MEC&F Expert Engineers : EXPLOSION AT GREENHILLS COAL MINE NEAR ELKFORD, B.C. SENDS 3 TO HOSPITAL

Sunday, April 5, 2015

EXPLOSION AT GREENHILLS COAL MINE NEAR ELKFORD, B.C. SENDS 3 TO HOSPITAL




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.