Why does the sanitary diaphragm valve leak when half-opened, but it won’t leak when fully opened?

Why does the sanitary diaphragm valve leak when half-opened, but it won’t leak when fully opened? Why does the sanitary diaphragm valve leak when half-opened, but it won’t leak when fully opened? Perhaps the diaphragm of the sanitary diaphragm valve is broken, and the material has leaked into the upper space of the diaphragm. This hole is the signal hole for checking whether the sanitary diaphragm valve is leaking. Each valve has a temperature limit, and leakage will occur if it is above or below this range. The following three reasons are for reference: 1. Why does the sanitary diaphragm valve leak when half-opened, but won't leak when fully opened? Perhaps the diaphragm of the sanitary diaphragm valve is broken, and the material has leaked into the upper space of the diaphragm. This hole is the signal hole for checking whether the sanitary diaphragm valve is leaking. Each valve has a temperature limit, and leakage will occur if it is above or below this range. The following three reasons are for reference: 1. The small hole of this sanitary diaphragm valve seems to be used for grease injection/exhaust/pressure relief. Leakage at half-open time should be the cause of the pressure difference between the front and rear. 2. The gate valve is not a valve with good sealing performance. The condensate temperature is 70-95 degrees. If you use rubber seals, it may leak. The rubber is a little bit worse. It can't survive 80 degrees. It will be washed and hardened by hot water for a long time. , Resulting in leakage. 3. If there is a problem with the sanitary diaphragm valve, it should leak when the valve is fully opened, and the temperature is still in the appropriate range.