Kenflo KCP series single-stage single suction pump and frequency conversion control system were put into use in the technical renovation of a water supply system in Shenzhen

The single-stage single suction pump has a small flow (generally within the range of 10-500m3 / h) and a lift of 10-100m. It is widely used in chemical processes and air conditioning systems. For some water supply systems with small flow, a single-stage single suction centrifugal pump can also be used.

Compared with the split double suction centrifugal pump, the single-stage single suction pump has lower cost and smaller floor area, which can be regarded as the advantage of the single-stage single suction pump. However, since the single-stage single suction pump usually adopts a cantilever structure, it is not as good as the split double suction centrifugal pump in terms of stability and vibration.

In a small water supply plant, three single-stage single suction centrifugal pumps are used as water supply pumps. Rated flow: 400m3 / h, rated lift: 40m, 2 in service and 1 for standby.

See the figure above for the original pump system. The single-stage single suction centrifugal pump with compact structure is adopted, and the professional term is direct coupled centrifugal pump. The structural feature is that the shaft of the motor is lengthened, the pump body has no bearings, and the impeller of the pump is hung on the shaft of the motor. The pump with this structure has the advantages of small size, small footprint and low cost. The disadvantages are that the reliability of the pump is relatively low, the load of the motor bearing is heavy, and the service life of the motor bearing is short. And because the motor shaft is lengthened and specially made, it also causes trouble in motor maintenance.

Because of this, the service life of these three pumps is short and the failure rate is high.

In addition, through observation, it was found that the valve installation position of the original pump system was also unreasonable. The expansion joint and the check valve were installed behind the outlet butterfly valve, which made it impossible to replace and repair the check valve online, and to repair and replace the expansion joint online. The pump cannot be removed.

The current electric control cabinet is equipped with a frequency converter, but it can only be used at startup, and the frequency cannot be automatically adjusted according to the outlet pressure during operation.

After communication with users, the technical transformation scheme is determined:

(1) Replace the Horizontal single-stage single suction centrifugal pump with a more reliable structure, use a standard frequency conversion motor, and use a coupling to connect and drive. The forces and moments on the impeller of the pump are supported by the bearings on the pump; The motor bearing is only responsible for supporting the motor rotor.

(2) The support system of the whole pump unit has been upgraded from 2 bearings to 4 bearings. The structural reliability is improved.

(3) The actual head demand of the user was measured. Through calculation, the pump with rated performance more suitable for the actual working condition was selected under the condition of maintaining the motor power unchanged.

(4) According to the changes of high and low peak periods of water use, frequency conversion speed regulation technology is adopted, which is applicable to the water supply pressure under different working conditions.

The transformation adopts the general contracting method, including the supply of equipment, the transformation of frequency conversion control cabinet, the removal of old pumps and motors, the installation of new pumps and motors, the reconstruction of concrete foundation, the replacement of check valves and valves, etc., which are all completed by kfl pumps.

Above: the constructors of kenfulai pump industry are working on site to install new pump units and valves.

Above: the electrical engineer of kenfulai pump is debugging the frequency conversion control cabinet on site.

Above: new pump unit after installation. The constructors of kenfulai pump industry are carrying out on-site sanitation restoration.

Above: start up and commissioning. Monitor the operation status according to the commissioning specifications of kenfulai pump.

Above: during the trial run, the user is checking carefully.