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Summary of Investigation Fatal Underground Coal Mine Explosion January 2, 2006 Sago Mine Wolf Run Mining Company. **Sketches are for demonstrative purposes only and are not exact replications**. Final Report. General Information Sequence of Events Seals SCSRs Barricade Rescue

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Presentation Transcript
slide1

Summary of Investigation

Fatal Underground Coal Mine Explosion

January 2, 2006

Sago Mine

Wolf Run Mining Company

**Sketches are for demonstrative purposes only and are not exact replications**

slide2

Final Report

  • General Information
  • Sequence of Events
  • Seals
  • SCSRs
  • Barricade
  • Rescue
  • Fuel
  • Flames and Forces
  • Ignition sources
  • Conclusion
  • Enforcement Actions
slide3

Area Previously Sealed

2nd Left Mains

1st Left

Sealed

Drift Openings

1st NE Mains

2nd Left Parallel

2 North Mains

1 Right

2 Right

SAGO MINE

sunday january 1 2006

Saturday December 31, 2005

Sunday January 1, 2006
  • The mine does not produce coal.
  • Two shifts perform maintenance.
  • At approximately 3:00 a.m., Fred Jamison and Terry Helms, mine examiners, entered the mine.
  • They pre-shift the track and belt entries in the mains and the 1st Left section and 2nd Left Parallel section.
  • Jamison arrived outside at 5:40 a.m. Helms traveled from 1st Left toward 2nd Left Parallel switch and remained underground.
  • The mine does not produce coal.
  • Day shift performs maintenance.
  • The mine is idle after the day shift is complete.

Monday January 2, 2006

slide5

Monday January 2, 2006

  • At 6:00 a.m., the 2nd Left Parallel section crew of 12 miners boarded a mantrip, entered the mine, and traveled to 2nd Left Parallel.
  • At 6:00 a.m., Fred Jamison walked from the surface to No. 2 Belt drive.
  • At 6:05 a.m., the 1st Left section crew of 12 miners plus 3 other miners entered the mine after switching to a larger mantrip to carry all of the miners. They dropped off two miners and continued to the 1st Left switch.
slide6

2 Left Parallel Section Crew

1st Left Section Mantrip

John Boni

Pat Boni

Thomas Anderson*

Alva Bennett*

James Bennett*

Jerry Groves*

George Hamner Jr.*

Jesse Jones*

Fred Jamison

David Lewis*

Randal McCloy Jr.

Martin Toler Jr.*

Fred Ware*

Jackie Weaver*

Marshall Winans*

Terry Helms*

Denver Anderson

Paul Avington

Gary Carpenter

Randall Helmick

Eric Hess

Owen Jones

Hoy Keith Jr.

Arnett Perry

Gary Rowan

Harley Ryan

Christopher Tenney

Anton Wamsley

Ronald Grall

Location of miners immediately prior to the explosion – 6:26 am

Survivors

Fatalities*

slide7

Monday January 2, 2006

Following the explosion:

  • Jamison and Pat Boni walked out of the mine.
  • The 1st Left section mantrip was at the 1st Left switch when the miners experienced a violent blast of air, smoke, dust and debris. They began to walk out of the mine in the track entry and then moved to the primary escapeway. Owen Jones remained in the mine.
  • Four managers entered the mine. They met John Boni and the miners from the 1st Left section mantrip, who were transported out of the mine.
  • Managers Toler, Wilfong, Schoonover, Hofer, and Jones repaired some ventilation controls up to 57 Crosscut, No. 4 Belt. Conditions eventually caused them to evacuate the mine. They arrived at the surface at 10:35 a.m.
slide8

2 Left Parallel Section Crew

Terry Helms*

Thomas Anderson*

Alva Bennett*

James Bennett*

Jerry Groves*

George Hamner Jr.*

Jesse Jones*

David Lewis*

Randal McCloy Jr.

Martin Toler Jr.*

Fred Ware*

Jackie Weaver*

Marshall Winans*

Location of miners remaining underground after 10:35 a.m.

Survivors

Fatalities*

slide9

The miners reboarded the mantrip and started outby on the track entry in an attempt to escape. During their travel outby, they encountered an atmosphere filled with smoke.

The miners walked to the Primary Escapeway at 11 crosscut and donned their SCSRs. They tried to evacuate, but encountered smoke and debris from damaged ventilation controls. They abandoned their escape attempt and returned to the face to barricade and await rescue.

The miners exited the mantrip at 10 crosscut after encountering debris on the track.

The miners barricaded in No. 3 Face, 2nd Left Parallel Section.

The 2nd Left Parallel crew exited the mantrip and was walking toward the face when the explosion occurred. The initial effects were noise, pressure, and a haze.

Ventilation controls were damaged by the explosion. Debris from the damaged ventilation controls was scattered throughout the area.

slide10

Marshall Winans*

Martin Toler Jr.*

Randal McCloy Jr.

Jackie Weaver*

Jerry Groves*

George Hamner Jr.*

Alva Bennett*

David Lewis*

James Bennett*

Thomas Anderson*

Fred Ware*

Jesse Jones*

No. 4 Entry

No. 3 Entry

The 12 miners from the 2nd Left Parallel section crew decided to barricade in the No. 3 Face. They installed curtains diagonally in the last open crosscut in No. 3 Entry, in the crosscut between No. 3 and No. 4 Entries, and in No. 3 Entry outby the last open crosscut.

No. 2 Entry

Location of the miners found by rescue teams

Curtain

Curtain

Survivors

Fatalities*

Curtain

slide11

SEALS

In-Mine Investigation

  • All 10 seals completely destroyed
  • No. 1 Seal
  • Several whole and partial Omega blocks remained after the explosion.
  • An exposed horizontal layer of BlocBond was easily removed from the remaining Omega blocks, indicating the lack of good bonding.
  • No BlocBond was observed in the vertical joints.
slide12

SEALS

In-Mine Investigation

  • All 10 seals completely destroyed
  • No. 10 Seal
  • No Omega blocks remained on the floor.
  • There were some indications of mortar on the ribs.
slide13

The darker material is the BlocBond.

SEALS

In-Mine Investigation and Interviews

  • The actual construction of the ten seals was different from the requirements of the MSHA approved plan and from the initial NIOSH testing of 40 inch thick Omega block seals.
  • The dimensions of two of the 10 seal locations (No. 1 – 21.7’ and 8.9” and No. 2 – 20.4’ and 8.7’) exceeded 20 feet wide and 8 feet high.
  • One seal was not set back at least 10 feet from the corner of the pillar.
  • Evidence indicates that BlocBond was spread on the mine floor dry as a base.
  • Vertical joints were not coated with at least ¼ inch thick BlocBond.
  • Wedges were driven parallel to the wood planks rather than perpendicular.
slide14

SEALS

  • Test were conducted at NIOSH’s Lake Lynn Experimental Mine.
  • First time tests were conducted within a completely sealed area.
  • Six explosion tests were conducted.
slide15

SEALS

Explosion Testing of OMEGA Block Seals

  • A properly constructed 40 inch Omega Block seal withstood an explosion pressure of 51 psi.
  • A Sago Seal withstood an explosion pressure of 21 psi.
  • The level of damage to the Sago Seal following the 93 psi explosion was not quite as severe as the level of damage observed during the underground investigation at the Sago Mine.
slide16

1st Left Section Mantrip

Denver Anderson

Paul Avington

Gary Carpenter

Randall Helmick

Eric Hess

Owen Jones

Hoy Keith Jr.

Arnett Perry

Gary Rowan

Harley Ryan

Christopher Tenney

Anton Wamsley

Ronald Grall

SELF-CONTAINED SELF-RESCUERS (SCSRs)

  • Only seven of the 13 miners who were at the 1st Left track switch donned their SCSRs during the evacuation.
slide17

2nd Left Parallel Section Crew

Thomas Anderson

Alva Bennett

James Bennett

Jerry Groves

George Hamner Jr.

Jesse Jones

David Lewis

Randal McCloy Jr.

Martin Toler Jr.

Fred Ware

Jackie Weaver

Marshall Winans

SELF-CONTAINED SELF-RESCUERS (SCSRs)

  • The 12 miners in 2nd Left Parallel section donned their SCSR units while trying to evacuate.
  • Randal McCloy stated that four of the miners had difficulties with their SCSRs.
slide18

SELF-CONTAINED SELF-RESCUERS (SCSRs)

  • RECORDKEEPING: A review of the mine operator’s records indicated that the 90 day test was not completed for all the units used on January 2, 2006.
  • This includes:
  • Thomas Anderson
  • Alva Bennett
  • James Bennett
  • Jerry Groves
  • George Hamner Jr.
  • Martin Toler, Jr.
slide19

SELF-CONTAINED SELF-RESCUERS (SCSRs)

TRAINING: A review of the Training Records indicated that the miners on 1st Left and 2nd Left Parallel were trained within the required one year.

slide20

SELF-CONTAINED SELF-RESCUERS (SCSRs)

  • TESTING: Although one SCSR from the 2nd Left Parallel miners (Jesse Jones) was over 10 years old, the test results from NIOSH indicated that all of the units produced oxygen.
slide21

SELF-CONTAINED SELF-RESCUERS (SCSRs)

Although all of the miners on the 2nd Left Parallel section donned their SCSR, they were exposed to high levels of CO for much longer than the one hour capacity for each SCSR.

slide22

Barricade

  • After the 2nd Left Parallel crew encountered smoke and gases during efforts to exit the mine on the mantrip, they attempted to find other possible exits. When these attempts failed, they retreated to the section and tried to isolate themselves from poisonous gases by building a barricade.
  • Records indicated the 2nd Left Parallel crew had been trained in the Mine Emergency Evacuation and Firefighting Program of Instruction.
  • The miners chose the No. 3 face of 2nd Left Parallel Section to erect their barricade.
  • The barricade was constructed with curtains recovered from the face area.
slide23

Volume of Barricade

568.6 cu. yd.

Volume of Barricade

881.5 cu. yd..

No. 4 Entry

No. 3 Entry

No. 2 Entry

Barricade

Experiments by the USBM show that a person in a confined space needs about one cubic yard of normal air each hour.

The volume of the larger area (curtain in the crosscut and the curtain in the entry) was about 881.5 cubic yards. This indicates that that there would be 73 cubic yards of air available for each of the 12 miners in the barricade.

The diagonal curtain was approximately 29 feet in length from rib to rib and balled up on the outby end, according to the captain of the McElroy mine rescue team.

The volume of the smaller area (diagonal curtain in the intersection) was about 568.6 cubic yards, which would be 47 cubic yards of air available for each of the 12 miners.

This shows that the miners had enough air to sustain them for at least 47 hours if they remained in the smaller area within the barricade and if normal air was in the barricade. This is about six hours longer than it took for mine rescue teams to reach the barricade.

rescue
Rescue
  • The graph illustrates the results of CO measurements obtained in the No. 1 Drift Opening. The air quality readings continued trending downward. While they were still at dangerous levels, it was determined that they were low enough to allow rescue efforts to commence. At 5:25 p.m., a mine rescue team entered the mine.
slide25

Barricade

  • The borehole entered the 2nd Left Parallel section at 5:35 a.m. at a depth of 258 feet.
  • The borehole intersected the section at 23 Crosscut, No. 6 Belt in the No. 4 entry, over the conveyor belt feeder, about 260 feet from the center of the barricade.
slide27

Two methane studies were conducted in the area previously sealed inby the 2 North Mains seals on February 7-9 and March 2-3, 2006.

  • The results of the studies show that at the time of the explosion, 347,300 cubic feet of methane had accumulated in the sealed area.

Fuel

Fuel

347,300 cubic feet of Methane

slide28

Fuel

  • MSHA conducted mine dust surveys during regular health and safety inspection prior to the accident.
  • The areas that were evaluated for incombustible content as required by 30 CFR section 75.403 included areas beginning approximately 600 feet outby the 2 North Mains seals and extending through the sealed area and into 2nd Left Mains.
  • This entire area could not be sampled because of excessive water, as per inspectors’ observations.
  • Mining had stopped because of increased water inflow and deteriorating roof conditions.
  • The area may have also been wet at the time of the explosion.
  • Coal dust may have been involved to a limited degree throughout the sealed area as the flame propagated.
slide29

Extent of flame

Flames and Forces

The post-explosion mine dust survey samples were subjected to Alcohol Coke Test. The coke test results indicate that the flame from the explosion remained within the sealed area.

slide30

Flames and Forces

2 psi on 2nd Left Parallel section

  • Forces
    • Explosion forces affected a large area of the mine.

<5 psi outby 2nd Left Parallel track switch

2 psi at 1st Left track switch

93 psi at 2 North Seals

slide31

Potential Ignition Sources

Potential ignition sources for the explosion were evaluated, including:

  • Electric circuits, cables and equipment,
  • Cutting and welding,
  • Mining operations,
  • Smoking,
  • Spontaneous combustion,
  • Roof falls, and
  • Lightning.
slide32

Potential Ignition Sources

Electric circuits, cables and equipment were examined. Some circuits and equipment were not energized prior to the explosion. There was no evidence that the ignition source originated from the mine’s underground electric circuits, cables or equipment in the active portion of the mine which includes the following:

  • power system,
  • conveyor belt system,
  • water pumps,
  • battery chargers,
  • trickle rock dusters,
  • Atmospheric Monitoring System,
  • pager phones, trolleyphone system, radios,
  • gas detectors, cap lamps,
  • electric equipment in the underground workshop, outby work area lighting, electric doors, and
  • 1st Left and 2nd Left Parallel section equipment.
slide33

Potential Ignition Sources

  • CUTTING AND WELDING - There were no cutting and welding operations on-going in or near the sealed area of the mine at the time of the explosion.
  • MINING OPERATIONS – Mining operations were not occurring within close proximity to the 2 North Mains seals. There was no person in or near the sealed area at the time of the explosion.

1st Left Section

Terry Helms

2nd Left Parallel Section

slide34

Potential Ignition Sources

  • SMOKING – There were no smoking articles found underground during the investigation.
  • SPONTANEOUS COMBUSTION – The mine had no history of spontaneous combustion and there was no evidence of spontaneous combustion found during the investigation.
slide35

Potential Ignition Sources

Roof Falls in the Sealed Area

Three roof fall areas noted prior to sealing.

Roof fall areas noted as having occurred before 1/27/06 during exploration after the explosion.

Roof fall areas noted during investigations after 1/27/06.

Origin of the Explosion

X = Sandstone beds noted in top of roof fall cavity & sample collected.

slide36

Potential Ignition Sources

Roof Falls in the Sealed Area

  • Shale is the predominant rock type visible in the roof fall rubble. This shale was classified as “laminated siltstone” with low quartz content in a soft matrix that inhibits quartz grain-to-grain contact.
  • This rock type was not as conductive to frictional heating or piezoelectric sparking as sandstones that have been suspected as ignition sources in roof falls.
slide37

Potential Ignition Sources

Roof Falls in the Sealed Area

Since there were no roof falls in the proximity of the origin of the explosion, wicking of methane from the roof falls to the origin was considered.

For wicking to occur, a methane layer must be continuous, within a range of 5% to 15%, and is generally associated with being located near the roof.

The burning methane layer may eventually contact a larger accumulation, resulting in an explosion.

However, a roof fall generates turbulence in the mine atmosphere mixing layers that may have been present.

Due to the mine atmosphere turbulence caused by a roof fall, distance, elevation, and uneven roof conditions from the observed falls to the origin of this explosion make this a highly unlikely ignition source.

slide38

Potential Ignition Sources

Roof Falls in the Sealed Area

Although a roof fall cannot be definitively excluded as a potential ignition source for this explosion, it is a highly unlikely source.

slide39

Cloud to ground lightning

Intra-Cloud lightning

Cloud to cloud lightning

Upward lightning

Potential Ignition Sources

LIGHTNING OVERVIEW

Types of lightning:

slide40

101

6:26:35

35

6:26:35

Potential Ignition Sources

LIGHTNING AS AN IGNITION SOURCE

Location of lightning strike reported by Vaisala’s National Lightning Detection Network (NLDN). Number on left represents the peak current in kilo-amps; number on right represents the time that the peak current was recorded.

Location of lightning strike reported by Weather Decision Technologies, Inc.’s U.S. Precision Lightning Network (USPLN). Number on left represents the peak current in kilo-amps; number on right represents the time that the peak current was recorded.

Sago Mine workings.

slide41

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

  • The Virginia Polytechnic Institute and State University’s Department of Geosciences concluded that it was most likely that a seismic event occurred at or near the Sago Mine within a four-second interval centered at 06:26:38 a.m. on January 2, 2006.
  • The AMS recorded the first presence of CO at 6:26:35 a.m.
  • The nearby lightning strikes recorded by NLDN and USPLN occurred at approximately the same time as the seismic event and the initial alarm of the AMS.
slide42

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

  • MSHA contracted with Sandia Corporation, Sandia National Laboratories (Sandia) to perform modeling and testing, to simulate if lightning energy could enter the mine by direct contact or indirect inductive coupling.
  • Sandia analyzed the lightning data and analyzed lightning strikes, flash locations and error ellipses.
  • Sandia searched for other lightning discharges that failed to meet detection standards.
slide43

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Several plausible lightning strike scenarios could lead to significant energy coupling into the Sago Mine. Three of those scenarios were evaluated to determine the most likely possibility.

slide44

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

  • A recorded strike occurred in the proximity of the mine, hitting a tree. Two apparent paths for energy from this recorded lightning strike to reach the portal are through:
    • telephone grounding system, or
    • high-voltage power system.
  • A lightning strike delivered from the surface area directly through a conductor over the sealed area, such as gas wells and their interconnected piping system or water in the strata overlying the sealed area.
  • A lightning strike over the sealed area indirectly energizing metallic objects within the sealed area.
slide45

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Scenario A – A recorded strike occurred in the proximity of the mine, hitting a tree. Two apparent paths for energy from this recorded lightning strike to reach the portal are through: 1) the telephone grounding system or 2) the high-voltage power system.

  • Sandia concluded that it is highly unlikely a 100,000 amperes lightning strike attached at the mine portal to the belt conveyor structure, trolley communication antenna, high-voltage cable grounding medium, and the track rail could generate sufficient voltage on the pump cable within the sealed area to initiate electrical arcing.
  • Therefore, it is not likely that methods discussed in this scenario could ignite methane in the sealed area.
slide46

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Scenario B – A lightning strike delivered from the surface area directly through a conductor over the sealed area, such as gas wells and their interconnected piping system or water in the strata overlying the sealed area.

  • Testing indicated that a direct, vertical low resistance metallic path or zone of reduced resistivity for lightning to travel from the surface to the sealed area did not exist.
  • Testing indicated that lightning energy would readily dissipate in the earth near the gas well or associated piping system rather than travel into the sealed area of the mine.
  • Water within the strata was eliminated as a conductive path because there was no flow of water observed near the origin of the explosion.
slide47

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Scenario C – A lightning strike over the sealed area indirectly energizing metallic objects within the sealed area.

This scenario is based on lightning occurring over the sealed area and indirectly transferring energy into the sealed area.

  • A horizontal portion from a recorded lightning strike may have traveled over the sealed area.
  • An unrecorded cloud to cloud, intra-cloud, a cloud to ground or an upward dischargemay have occurred over the sealed area. (Lightning detection systems have limitations and do not record all lightning strikes.)
slide48

Ignition Origin

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

INDIRECT ENERGY TRANSFER TO SEALED AREA

The mine operator abandoned a submersible pump, its controller and a No. 6 AWG, 2,000 Volt cable with a male cable coupler in the 2nd Left Mains area prior to sealing.

2 North Mains Seals

slide49

Potential Ignition Sources

LIGHTNING OVERVIEW

Horizontal discharge above the mine creates electromagnetic field inducing voltage in pump cable.

Pump cable arcs causing ignition.

Seal

Pump and cable

Accumulated Methane

Sealed Area

slide50

Potential Ignition Sources

LIGHTNING OVERVIEW

An unrecorded direct strike above the mine creates an electromagnetic field inducing voltage in the pump cable.

The pump cable arcs causing ignition.

Seal

Pump and cable

Accumulated Methane

Sealed Area

slide51

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Scenario C – A lightning strike over the sealed area indirectly energizing metallic objects within the sealed area.

  • Sandia’s field measurements and analysis indicate that significant electromagnetic energy can be coupled into the sealed area of the mine.
  • A lightning source would create an electromagnetic field similar to a magnetic field that is produced between the north and south poles of a magnet.
slide52

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

slide54

POTENTIAL IGNITION SOURCES

LIGHTNING AS AN IGNITION SOURCE

Scenario C – A lightning strike over the sealed area indirectly energizing metallic objects within the sealed area.

  • The electromagnetic energy is radiated through earth onto the pump cable that acts like a receiver or antenna. The electromagnetic energy induces a voltage onto the pump cable which generates an arc in the explosive methane mixture in the sealed area.
  • Measurements and analyses indicate that the pump cable is the most likely receiver of electromagnetic energy in the sealed area.
  • This is the most likely ignition source for this explosion.
slide55

CONCLUSION

  • On January 2, 2006, an explosion occurred at approximately 6:26 a.m. in the mined-out area known as 2 North Mains and 2nd Left Mains of the Sago Mine.
  • Methane had accumulated in the sealed area.
  • Lightning was the most likely ignition source for the explosion.
  • The energy transferred onto an abandoned pump cable in the sealed area.
  • This subsequently caused an arc which ignited an explosive mixture of methane.
slide56

CONCLUSION

  • The ensuing explosion generated forces more than 93 psi and destroyed the seals, filling portions of the mine with toxic levels of carbon monoxide.
  • One miner died of carbon monoxide poisoning shortly after the explosion.
  • The 2nd Left Parallel miners’ attempt to evacuate was unsuccessful and they barricaded themselves on the 2nd Left Parallel section.
  • The barricade was not able to prevent high levels of carbon monoxide from reaching the miners before they could be rescued.
  • As a result, 11 additional miners perished and one survived.
slide57

ENFORCEMENT ACTIONS

  • A 103(K) order was issued on the morning of the accident to insure the safety of all persons at the mine.
  • 149 citations/orders were issued. Some examples are as follows:
  • The 2 North Main seals were not built in accordance with the approved ventilation plan.
  • MSHA and mine rescue teams were not immediately notified of the accident.
  • Five electrical circuits entering/exiting the mine did not have lightning arrestors.
  • Several miners did not don their SCSRs.