Major loss in hydroelectric power plant | Kerugian besar pada pembangkit listrik tenaga air

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Major loss in hydroelectric power plant

Sayano-Shushenskaya is one of the world’s biggest hydro power plants. Years of overloading the turbines and inadequate maintenance were probably behind the major accident in 2009. Could greater care have prevented the catastrophe?

03.08.2011
 
 

On 17 August 2009, a turbine unit was torn out of its anchorage by fluctuating water pressure and catapulted into the air in the Sayano-Shushenskaya hydroelectric power plant in Russia. Weighing in at around 2,000 tonnes, the turbine destroyed the 27-m-high roof of the turbine hall, as well as several nearby structures and plant parts. Propelled by the pressure of a 200-m water column, an incredible 360 cubic metres of water per second shot through the entire turbine hall, including the lower floors, causing numerous short circuits and immediate failure of the power plant. Those units which were still in operation sustained various degrees of mechanical and electrical damage. All in all, 75 people were killed and many others injured.

Clear warning signs had been ignored

The damaged turbine unit was extensively overhauled in 2000 and 2005, followed by another minor overhaul in the spring of 2009. At the same time, a new control system was installed so that the hydro power plant could be controlled externally in line with grid requirements. This system was not adapted exactly to the installed turbines.

After the turbine was recommissioned, the vibrations measured in the turbine rotor were only just below the maximum permitted by the manufacturer. However, in the following weeks and months, these vibrations did not stabilise, but instead increased steadily, presumably exceeding the permitted maximum by June 2009. Nevertheless, the turbine remained in operation. Fatigue cracks appeared in the retaining bolts. The bolts sheared as soon as the water pressure was sufficiently high to cause residual forced rupture. The turbine cover with turbine rotor and generator weighing around 2,000 tonnes lost its anchorage in the foundation and led to the accident.

Catastrophe court case

Even today, it is unclear why neither the plant management nor the operators halted the turbine which had been vibrating strongly for many months. Many documents are still in the hands of the judiciary. Others were reputedly washed away by the water. After the water had been pumped out of the turbine hall, 49 of the 80 retaining bolts holding the turbine cover in place were subjected to metallographic analysis. Six of them did not even have a nut. They may have been forgotten when the turbine was last serviced. Investigations by the public prosecutor are still ongoing. One year after the accident, charges were filed against the people responsible in the plant operating company and in the maintenance companies. The plant’s operator plans to completely replace all ten turbines between 2011 and 2014.

Sayano-Shushenskaya: Years of overloading the turbines and inadequate maintenance were probably behind the major accident in 2009. © Munich Re
View of the damaged turbine cover and severed yellow turbine rotor shaft. The holes accommodating the 80 bolts are clearly visible around the outer circumference.
 

Improper plant operation

The catastrophe could have been prevented if the machines had been operated in base load mode as specified. Also, basic principles ensuring trouble-free operation, such as investigation of the causes leading to the increase in vibrations, were disregarded here. Even when the vibrations had increased to five times the permitted level, the unit was not switched off. Moreover, necessary maintenance work was evidently performed inadequately or not at all.

“Professional risk management can help prevent such catastrophes. But regular maintenance and proper use of machinery are indispensable, the more so towards the end of a machine’s originally planned life span”, Bernd Richter, an engineer and Claims Manager in Munich Re’s Europe and Latin America unit, and Klaus Wenselowski, head of the Property Claims Management unit at Munich Re’s Global Clients/North America division explain. “To prevent such major losses from occurring, we assist our clients in setting up risk management programmes and attach great importance to compliance with agreed measures and guidelines.”

Free translation:

Kerugian besar pada pembangkit listrik tenaga air

Sayano-Shushenskaya adalah salah satu pembangkit listrik tenaga air terbesar di dunia. Bertahun-tahun turbin dibebani dengan perawatan yang tidak memadai diduga berada di balik kecelakaan besar pada tahun 2009. Bisakah perawatan yang lebih baik mencegah bencana?

 

Pada tanggal 17 Agustus 2009, sebuah unit turbin robek dan keluar dari jangkarnya dengan tekanan air yang berfluktuasi dan melambung ke udara di pembangkit listrik tenaga air Sayano-Shushenskaya di Rusia. Beratnya sekitar 2.000 ton, turbin menghancurkan atap aula turbin setinggi 27 m, serta beberapa struktur dan bagian-bagian pembangkit di sekitarnya. Didorong oleh tekanan 200 m kolom air, 360 meter kubik air yang luar biasa melesat menembus seluruh ruang turbin, termasuk lantai bawah, menyebabkan banyak korsleting dan sesaat itu pula pembangkit listrik berhenti berfungsi. Unit-unit yang masih beroperasi mengalami berbagai tingkat kerusakan mekanis dan listrik. Secara keseluruhan, 75 orang tewas dan banyak lainnya terluka.

Tanda-tanda peringatan yang jelas telah diabaikan

Unit turbin yang rusak dirombak secara ekstensif pada tahun 2000 dan 2005, diikuti oleh perbaikan kecil lainnya pada musim semi 2009. Pada saat yang sama, sebuah sistem kontrol baru dipasang sehingga pembangkit listrik tenaga air dapat dikontrol secara eksternal sesuai dengan kebutuhan jaringan. Sistem ini tidak disesuaikan persis dengan turbin yang dipasang.

Setelah turbin diaktifkan kembali, getaran yang diukur dalam rotor turbin tepat di bawah maksimum yang diizinkan oleh pabrikan. Namun, dalam minggu-minggu dan bulan-bulan berikutnya, getaran-getaran ini tidak stabil, tetapi malah meningkat dengan stabil, mungkin melebihi angka maksimal yang diizinkan pada Juni 2009. Meskipun demikian, turbin tetap beroperasi. Retakan akibat kelelahan muncul di baut penahan. Baut dicukur segera setelah tekanan air cukup tinggi untuk menyebabkan pecahnya paksa residu. Penutup turbin dengan rotor dan generator turbin dengan berat sekitar 2.000 ton kehilangan jangkarnya di pondasi dan menyebabkan kecelakaan.

Kasus pengadilan bencana

Bahkan hari ini, tidak jelas mengapa manajemen pabrik maupun operator menghentikan turbin yang telah bergetar kuat selama berbulan-bulan. Banyak dokumen masih berada di tangan pengadilan. Yang lainnya konon hanyut oleh air. Setelah air dipompa keluar dari ruang turbin, 49 dari 80 baut penahan yang memegang penutup turbin di tempat menjadi sasaran analisis metalografi. Enam dari mereka bahkan tidak punya mur baut. Mereka mungkin telah dilupakan ketika turbin terakhir diservis. Investigasi oleh jaksa penuntut umum masih berlangsung. Satu tahun setelah kecelakaan itu, tuntutan diajukan kepada orang-orang yang bertanggung jawab di perusahaan yang mengoperasikan pembangkit dan di perusahaan pemeliharaan. Operator pabrik berencana untuk sepenuhnya mengganti semua turbin antara 2011 dan 2014.

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Pimpinan pemerintah Rusia mengunjungi area kecelakaan

Sayano-Shushenskaya: Years of overloading the turbines and inadequate maintenance were probably behind the major accident in 2009.Gambar tutup turbin yang rusak dan poros rotor turbin kuning yang terputus. Lubang yang menampung 80 baut terlihat jelas di sekitar lingkar luar.

Operasional pabrik yang tidak benar

Bencana bisa dicegah jika mesin-mesin telah dioperasikan dalam mode beban dasar seperti yang ditentukan. Juga, prinsip-prinsip dasar yang memastikan operasi bebas masalah, seperti penyelidikan penyebab yang menyebabkan peningkatan getaran, diabaikan di sini. Bahkan ketika getaran telah meningkat hingga lima kali level yang diizinkan, unit tidak dimatikan. Selain itu, pekerjaan pemeliharaan yang diperlukan ternyata dilakukan tidak memadai atau tidak sama sekali.

“Manajemen risiko profesional dapat membantu mencegah bencana semacam itu. Tetapi pemeliharaan rutin dan penggunaan mesin yang tepat sangat diperlukan, terlebih menjelang akhir masa hidup mesin yang direncanakan semula”, Bernd Richter, seorang insinyur dan Manajer Klaim di Munich Re’s Europe and Latin Unit Amerika, dan Klaus Wenselowski, kepala unit Manajemen Klaim Properti di divisi Klien Global / Amerika Utara Munich Re menjelaskan. “Untuk mencegah kerugian besar seperti itu terjadi, reasuransi dapat membantu klien dalam menyiapkan program manajemen risiko dan sangat mementingkan kepatuhan dengan langkah-langkah dan pedoman yang disepakati.”

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