International Science Index


10002429

Failure Analysis of Pipe System at a Hydroelectric Power Plant

Abstract:In this study, failure analysis of pipe system at a micro hydroelectric power plant is investigated. Failure occurred at the pipe system in the powerhouse during shut down operation of the water flow by a valve. This locking had caused a sudden shock wave, also called “Water-hammer effect”, resulting in noise and inside pressure increase. After visual investigation of the effect of the shock wave on the system, a circumference crack was observed at the pipe flange weld region. To establish the reason for crack formation, calculations of pressure and stress values at pipe, flange and welding seams were carried out and concluded that safety factor was high (2.2), indicating that no faulty design existed. By further analysis, pipe system and hydroelectric power plant was examined. After observations it is determined that the plant did not include a ventilation nozzle (air trap), that prevents the system of sudden pressure increase inside the pipes which is caused by water-hammer effect. Analyses were carried out to identify the influence of water-hammer effect on inside pressure increase and it was concluded that, according Jowkowsky’s equation, shut down time is effective on inside pressure increase. The valve closing time was uncertain but by a shut down time of even one minute, inside pressure would increase by 7.6 bar (working pressure was 34.6 bar). Detailed investigations were also carried out on the assembly of the pipe-flange system by considering technical drawings. It was concluded that the pipe-flange system was not installed according to the instructions. Two of five weld seams were not applied and one weld was carried out faulty. This incorrect and inadequate weld seams resulted in; insufficient connection of the pipe to the flange constituting a strong notch effect at weld seam regions, increase in stress values and the decrease of strength and safety factor.
References:
[1] V. Vineesh V, and A. I. Selvakumar, “Design of Micro Hydel Power Plant,” International Journal of Engineering and Advanced Technology, vol. 2, 2012, pp. 136-140.
[2] B.A. Nasir, “Design of Micro - Hydro - Electric Power Station,” International Journal of Engineering and Advanced Technology, vol. 2, 2013, pp. 39-47.
[3] H. Sharma, and J. Singh, “Run off River Plant: Status and Prospects,” International Journal of Innovative Technology and Exploring Engineering, 2278-3075, vol. 3, 2013, pp. 2278-3075.
[4] M. Çalamak, and Z. Bozkus, “Protective Measures against Waterhammer in Run-of-River Hydropower Plants,” Digest, vol.12, 2012, pp. 1623-1636.
[5] T.W. Choon, L.K. Aik, L.E. Aik, and T. T. Hin, “Investigation of Water Hammer Effect through Pipeline System,” International Journal on Advance Science Engineering Information Technology, vol. 7, 2012 pp. 48-53.
[6] S. Dursun, and Z. Bozkus, “Numerical Investigation of Protection Measures Against Water Hammer in the Yesilvadi Hydropower Plant,” 11th International Congress on Advances in Civil Engineering, Istanbul 2014.
[7] J. Wood, “Waterhammer Analysis—Essential and Easy „and Efficient” Journal of Environmental Engineering, vol. 8, 2005, pp. 1123-1131.
[8] A. Leishear, Fluid Mechanics, Water Hammer, Dynamic Stresses, and Piping Design, ASME, New York, 2012.
[9] A. Dudlik, S.B. Handajani, Schönfeld, S. Schlüter, H. Fahlenkamp, and H.M. Prasse, “Prevention of Water Hammer and Cavitational Hammer in Pipeline Systems,” Chemical Engineering & Technology, vol. 09, 2002; pp. 888-890.
[10] K. Paffel,” The number One Problem in a Steam System: Waterhammer,” Chemical Engineering, vol. 4, 2008, pp. 1-4.
[11] G. Gjetvaj, and M. Tadic, “The Effect of Water Hammer on Pressure Increase in Pipelines Protected by an Air Vessel,” Technical Gazette, vol. 21, 2014, pp. 479-484.
[12] S. Mohamed, M. Ghidaoui, Z. Duncan, and H. Axworthy, “A Review of Water Hammer Theory and Practice,” Applied Mechanics Reviews, vol. 58, 2005, pp. 49-76.