The self discharging valve seat (Figure 1) is also called the upstream sealing automatic pressure relief valve seat. Upstream sealing means that the upstream valve seat plays a sealing role when the gate is used. When the pipeline is under low pressure or no pressure, the spring set at the back of the valve seat provides the initial sealing preload to ensure the sealing performance under this state. When the pipeline is under normal pressure, the upstream valve seat is pushed to the spherical surface by the medium pressure to form a seal. Automatic pressure relief means that when the pressure in the middle chamber of the valve rises (usually 1.33 times higher than the nominal pressure according to API6D), the pressure in the middle chamber reverses the valve seat,

The valve needs maintenance. If this work is done well, the service life of the valve can be extended. The maintenance of the valve will be introduced below. Custody and maintenance
1. The purpose of storage and maintenance is not to damage the valve or reduce the quality during storage. In fact, improper storage is one of the important reasons for valve damage.
2. The valves shall be kept in order. Small valves shall be placed on the shelf, and large valves can be arranged in order on the warehouse floor. They shall not be stacked in disorder, and the flange connection surface shall not contact the ground. This is not only for the sake of beauty, but mainly to protect the valve from damage.
3. These unnecessary losses should be avoided due to improper storage and handling, broken handwheel, misaligned valve stem, loosening and loss of fixed nuts between handwheel and valve stem, etc.
4. For valves that are not used for a short time, asbestos packing shall be taken out to avoid electrochemical corrosion and damage to the valve stem.
5. The valves that have just entered the warehouse shall be checked. If rain or dirt enters during transportation, they shall be wiped clean and then stored.
6. The inlet and outlet of the valve shall be sealed with wax paper or plastic sheets to prevent dirt from entering.
7. The valve machining surface that can rust in the atmosphere shall be coated with antirust oil for protection.
8. The valves placed outdoors must be covered with waterproof and dustproof articles such as linoleum or tarpaulin. The warehouse where valves are stored shall be kept clean and dry.