Principle Of Operation

Flow Path Most canned pumps, when pumping relatively clean fluids, will channel a small portion of the process fluid through the motor section. This fluid cools and lubricates the bearings and removes heat generated by the induction motor. The circulation path can be either external or internal to the pump. With external circulation (see Figure 4), the recirculation fluid is piped outside of the pump, through a filter, and then into the motor section of the unit. The filter assembly (see Figure 5) is self-cleaning and located in the discharge flange of the pump. Pumps having internal circulation have the recirculation contained within the pump. Filtering the recirculation liquid is not available with internal circulation.

In either external or internal circulation, the flow path is from the high pressure area of the pump (pump discharge or pump chamber at the tip of the impeller) returning to the low pressure area (near the hub or eye of the impeller). The amount of liquid recirculated through the motor section ranges from 2 to 16 gpm (7.5 to 60 l/m).

Many recirculation flow path modifications are available to allow a canned motor pump to pump any type of fluid. When pumping volatile fluids, the motor section can be pressurized by an auxiliary impeller located on the rotor. The recirculation fluid, which normally returns to the eye of the impeller, is channeled to the pressurized section of the liquid end, increasing the pressure in the motor section. This design allows a volatile fluid to remain liquid even with a temperature increase caused by motor heat (see Figure 6). Another method to handle fluids near their boiling point is to reverse the recirculation flow path. Instead of returning the heated liquid back to the eye of the impeller, the recirculation liquid is removed from the pump and returned to the suction vessel.

High temperature and slurry applications can be handled by canned motor pumps by isolating the bearings from the pumped fluid. The recirculating fluid in the motor section

FIGURE 4 External circulation flow path
Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook

Post a comment