Optimizing Steam to Electricity Ratio in Crude Palm Oil Refinery Captive Power Plant: A Six Sigma-DMAIC Capability Assessment
Abstract
This study applies the Six Sigma-DMAIC (Define, Measure, Analyze, Improve, Control) methodology combined with process capability analysis to enhance energy efficiency, specifically by reducing the steam to electricity ratio of a steam turbine. Initial measurements indicated a steam-to-electricity ratio of 4.5 to 5.34 kg/kWh, highlighting high steam consumption and poor efficiency. The process was unstable, with Cp and Cpk values of 0.30 and -0.16, and a defect rate exceeding 560,000 DPMO. Using an Ishikawa diagram, a vacuum leak in the steam turbine condenser was identified as the main cause of excessive steam consumption. After repairing the condenser, monitoring showed significant improvements, with the steam to electricity ratio reducing to 3.0 – 4.0 kg/kWh. Process capability improved, with Cp increasing to 1.39, Cpk to 1.02, and Z-bench to 3.05 (equivalent to 1,143 DPMO). The Anderson-Darling test confirmed a normal distribution (p-value = 0.464). Six Sigma-DMAIC effectively optimized steam turbine performance.
##Keywords:##
Six sigma, DMAIC, process capability, steam turbine, energy efficiency, Cp, Cpk, Z-bench, Anderson-Darling.
Published
Dec 3, 2025
How to Cite
ANGGRIAWAN, Akbar; SUSILAWATI, Anita; MAINIL, Rahmat Iman.
Optimizing Steam to Electricity Ratio in Crude Palm Oil Refinery Captive Power Plant: A Six Sigma-DMAIC Capability Assessment.
Journal of Ocean, Mechanical and Aerospace -science and engineering-, [S.l.], v. 69, n. 3, p. 240-252, dec. 2025.
ISSN 2527-6085.
Available at: <https://isomase.org/Journals/index.php/jomase/article/view/552>. Date accessed: 24 may 2026.
doi: http://dx.doi.org/10.36842/jomase.v69i3.552.
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[7] Thamir, I., & M. M. R. (2013). Effects of isentropic efficiency and enhancing strategies. Journal of Mechanical Engineering and Sciences, 4, 383–396.
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[10] Setiamitra, G. A., & Subroto, A. (2023). Analysis of Lean Sigma-DMAIC implementation with environmental considerations in oil & gas industry (Case study: Onshore Field ABC Terminal Field). Maksimum: Jurnal Manajemen, 9(2), 166–178. https://doi.org/10.37403/mjm.v9i2.571.
[11] Sony, M. (2019). Lean Six Sigma in the power sector: Frog into prince. Benchmarking, 26(2), 356–370. https://doi.org/10.1108/BIJ-10-2017-0276.
[12] Rajashekharaiah, J. (2016). Six sigma benchmarking of process capability analysis and mapping of process parameters. Journal of Operations and Supply Chain Management, 9(2), 60–71. https://doi.org/10.12660/joscmv9n2p60-71.
[13] Munyaka, B. J. C., Chenal, J., & Kanyinda, K. (2024). Optimizing Manufacturing Efficiency: A Six-Sigma DMAIC Approach to Reduce Operational Gaps. International Journal of Innovative Science, Engineering & Technology, 11(1), 72-85.
[14] Monday, L. M. (2022). Define, measure, analyze, improve, control (DMAIC) methodology as a roadmap in quality improvement. Global Journal of Quality and Safety in Healthcare, 5(2), 44–46. https://doi.org/10.36401/jqsh-22-x2.
[15] Yamada, S. (2020). Are you ready for kaizen in your clinical practice? Circulation Journal, 84(4), 546–548. https://doi.org/10.1253/circj.CJ-20-0087.
[16] Douglas, M. C. (2013). Introduction to statistical quality control (7th ed.). John Wiley & Sons.
[17] Tseng, C. C., Chiou, K. C., & Chen, K. S. (2022). Estimation of the Six Sigma quality index. Mathematics, 10(19). https://doi.org/10.3390/math10193458.
[18] Kane, V. E. (1986). Process capability indices. Journal of Quality Technology, 18(1), 41–52. https://doi.org/10.1080/00224065.1986.11978984.
[19] Jäntschi, L., & Bolboac?, S. D. (2018). Computation of probability associated with Anderson–Darling statistic. Mathematics, 6(6). https://doi.org/10.3390/math6060088.
[20] Nimon, K. F. (2012). Statistical assumptions of substantive analyses across the general linear model: A mini-review. Frontiers in Psychology, 3, Article 322. https://doi.org/10.3389/fpsyg.2012.00322.
[21] Hoekstra, R., Kiers, H. A. L., & Johnson, A. (2012). Are assumptions of well-known statistical techniques checked, and why (not)? Frontiers in Psychology, 3, Article 137. https://doi.org/10.3389/fpsyg.2012.00137.
