Evaluation of MCM hygrometer and validation system during - Case Study


Courtesy of Moisture Control & Measurement Ltd

Evaluation of an MCM moisture analyser and validation system during start up of Platformer 4 at Shell Bukom, April 2005.

Platformer start up requires an accurate knowledge of moisture levels in order too prevent over cracking, help optimise yields and prevent early catalyst damage. The presence of chloride and other contaminants during start up often affect the water content analysers which can quickly drift out of calibration tolerance before their next scheduled recalibration. MCM claim to have a faster, more robust technology that will give more reliable data.

Objective Of The Evaluation
Shell can benefit from using faster validating instruments and employing validation methods that can quantify the changes in sensitivity, in order to provide more accurate data. It was agreed to compare the existing inline Panametrics hygrometer against MCM's technology, under real start up conditions of Platformer 4. MCM were invited to Shell Bukom to begin tests during the adjustment to normal operating condition when the 'platformate was to be run down to high octane Tk\ this being the most critical point of the start up process.

MCM Technology
The MCM hygrometer uses a heated silicon sensor that the manufacturer claims to be very fast responding* and generally less prone to the effects of such contaminants due to a feature that dries the sensor within 30 seconds. It maintains a stable elevated operating temperature, maintaining traceability to its calibration data and claims to provide a degree of resistance to volatile contaminants by virtue of the sensor drying function, called 'push purge'.

'Interestingly, Shell's engineering and Design document also states the Silicon sensor technology to be faster and preferred to aluminum oxide or electrolytic (P205) when using this drying feature. See reference in appendix f. (Dep

MCM's Validation Methodology
In order to validate any collected data, it was proposed to establish a validation system within the laboratory using calibrated hygrometers and a moisture source running continuously in equilibrium as a control system.

The MCM Portable Hygrometer to be tested on Plant gas was to be compared periodically with the 'master* Hygrometer monitoring both a 'dry' and wet' reference gas.

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