2.7 Auxiliary Equipment of the Water Conveyance System

2.7.1

Pumping station under one of the following conditions should be installed with vacuum pumping system and water filling system,and the vacuum pumping system shall be well sealed.

1 Axial flow pumping station and mixed flow pumping station with siphoning outlet passage.

2 Large-scaled centrifugal pumping station with a high or medium head which requires initial pump priming.

3 The submerged depth of the impeller center of horizontal pump is less than 3/4 of the impeller diameter.

2.7.2

Two vacuum pumps should be installed as mutual spare ones,and the determination of the capacity should meet the following requirements:

1 The time of axial flow pump and mixed flow pump vacuuming the maximum air volume in the passage should be 10 to 20min.

2 The air exhausting and water filling time for one centrifugal-pump should not exceed 5min.

2.7.3

As for pumping station with siphoning outlet passage,the negative hump pressure of units in operation may be used to vacuumize another unit which will be started,but the pumping time shall not exceed 10-20min.

2.7.4

The water filling height should not be less than 2/3 of the design head of pump for the pressure water conveyance system of large-scaled centrifugal pumping stations with a high or medium head.Two filling pumps should be provided and no standby pump is needed.The filling time shall be determined according to the condition of the pressure water conveyance system.