Mechanical Seal faces are the most vulnerable parts of any mechanical seal, but other parts such as the secondary sealing elements like O-rings, bellows, polymer wedges or metal parts such as springs, drive pins, or set screws also may affect the life of the seal.
Mechanical Seal failures may be categorized on the basis of MTBF [Mean time between Failures] as either Infant, mid life or Wear-out. Infant failures are most often caused by incorrect seal selection, installation or startup.
Mid life failures occur unexpectedly after a considered run period. Mid-life failures are quite difficult to predict because they are usually the consequence of a process operation or equipment induced transient, which could not be tolerated by the face materials. Transient operating conditions may be as a result of a malfunction of a component in the pump or an unintended process deviation.
Wear-out failure is occurred due to ending of any of the faces. It is ultimate and most satisfactory for Manufacturer and user if happens naturally. However time of worn out of faces depends on the various factors.
Common distress symptoms of seal face failure are pitting, blistering, chipping, grooving, heat and thermal shock cracks.
Life of a seal depends on a large extent on its ability to maintain a thin fluid film in between the mating faces and duration and extent of mechanical contact between the rubbing areas of these faces. Too much contact may overheat the materials; not enough contact may cause high leakage rates.
Finally "A cool seal is a good seal" therefore make seal faces cool to become cool from seal failure.