Priming in Centrifugal Pumps

Priming is an essential process in centrifugal pumps that involves filling the pump casing and suction pipe with a liquid to remove any air that may be trapped in these parts. The correct answer to this question is option B, which states that priming is necessary in centrifugal pumps to remove air in the suction pipe and casting.

Why is Priming Necessary?

The presence of air in the suction pipe and casing of centrifugal pumps can cause several problems, including:

- Reduced pump efficiency: Air reduces the density of the liquid, which reduces the pump's ability to lift or move the liquid.
- Cavitation: Air bubbles in the pump can cause cavitation, which is the formation of small vapor-filled bubbles that can damage the pump impeller and other parts.
- Dry running: If the air is not removed, the pump may run dry, which can cause mechanical damage and reduce the pump's lifespan.

Therefore, priming is necessary to ensure that the pump is filled with liquid and free of air, which allows it to operate efficiently and effectively.

How is Priming Done?

Priming can be achieved through different methods, depending on the type of pump and the application. Some of the common methods include:

- Manual priming: In this method, the operator manually fills the pump casing and suction pipe with liquid using a funnel or hose. It is commonly used in small pumps or emergency situations.
- Self-priming pumps: These pumps have a built-in mechanism that allows them to evacuate air automatically and prime themselves. They are commonly used in applications where the pump must start and stop frequently.
- Vacuum priming: This method involves using a vacuum pump or ejector to create a vacuum in the suction pipe and casing, which draws liquid from the source and removes air. It is commonly used in large pumps and applications where the liquid source is below the pump level.

Conclusion

In conclusion, priming is necessary in centrifugal pumps to remove air in the suction pipe and casing, which can cause several problems if not removed. Different methods can be used to achieve priming, depending on the pump type and application.