Your reference electrode in an amine treating unit is not failing — it already failed.
Ag/AgCl reference electrodes in sour service read 15 to 20 mV high within weeks of installation. The silver chloride surface reacts with H₂S, forming Ag₂S. The reference potential shifts, and every measurement downstream is wrong by 0.25 to 0.35 pH units.
The operator doesn’t know. The pH reads “in spec.” Control loops chase a false setpoint. Amine degradation accelerates. The reboiler scales.
Three practical corrections:
- Replace the fill solution every 4 weeks, not every 6 months.
- Measure the slope and offset against two fresh buffers monthly. Track the drift.
- If the offset exceeds ±10 mV at pH 7.00, the reference is compromised — not the glass.
The glass electrode gets blamed. It isn’t the glass. It never was.