Advantages: 1. It is convenient and quick to open and close, labor-saving, small fluid resistance, and can be operated frequently. 2. Simple structure, small size and light weight. 3. The mud can be transported, and the liquid accumulation at the pipe mouth is the least. 4. Under low pressure, good sealing can be achieved. 5. Good adjustment performance. Disadvantages: 1. The operating pressure and working temperature range are small. 2. Poor sealing.