Automated water determination in insulating oils

Because of the low water content of insulating oils (typically in the low ppm range), an accurate determination is best performed coulometrically

However, the automated determination of low water contents used to prove difficult in the past.

For some time now, the only option for the automated coulometric determination has been the 774 Oven Sample Processor, which uses a system that is sealed against ambient humidity.

The procedure involves weighing the samples into vials that are then hermetically sealed with a septum.

The automated MaTi 4 KF pipetting system takes advantage of the vial technique's benefits.

The samples are placed on the rack in hermetically sealed vials and then transferred for titration to the impermeable KF Coulometer cell, whose contents are conditioned between determinations.

The pipetting system applied consists of a double hollow needle, a Dosing Unit and pipetting tubing.

This system has been used to test different insulating oils whose water contents ranged from 17 to 34 ppm.

The results were compared with those obtained by non-automated determinations.

The water contents obtained with the pipetting system show good reproducibility and agree well with those found using manual sample introduction.

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