Key Points To Note When Using Shielded Pumps

Feb 11, 2025

There are actually many technical points that need to be learned during the use of water pumps, and the same goes for shielded pumps.
There is an annular gap of about 0.7mm between the stator and rotor, through which the pumped liquid passes to cool the motor when the pump is in operation.
Shielded pump is an unsealed pump, in which both the pump and the driving motor are sealed in a pressure vessel filled with the pumped medium. This pressure vessel has only a static seal and is powered by a set of wires to provide a rotating magnetic field and drive the rotor.
Not all shielded pumps on the market are suitable for use as circulating water pumps in heat pump water heaters.
For example, if the tap water is hard water, the residue of tap water contains Ca++, HCO3-, FE+, Mg+, Cr plasma, and scaling will occur in the water pump and pipeline after long-term use. Because the lubrication of the shaft and bearings of the shielded pump relies on the lubrication of the conveyed medium, scaling problems cannot be avoided. Especially during prolonged shutdown, when water stays in the pump, scale may cause blockage of the shaft and bearings. As a result, after the heat pump water heater is started, the water pump cannot be started, leading to excessive exhaust temperature and continuous opening of the compressor protector.
Shielded pumps require clean water delivery due to the use of departmental fluids to cool the motor and the small gap between the stator and rotor. Otherwise, it may block the shielding gap, affect the cooling and lubrication of the pump, and cause the motor to burn out. In addition, the system must have anti freezing measures to ensure that the water in the water pump does not freeze in low-temperature environments, which may affect the start or even damage of the water pump.
In terms of selection, it is necessary to choose a suitable water pump. If an excessively large water pump is selected, the system pressure will increase while the flow rate will also increase, which will cause more scale to settle in the pump. An excessively large water pump can result in greater energy consumption and increased noise. The versatility of the water pump can be increased by selecting a variable speed pump.