In refining units, high-temperature hot oil pumps often develop seal leakage and increasing heat after long service; OEM spare parts are slow and expensive, directly affecting normal production. For the customer's on-site conditions, our technical team comprehensively measured pump shaft runout, seal chamber pressure and medium temperature, and completed the upgrade with a tandem double-end-face seal combining imported sealing faces and localized manufacturing. After replacement the unit ran two weeks without leakage, with vibration and temperature within standard ranges; procurement cycle and cost of seal spare parts were cut by about 60% and 40% respectively versus the OEM solution. We also set up a full lifecycle ledger for the customer's mechanical seals, enabling proactive maintenance alerts based on operating hours and avoiding sudden shutdowns.