Sealing modification of circulating water pump disc root

The circulating water pump in the power workshop of a state-owned chemical plant has a speed of 980r/s, medium: water (clean water), temperature: 18-22 ℃, outlet pressure: 5.6kg. There are a total of 5 pumps in this workshop, sharing one outlet pipeline. The other 4 pumps cannot be closed, and the check valves of all pumps do not work (when the outlet valve is opened, it is easy to return water, causing excessive current at the moment of pump start and destructive damage to the motor). In the case of inflexible outlet valves, a sealing modification was carried out.