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Selection of Valve Electric Actuator Models

Selection of Valve Electric Actuator Models

Sep 26,2022

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Balanced Bellows Safety Valve


Safety valve is an automatic valve, and it also belongs to the category of pressure relief valve. When the medium pressure in the protected system exceeds the set pressure value, it will automatically open; when the medium pressure returns to the normal working pressure value, that is, when the system pressure is lower than the valve set pressure, the valve disc will automatically return to its seat. The good or bad performance of the valve flap opening and reseating represents whether the stability of the safety valve is good, and the stability of the valve is closely related to the company's production efficiency.


During the production process, there is often residual back pressure in the system at the outlet of the safety valve or in the back pipeline, which often causes the valve core to fail to take off or seat accurately. According to this phenomenon in actual production, MstnLand will introduce a balanced bellows safety valve product to solve such problems in a targeted manner. Starting from the concept of back pressure, we can discuss it in two parts. The first part is the discharge back pressure, which mainly refers to when the system medium pressure exceeds the set pressure, the valve flap is opened and discharged through the outlet side of the safety valve. Back pressure builds up during the process. The second part is the additional back pressure, which refers to the static pressure that exists at the outlet of the safety valve when the device is running. It is a back pressure caused by the incomplete discharge of other pressure sources in the venting system.

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The balanced bellows safety valve is similar in structure to other spring-type safety valves, and is composed of valve body, valve disc, valve cover, valve cap, valve seat, spring and spring seat and other components. The difference from other common safety valve parts is that this product is designed with a metal bellows. After adding this structure, it will solve the problem that the safety valve is insensitive to jumping or closing. The essential reason why the bellows safety valve can effectively solve such problems is because the bellows has several advantages.


First, the bellows occupies the longitudinal acting surface, which greatly reduces the pressure acting on the sealing parts by the longitudinal force.


Second, the use of omega-shaped bellows can eliminate the back pressure from the outlet through its own deformation and the change of the shape after being subjected to force, so that the back pressure does not affect the normal opening or return of the safety valve spool.


Third, the bellows structure can effectively prevent the working medium from contacting valve structural components such as the valve stem, so as to prevent the valve material from being corroded, and naturally prolong the service life of the valve.


Fourth, because the bellows and the valve stem or the bellows and the guide sleeve are connected by welding, which is firm and reliable, it can well prevent the leakage of flammable, explosive, toxic and harmful media, and avoid accidents that endanger the life and safety of production operators.

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In addition, due to the use of metal bellows, both its heat dissipation effect and corrosion resistance are relatively strong. Depending on the medium, we can also use PTFE non-metal bellows, which can be well bent, elongated or compressed. The function of the balanced bellows safety valve is not omnipotent. The back pressure is in the range of 10% to 50% of the set pressure. Choosing a balanced bellows safety valve can solve the problem of back pressure interference. When the back pressure is less than 10% of the set pressure, there is no need to use a safety valve with bellows, and a general safety valve can be used directly.


Stability issues affecting safety valve performance are more complex than just back pressure issues. Therefore, specific problems still require specific analysis, which can be analyzed from the perspective of the valve, or combined with the perspective of the production process. If you encounter any problems in the valve selection process, you can contact MstnLand. We will analyze the selection knowledge of safety valve in detail for you, and select a cost-effective product.


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