Before replacing a pump, which of the following actions is not necessary?

When preparing to replace a pump, it is essential to ensure that the system is safe to work on and that there are no fluids that could escape or cause hazards. Closing the suction and discharge valves is a necessary step in this process, as it helps to isolate the pump from the rest of the system. This action minimizes any risk of accidental flooding or pressure release when the pump is removed.

Conversely, opening the discharge valve prior to replacement is not a typical requirement because it could allow for the flow of liquids, posing safety risks. Draining the pump casing is important to prevent any spillage during the replacement and to ensure the workspace is safe. Inspecting the pump alignment is also vital to ensure that any future reinstallation goes smoothly without causing issues related to misalignment, which can lead to inefficiency or damage.

Thus, the action that is not necessary prior to replacement is closing the suction and discharge valves, as it is a standard procedure to do so for safety and operational integrity.