Benefits Of Rotary Lobe Pumps - Part 2

Continuing from part 1...

The rotary lobe pumps are ideal replacements for the centrifugal pumps for different slurry and sludge applications. The centrifugal pumps can be affected by air or by inadequate NPSH, or net positive suction head. If the centrifugal pumps are not operated within 10% of their best efficiency point, any operation can cause shaft deflection, cavitation and also vibration, which in turn damages the internal parts of the pump and also minimizes the effective life of the centrifugal pump.

The rotary lobe pump on the other hand has the capability to pump out the air and water, it will not cavitate or vibrate because of the inadequate net positive suction head. The lobe pumps are very efficient at all points during their operation. Unlike the centrifugal pumps, the output provided by the rotary lobe pumps is generally not affected by the viscosity. The rotary lobe pumps operate at 200-300 RPM's for abrasive applications, and at 500-600 RPM's for non abrasive application. The centrifugal pumps on the other hand operate at 1800 RPM's. The difference in the speed shows that the centrifugal pump mix and agitate the fluid that is being pumped out, whereas the rotary lobe pump operates at much lower RPM and slowly moves the liquid out of the pump.

Another significant benefit provided by the rotary lobe pumps is the fact that the lobe pump has the ability to create a vacuum which captures the liquid inside the pump and makes it self priming without separating the air from the liquid. In addition, the centrifugal pumps need to be equipped with special separate mechanism in order to separate the air from the liquid. Such mechanism can be easily clogged by various solid or viscous materials. In the case of the centrifugal pumps, additional force is required to bring the fluid into the pump.

The rotary lobe pumps can be used in various liquid transfer process that involve thick or thin sludge, slurries or even mud. They posses the following benefits when compared with the progressive cavity pumps:

• The rotary lobe pumps have the ability to operate in dry condition for certain period.
• They require lower maintenance and bear lower repair costs.
• Do not require large space. In addition, the progressive cavity pumps require larger space when removing the rotor and the stator.
• The seal and the wear plates of the rotary lobe pump can be replaced easily without removing the attached piping.

When comparing the rotary lobe pumps and the progressive cavity pump in terms of the efficiency provided, it is essential to separate the volumetric efficiency from the overall efficiency. The pump tightness generally is described by the volumetric efficiency. Small sized progressive cavity pumps with smaller displacement capacity provide higher volumetric efficiency. The rotary lobe pumps with larger displacement capacity have greater volumetric and overall efficiency. Other significant benefits of the rotary lobe pumps are: small overall dimension, higher capacity, high efficiency, no vibrations, less friction provided by the rotary lobe pump, easy lobe change, stable operation in wear situations, fast running pump.