The component of a centrifugal pump installed on the end of a suction pipe to hold the priming is known as a...

The component of a centrifugal pump that is specifically designed to be located on the end of a suction pipe to maintain the prime is known as a foot valve. The primary function of a foot valve is to prevent the backflow of water from the pump and to keep the suction line filled with liquid, ensuring that the pump stays primed and can operate efficiently.

When the pump is off, the foot valve closes, preventing water from flowing back into the source from which it was drawn. This is essential for maintaining the prime of the pump, allowing it to start quickly without needing to draw water again from the source every time it is activated. A properly functioning foot valve is critical in applications where the pump may not be continuously operational, as it holds a capacity of liquid ready for immediate use when the pump is started.

In this context, the other options do not serve this purpose. The casing is an enclosure for the pump components, the drain is used to remove excess liquid from the system, and the ventilator is designed to allow air to escape but is not involved in maintaining priming. Thus, the foot valve directly fulfills the requirement of holding the priming in a suction pipe.