Trial Success for pH Electrodes in LNG Plant

Introduction

At a large LNG plant in Brunei trials have been carried out on the new Refex pH electrodes. Two sets of the Refex electrodes (RM-5810 reference electrode and RM-5610 pH glass electrode) have been retrofitted into the existing Rosemount 381 immersion systems. These new electrodes were installed in the pH measurement of Flocculators A5301 (Tag no. 53-QT-7) and A5308 (Tag no. 53-QT-12) for 90-days trial run. These two existing pH meters were selected for the following reasons: Drifting pH values, Frequent cleaning of the electrodes, Frequent calibration of the meter, Replacement of glass electrodes between 6 to 12 months.

Observation

The Refex RM-5610 pH glass electrode paired with Refex RM-5810 reference electrode was observed to be reliable, accurate and required less cleaning maintenance for the pH measurement for the flocculators. During the trial run, a remarkable reduction in cleaning frequency of the electrodes and calibration was noted. The pH values were found to be within the control limit for both meters, although much of the errors tend to be on the positive side of the deviation which means that there is still a systematic error in the system. Nevertheless, systematic error is not a concern in this electrode replacement.

Conclusion

Although the plant has been using the Refex pH electrodes with its Rosemount 318 assemblies for just three months, the introduction of the Refex electrodes is said to have transformed its pH measurement. Since the introduction of the Refex electrodes into the existing system, the pH measurement was claimed to produce accurate, reliable, stable and less cleaning maintenance and calibration. The LNG plant will continue to use the Refex pH electrodes that are currently still running now. The LNG plant will also be considering the replacement of other conventional pH/reference electrodes throughout the plant to these Refex pH electrodes in the future.