Shenzhen Hitachi Valve Co., Ltd. professional agent imported brands - the United States can be OKE safety valve Imported safety valves are important safety accessories for boilers, pressure vessels and other pressurized equipment. Its operational reliability and performance are directly related to the safety of equipment and people, and are closely related to energy conservation and environmental protection. In the design of petrochemical plants, with the increase in the equipment and pipelines involved in the medium and high pressure levels, the use of safety valves has increased accordingly. Therefore, the correct and reasonable arrangement of the safety valve is particularly important. 1 General Safety valves are important safety accessories for boilers, pressure vessels and other pressurized equipment. Its operational reliability and performance are directly related to the safety of equipment and people, and are closely related to energy conservation and environmental protection. In the production process of petrochemical companies, due to operational errors, failure of the instrument, mechanical failure, etc., the pressure of the medium in the equipment or pipeline is increased, which may cause damage to equipment and pipelines, and even cause life-threatening hazards to personnel. After the safety valve is installed on the equipment or pipeline, the safety valve opens automatically when the pressure exceeds the specified value, and the medium is discharged outside the system, thereby preventing production accidents caused by the pressure in the equipment or the pipeline exceeding its safety value. Therefore, the safety valve is widely used in petrochemical production facilities, and it plays an important role in protecting the safety of personnel and the normal operation of production. 4 Conclusion The correctness of the safety valve settings plays an important role in the safe production of the entire device system. The design and selection of safety valves are also crucial for the design and use of pressure vessels and pressure pipes. Therefore, design should be caused. Workers attach great importance to it, otherwise safe production becomes empty talk. Non Woven Pillowcase Making Machine
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Safety valve installation and safety valve selection design 
2 classification safety valve is a valve for safety protection and belongs to automatic valve type. According to the safety valve disc opening height can be divided into micro-relief safety valve and full-open safety valve, micro-lift safety valve opening stroke height: ≤ 0.105d0 (minimum discharge throat diameter), generally used for displacement is not Large fluid lines; fully open safety valve opening height: ≤ 0.25d0 (minimum discharge throat diameter), large emissions; divided by the valve body structure, can be divided into closed and non-closed two. Closed-type safety valves, which exclude the leaked medium, are discharged along the outlet to designated locations and are generally used in toxic and corrosive media. For air and steam safety valves, non-enclosed safety valves are often used; safety valves are divided according to the structure and can be divided into the following four types:
2.1 heavy vertical type. With a heavy vertical load, it is directly applied to the valve flap. Has been gradually phased out.
2.2 Lever suspended. The heavy load is applied to the valve flap by the lever. It is generally suitable for steam or air with a pressure relief of 0.6 MPa and a temperature below 250°C. Due to the bulkiness of lever-type safety valves, the range of choice is limited.
2.3 spring type. The spring type safety valve mainly relies on the spring force acting on the valve flap to control the opening and closing of the valve, and has the advantages of compact structure, small size, light weight, and reliable opening and closing movement. Process equipment, safety valves on the pipeline generally use spring type, small valve body, good sensitivity, suitable for all kinds of gas, liquid pressure relief. Spring-loaded safety valves are closed and non-enclosed. Generally, flammable, explosive, or toxic media should be closed. Steam or inert gas can be used without closure. There are also wrenches and spring-loaded safety valves. Without a wrench. The role of the wrench is mainly to check the degree of flexibility of the valve, and sometimes it can also be used as manual emergency relief.
2.4 Pilot (pulse). The pilot valve is connected to the main valve and the main valve is actuated by the impulse action of the pilot valve. Suitable for large diameter, large displacement and high pressure systems. The pilot-operated safety valve and pilot valve are connected with seamless tubes. The pilot valve senses the controlled pressure signal and controls the opening and closing of the main valve. Its action process is: When the pressure before the valve safety valve is lower than the setting pressure, the pilot valve setting spring pushes the valve core to the sealing surface of the valve seat, and the gas medium enters the upper cavity of the valve core of the main valve through the guide valve to make the valve core down. Move tightly to the valve seat, the pilot valve and the main valve are in a closed state without leakage; when the pressure in front of the valve reaches or exceeds the setting pressure, the medium pressure overcomes the setting pressure, and the spring pushes the pilot valve core upward and the pilot valve is The force area is converted from the area of ​​the spool to the force area of ​​the piston. The increase of the force increases the force of the force and the pilot valve opens. The gas in the upper chamber of the main valve sleeve is exhausted from the outlet of the pilot valve, the main valve is opened, the medium is quickly discharged, and the piston travels to the maximum position. When the medium pressure is discharged to a certain pressure, the pressure across the piston orifice will cause the pressure difference between the upper and lower ends of the piston to be balanced. The pressure difference between opening and closing is achieved by the pressure difference between the upper and lower ends of the piston. When the pressure drops back to work Below the pressure, under the action of a small spring force, the valve core moves down to achieve its seal. The pilot valve closes and the main valve closes.
3 Installation of Safety Valves In the design of petrochemical plants, with the increase in equipment and pipelines involved in medium and high pressure levels, the use of safety valves has also increased. Therefore, the correct and reasonable arrangement of the safety valve is particularly important.
3.1 Safety valves on equipment or pipelines should generally be mounted vertically and as close as possible to the equipment or piping being protected. However, in the case of a safety valve provided in a liquid pipe, a heat exchanger, or a container, it may be installed horizontally when the valve is closed and the pressure may rise due to thermal expansion.
3.2 The safety valve should generally be installed in a place that is easy to overhaul and adjust. There must be enough working space around. Such as: vertical container safety valve, DN80 or less, can be installed in the platform on the outside; DN100 or more installed on the platform outside the platform, with the help of the platform can repair and repair the valve. It should not be installed on the dead end of long horizontal pipes to avoid accumulation of solids or liquids.
3.3 The safety valve installed on the pipeline shall be located in a place where the pressure is relatively stable and there is a certain distance from the source of the fluctuation. See Figure 1 and Table 1.
3.4 When the safety valve is discharged to the atmosphere, the discharge nozzle of a general harmless medium (such as air, etc.) should be higher than the operating platform, equipment or ground of more than 2.5m above the discharge radius in the range of 715m. For corrosive, flammable or toxic media, the discharge port should be more than 3m above the operating platform, equipment or ground within a radius of 15m.
3.5 When the outlet of the safety valve is connected to the pressure relief manifold, the main pipe should be inserted at an angle of 45° from the upper part along the flow direction, so as to prevent the condensate in the main pipe from pouring into the branch pipe and reduce the back pressure of the safety valve. When the safety valve pressure is greater than 710MPa, 45° insertion must be used, as shown in Figure 2a.
3.6 Wet gas pressure relief system There should be no bag-shaped effusion in the discharge pipe. The installation height of the safety valve should be higher than the pressure relief system. If the outlet of the safety valve is lower than the pressure relief manifold or the discharge pipe needs to be raised to access the manifold, a liquid storage tank, level gauge or manual drain valve should be installed at a place easily accessible at a low place and periodically discharged to a closed system to prevent bagging. Shaped tube effusion. In addition, in cold areas, the bag-shaped pipe section requires steam heating and antifreeze. The steam heating pipe also vaporizes the condensate in the bag-shaped pipe to avoid accumulation of liquid. However, even with the heat tracer, a manual drain valve is still necessary.
3.7 Safety valve outlet pipe design should consider the back pressure does not exceed a certain value of the safety valve constant pressure. For spring-loaded safety valves, the back pressure of normal type is generally not to exceed 10% of the valve constant pressure, and the back pressure of bellows type (balanced type) is generally not to exceed 30% of the safety valve pressure; for pilot-operated safety valves, the back pressure Do not exceed 60% of the constant pressure of the safety valve. The specific values ​​should be referred to the manufacturer's sample and determined by the process calculation.
3.8 When gas or steam is discharged into the atmosphere from the outlet of the safety valve, it is generated on the centerline of the outlet pipe in the direction opposite to the direction of flow, called the reaction force of the safety valve. The influence of this force should be taken into account when designing the outlet pipe of the safety valve. Such as: safety valve outlet pipe should be set fixed bracket; when the safety valve inlet pipe section is long, the pressure vessel wall should be reinforced. 