop: To maintain accuracy, a feedback loop is established between the control system and sensors monitoring process variables. If the system detects a deviation from the setpoint, it sends a correction signal to the actuator to adjust the valve position. This continuous feedback mechanism ensures precise and reliable control.

 

Flow Through Control Valve

When the fluid passes through the regulating valve, the resistance of the fluid affects the pressure drop. At the same time, the flow rate increases proportionally, and the larger the resistance is, the larger the flow rate is. For different fluid conditions, the energy change through the valve will affect air noise and cavitation problems.

 

Solutions for Aerodynamic Noise

One of the forces that control the flow rate through the valve is the aerodynamic noise of the fluid. Through the multi-stage squirrel cage structure, the energy generated by continuous absorption of pressure drop will be controlled to an acceptable range of flow rate through the valve.

 

Solutions for Cavitation

By controlling the pressure above the critical pressure (PVC), cavitation can be controlled. Through the multi-stage structure, the pressure drop can be absorbed continuously to generate energy, the resistance of the flow channel increases, and PVC can be controlled, so cavitation can be avoided.

 

Types of Control Valves

Globe Valves

Globe valves are one of the most commonly used control valves. Their design features a spherical body, allowing for precise flow control through an adjustable plug and seat arrangement. These valves are suitable for applications where fine control over flow is essential. The globe valve’s primary advantage lies in its ability to handle moderate to high pressure and its linear flow characteristics, making it ideal for throttling applications.

Ball Valves

Ball valves use a spherical ball with a hole through it to control the flow of fluids. When the ball is rotated, the hole aligns with the pipe to allow flow, or it is perpendicular to block it. Ball valves are popular in applications requiring a simple on/off function or where quick shut-off is necessary. Their robust design makes them suitable for high-pressure systems and they are often used in industries such as oil and gas, chemical processing, and water treatment.

Butterfly Valves

Butterfly valves consist of a disc that rotates to regulate flow. The valve’s compact design and lightweight construction make it a popular choice for large pipelines, especially where space is limited. They are widely used in applications involving large volumes of liquids or gases, such as HVAC systems, water distribution networks, and chemical processing. Butterfly valves are particularly useful for handling low-pressure and low-flow conditions.

Gate Valves

Gate valves are primarily used for fully opening or closing a pipeline. While they can be used in throttling applications, they are generally not recommended due to their less precise control. Gate valves are typically used where a full-on or full-off operation is required, such as in water, oil, or gas pipelines. Their simple design and ability to handle high-pressure systems make them a staple in industries like power generation and petrochemical processing.

Diaphragm Valves

Diaphragm valves use a flexible diaphragm to control fluid flow. The diaphragm is pressed against the seat, blocking the flow when the valve is closed. These valves are often used in applications involving corrosive fluids or systems requiring hygienic conditions, such as the pharmaceutical and food processing industries. Diaphragm valves offer tight shutoff and are ideal for controlling abrasive and viscous fluids.

Pressure Relief Valves

Pressure relief valves are designed to protect systems from overpressure by automatically releasing fluid when a preset pressure is exceeded. These valves are crucial in preventing equipment damage and ensuring system safety in industries like oil and gas, chemical production, and power plants. They are typically installed in systems where pressure fluctuations can lead to catastrophic failures if not controlled.

Check Valves

Check valves prevent backflow by allowing fluid to flow in one direction only. These valves are widely used in systems where backflow could damage equipment or disrupt operations, such as in water and wastewater treatment plants, pumping stations, and industrial piping systems. Check valves come in different designs, including swing, ball, and lift types, to suit various application needs.

Control Valves with Actuators

Many control valves are equipped with actuators, which provide the force needed to operate the valve automatically. Actuators can be pneumatic, hydraulic, or electric, and they provide precise control over valve movements. Pneumatic actuators are the most common and are used in systems where air pressure is available. Electric actuators offer high precision and are widely used in applications requiring accurate flow or pressure control.

 

Product Features

• Simple calculation and selection;
• Simple and convenient maintenance;
• Compact and reasonable design; long service life;
• Integrated controller and actuator can be provided;
• Body diameter from DN20 to 500 (3/4″ to 20″);
• Pressure rating from PN1.0 to 42.0MPa (ANSI 150 to 2500LB);
• Wide range of available types.

 

Advantages and Disadvantages of Control Valves

Control valves play a crucial role in managing the flow, pressure, and temperature within various industrial systems. Below are the key advantages and disadvantages of control valves:

Advantages:

1. Precise Control: Control valves allow for accurate regulation of flow rates, pressures, and temperatures, essential in maintaining optimal system performance.
2. Durability: These valves are designed for long-term service, providing reliable operation even in demanding industrial environments.
3. Space-Efficient Design: With their compact size, control valves help conserve valuable space within processing systems, enabling efficient layout planning.
4. Rapid Response: Control valves are equipped to respond quickly to changes in system parameters, ensuring real-time adjustments for consistent operation.
5. Reduced Pressure Drop: By providing smooth flow control, they minimize pressure drops across the system, helping to improve energy efficiency.
6. Versatile Applications: Control valves are used across various industries for flow throttling, on-off control, and pressure regulation in applications ranging from HVAC systems to chemical processing and water treatment.

Disadvantages:

1. Control Signal Dependency: A key disadvantage is the need for a continuous control signal throughout operation. Any interruption or failure in the control signal can result in improper valve functioning.
2. Complex Maintenance: Depending on the type, control valves may require regular maintenance and calibration to maintain optimal performance, especially when exposed to high pressures or aggressive fluids.
3. Cost: High-performance control valves, especially those made from materials like stainless steel or exotic alloys, can be expensive to install and maintain.
4. Potential for Wear and Tear: Components such as the valve actuator or seals may wear over time, leading to reduced efficiency and the need for replacements.

 

Applications of Control Valves

Control valves play a vital role in managing fluid dynamics across various industrial sectors, ensuring safety, efficiency, and compliance with regulatory standards. Below are the key applications where control valves are essential:

Oil and Gas Industry

In the oil and gas industry, control valves regulate the flow, pressure, and temperature of crude oil, natural gas, and refined products. They prevent pipeline ruptures and ensure the safe transportation of hydrocarbons by maintaining optimal flow and pressure levels. Control valves are also critical in offshore platforms for managing the flow of gas and oil extraction.

Chemical and Petrochemical Processing

Control valves are indispensable in chemical and petrochemical plants, where they regulate reactants and products in various stages of production. They help maintain precise temperatures, pressures, and flow rates, ensuring efficient and safe chemical reactions. For instance, in reactors and distillation columns, control valves help optimize production while preventing dangerous conditions like overpressure or thermal damage.

Power Generation

In power plants, control valves are integral to managing steam flow in turbines, controlling feedwater, and maintaining the temperature of the steam cycle. They ensure efficient electricity generation and prevent damage to critical equipment by controlling thermal conditions within the system. Additionally, they help maintain cooling systems to prevent overheating and optimize energy usage.

Water and Wastewater Treatment

Control valves are used extensively in water and wastewater treatment plants to regulate the flow of water and chemicals during purification and treatment processes. By controlling the flow of chlorine, fluoride, and other treatment chemicals, control valves ensure the water is safe for consumption and meets environmental discharge standards.

 

Maintenance and Troubleshooting of Control Valves

Proper maintenance and troubleshooting are essential to keep these valves functioning efficiently, preventing costly downtime and maintaining system performance. This section focuses on common issues that affect control valves and practical approaches to troubleshoot and resolve these problems effectively.

Common Problems and Solutions for Control Valves

1. Leaking Valves
   Leakage is a frequent issue, usually caused by worn-out seals or damaged valve bodies. If a valve is leaking, it’s important to first identify the cause, which might be deteriorated seals, valve seat damage, or improper installation. To resolve this, the valve must be disassembled, the damaged components replaced, and the valve reassembled to ensure a tight seal.
2. Sticking Valves
   Control valves can stick due to debris buildup, corrosion, or insufficient lubrication. When a valve fails to move freely, it compromises the flow control process. To fix this issue, cleaning the valve and replacing any damaged parts, such as the valve seat or actuator components, is necessary. Ensuring the valve operates smoothly after reassembly is critical to restoring performance.
3. Noisy or Vibrating Valves
   Excessive noise or vibration is often a sign of cavitation, misalignment, or turbulence within the valve system. These issues can result in damage over time, affecting the longevity of the valve. A thorough inspection is needed to adjust internal components, replace worn-out parts, or install noise-reducing devices to mitigate the problem.
4. Erratic Valve Operation
   If the valve is not responding as expected, it could be due to issues with the actuator or the control signal. The actuator might be malfunctioning, or the control system could be providing faulty signals. Testing and inspecting the actuator, controller, and signal lines are vital steps to determine the root cause and restore reliable valve performance.
5. Inconsistent Flow Rates
   Control valves are designed to regulate flow consistently. In cases of fluctuating or inconsistent flow rates, the issue may stem from clogged valve ports, worn valve trim, or improper valve sizing. Diagnosing this involves disassembling the valve, cleaning or replacing the necessary parts, and adjusting the valve trim to ensure proper flow regulation.

Troubleshooting Process

To efficiently troubleshoot a control valve, a systematic approach should be followed:

1. Identify the Problem
   Begin by analyzing the symptoms and operational issues the valve is exhibiting. Common signs include leakage, inconsistent flow, noise, or erratic valve movement. Identifying the specific problem helps narrow down potential causes.
2. Inspect the Valve and Actuator
   Perform a visual inspection of both the valve and its actuator. Look for visible signs of damage, corrosion, or misalignment. Ensure that all connections are secure, and the actuator is mounted correctly.
3. Check for Leakage
   Conduct a leak test to locate the source of leakage. Valve seats, seals, and packing glands should be thoroughly checked for wear and damage. Replacing any faulty components is crucial to restoring the valve’s sealing capacity.
4. Verify Calibration
   A valve that is not properly calibrated can lead to performance issues. Check the valve’s calibration settings and ensure that they align with the system’s required operating conditions. Adjust as needed to optimize the valve’s response.
5. Clean and Replace Faulty Parts
   If the valve is sticking or experiencing inconsistent flow, cleaning or replacing the affected parts may be necessary. Contaminants or debris can obstruct the flow path, reducing the valve’s efficiency. Ensure that all components are free of blockages and functioning properly.
6. Lubricate Moving Components
   Proper lubrication is vital for maintaining the valve’s smooth operation. If the valve components are not moving freely, it could indicate a lack of lubrication. Applying the appropriate lubricant can prevent sticking and reduce wear and tear on the moving parts.
7. Test and Adjust
   Once the valve has been inspected, cleaned, and repaired, it should be tested to ensure it operates correctly. Adjust the settings as needed to confirm that the valve responds to control signals appropriately and regulates the flow or pressure accurately.

 

Control Valve Spillage Reference Table

Leakage Level	Maximum Seat Leakage				Test Medium	Test Pressure
II	0.5% Rated Cv				10~52°C Air or Water	Among differential pressure of 0.35 MPa or operating differential pressure, it is needed to choose the one with smaller value
III	0.1% Rated Cv
IV	0.01% Rated Cv
V	5×10⁴ m1/min/in (Seat Diameter)/psi (Pressure Difference);				10~52°C  Water	Working Pressure Difference
VI	Seat Diameter		mL/min	Number of Bubbles Per Minute	0~52°C Air or Nitrogen Water	Among differential pressure of 0.35 MPa or operating differential pressure, it is needed to choose the one with smaller value
	in	mm
	1″	25	0.15	1
	1/2″	38	0.3	2
	2″	51	0.45	3
	3″	76	0.9	6
	4″	102	1.7	11
	6″	152	4	27
	8″	203	6.75	45

Air-to-open (type K) refers to that the greater the air pressure into the actuator is, the greater the valve opening is; when the air is lost, the valve is closed, which is called FC (Fail Close).

Air-to-close (type B) refers to that the greater the air pressure into the actuator is, the smaller the valve opening is; the valve is fully open when the air is lost, which is called FO (Fail Open).

The selection of the control valve shall be determined according to the specific process conditions.

• FC—The control valve is closed in case of air feed failure.
• FO—The control valve is opened in case of air feed failure.
• FL—When the air feed is interrupted, the position of the control valve remains unchanged (holding position).
• FLC—When the air feed is interrupted, the position of the control valve remains unchanged (holding position); the valve is closed in case of a small signal.
• FLO—When the air feed is interrupted, the position of the control valve remains unchanged (holding position); the valve is opened in case of a small signal.
• LC—Refers to the valve being locked in the closed state, which is not allowed to be open.
• NC—Normally closed, refers to the valve being closed in general, but may be opened in special cases.
• LO—Refers to the valve being locked in the open state. That is to say, the valve is not allowed to be closed, and local valves are generally not installed before and after it.
• NO—Refers to normally open valve, but may be closed in special cases.

 

Comparison Table of Rated Pressure and Saturated Steam Temperature

Pressure (MPa)	Temperature (°C)	Pressure (MPa)	Temperature (°C)	Pressure (MPa)	Temperature (°C)	Pressure (MPa)	Temperature (°C)	Pressure (MPa)	Temperature (°C)
0.1	119.61	2.3	220.75	4.5	257.56	6.7	282.52	8.9	301.9
0.2	132.87	2.4	222.9	4.6	258.87	6.8	283.5	9	302.69
0.3	142.92	2.5	224.99	4.7	260.16	6.9	284.47	9.1	303.48
0.4	151.11	2.6	227.01	4.8	261.44	7	285.42	9.2	304.26
0.5	158.07	2.7	228.98	4.9	262.69	7.1	286.37	9.3	305.03
0.6	164.17	2.8	230.89	5	263.92	7.2	287.31	9.4	305.79
0.7	169.6	2.9	232.76	5.1	265.14	7.3	288.23	9.5	306.55
0.8	174.53	3	234.57	5.2	266.34	7.4	289.15	9.6	307.3
0.9	179.03	3.1	236.34	5.3	267.52	7.5	290.06	9.7	308.05
1	183.2	3.2	238.07	5.4	268.68	7.6	290.96	9.8	308.79
1.1	187.08	3.3	239.76	5.5	269.83	7.7	291.85	9.9	309.52
1.2	190.71	3.4	241.42	5.6	270.96	7.8	292.73	10	310.25
1.3	194.13	3.5	243.03	5.7	272.08	7.9	293.6	10.5	313.82
1.4	197.36	3.6	244.62	5.8	273.19	8	294.47	11	317.26
1.5	200.43	3.7	246.17	5.9	274.27	8.1	295.32	11.5	320.57
1.6	203.35	3.8	247.68	6	275.35	8.2	296.17	12	323.87
1.7	206.14	3.9	249.17	6.1	276.41	8.3	297.01	12.5	336.89
1.8	208.82	4	250.63	6.2	277.46	8.4	297.85	13	339.9
1.9	211.39	4.1	252.07	6.3	278.5	8.5	298.67	13.5	342.82
2	213.85	4.2	253.48	6.4	279.52	8.6	299.49	14	345.66
2.1	216.23	4.3	254.86	6.5	280.53	8.7	300.3
2.2	218.53	4.4	256.22	6.6	281.53	8.8	301.11

 

Control Valve Standards and Regulations

1. Industry Standards for Control Valves

Numerous organizations set global standards to guide the design, manufacturing, and operation of control valves. These standards ensure uniformity, safety, and reliability across industries. Prominent standards include:

• ISO Standards: The International Organization for Standardization (ISO) provides comprehensive guidelines for quality management and operational standards. For instance, ISO 9001 dictates the quality control processes essential for control valve manufacturers to maintain high standards.
• ANSI/ISA-75: This standard, developed by the American National Standards Institute (ANSI) and the International Society of Automation (ISA), offers guidelines for valve sizing, performance, and testing. It ensures that control valves meet specific flow and pressure requirements, ensuring performance under varying system conditions.
• API Standards: The American Petroleum Institute (API) focuses on the oil and gas sector, offering detailed specifications such as API 526, which pertains to the design and performance standards for pressure relief valves, a subset of control valves often used in these industries.
• ASME Codes: The American Society of Mechanical Engineers (ASME) sets standards that govern the mechanical design, operation, and safety of valves across multiple sectors, ensuring that they can withstand high pressures and extreme temperatures, especially in power plants and other high-risk environments.

2. Regulatory Compliance

Control valves must adhere to both international and regional regulatory requirements, which vary depending on the application and industry. These regulations are critical to ensure that control valves function safely and efficiently, especially in hazardous environments.

• OSHA and EPA: In the United States, the Occupational Safety and Health Administration (OSHA) regulates workplace safety, including the handling of control valves in potentially dangerous environments. The Environmental Protection Agency (EPA) establishes environmental standards, ensuring that valves used in certain systems do not contribute to harmful emissions or environmental contamination.
• EU Directives: In the European Union, the Pressure Equipment Directive (PED) ensures that control valves meet the necessary design, manufacturing, and testing standards for pressure-containing equipment. Similarly, the ATEX Directive governs valves used in explosive atmospheres, ensuring they are designed to prevent sparks or leaks that could ignite hazardous materials.
• Industry-Specific Regulations: Certain sectors like the oil and gas industry follow more stringent standards like API and ASME regulations to ensure the safety and reliability of valves in critical applications.

3. Key Compliance Considerations

Achieving regulatory compliance for control valves requires a comprehensive approach that spans design, installation, operation, and maintenance:

• Design and Material Selection: Control valves must be made from materials compatible with the fluids they control, ensuring long-term durability and resistance to corrosion or wear. Additionally, the pressure, temperature ratings, and flow capacities must match the specific needs of the application.
• Installation and Testing: Proper installation is crucial for ensuring optimal valve performance. Calibration and functional testing must be conducted post-installation to confirm that valves operate as expected under all conditions.
• Operational Monitoring: Once in operation, control valves must undergo routine inspections and preventive maintenance to identify wear or malfunction before they lead to system failures. These checks are essential for ensuring long-term compliance with safety standards.
• Documentation and Auditing: Organizations must maintain detailed records of valve specifications, inspections, repairs, and performance testing. This documentation ensures that compliance can be demonstrated during audits and inspections.

4. Best Practices for Compliance

To ensure consistent regulatory compliance, organizations should implement a systematic approach that includes:

• Developing a Compliance Plan: A well-structured compliance plan that outlines the standards and regulations relevant to control valves is essential. This plan should cover all aspects, from valve selection to testing and maintenance.
• Proactive Maintenance: Preventive maintenance and regular inspections help avoid downtime and ensure that valves continue to operate within regulatory guidelines.
• Engagement with Regulatory Bodies: Staying in regular contact with relevant regulatory bodies and attending industry conferences will help keep an organization informed about any changes in the standards or regulations.

 

Comparison Table for Nominal Pressure of Control Valve

American Standard Class	150	300	400	600	900	1500	2500
Japanese Standards K Class	10	20	30	40	63	100
Chinese Standards MPa	1.6 (2.0)	4.0 (5.0)	6.3 (6.8)	10	16.0 (15.0)	25	42

Note: Nominal pressure and class are different in temperature criteria. Therefore, they have no strict corresponding relationships except corresponding relationships of their rough parameters.

 

Test Pressure Gage for Valve Testing (National standards, American standard)

Pilot Project	Nominal Pressure (MPa)							Nominal Pressure (Class)
Nominal Pressure (MPa)	0.6	1	1.6	2.5	4	6.4	10	150	300	400	600	800	900	1500
Shell (strength) Pressure Test (MPa)	0.9	1.5	2.4	3.8	6	9.6	15	3.1	7.8	10.3	15.3	20.1	23.1	38.4
High Pressure Seal on Seal Pressure Test (MPa)	0.7	1.1	1.8	2.8	4.4	7.1	11	2.2	5.5	7.6	11.2	14.7	17.1	28.1
Low Pressure (Gas) Seal Pressure Test (MPa)	0.5–0.7							0.5–0.7

Note: 1.Under a shell pressure test of 100°F (38°C), it is required to be no less than 1.5 times of the rating value. 2.Under a seal pressure test of 100°F (38°C), it is required to be no less than 1.1 times of the rating value.

 

Temperature and Pressure Comparison Table for Body Materials Under Japanese Standards

Temperature (°C)	10K	20K	30K		40K
	SCPH2	SCPH2	SCPH2	SCPH21	SCPH2	SCPH21
-10 ~ 120	1.37	3.33	4.99	4.99	6.66	6.66
~220	1.17	3.03	4.5	4.5	6.07	6.07
~300	0.98	2.84	4.21	4.21	5.58	5.58
~350		2.54	3.82	3.82	5.09	5.09
~400		2.25	3.33	3.72	4.5	4.99
~425		1.96	2.94	3.52	3.92	4.7
~450						4.41
~475						4.11
~490						3.92
~500						3.72
~510						3.52

Temperature (°C)	PN16	PN40	PN63	PN100
	ZG230-450
-10 ~ 200	1.6	4	6.3	10
~250	1.4	3.5	5.4	9
~300	1.2	3	4.8	7.5
~350	1.1	2.6	4	6.6
~400	0.9	2.3	3.7	5.8
~425	0.8	2	3.2	5
~435	0.7	1.8	2.8	4.5
~445	0.62	1.6	2.5	4.2
~455	0.57	1.4	2.3	3.6

 

Temperature and Pressure Comparison Table for Body Materials Under National Standards

Temperature (°C)	PN16 (ZG0Cr18Ni9)	PN40 (ZG0Cr18Ni9)	PN63 (ZG0Cr18Ni9)	PN100 (ZG0Cr18Ni9)
-50 ~ 200	1.6	4	6.3	10
~300	1.4	3.5	5.4	9
~400	1.2	3	4.8	7.5
~480	1.1	2.6	4	6.6
~520	0.9	2.3	3.7	5.8
~560	0.8	2	3.2	5

 

Conclusion

Control valves play an essential role in maintaining operational efficiency, safety, and reliability in numerous industries. Understanding the types, components, and working principles of control valves will help engineers and technicians optimize system performance and minimize the risk of failure. Whether you’re dealing with complex industrial systems or simple fluid management tasks, a reliable control valve can make all the difference in keeping things running smoothly.

By the end of this article, you should have a comprehensive understanding of how control valves operate, why they are vital in various sectors, and how selecting the right type of control valve can improve both safety and efficiency in your processes.