Barrier seal is the media used for the flushing of mechanical seal faces. The heat generated (because of physical contact and friction) between a pair of mechanical seal (Normally one face rotary whereas the the is stationary) faces is being carried away by the barrier fluid which is being recirculated after proper cooling. The barrier Seal also create a barrier between the process fluid and flushing fluid. It is being kept at a higher pressure than process fluid in order to always ensure that only barrier fluid film remain across the seal faces all the time.

  Barrier seal of seals is strongly dependent on the proper protocols for using them. These protocols are the official and unofficial procedures used for seal procurement, storage, record keeping, installation, inspection, removal, disposal, reporting, interpreting findings, and training. With a good protocol, a modest seal can provide excellent security. On the other hand, a sophisticated seal used poorly may be worse than useless if naively trusted.