By Douglas J. Smith IEng,
"No, the safety discipline may not be perfect. But ours is an industry where even almost perfect just isn't good enough." This quote by Donald Tanner, Executive Director, National Board of Boiler and Pressure Vessel Inspectors sums up in a nutshell the need to be vigilant in the operation of power plants
In the industrial revolution of the early 1800s, deaths and injuries from boiler explosions and other pressure vessels were a daily occurrence. As larger and larger boilers were constructed the loss of life from explosions continued to increase.
Although the loss of life was unacceptable, it was only after a major boiler exploded on board a riverboat in 1865, killing 1,238 passengers, that the public finally demanded action to make boilers and other pressure vessels safer. The outcome of this was the formation of Hartford Steam Boiler Inspection and Insurance Company in 1866.
The concept of insuring plant equipment against loss and inspecting it for safety was developed by Hartford. In 1879, Hartford wrote the first boiler construction standard "Uniform Steam Boiler Specifications." This was followed in 1914, when the American Society of Mechanical Engineers (ASME) wrote and published the first American "Boiler and Pressure Vessel Code." This standard is now accepted worldwide.
Because of the need for uniform adoption of the ASME Code the boiler inspectors of the U.S. and Canada formed the National Board of Boiler and Pressure Vessel Inspectors. Today, the National Board of Boiler and Pressure Vessel Inspectors regulates the construction, repair and inspection of boilers and pressure vessels in the United States and Canada.
Accidents Still Occur
Even though there has been a drastic reduction in accidents over the years, power plants continue to report accidents involving personnel. Recently a worker at the Ebensburg cogeneration plant in Pennsylvania was fatally injured and three others were scalded from a sudden blast of steam and ash. The workers had been in the process of rigging scaffolding in the furnace when leaking water splashed on the hot ash in the bottom of the boiler.
Early this year another death occurred at the Kenneth Coleman generating plant in Kentucky. In this instance a painter/insulator was working at the plant when a boiler explosion caused him to fall 6 to 8 feet. His death was caused by head injuries when he fell. Fortunately, no one else was hurt.
In 1999, a boiler explosion occurred on Unit 3 at Pacific Gas & Electric's 170 MW Hunters Point power plant. At the time of the accident the unit was being ramped down. However, no injuries were reported from this incident. Coal pulverizer explosions occur frequently and in 1999 an explosion at a Georgia power plant injured seven employees, one of whom died from his injuries.
A more serious accident happened in April 1999 at Tampa Electric's Gannon Station when a hydrogen explosion occurred in the generators of Unit 6. At the time it was determined that the explosion occurred because an access cover was opened before the unit had been purged of hydrogen. In this accident 42 people were injured, including three fatalities.
Incidents Reported in 2000
Every year, the National Board of Boiler and Pressure Vessel Inspectors issues what they call an "incident report." The report covers all incidents reported on power boilers, steam and water boilers and unfired pressure vessels. The table outlines the incidents reported for power boilers in 2000.
According to the report, deaths were down 33 percent and injuries dropped 80 percent in 2000 over that of 1999. In addition, the injury-per-accident ratio went from one injury for every 16 incidents in 1999 down to 1 injury for every 99 incidents in 2000.
Although Donald Tanner, executive director for the National Board, states that the 2000 results make it sound almost perfect, one should not dismiss the reality that 1999 was an unusual year for catastrophic deaths and injuries. In 1999, a single power boiler incident resulted in 14 injuries and six deaths and one unfired pressure vessel incident killed two people and injured 50 others, Tanner said.
A recent editorial in the National Board Bulletin states, "If there is one telling statistic of significant concern in the 2000 incident report it is the 24 percent increase in the total number of boiler and unfired pressure vessel accidents." Operator error and/or poor maintenance accounted for 53 percent of the incidents, says Tanner.
Even though the power industry has come a long way since the late 1800s, the industry must remain vigilant to reduce further accident. One suggestion to avoid accidents is to establish a procedure for keeping adequate operating logs of the operation and maintenance of power plant equipment, says the National Board of Boiler and Pressure Vessel Inspectors. In addition, plant personnel must be instructed on correct operating procedures.
Monthly safety meeting should be conducted to discuss safety problems and what is being done to rectify the problems. These meeting should also review standard safety procedures for removing equipment from service for maintenance.