Reason for centrifugal pump not taking suction?

There may be various reasons that centrifugal pump is not taking suction, the following are the some of the reasons:

• check valves are open.
• suction line have cracks/ leakage,
• priming check.
• check for ingress of air.
• suction line joints
• wear ring clearance excessive.
• impeller securing arrangement detached.