1. Basic types of pressure relief valves
The working principle of a pressure relief valve is to discharge pressure through the displacement of a valve disc or diaphragm, and it is usually divided into the following types:
1. Spring-loaded Pressure Relief Valve
A spring-loaded pressure relief valve adjusts the opening and closing of the valve through the preset force of the spring. When the system pressure reaches the set value, the valve disc automatically opens under the action of the spring pressure to release the pressure. When the pressure returns to normal, the valve disc closes. Spring-loaded pressure relief valves are commonly used in small to medium-sized systems, with simple structure and economical price.
2. Diaphragm Pressure Relief Valve
Diaphragm pressure relief valves use elastic diaphragms to respond to pressure changes. When the system pressure exceeds the set value, the diaphragm deforms and pushes the valve disc open, thereby releasing pressure. Diaphragm pressure relief valves have a compact structure and good sealing performance, and are suitable for occasions requiring high sealing and precision.
3. Piston Pressure Relief Valve
Piston pressure relief valves use the displacement of the plunger to control the opening and closing of the valve. When the system pressure exceeds the set value, the plunger pushes the valve open to release excess pressure. Piston pressure relief valves are suitable for high pressure and high flow occasions and can withstand large workloads.
4. Pneumatic Pressure Relief Valve
Pneumatic pressure relief valves use pneumatic drive to control the opening and closing of the valve. When the system pressure exceeds the set value, the pneumatic device automatically opens the valve to release the pressure. Pneumatic pressure relief valves are often used in situations where automated control is required, especially in large-scale industrial production.
5. Electric Pressure Relief Valve
Electric pressure relief valves use electric drive devices to adjust the opening and closing of the valve, and are suitable for systems that require precise control. Electric pressure relief valves are usually equipped with sensors that can monitor the pressure changes of the system in real time and perform precise pressure relief operations.
2. Key factors in purchasing pressure relief valves
When purchasing pressure relief valves, the following key factors need to be considered:
1. Working pressure and set pressure
The main function of the pressure relief valve is to protect the system from damage caused by excessive pressure, so the set pressure (that is, the pressure at which the valve starts to release pressure) is very important. Select the rated pressure range of the pressure relief valve according to the design pressure and maximum working pressure of the system. It is necessary to ensure that the set pressure of the selected valve is higher than the normal working pressure of the system, but lower than the maximum pressure of the equipment.
- Common set pressure range: Usually, the set pressure of the pressure relief valve is selected between the safe working pressure and the maximum allowable pressure of the system.
2. Flow capacity
The flow capacity of the pressure relief valve determines how much fluid it can discharge when it is under pressure relief. The flow capacity is usually related to the size of the pipeline, the nature of the medium and the pressure of the system. When selecting, you should ensure that the valve has sufficient discharge capacity based on the flow requirements of the system.
- Calculated flow capacity: The flow capacity of the pressure relief valve should match the maximum flow of the pipeline to ensure that when the valve is opened, it can effectively discharge excess pressure.
3. Media type and temperature range
The material and sealing method of the pressure relief valve should be selected according to the properties of the medium in the pipeline. Different media have different requirements for materials, especially corrosive and viscous media, which require the selection of appropriate valve materials and sealing methods.
- Common media: steam, liquid, gas, etc.
- Temperature range: When selecting, make sure that the pressure relief valve can adapt to the temperature conditions of the system.
4. Valve material and corrosion resistance
Since pressure relief valves are often used in high-pressure systems, the selected materials must have sufficient strength and corrosion resistance. Especially in the chemical, petroleum and other industries, pressure relief valves must be resistant to corrosion and high temperatures.
- Common materials: stainless steel, alloy steel, copper alloy, cast iron, etc.
5. Installation method and size
The installation method and size of the pressure relief valve must match the size of the pipeline system. Common connection methods include flange connection, threaded connection and welding connection. When selecting, you need to consider the valve interface size, installation space and ease of operation.
- Connection method: Select a suitable connection method according to the interface of the pipeline.
6. Leakage rate
The sealing performance of the pressure relief valve directly affects the pressure relief effect. The leakage rate should be as low as possible to avoid excessive leakage of the medium when the system pressure reaches the set value. Select valve materials and designs with good sealing to ensure the safety of the system.
7. Response time and opening pressure
The response time of the pressure relief valve determines its reaction speed when the system pressure reaches the set value. A pressure relief valve with a short response time and quick response should be selected to ensure that the system pressure does not exceed the safety range.
- Response time: A pressure relief valve that can be opened quickly should be selected to avoid damage to the equipment caused by excessive pressure.
8. Maintenance and maintenance
Pressure relief valves need to be inspected and maintained regularly to ensure their long-term stable operation. When purchasing, you can consider models that are easy to maintain and have low maintenance costs. The valve's detachable design, wear resistance, and maintenance cycle are also factors that need to be considered when selecting.
3. Common applications of pressure relief valves
Pressure relief valves are widely used, especially in industries that require high-pressure protection, where they play a vital safety role. Common application areas include:
1. Boilers and pressure vessels
In boilers and pressure vessels, pressure relief valves are used to prevent equipment damage or explosion caused by excessive pressure. Commonly used in steam boilers, hot water boilers, gas storage containers and other equipment.
2. Oil and Gas
During the storage and transportation of oil and gas, pressure relief valves are used to prevent the pressure in oil and gas pipelines or storage tanks from exceeding safety limits, ensuring the safe transportation of oil and gas.
3. Chemical and Pharmaceutical Industries
Pipelines and reactors in the chemical and pharmaceutical industries need to be kept within a safe pressure range, and pressure relief valves are used to prevent the system from exceeding the pressure limit during the production process.
4. Water Supply System
In urban and industrial water supply systems, pressure relief valves are used to protect pipelines from damage caused by excessive water pressure and ensure safe and stable operation of pipelines.
5. Power and Energy
In the power industry, especially in high-pressure systems such as nuclear power plants and thermal power plants, pressure relief valves are used to prevent damage caused by excessive steam pressure.
6. Liquid and Gas Transportation
In liquid and gas transportation pipelines, pressure relief valves are used to control and protect the pressure of the pipeline system to ensure the long-term safe operation of the pipeline.
4. Selection Case
Suppose a chemical plant needs to select a pressure relief valve for its tank system, which is required to effectively prevent the pressure in the tank from being too high and avoid the risk of explosion. The following selections can be considered:
- Material selection: Stainless steel or alloy steel to ensure corrosion resistance and high temperature resistance.
- Type selection: Spring-loaded pressure relief valve or plunger-loaded pressure relief valve, which can open quickly under high pressure.
- Set pressure: According to the maximum working pressure of the tank and the set pressure of the safety valve, select a reasonable set value to ensure that the safety valve is activated before the dangerous pressure.
- Flow capacity: According to the exhaust requirements of the tank, select a suitable flow capacity to ensure that the gas can be effectively discharged during pressure relief.
5. Conclusion
When purchasing a pressure relief valve, multiple factors must be considered comprehensively according to actual application requirements, such as working pressure, flow capacity, medium type, valve material, installation method and maintenance requirements. Correct selection can not only ensure the safety of the system and prevent equipment damage caused by excessive pressure, but also improve the stability and operation efficiency of the system.
During the purchase process, pay special attention to the following points:
- Precise set pressure: The set pressure must be accurate to ensure that the system can release pressure in time when the dangerous pressure is reached, while avoiding unnecessary discharge.
- Appropriate flow capacity: The flow capacity of the pressure relief valve should match the needs of the system to ensure that the valve can discharge enough medium when the pressure is too high to prevent excessive pressure from causing damage to the equipment.
- Corrosion resistance and high temperature resistance: It is crucial to choose the right material, especially in the chemical, petroleum, natural gas and other industries. The material of the pressure relief valve must have corrosion resistance and high temperature resistance to adapt to the harsh working environment.
- Ease of installation and maintenance: The installation and subsequent maintenance of the pressure relief valve should be convenient to reduce maintenance costs and downtime in long-term use.
Finally, reasonable selection and regular inspection and maintenance are the key to ensure the long-term and stable operation of the pressure relief valve. Through effective selection and management, the pressure relief valve will become an indispensable part of protecting the safety of pipelines and equipment and improving system stability.
In general, as an important safety protection device, the purchase and maintenance of the pressure relief valve cannot be taken lightly. Correct selection of pressure relief valve can not only protect the safety of equipment and personnel, but also ensure the efficient and continuous operation of the production system.