Installation location and precautions of safety valves

As an automatic valve, the safety valve opens when the system pressure exceeds the predetermined safety value and discharges excess media to prevent the system pressure from continuing to rise, thereby protecting the safety of equipment and personnel. Correctly selecting the installation location of the safety valve and following relevant precautions are the key to ensuring its reliable operation. Working principle of safety valve The safety valve is generally composed of main components such as valve seat, valve core, spring, etc. When the pressure in the system is normal, the spring force presses the valve core tightly against the valve seat, and the valve is in a closed state. Once the system pressure rises and exceeds the opening pressure set by the spring, the medium force overcomes the spring force, pushes the valve core upward, the safety valve opens, and the medium begins to discharge. As the medium is discharged, the system pressure drops. When the pressure drops to the return seat pressure set by the spring, the spring force presses the valve core back to the valve seat again, the valve closes, and the system returns to normal operation.

Common installation locations

Pressure vessels

Top installation: For most pressure vessels, such as steam boilers, compressed air storage tanks, etc., the safety valve is usually installed on the top of the container. This is because gas or steam will accumulate at the top of the container, and the top installation enables the safety valve to sense the change in pressure in the container the fastest. For example, in a steam boiler, steam is generated and gathered at the top. The safety valve installed at the top can monitor and control the steam pressure in time to prevent overpressure. If it is installed on the side or bottom, the safety valve may respond late due to factors such as resistance in the rising process of steam.

Close to the gas phase space: In some pressure vessels with gas and liquid phases, such as reactors, the safety valve should be installed close to the gas phase space. Taking the reactor in the petrochemical industry as an example, gas may be generated during the reaction process, and the gas gathers in the gas phase space above the container. Installing the safety valve close to the gas phase space can ensure rapid action when the gas phase pressure increases, avoiding the safety valve from affecting the accurate perception of the gas phase pressure due to the presence of the liquid phase. If the installation position is improper, such as too close to the liquid phase area, the liquid phase may hinder the normal opening of the safety valve, and even cause the safety valve to misjudge the pressure situation.

Pipeline system

The starting end of the pipeline: In some pipeline systems that transport flammable, explosive or toxic media, the safety valve is installed at the starting end of the pipeline. For example, when the natural gas transmission pipeline is output from the gas source station, a safety valve is installed at the starting end, which can be activated in time when the gas source pressure suddenly increases, preventing excessive pressure from damaging the entire pipeline system, and avoiding serious safety accidents caused by pipeline rupture, such as fire, explosion or toxic gas leakage.

Pipeline branch: When there are branches in the pipeline, installing a safety valve at the branch can effectively protect the branch pipeline and its connected equipment. For example, in the heating network, branch pipelines in different areas may have abnormal pressure due to flow regulation, equipment failure and other reasons. Installing a safety valve at the branch can provide pressure protection for the specific situation of each branch to prevent excessive pressure in a branch from affecting the normal operation of other branches and the entire pipeline network.

Pump outlet pipeline: For the pump delivery system, the safety valve is generally installed on the pump outlet pipeline. Taking a chemical centrifugal pump as an example, when the pump outlet valve is suddenly closed or the downstream pipeline is blocked, the pump outlet pressure will rise sharply. At this time, the safety valve installed in the pump outlet pipeline can be opened quickly to release the excess pressure and protect the pump body and pipeline from damage. If the safety valve is installed on the pump inlet pipe, due to the suction effect of the pump, the inlet pressure is usually lower than the outlet pressure, and it cannot play an effective protective role when the pump outlet pressure rises abnormally.

Other equipment

Compressor: In the compressor system, the safety valve is installed on the outlet pipe of the compressor. The compressor compresses the gas when working, and the outlet pressure is high. When the outlet pressure exceeds the safety range due to internal failure of the compressor or blockage in the downstream system, the safety valve installed in the outlet pipe opens to release the pressure to prevent the compressor from being damaged due to overpressure. For example, the air compressor provides compressed air for pneumatic equipment. If the outlet pressure is out of control, it may cause serious consequences such as damage to the compressor seal and cylinder rupture. The installation of the safety valve can effectively prevent such situations from happening.

Heat exchanger: For the heat exchanger, the installation position of the safety valve needs to be determined according to its working principle and the flow direction of the medium. In the shell and tube heat exchanger, if the medium pressure in the tube side is high and overpressure may occur, the safety valve can be installed on the outlet pipe of the tube side; if there is a risk of overpressure in the shell side medium, it is installed on the outlet pipe of the shell side. For example, in a steam-water heat exchanger, if the pressure on the steam side is not properly controlled, overpressure may occur. At this time, installing a safety valve in the steam side outlet pipe can discharge steam in time when the pressure is too high, prevent the heat exchanger from being damaged due to overpressure, and avoid safety accidents such as leakage.

Installation precautions

Pre-installation inspection

Model and specification matching: Before installation, you must carefully check whether the model and specifications of the safety valve match the working pressure, temperature, medium and other parameters of the equipment or pipeline system. Different types of safety valves are suitable for different working conditions. For example, spring-type safety valves are suitable for general pressure systems, while pilot-operated safety valves are suitable for systems with higher pressure and more precise control requirements. If the safety valve model is selected incorrectly, it may not be opened or closed normally and cannot play an effective protective role. For example, if a safety valve with a rated pressure that is too low is installed in a high-pressure system, the safety valve will open frequently, affecting the normal operation of the system; conversely, if the rated pressure is too high, the safety valve may not be opened in time when overpressure occurs. Appearance and integrity inspection: Check whether the appearance of the safety valve is damaged or deformed, and ensure that the internal components such as the valve core and spring are intact and free of jamming. For newly purchased safety valves, they may be hit during transportation, resulting in appearance damage or displacement of internal components. For example, if the valve core is slightly deformed or stuck by foreign objects, it will affect its normal operation under pressure, causing the safety valve to fail to open and close accurately. Verification certificate: The safety valve must have a valid verification certificate to ensure that it has been professionally verified before installation, and parameters such as opening pressure and return pressure meet the design requirements. The verification certificate is an important basis for the qualified performance of the safety valve. Safety valves that have not been verified or failed the verification are strictly prohibited from being installed and used. For example, some safety valves may have changes in spring performance after long-term storage, resulting in inaccurate opening pressure. Verification can be discovered and adjusted in time to ensure that they can work normally after installation.

Installation process requirements

Correct installation direction: The safety valve must be installed in the specified direction. Generally, the inlet and outlet directions of the safety valve should be consistent with the flow direction of the medium. For example, for a vertically installed safety valve, its inlet should be located at the bottom and the outlet at the top to ensure that the medium can smoothly enter the safety valve and be discharged normally when it is opened. If the installation direction is wrong, such as reverse connection of the inlet and outlet, the safety valve may not open normally, or the medium cannot be discharged smoothly after opening, resulting in the inability to effectively reduce the pressure, which seriously affects its protection function. Firm and reliable connection: The connection between the safety valve and the equipment or pipeline should adopt a suitable connection method, such as flange connection, threaded connection, etc., and ensure that the connection is firm. When using flange connection, pay attention to the selection and installation of gaskets. The gasket should be able to withstand the pressure of the system and the corrosion of the medium, and the installation should be flat to avoid leakage. When threading, the thread matching accuracy and tightening torque should be ensured to prevent leakage due to loosening. For example, in a high-pressure pipeline system, if the connection part of the safety valve is loose, the medium may leak under pressure, causing a safety accident. Avoid additional stress: During the installation of the safety valve, avoid applying additional stress to the safety valve. For example, during the pipeline installation process, if the safety valve is forcibly connected to the pipeline, the safety valve may be subjected to stress such as stretching and bending, affecting the normal operation of its internal components. Appropriate installation technology should be adopted, such as setting a flexible connection or compensator between the pipeline and the safety valve to absorb the displacement of the pipeline caused by thermal expansion and contraction, etc., to ensure that the safety valve is not affected by additional stress.

Post-installation commissioning and maintenance

Commissioning: After the safety valve is installed, it must be debugged to ensure that its parameters such as opening pressure and return seat pressure meet the design requirements. The commissioning process should be carried out strictly in accordance with relevant standards and operating procedures, and generally requires the use of professional pressure calibration equipment. For example, by slowly increasing the system pressure, observe whether the opening pressure of the safety valve is within the set range. When the pressure decreases, check whether the return seat pressure of the safety valve is normal. If the debugging finds that the parameters do not meet the requirements, the spring compression or other regulating devices of the safety valve should be adjusted in time until the design requirements are met. Regular maintenance: Regularly maintain the safety valve, including appearance inspection, cleaning, lubrication, etc. Regularly check whether the appearance of the safety valve is corroded or damaged, and clean up impurities and dirt in the inlet and outlet pipes of the safety valve in time to prevent them from clogging the safety valve. Lubricate the moving parts of the safety valve, such as the valve core and spring, to ensure its flexible movement. For example, in some chemical production environments, the medium is corrosive and the safety valve is susceptible to corrosion. Regular anti-corrosion treatment and maintenance can extend its service life and ensure its normal operation. Regular calibration: The safety valve should be calibrated according to the prescribed period. The calibration period is generally determined according to the use of the equipment, the characteristics of the medium and other factors, usually one year. During the calibration, the safety valve should be removed from the system and sent to a professional calibration agency for comprehensive inspection and debugging. Through regular calibration, the performance changes of the safety valve during use can be discovered in time to ensure that it is always in good working condition and effectively play a safety protection role.

The correct installation position of the safety valve and strict compliance with the installation precautions are crucial to ensure the safe operation of equipment and systems. In actual engineering applications, the installation position of the safety valve must be reasonably selected according to the characteristics of different equipment and pipeline systems, and various inspections, commissioning and maintenance work must be done before, during and after installation to ensure that the safety valve can operate accurately and reliably, providing solid safety guarantees for industrial production. Only in this way can we effectively prevent various safety accidents caused by overpressure, protect the lives of personnel and the property of enterprises, and promote the stable and sustainable development of industrial production.