Sanitary safety valve

The selection of suitable sanitary safety valves should be considered from the following aspects: 1. The structural form mainly depends on the process conditions, working medium, and characteristics of the equipment. Spring type safety valves are often used when the discharge capacity of boilers and pressure vessels is not large, otherwise it is better to choose full opening safety valves. $n2、 If the medium is toxic, flammable, and explosive, a closed safety valve $n3 should be selected. Each safety valve has its own working pressure range, and the selection should be based on actual needs. $n4、 The discharge capacity of the selected safety valve must be greater than the discharge capacity of the equipment, in order to ensure that some media is discharged and avoid pressure

Sanitary grade safety valves must undergo pressure testing before they can be used.

1. Before the safety valve leaves the factory, its opening pressure should be adjusted one by one to the set value required by the user. If the user requests the working pressure level of the spring, it should be adjusted according to the lower limit value of the pressure level before leaving the factory.

2. Before installing the safety valve on the protected equipment or before installation, the user must readjust it at the installation site to ensure that the set pressure value of the safety valve meets the requirements.

3. Within the working pressure range indicated on the nameplate, the opening pressure can be adjusted by rotating the adjusting screw to change the compression of the spring.

4. Before rotating the adjusting screw, the inlet pressure of the valve should be reduced to below 90% of the opening pressure to prevent the valve disc from being driven to rotate when rotating the adjusting screw, which may damage the sealing surface.

5. To ensure accurate opening pressure values, the medium conditions during adjustment, such as medium type, temperature, etc., should be as close as possible to the actual operating conditions. When the type of medium changes, especially when the accumulated state of the medium is different (such as from liquid phase to gas phase), the opening pressure often changes. When the working temperature increases, the opening pressure generally decreases. Therefore, when adjusted at room temperature and used for high temperatures, the set pressure value at room temperature should be slightly higher than the required opening pressure value. The degree of height is related to the valve structure and material selection, and should be based on the manufacturer's instructions.

6. Conventional safety valves are used to fix the additional back pressure. When the opening pressure is adjusted after inspection (the back pressure is atmospheric pressure at this time), the setting value should be the required opening pressure minus the additional back pressure.

Maintenance of hygiene grade safety valves:

1. The safety valve should have a device to prevent the heavy hammer from moving on its own and a guide frame to limit the deviation of the lever. The spring type safety valve should have a lifting handle and a device to prevent the adjustment screw from being easily turned.

2. It should be installed vertically at the position of the boiler merchant and the collection box. No outlet pipe or valve for steam shall be installed between the safety valve and the drum or manifold.

3. The cross-sectional area of the connecting pipe between the safety valve and the boiler should not be less than the inlet cross-sectional area of the safety valve. If several safety valves are installed together on a short pipe directly connected to the drum, the cross-sectional area of the short pipe should not be greater than 1.25 times the exhaust area of all safety valves.

4. For boilers with a rated steam pressure less than or equal to 3.82MPa, the safety valve throat diameter should not be less than 25mm; for boilers with a rated steam pressure greater than 3.82MPa, the safety valve throat diameter should not be less than 20mm.

5. Safety valves should generally be equipped with exhaust pipes, which should lead directly to a safe location and have sufficient cross-sectional area to ensure smooth exhaust. The bottom of the safety valve exhaust pipe should be equipped with a drainage pipe connected to a safe location, and valves are not allowed to be installed on both the exhaust pipe and the drainage pipe.

6. The safety valve of the pressure vessel is directly installed on the position of the pressure vessel body. The safety valve of liquefied gas storage tanks must be installed in the gas phase area. Generally, a short pipe can be used to connect with the container, and the diameter of the short pipe of this safety valve should not be less than the valve diameter of the safety valve.

7. Valves are generally not allowed to be installed between safety valves and containers. For containers with flammable, explosive or viscous media, a shut-off valve can be installed for the convenience of cleaning or replacing the safety valve. The shut-off valve must be fully opened and sealed with lead during normal operation to avoid tampering.

8. Boilers with a rated evaporation capacity greater than 0.5t/h shall be equipped with at least two safety valves; Boilers with a rated evaporation capacity of less than or equal to 0.5t/h shall be equipped with at least one safety valve. Safety valves must be installed at the outlet of the separable economizer and the outlet of the steam superheater.

9. For pressure vessels with flammable, explosive or toxic media, the medium discharged from the safety valve must have safety devices and recovery systems. The installation of lever type safety valves must maintain a vertical position, and spring safety valves must also be installed vertically to avoid affecting their operation. During installation, attention should also be paid to coordination, coaxiality of parts, and ensuring that all bolts are evenly stressed.

10. The outlet of the safety valve should be unobstructed to avoid back pressure. If a discharge pipe is installed, its inner diameter should be larger than the outlet diameter of the safety valve. The discharge port of the safety valve should be protected against freezing. For containers containing flammable, toxic, or highly toxic media, the discharge pipe should be directly connected to a safe outdoor location or have proper treatment facilities. No valves are allowed to be installed in the discharge pipe.

11. Newly installed safety valves should be accompanied by a product qualification certificate. Before installation, they should be recalibrated, sealed with lead, and issued with a safety valve calibration certificate.

12. No valves shall be installed between pressure equipment and safety valves. For containers containing flammable, explosive, toxic or viscous media, globe valves may be installed for easy replacement and cleaning. The structure and diameter size of the globe valve should not hinder the normal operation of the safety valve. During normal operation, the shut-off valve must be fully opened and sealed with lead.

Safety valves belong to the category of automatic valves, mainly used in boilers, pressure vessels, and pipelines to control pressure not exceeding the specified value, playing an important protective role in personal safety and equipment operation.