A leaking mechanical seal tells you where the liquid escaped. It does not tell you why. The cause may be the seal, but it may also be dry running, poor liquid supply, shaft movement, vibration, installation damage or a changed process.
Record when the leak appears. Does it start on commissioning, only at speed, after a product change, or after a clean? Inspect the faces for heat marks, chipping and uneven contact. Check the sleeve, shaft movement, bearing condition and seal chamber. Confirm the pump has liquid and that any flush or barrier system is doing what its design requires. Keep the used faces and elastomers rather than throwing away the evidence.
If a new seal fails in the same position and the same way, replacing it again is not a diagnosis. I would compare the failure pattern with the operating record before choosing a different seal. A sound seal in the wrong conditions will still fail.
Andrew Sykes | Acumen Seals & Pumps Limited | Independent mechanical seals and sealing specialist