The financial implications of imposed plant shutdown in relation to corrosion induced failures on petroleum heaters

• Main Author: Palisoc, Ricardo J.
• Format: text
• Published: Animo Repository 1989
• Subjects: Petroleum refineries > Equipment and supplies; Tube-steel heaters; Plant shutdowns
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1276
• Institution: De La Salle University

The study aims to find out the duration of heater shutdown which mitigates heater tube corrosion failure, the financial implications of imposed plant shutdowns in relation to corrosion induced failures on petroleum heaters, the development of a mathematical model to correlate shutdown duration with its corresponding cost implications, and management implications in general, that can be developed from the above experiences of this Philippine Oil Refinery. Data gathering was done on a number of shutdown days, incidence to failures, and repair costs observed. In line with the stated correlation hypothesis, data analyses were undertaken. Laboratory experiments were used to simulate corrosion problems validations of results were established from laboratory scale up to refinery scale observations. Through the use of statistical methods, the regression of the dependent variable versus independent variables were observed. Based on mathematical equations derived, the data were fed to the computer for speed and accuracy. During prolonged shutdowns, with acidic films attacking the cold heater tubes, additional tubes fail from dew point corrosion direct acid attack on one heater alone can cause tube thin-out, rapid loss of tube life and if undetected can lead to a crash shutdown after the heater resumes firing heater repair cost along with opportunity cost increases, resulting in a bigger total cost.On the basis of these findings, dew point corrosion failures on heater tubes can be minimized if the shutdown duration is kept within 30 days. The undetected thinned-out tubes which were reduced to 30 percent of its original thickness via direct acid attack can cause a crash shutdown, e.g. 32 days after start-up. Mathematically, it can be expressed as follows:a) incidence of tube failure - Yf Yf = -19.504 + 0.2627X1 + 0.2378X2 + eb) Repair cost = Yr Yr - -113.658 + 1.796370X1 + 5.8147X2c) Total cost is minimized if the shutdown duration is kept to within 30 days Tc = P30,000 + P90 M.