1. Simple, compact structure and small size;
2. Smooth and reliable transmission;
3. A large output torque can be obtained;
4. The output torque can be accurately adjusted through the constant pressure relief valve, including the adjustment of the opening and closing torque, and can even be directly reflected through the hydraulic instrument;
5. Convenient speed adjustment;
6. When the power is suddenly interrupted due to an accident, the accumulator can still be used for one or several power operations. This is of special significance for the automatic emergency shut-off valve and wellhead blowdown valve of long-distance pipelines.

1. The oil temperature is greatly affected by the ambient temperature. The change in oil temperature causes the viscosity of the oil to change, affecting the operation;
2. The piping is troublesome and prone to leakage;
3. It is not suitable for various operations on the signal (such as signal amplification, memory, logical judgment, etc.)