Question

A centrifugal pump with backward curved blades is

1. Always Stable
2. Never Stable
3. Sometimes Stable

A centrifugal pump with forwarding curved blades is

1. Always Stable
2. Never Stable
3. Sometimes Stable

A centrifugal pump with straight blades is

1. Always Stable
2. Never Stable
3. Sometimes Stable

Answer 1

1. always stable

2. sometimes stable

3. sometimes stable

here, radial blades means straight blades

For both radial and forward facing blades, the power is rising monotonically as the flow rate is increased. In the case of backward facing blades, the maximum efficiency occurs in the region of maximum power. If, for some reasons, Q increases beyond p there occurs a decrease in power. Therefore the motor used to drive the pump at part load, but rated at the design point, may be safely used at the maximum power. This is known as self-limiting characteristic. In case of radial and forward-facing blades, if the pump motor is rated for maximum power, then it will be under utilized most of the time, resulting in an increased cost for the extra rating. Whereas, if a smaller motor is employed, rated at the design point, then if Q increases above Qp the motor will be overloaded and may fail. It, therefore, becomes more difficult to decide on a choice of motor in these later cases (radial and forward-facing blades) Forward facing(P900) Radial (B-90°) Backward facing(B. 90) K1