Journal of Petroleum & Environmental Biotechnology

Control charts in the demineralized water

World Congress on Petroleum and Refinery

July 21-22, 2016 Brisbane, Australia

Luis Miguel Grilo

Universidade Nova de Lisboa, Portugal

Posters & Accepted Abstracts: J Pet Environ Biotechnol

Abstract:

In the Chemical Laboratory of a Portuguese thermoelectric central, control charts are used to monitor the soluble silica content in the demineralized water. This continuous variable is measured and controlled in order to keep the equipment operating in the best conditions and allowing extension of its useful life. Since we only have samples of one measure, individual control charts for the silica content is obtained based on average moving range, once in this case study this variable could be considered approximately normal distributed. Because the sample size available is small and it is difficult to fit a model, robust control limits using a non parametric method based on empirical quantiles (that performs also well under the normality of the observations, according to some simulations studies) are also estimated with the bootstrap procedure. The comparison of control limits obtained with different approaches and with (out) an outlier is very important for technicians since the value of silica should be as small as possible. The process capability study also developed shows that the process does not stay within the engineering specification limits, although it seems stable.

Biography :

Email: lgrilo@ipt.pt