Why dry-running protection pays for itself

Dry running is the most common cause of premature mechanical seal failure we see. A pump that loses suction for a few seconds heats the seal faces until the elastomers harden and the faces crack; the pump then runs apparently normally until the seal fails weeks later.

Protection does not have to be expensive. For clean liquids, a level switch or flow switch interlocked to the starter will catch the common case of a suction tank running low. For duties where the pump starts against a closed valve, a pressure switch on the discharge is enough.

Where the process makes suction loss routine — tanker unloading, intermittent transfer, self-priming duties — the better answer is often to specify a pump that tolerates dry running by design rather than to add instrumentation. Air operated diaphragm pumps, and some hollow disk and progressive cavity designs, survive short dry periods that would destroy a standard centrifugal pump.

The planning question is simple: what happens to this pump when suction is lost, and does anything stop it before the seal does?