Opening principle of Besa safety valve in Italy

Opening principle of Besa safety valve in Italy

BESA's main product lines:

139 threaded connection safety valve

240F threaded connection safety valve

249 threaded connection safety valve

130 flange connected safety valve

240 flange connected safety valve

250 flange connected safety valve

260 flange connected safety valve

280 flange connected safety valve

290 flange connected safety valve

Opening principle of Besa safety valve in Italy

BESA safety valve relies directly on the pressure of the medium to produceTo overcome the force exerted on the valve disc by generating force Mechanical load causes the safety valve to open ，The mechanical load acting on the valve disc mainly comes fromheavy hammer 、Heavy hammer with lever or compression spring， This is almost a fixed mechanical load .To ensure the sealing performance of the safety valve ，It is inevitable that the sealing surface of the valve seat and the sealing surface of the valve disc will be affected There are strict requirements for flatness and surface roughness .Although for safety valves loaded with compression springs ，You can adjust the spring force by To achieve sealing ，But there are strict requirements for the sealing pressure difference .secretSealing pressure difference is the difference between the set pressure and the working pressure .Sealing pressure difference Must be high enough ，To ensure sufficient sealing force ，Thus achieving sealing during normal operation of the device .The sealing pressure difference should be less than the opening pressure Closing pressure difference ，To ensure that the safety valve opens above the working pressure.

The recommended minimum sealing pressure difference is usually ，When the work pressure is less than or equal to 7MPa Time is the set pressureforce 10% , But not allowed less than 35KPa； When the work pressure is greater than 7MPa time ，To set the pressure 7% .For metal sealed safety valves ，If make Used for toxic purposes 、corrosive 、Low temperature or particularly valuable media ，Or when the system pressure is at the outlet of a reciprocating pump or compressor 口 Like in the pipeline ，For fluctuating situations ，Then it may be necessary to increase the above sealing pressure difference.

Furthermore ，The opening and closing pressure difference of safety valves used for gas or steam can be as high as 15%； The safety valve for liquids can reach up to 20% .thus ，If the safety valve needs to be closed at a pressure not lower than the working pressure ，Sealing pressure difference is necessaryTo increase accordingly.

The opening and closing pressure difference is the difference between the set pressure and the reseating pressure .From an economic perspective ，The opening and closing pressure difference should be minimized as much as possible ，To avoid Avoid unnecessary media loss .But from the perspective of the stability of the safety valve action ，I also hope to have a large opening and closing pressure difference .Therefore, we had no choice but to Take a compromise approach.

In the specifications related to safety valves, there are often provisions for the limit value of the opening and closing pressure difference .International Standard ISO 4126 middle ，for use Recommended opening for gas or steam safety valves and safety relief valvesThe limit value of closed pressure difference is as follows.

1) If the opening and closing pressure difference is adjustable，The lower limit value is2. 5% , The upper limit value is7% .But the following situations are exceptions： If the valve seat hole diameter less than 15mm, The opening and closing pressure difference should not exceed 15% .If the set pressure is less than 300kPa, The opening and closing pressure difference should not exceed 30kPa.

2) If the opening and closing pressure difference is not adjustable ，The upper limit value is 15% .

In the above international standards ，For safety valves used for liquids ，The recommended maximum value for the opening and closing pressure difference is 20% .

The opening pressure difference is the difference between the opening pressure and the set pressure of a fully open safety valve .Move when the safety valve is in a slightly open state From the perspective of the production stage ，I hope the pressure difference can be reduced .But if the opening pressure difference is too small ，For gases or vapors For safety valves ，Leakage at the sealing surface may cause the safety valve to jump open prematurely .Due to insufficient traffic at this time Keep the safety valve fully open ，As a result, the safety valve will rapidly open and close continuously .in application ，Yi'an The structure of the entire valve is different ，The opening pressure difference of a fully open safety valve used for gas or steam is 1% ~ 5% within the scope of； And used for liquid The opening pressure difference of the safety valve of the body can be 6% ~ 20% Between changes.

In summary ，Safety valves not only have strict requirements for sealing ，And for the set pressure 、returnSeat pressure 、Opening pressure、 There are strict requirements for emission pressure, etc .This requires the manufacturing process of safety valves ，To ensure the sealing and operation of the safety valve Sensitivity of work ，There are strict requirements for the flatness and surface roughness of the valve seat sealing surface and valve disc sealing surface ，Its table The numerical value of surface roughness is Ra0. 2μm below ，Also on the manufacturing scale of springsinch 、material 、Heat treatment has strict requirements .Ensure that the manufacturing of springs meets the requirements of the design drawings ，This is the only way to ensure all the performance of the safety valve.