Two Kinds of Black Swan Events-COVID-19 and Boiler drum level Accidents
COVID-19 was the Black Swan event of 2020.
The global impact of COVID-19 has been severe. The novel coronavirus dubbed “COVID-19” was recognized as globally significant by January 2020. By March 11, it was declared a “global pandemic.” As of May 19, 2020, there have been 4782,539 diagnosed globally, accompanied by 317,566 deaths.
Currently, the COVID-19 virus is already widespread, and is continuing its advance. World Health Organization (WHO) General Director Tedros Adhanom Ghebreyesus recently predicted that the COVID-19 virus will continue to exist for a long time, and that the road ahead will be long. Many countries have taken steps to slow the spread of the disease, but COVID-19 is virulent and dangerous. Early evidence makes it increasingly clear that most of the world’s population is a risk, and that the epidemic is likely to flare up again and again. The spread of this epidemic is virulent, and its effects on economic losses and impacts are unpredictable. We have witnessed the casualties caused by the Covid-2019, we have felt the pain and helplessness caused by the separation of relatives and friends and we have also experienced the economic losses caused by the epidemic. Because of the epidemic, many industries have been seriously affected. Schools are closed and the global economy has slumped. The Covid-2019 has deeply and comprehensively affected lives and operations of every one of us and each and every country.
We have also seen the efforts of many countries and people in responding to the COVID-19. People are isolated at home; caring people and companies have donated money and material; medical supply factories and medical companies are working to reduce the loss caused by the Coivd-2019. Some countries have achieved some level of victory in controlling the spread of the virus. But other countries did not pay attention to the initial stage of the epidemic. Some regions experienced large scale, uncontrolled outbreaks by not taking adequate steps to quarantine its population and limit gatherings.
The response to the international “Black Swan” event has varied widely from one region to another. Some took the warning seriously and responded effectively. Others waited until it was too late. The industry that I serve has the same varied response to another major problem – boiler drum level instruments. For many years, the warning has been crystal clear. Traditional boiler drum level instruments are plagued with errors and problems. Some, recognizing the potential for a company-sized “Black Swan” event have responded appropriately. Others have ignored the clear and present danger.
According to the statistical analysis of power system boiler accidents, there were 27 water shortage accidents and 45 full water accidents in one country during the four years from 1982 to 1985. In total, 1 to 3 boilers suffered large-scale damage of the water wall pipes due to water shortage. "The prominent reason is that the water level gauge is malfunctioning, the instruction is incorrect, causing misjudgment and misoperation or the water level protection refuses to operate." In the three years from 1986 to 1989, there were 121 accidents of full drum water and water shortage, accounting for 11.2% of boiler operation liability accidents.
In December 1997, a thermal power plant in QinHuangDao, China experienced a low low water level event in which low low water level protection and backup protection failed due to several reasons. One, the boiler drum water level gauge had a too-small range. Two, the conductivity probe instrument showed that there WAS water in the boiler drum (since the reading error was very large). Three, the power plant operations staff misjudged the situation. The end result? The boiler was operated in this condition for an extended period of time causing enormous overheating damage to the top of the boiler. A major outage was required to repair the extensive damage of this major accident, costing an estimated $440,000 for the repair and far more due to the unavailability of the unit for the duration of the forced outage.
In April 2008, another power plant had a failure of its low low level protection system for the boiler drum. This event caused more than 70 tubes of the waterwall section to suffer serious damage. The repair cost was $170,000, along with the financial loss of unit unavailability for the 59 day duration of the repair, estimated to be at least $2.68 million.
Boiler out of water accident leads to water wall damage
On January 25, 1990, another power plant had an event in which the boiler drum level went to the top of the drum. During the recovery process after the boiler fires were tripped, water continued to enter the boiler due to excessive leakage of a control valve. This pushed water into the superheat section of the boiler, dropping its temperature sharply, and pushing water into the steam turbine, deforming static components and causing a bent turbine shaft.
The turbine rotor had three stages of blades replaced during an overhaul in 2009. During the overhaul of the same unit in 2018, erosion and severe pitting was detected in the high pressure cylinder rotor blades of the turbine. This phenomenon is due to the fact that the water level of the boiler drum had been operated excessively high over a long duration of time, causing the steam quality delivered to the turbine to be poor, causing the turbine blade and component damage. The safety and reliability of the turbine, as well as personnel safety, were adversely affected.
Long-term high water level operation leads to water carryover and serious deposit on steam turbine blades in one power plant
Excessively high or drastic fluctuations in the water level of the boiler drum will cause steam quality deterioration and water carryover, resulting in deposit on the heated surface. In severe cases, it will cause steam turbine water shock vibration and blade damage; and low water level will cause blow-down failure, and the dosing is added into the furnace to enter into the steam, Or even cause the down-comer to carry steam, affecting the boiler water circulation conditions, causing large-area blasting which seriously affect the safety of the power plant operation and personnel safety.
The accident of the power plant not only caused huge economic loss to the power plant, but also have caused many power plant personnel to lose their job, and suspend their work, which has affected their family life and future development of the relevant personnel. Are these real and painful examples worthy of our consideration?
Based on years of market research and engineering research, we have provided personal personnel safety services and solutions for power plants for more than 20 years. We trust that the current water level measurement system cannot meet the requirements for accurate measurement of the real water level, which will lead to a high frequency of various types of full water, out of water and MFT accidents. In the meantime, some power plants personnel are paralyzed and indifferent to the problems existing in the water level of the boiler drum, and even take a negative attitude towards the related problems even if they are known. For the obvious deviations in the operation of each water level gauge of the power plant, the deviations from the water mark in the drum and the designed operation water level, they do not care or correct. And just wait and postpone. The attitude accelerated the accident. Committed to the field of water level measurement for more than 20 years, we trust that the higher the steam drum pressure and load values is, the more obvious the problems with the water level will be, and the more attention needs to be paid. According to our statistics, generally when the drum pressure exceeds 1,400psi, the water level measurement deviation can reach to 2 inches. When the steam drum pressure exceeds 2000psi, the water level measurement deviation can reach to 4 inches or even greater.
The truth we have always followed is that there are always clues in observation, and we can always find clues to the future. But this epidemic infectious disease caught us off guard. Almost all people who care about the development of the situation seem to be convinced that they understand what is happening, but in fact, every day something completely unexpected is happening, but people do not realize that they have predicted this. It's just that people don’t find the connection and trace back to the truth behind the appearance of things.
Hereby the maintenance personnel, operating personnel and Instrument & control personnel of the power plant are urged to pay attention to various factors that can cause personal safety problems. Please measure the water level line of the drum, check the errors of the drum water level gauges of different principles and the deviation between them, and find out the solution as soon as possible, and strangle the disaster in the bud. Our waiting attitudes in life and work, limited cognition, and the mentality to refuse to accept new things will make us miss the best opportunity, miss the opportunity to seek deep experience through appearance and facts. So the phenomenon of such black swan events that caused adverse effects can be seen everywhere! The black swan event of the Covid-2019 makes us alert. Negative information causes us to think deeply. It will spur us to make continuous progress and perfection, and make us better. If there is a problem with your measurement system, we sincerely invite you to summarize the existing problems of water level measurement, and trace the source with us!
Let us treat the hidden dangers of the water level measurement of the steam drums in the same way that we treat the COVID-19 problem – taking necessary action when it is called for. In this way, we can work together to save more families.