APRIL 5, 2015
Three people were sent to hospital after an explosion at the
Greenhills coal mine outside Elkford, B.C.
The blast happened in the pulverizing room, where coal is
ground for combustion, on the morning of April 5. Two men and a woman outside
the room at the time of the explosion were taken to hospital to be treated for
third-degree burns and smoke inhalation.
Interior Health says one victim was sent to hospital in
Fernie while two others were sent to Sparwood.
By mid-afternoon, one person had been discharged while two
remained in hospital. Of the two still in hospital, one was transferred by air
ambulance from Sparwood to the Foothills Medical Centre in Calgary with serious
but non-life threatening burn injuries. The other was still in a B.C. hospital,
but Interior Health told Global News they are likely to be transferred to
Calgary as well.
A statement from Teck Resources Ltd., which operates the
Greenhills mine, says “the cause of the incident is not known at this time.”
A B.C. government spokesperson says the Chief Inspector of
Mines, who is responsible for investigating accidents at mine sites, has
dispatched two mine inspectors to the site.
According to Teck’s website, Greenhills is located eight
kilometres north of Elkford and “coal mined at Greenhills is used to produce
steel.”
In 2012, Greenhills, which consists of 11,806 hectares
of coal lands, reported $845 million in revenue, making it the fourth largest
mine in B.C. at the time.
The mine was temporarily closed in 2010 due to an explosion
in a coal dryer. Four people suffered minor injuries stemming from smoke
inhalation.
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WHY DO COAL MINES
EXPLODE?
The cause of the massive explosion that killed at least 25
miners in West Virginia yesterday remains unknown. But officials think methane
gas likely contributed to the fatal blast at Massey Energy Co.'s Upper Big
Branch mine.
There are two main types of coal mine explosions: methane
explosions and coal dust explosions.
Methane explosions occur in mines when a buildup of methane
gas, a byproduct of coal, comes into contact with a heat source, and there is
not enough air to dilute the gas to levels below its explosion point, said Yi
Luo, an associate professor of mining engineering at West Virginia University.
"In most U.S. coal mines, each ton of coal contains
between 100 to 600 cubic feet (2.83 to 17 cubic meters) of methane," Luo
told Life's Little Mysteries. "When air contains 5 percent to 15 percent
of methane, it can explode."
Deadly mix
Methane, the main component of natural gas, is combustible,
and mixtures of about 5 percent to 15 percent in air are explosive. When air
contains approximately 9.5 percent of methane (the most dangerous
concentration), it reaches the perfect oxidation point, which means that the
right amount of fuel is mixing with the right amount of oxygen, said Luo. This
produces water, carbon dioxide and a lot of amount of heat.
"It does not [require] much heat to ignite the
combustion process and therefore methane explosion can accelerate very
fast," Luo said.
The heat generated by this process raises the temperature of
the air within the mine, which causes it to expand in volume. Since hot air
cannot expand easily underground, pressure builds in the mine. If this pressure
is high enough, it can cause the air ahead of the combustion zone to compress
and cause a shock wave, Luo explained.
Ventilation is the most common method to avoid such methane
explosions in coal mines. Large fans are used to blow air out or draw air into
mines, but Luo stated that mine ventilation is still a complicated science.
"In coal mines, we are required to control the
concentration [of methane to] less than 1 percent," he said. "But
there are hard places to ventilate where concentration could get into the
explosive range."
Mine explosions can also be triggered when fine particles of
coal dust come into contact with a source of heat.
While methane is easier to ignite, the explosion pressure
and heat value of methane is not as high as coal dust. In most cases, dust
explosions are first caused by methane explosions, said Luo.
"Dust explosion needs a very high concentration of dust
suspended in the air, which is very hard to find in a mine environment,"
Luo explained.
But, the shock wave caused by methane explosions can blow up
coal dust within the mine, and the heat generated by the methane reaction can
ignite the dust, which greatly intensifies the energy of the explosion.
Worst case
So, in a worst case scenario, a methane explosion has the
potential to ignite a more catastrophic coal dust explosion.
Coal mines in the United States have taken safety measures
to avoid dust explosions, including spreading limestone powder over the coal
dust. Limestone powder makes it more difficult for shock waves from methane
explosions to blow up particles of coal dust, said Luo.
"Limestone also absorbs a great amount of heat
generated from the [methane] explosion," Luo said. "It will either
stop the chain reaction or reduce the intensity of the explosion."
The Massey Energy Co. explosion this week is the worst
mining disaster in the United States in more than two decades, and this latest
catastrophe adds to a long history of coal mine tragedies in an industry that
is notoriously risky and dangerous.
Since 1839, there have been 501 known U.S. coal mine
explosions that killed at least five people each, according to the National
Institute for Occupational Safety and Health. In addition, at least 52 coal
mine fires have killed at least five people each. The worst of these disasters
was an explosion that killed 362 people in a coal mine in Monongah, W.Va in
1907.
An explosion similar to this week's occurred at Sago Mine in
Buckhannon, W.Va in 2006 that killed 12 miners.
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Potential for Natural Gas and Coal Dust Explosions in Electrical Power Generating Facilities
Technical Information Bulletin
TIB 00-11-06
This TIB is not a new standard or regulation and it creates
no new legal obligations. It is advisory in nature, informational in content,
and is intended to assist employers in providing a safe and healthful
workplace.
OSHA's Directorate of Technical Support (DTS) issues
Technical Information Bulletins (TIBs) to provide information about
occupational hazards and /or to provide information about noteworthy,
innovative, or specialized procedures, practices and research that relate to
occupational safety and health. DTS selects topics for TIBs from recognized
scientific, industrial hygiene, labor, industry, engineering, and/or medical
sources.
The Occupational Safety and Health Act requires employers to
comply with hazard-specific safety and health standards. In addition, employers
must provide their employees with a workplace free from recognized hazards
likely to cause death or serious physical harm under Section 5(a)(1), the
General Duty Clause of the Act. Employers can be cited for violating the
General Duty Clause if there is a recognized hazard and they do not take
appropriate steps to prevent or abate the hazard. However, the failure to
implement TIB recommendations is not, in itself, a violation of the General
Duty Clause.
Citations can only be based on standards, regulations, and the
General Duty Clause.
Further information about this bulletin may be obtained by
contacting OSHA's Directorate of Technical Support and Emergency Management
(formerly Directorate of Technical Support) at 202-693-2300.
Purpose
The purpose of this Technical Information Bulletin is:
to remind employers who operate electrical power generation
facilities about potential explosion hazards during boiler start up, operation,
and shutdown;
to provide guidance to the Occupational Safety and Health
Administration (OSHA), and State Plan Compliance Safety and Health Officers
regarding prudent practices established by the National Fire Protection
Association (NFPA) and the American Society of Mechanical Engineers (ASME) for
the safe operation of boilers and furnaces in electrical power generating
facilities;
and to provide guidance to safety professionals who serve the
power generation industry including consultants, insurance auditors, and others
who provide services and equipment to the industry.
Background
The State of Michigan is one of 23 States that have chosen
to retain authority for occupational safety and health law enforcement under a
State Plan approved by OSHA. Therefore, the General Industry Safety Division
(MIOSHA), under the Bureau of Safety and Regulation (BSR), Michigan Department
of Consumer and Industry Services (CIS), investigated a power plant explosion
in 1999 that resulted in 6 fatalities and 14 serious injuries. The primary
explosion resulted from an unintentional natural gas buildup in the furnace of
an idle power boiler and was followed by a secondary explosion of disturbed
coal dust. MIOSHA found coal dust accumulations throughout the powerhouse on
ledges, structures, and equipment. This boiler was fired with natural gas,
coal, and blast furnace gas to produce steam to power the turbines.
Jurisdictional Issues
Both MIOSHA and the Boiler Division of the Michigan Bureau
of Construction Codes responded following the explosion. The Boiler Division
had limited jurisdiction and could investigate only the wet-side of the boiler
(i.e., the pressure vessel in which the steam is generated). MIOSHA had
jurisdiction over all other aspects of the matter including compliance with
MIOSHA regulations - e.g., R408.18602 (adopting the Federal OSHA standard, 29
CFR 1910.269 on Power Generation), and R408.18502 (adopting the Federal OSHA
Standard, 29 CFR 1910.147 on Lockout/Tagout); R408.1011 (a), MIOSHA's analogue
to Federal OSHA's General Duty Clause, Section 5 (a)(1) of the OSHAct (P.L. 91
- 596 December 29, 1970, and its amendments).
Incident Description
Based on interviews and observations, and after reviewing
relevant documentation, the investigators developed a chronology of events leading
to the explosion. Employees were raking the boiler offline in preparation for
its annual licensing inspection. Prior to the time of the explosion, blast gas
and pulverized coal systems were eliminated as fuel sources, and maintenance
personnel were blanking the two main 10-inch natural gas lines.
Power Service Operators (PSO's) were required to shut up the
30 natural gas valves, including pilots, ignitors, and burners located on two
different floors.
Maintenance personnel blanked, disconnected, and/or capped 6
of the 30 natural gas lines and valves. PSOs monitored induced draft, forced
draft, primary fans, steam pressure, temperature, and water levels during the
shut down. During this process, PSOs failed to close one of the two 10 inch
main natural gas shutoff valves feeding the burners. As a result, natural gas
was trapped between shutoff valves and burner control valves, and the burner
control valve subsequently was reopened to vent the trapped gas into the
furnace box. This allowed the natural gas at line pressure to flow into the
furnace box for approximately 2 minutes. The primary explosion occurred when
this gas encountered ignition sources, such as hot or smoldering ask in the
superheater or generating tubes, or possibly a spark from the electrostatic
precipitator. A secondary explosion resulted from disturbed coal dust dispersed
during the initial explosion.
Investigation Findings
The investigators identified the following engineering
control and work practice deficiencies, which were cited under the Power
Generation and the Lockout/Tagout Standards, as well as the General Duty
Clause:
Lack of adequate combustion controls: Inoperative flame
monitor and burner safety devices.
Lack of burner/ignitor control system: Inoperative pilot
ignitors. Pilots were lit with a glove soaked in alcohol.
Purging of natural gas into an idle furnace: The natural gas
valve train not equipped with a double block and bleed to atmosphere.
Lack of proper identification of isolation valves, butterfly
valves, pilot valves, and ignitor valves: Valves were improperly marked or
identified, and improperly located for boiler shutdown and startup operations.
Failure to establish proper written procedures for
startup/shutdown of boilers:
Written procedures are necessary due to personnel
changes associated with shift assignments, the complexity of boiler shutdown,
and the infrequency of shutdowns.
Failure to control accumulations of appreciable coal dust:
Poor housekeeping allowed coal dust to accumulate throughout the facility (e.g.,
on floors, ledges, structures, beams and equipment).
Failure to institute proper lockout procedures specific to
boilers: No specific procedures for boilers or for release from lockout;
lockout devices were not identified during blanking operations.
Failure to conduct adequate/effective job briefings:
Employee briefings were not conducted prior to the boiler shutdown. Briefings
would have revealed that two employees had not performed this task within the
last year and that employees needed to be retrained.
Failure to provide adequate training, procedures, and
certifications of proficiency for employees assigned to boiler operations.
The investigators also found that individual departments
within the powerhouse handled safety-related issues. This produced a situation
where safety issues potentially went unrecognized and where information
regarding safety was not necessarily shared with the appropriate personnel. For
example, insurance audits and engineering studies recommending modifications to
combustion/safety controls were viewed as operational issues without
consideration for, or input from, the safety department.
Recommendations
The investigators concluded that this accident may have been
prevented if industry standards such as those identified below, had been
followed:
NFPA 8502, "Standard for the Prevention of Furnace
Explosions/Implosions in Multiple Burner Boilers;"
NFPA 8503, "Standard for Pulverized Fuel Systems;"
ASME, BPVC Section VII, "Recommended Guidelines for the
Care of Power Boilers;" and
ASME B31.1, "Power Piping."
NFPA Standard 85B, "Standard for Prevention of Furnace
Explosions in Natural Gas-Fired Multiple Burner Boiler-Furnaces," which
was an earlier version of NFPA 8502, Section 2-1.3(b), identified "fuel
leakage into an idle furnace and the ignition of the accumulation by a spark or
other source of ignition" as one of the most common explosive conditions
in connection with the operation of a boiler-furnace. Based on the evidence in
the case file for this investigation, the MIOSHA/OSHA investigative team
recommends that:
When boilers are manually operated in lieu of automated
combustion/safety controls, additional emphasis must be placed on work
practices. Necessary elements for emphasis include written operating
procedures, job briefings, verification checklists, training, proficiency
testing, and maintenance of training records.
When equipment nears the end of its useful life, the
employer must be particularly diligent, as well as vigilant, with respect to
maintenance. Boiler safety controls (e.g., flame monitors) must be operational
and well maintained.
Coal dust accumulations must be recognized as a serious
hazard and housekeeping must be performed with diligence to control and/or
limit coal dust accumulations.
To ensure safety there must be clear lines of communication
among all power plant entities, including: the safety department, employee
safety and health representatives, security department, maintenance,
operations, and management. A comprehensive safety committee representing all
these organizational functions is essential.