Selection of welding method for welding test pieces of marine parts: during thick plate welding, under the rapid heating of welding thermal cycle, the metal in the base metal near the seam or between the weld layers of multi-layer welding will melt again and form liquid phase locally. When cooling at a high speed, it is easy to cause the generation of liquid crack, reheat crack and hydrogen induced delay crack in the thermal response zone. Measure the insulation strength of the motor If less than 5m ω， The motor may be damp or damaged. If the motor is only affected with damp, it can drive the damp by itself after the motor operates for a period of time; otherwise The motor must be repaired or replaced To avoid damage to the pump due to poor operation. The pressure reducing valve shall be installed vertically, and a filter shall be installed at the inlet of the pressure reducing valve to prevent debris from blocking and hindering the pressure reducing performance. A stop valve is installed at the inlet and outlet of the pressure reducing valve to facilitate maintenance in case of failure of the pressure reducing valve. The pressure reducing valve shall be installed with a stop valve in parallel, so that the system can maintain operation during the maintenance of the pressure reducing valve. Set a pressure gauge before and after the pressure reducing valve to observe the pressure reducing condition. A safety valve is installed behind the pressure reducing valve to ensure the safety of the pipeline after the pressure reducing valve fails.