A standard pump mechanical seal is not designed to run dry at any speed faster than turning by hand to perform the coupling alignment. If you need a seal which can run dry, you should consider a dry gas seal. One major seal manufacturer makes a secondary seal that is designed to run dry without lifting off on dry gas. But, that seal will not perform well if you expect occasional dry run with liquid present the rest of the time. Additional details about the pump and service conditions would be helpful.
