Sensors supplied by Yokogawa UK have helped BP to solve the problem of providing accurate pH measurements on boiler feed water at the company's Hull plant
Boiler feed water is one of the primary industrial uses for pure water, and effective chemical treatment of the feed water is a vital part of maintaining the useful operating life and minimising maintenance costs of the boiler.
In order to ensure that the chemical treatment is working effectively, pH measurements on the water are necessary, but because water of this purity has almost no electrolytic conductivity, the accurate measurement of pH presents a significant challenge.
Prior to selecting the Yokogawa system, BP had tried a number of different sensors, but all had presented significant problems in terms of accuracy and reliability, requiring high levels of maintenance and operator intervention.
In contrast, the Yokogawa units were successful from the day they were installed, requiring virtually no maintenance, producing accurate and reproducible results, and providing easy to integrate into existing automatic monitoring and control systems.
In order to achieve successful pH measurements in pure water, the correct electrodes and electrode holder have to be used to eliminate problems with reference junction potentials, slow glass electrode response and surface static charges.
The ideal analyser also has to be selected to eliminate ground-loop problems and to allow for accurate temperature compensation for both the Nernst potentials and the dissociation constant of pure water.
In addition, sensor diagnostic facilities have to be provided to give the operator the ability to be sure that the measurement loop is functioning properly.
Comments Paul Carrington, product manager for Analytical Products with Yokogawa UK, 'BP's successful experience with Yokogawa sensors is a vindication of the time and effort we have put into developing this technology.
As a result, we now have the appropriate electrodes, sensor holders, and analysers to provide accurate and reliable pH measurements in high-purity water.'
