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UNITED STATES
DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION

COAL MINE SAFETY AND HEALTH

REPORT OF INVESTIGATION

Underground Coal Mine

Fatal Machinery Accident
December 4, 2000

Sanborn Creek Mine
Oxbow Mining, Inc.
Somerset, Gunnison County, Colorado
ID No. 05-04452

Accident Investigators

Jerry O.D. Lemon
Coal Mine Safety and Health Inspector

Sarah A. Perry
Coal Mine Safety and Health Specialist

Ronald Medina
Mechanical Engineer

Anita L. Goodman
Training Specialist

Originating Office
Mine Safety and Health Administration
District 9
P.O. Box 25367
Denver, Colorado 80225-0367
John A. Kuzar, District Manager


Report Release Date: 05/31/2001



OVERVIEW


On Monday, December 4, 2000, at approximately 9:30 a.m., Thomas Emmons, age 37, tailgate shearer operator, was fatally injured at the No. 76 shield near the tailgate of the 12 North longwall. Emmons was struck in the face with a high pressure emulsion hose and fittings after a hydraulic fitting broke, allowing the hose and fittings to whip violently in the shield walkway. A second miner, Donald McGovern, longwall faceman, was standing behind the victim and was knocked into the No. 77 shield. Witnesses stated that the hydraulic hose and fittings whipped violently for approximately three to four seconds before hydraulic pressure released and the pressure cut-out switch shut down the main hydraulic pumps.

Just prior to the accident, the crew had completed the face cut into the tailgate end of the longwall. Emmons had turned the tailgate drum cowl over to start tramming the shearer to the headgate when the hydraulic fitting broke.

First aid was administered to both Emmons and McGovern. They were transported by separate ambulances to the Paonia Medical Clinic and then to the Delta County Memorial Hospital in Delta, Colorado, where Emmons was pronounced dead. McGovern received minor injuries in the accident and was treated at the hospital and released.

The direct cause of the accident was the failure of a �-inch female by 1-inch male Dayco staple lock fitting in the tailgate high pressure emulsion feed hose. This fitting failed due to faulty support of the high pressure emulsion hose, fittings, backflush filter, and shutoff valve located over the walkway at the No. 74 shield in the longwall tailgate. The method of routing and supporting the hose allowed an excessive external bending load to be applied to the fittings. The cumulative effect of repetitive internal and external forces and motions due to this method of installation eventually caused the fitting to fail. The absence of any clamps or restraints on the pressurized emulsion hose allowed it to break free and whip violently, resulting in the fatal injury. A metallurgical evaluation of the failed fitting by an independent testing laboratory did not detect any material defects.

GENERAL INFORMATION


The Sanborn Creek Mine is a non-union underground coal mine located 0.25 miles east of Somerset, Gunnison County, Colorado on State Highway 133. The mine is operated by Oxbow Mining, Inc., a subsidiary of Oxbow Carbon & Minerals, Inc. of West Palm Beach, Florida. The mine was opened in 1991, by Somerset Mining Company and was purchased by Oxbow Carbon & Minerals, Inc. in 1996.

The mine was opened with three drift portals; an intake (Portal No. 2), a belt (Portal No. 3), and a return (Portal No. 4), on the strike of the outcropping C-seam. In 1992, three rock slopes were driven from the C-seam down to the B-seam. C-seam development ceased and all future production continued in the B-seam. The dip of the seams averaged 5 degrees to the northeast, and the separation between the seams averaged 50 feet. Overburden for the B-seam ranged from 1,200 - 2,400 feet. Ventilation was provided by fan No. 1, a 200 hp, 480 VAC, model 84-26.5-BD, Joy exhaust fan, located at the C-seam return portal (Portal No. 4).

In 1996, additional air was needed for mine ventilation. Due to geologic and physical constraints at the portal area, an intake rock slope (Portal No. 1) was developed from the C-seam to the surface. This intake rock slope outcropped above the intake portal (Portal No. 2). In addition to the rock slope, two shafts were developed within the mine between the B- and C-seams, one for intake and one for return. Also, a Petition for Modification for the use of belt air was granted on September 12, 1996. The intake air for the belt entry was introduced at the portal. Ventilation was then provided by fan No. 2, a 1,500 hp, 2,300 VAC, model 8HUA108, Jeffrey exhaust fan, located at the C-seam return portal (Portal No. 4). Fan No. 1 was used as a backup to the No. 2 fan. The two fans were installed in parallel at Portal No. 4.

In 1998, an exhaust shaft was developed from the B-seam at crosscut No. 56 in the 2nd East Mains to the surface. The No. 2 exhaust fan was placed in idle status and mine ventilation was then provided by fan No. 3, a 2,250 HP, 2,300 VAC, model 8HUA108, Jeffrey exhaust fan. The mine liberates an average of 6,600,000 cubic feet of methane per day.

Room and pillar mining methods had initially been used in conjunction with continuous mining machines, electric shuttle cars, and belt conveyors for production. In 1998, a longwall was purchased and the mine converted from the standard room and pillar mining method to development of 3-entry gateroads and a retreating longwall system.

The mine employed 173 underground miners and 38 surface employees. Approximately 11,800 tons of coal were produced daily from one continuous mining development section and the retreating longwall section. The mine worked three nine-hour shifts per day with coal produced on the day and night shifts. Maintenance was performed on the graveyard shift. The mining height on the longwall face was approximately 11 feet.

The last Mine Safety and Health Administration Safety and Health Inspection (AAA) was completed on July 10, 2000, and a AAA inspection was on-going at the time of the accident. The Non-Fatal Days Lost (NFDL) incidence rate (not including office workers) for the mine for 2000 is 11.25. The NFDL rate for the nation for 2000 is 8.39.

The principal management officers of the mine at the time of the accident were:
James T. Cooper .......... Vice-President of Operations
Walter L. Wright .......... Mine Manager
Randy Litwiller .......... Mine Superintendent
Terrance Hayes .......... Safety Director
Robert Koch .......... Chief Engineer
Kevin L. Lee .......... Longwall Maintenance Foreman
Joseph Ternyik .......... Longwall Coordinator
DESCRIPTION OF THE ACCIDENT


On Monday, December 4, 2000, the 12 North longwall crew, supervised by Peter Darland, entered the mine at 7:00 a.m., and arrived on the section at approximately 7:30 a.m. The graveyard shift crew was relieved at the face. Darland talked to the graveyard shift foreman, who had conducted the preshift examination for the day shift, and was told that no safety problems were detected. The belt tailpiece was moved up and mining started at approximately 8:00 a.m. Approximately 2.5 face passes were mined prior to the accident.

At about 9:30 a.m., Thomas Emmons, victim and tailgate shearer operator, and James Blue, headgate shearer operator, completed the face cut into the tailgate with the Joy 4-LS shearer. Emmons stood on the toe of the No. 76 shield and turned the shearer drum cowl over to start tramming the shearer to the headgate. Donald McGovern, longwall faceman, stood behind Emmons on the toes of the Nos. 76 and 77 shields. Suddenly without warning, a loud pop, described as similar to a gun going off, was heard. Emulsion oil began to spray all over and the high pressure emulsion hose and fitting whipped back and forth in the shield walkway. The hose and fitting struck Emmons in the face, causing fatal injuries.

McGovern was knocked into No. 77 shield. Witnesses stated that the hose and fitting whipped around in the walkway for three to four seconds before the pressure bled off and the pressure cut-out switch shut down the main hydraulic pumps.

Miners in the area called for the first aid supplies and backboard which were kept near the headgate. First aid was administered to Emmons and McGovern, and Emmons was placed on the backboard stretcher. Both miners were transported to the surface by underground ambulance. They were transported by ambulances to the Paonia Medical Center and then to the Delta County Memorial Hospital in Delta, Colorado where Emmons was pronounced dead. McGovern was examined, treated for minor injuries, and released from the hospital.

INVESTIGATION OF THE ACCIDENT


MSHA inspector, Danny C. Cerise, was at the mine when the accident occurred and inspector William E. Vetter arrived shortly afterwards. Cerise issued a Section 103(k) order at 10:15 a.m., December 4, 2000, to ensure the safety of all persons until an investigation could be conducted. Cerise, Vetter, and company officials traveled underground to the accident site to secure the area and to conduct a preliminary investigation.

The MSHA accident investigation team assembled at the MSHA Delta, Colorado office on December 5, 2000. Jerry O.D. Lemon, Coal Mine Safety and Health Inspector from Price, Utah was assigned as the lead investigator. The investigation team consisted of Sarah A. Perry, Coal Mine Safety and Health Specialist from the Denver, Colorado District 9 office; Ronald Medina, Technical Support Mechanical Engineer from Triadelphia, West Virginia; and Anita L. Goodman, Educational Field Services Specialist from Delta, Colorado.

The on-site investigation started at the mine on December 6, 2000. A joint investigation was conducted by MSHA, the Colorado Mine Safety and Training Program, and the Gunnison County Sheriff's Department. Management and miners from Oxbow Mining, Inc. cooperated and participated in the investigation. A list of those persons participating in the investigation is contained in Appendix A.

Interviews with witnesses and mine personnel were conducted at the mine on December 6, 2000. A list of those persons interviewed is contained in Appendix B. The interviews were not tape recorded. Notes of the interviews were taken by the investigators.

The Section 103(k) order was terminated by Inspector Lemon at 11:00 p.m., December 6, 2000, following an examination of the longwall face to inspect the guards, chains, and strain clamps that were installed to prevent a similar accident.

DISCUSSION

1. GENERAL INFORMATION: The 77 shield longwall was approximately 500 feet in width. The shields and face conveyor were manufactured by DBT America, Inc. (DBT), formerly Mine Technik America, Inc. (MTA). Hydraulic pressure for the longwall was supplied by three Type 3K200153, Hauhinco pumps. Each pump was driven by a 250 Horsepower, Type CJ5B Louis-Allis electric motor. During normal operation, two pumps ran, with the third being on standby. Hydraulic pressure was supplied to both the tailgate and headgate ends of the longwall. The 1�-inch hydraulic hose that struck the victim was the pressure supply line for the tailgate end of the longwall. This line had been added to the longwall by Oxbow personnel on November 7, 2000, and was not part of the original assembly provided by the manufacturer. As originally supplied by the manufacturer, only the headgate end of the longwall was provided with a pressure supply line. Oxbow personnel stated that the tailgate supply line was added to improve hydraulic pressure and flow at the tailgate end of the longwall.

   The 12 North longwall started production on November 8, 2000. The mining height on the longwall face was approximately 11 feet. The shearing machine was a Joy Mining Machinery (Joy) Model 4-LS, double cutterhead shearer, which was operated by radio remote control.

   At the start of the shift on December 4, 2000, the shields and face controls were put on shearer automation. Two representatives from DBT and one from Joy were on the longwall face at the time of the accident.

2. PUMP PRESSURE: The pumps were operated during the investigation and the supply pressure was found to cycle between approximately 4,000 psi and 4,400 psi. The Operating Manual for the support shields states that the nominal working pressure for the shields is 4,640 psi, plus/minus 10%. It was reported that the hydraulic pressure at the time of the accident was approximately 4,250 psi to 4,500 psi. The rated flow rate from each pump, at this pressure, is 82 GPM. The pumps were provided with an automatic shutoff system.

   If a large pressure drop occurred (such as if a line broke) a pressure switch was designed to automatically sense the pressure drop and cut power to the electric pump motors. The pressure switch was located in the pump station manifold outlet.

3. RING MAIN: The hydraulic pressure supply to the tailgate was carried by a 2-inch diameter specially designed steel pipe with flexible joints that ran the length of the conveyor panline. This line is commonly referred to as the ring main. A 1�-inch inside diameter (ID) Dayco, Eastman Coal Master Iron Clad Mine Hose, CM 4HP20, with a rated working pressure of 5,000 psi, approximately 15 feet long was connected to the end of the pipe near the tailgate. This 1�-inch hose terminated at a junction block located near the base of the conveyor at the tailgate end of the longwall and was secured to the conveyor with a chain.

4. HYDRAULIC CONNECTIONS FROM THE JUNCTION BLOCK TO THE SHIELDS: The hydraulic connections for the tailgate pressure feed line from the junction block to the main shield pressure line, consisted of the following:

   a) A Dayco 1�-inch ID, 7-foot long, Eastman Coal Master Iron Clad Mine Hose, with a 5,000 psi rated working pressure (hose 1).

   b) Hose 1 was coupled to a second 7-foot long hose section (hose 2) of the same type. The other end of hose 2 was connected to a series of fittings that ultimately connected to the inlet of a backflush filter. The fitting that broke was the �-inch female by 1-inch male Dayco staple lock fitting that entered the backflush filter inlet port. The complete series of fittings from the end of hose 2 to the backflush filter inlet consisted of the following staple lock fittings: 1�-inch female by 2-inch male; 2-inch female by 2-inch female; 2-inch male by �-inch male; and lastly the �-inch female by 1-inch male fitting (this is the one that broke). These fittings are referred to as steel clip fastener fittings by SAE convention. They are commonly referred to as staple lock fittings.

   c) Exiting from the backflush filter were additional fittings and a manual shut off valve. The total length of the series of fittings, including the backflush filter and shutoff valve, was 34� inches, as installed in the mine. The backflush filter was a rectangular box measuring 7 inches by 5� inches by 1� inches. The series of fittings on the inlet side was 10� inches long and the series of fittings (including the shutoff valve) on the outlet side was 17 inches long.

5. FAILED FITTING DESCRIPTION: The broken fitting was manufactured in England by Stecko, which is a part of Dayco Europe Limited and was distributed in the United States by Dayco. A design drawing of the fitting was obtained from Dayco Europe (Drawing No. 681 3101 651 1100 dated 24/02/89). The broken fitting was measured and found to conform with the drawing. It is common industry practice to use this type of fitting in high pressure longwall installations such as at the Sanborn Creek Mine.

6. METALLURGICAL EVALUATION: The broken �-inch female by 1-inch male Dayco fitting was metallurgically examined at the Touchstone Research Laboratory, Ltd., located in Triadelphia, West Virginia, to determine the nature of the failure. Touchstone is an independent laboratory. The fracture surface of the fitting was examined by a Touchstone metallurgist using a scanning electron microscope. The microstructure was examined, Rockwell Hardness tests were conducted, and an elemental analysis of the fitting was conducted.

   After evaluating the failed fitting, the Touchstone metallurgist, H. L. Stauver, concluded that:

   a) The elemental analysis did not demonstrate any obvious material defect in the failed fitting.

   b) The Rockwell hardness tests indicated a tensile strength of 78,000 psi. This would meet or exceed the requirements for tensile strength specified in SAE J1467 Jun 93. (SAE J1467 Jun 93 covers requirements for steel clip fastener fittings intended for use in hydraulic systems in mining applications such as longwalls.)

   c) The microstructure did not show any anomalies that would explain the failure.

   d) It was H. L. Stauver's belief that the fitting failed as a result of a bending force large enough to cause the fracture to occur as a single event.

   A copy of the complete Touchstone report is contained in Appendix D.

7. PHYSICAL EXAMINATION: The following observations of the 34�-inch long series of fittings, including the backflush filter and shutoff valve, indicated that the broken fitting and other components in the assembly had been exposed to a bending load.

   a) The shoulder of the broken fitting section that remained in the inlet side of the filter was mushroomed and shiny at the lower edge, where the swivel collar would have contacted it; if subjected to a downward bending load. The top inside diameter of this fitting was also marred (opposite to the mushroomed side) where the male fitting connecting to it would have contacted the fitting, if it had been subjected to a bending load in the downward direction. At MSHA's request, photographs of this deformation were included in the Touchstone report.

   b) The male end of the fitting that was mated to the broken fitting was visibly bent. This fitting was attached to the hose that whipped violently.

   c) The fitting attached to the outlet side of the backflush valve was removed and examined and it also was visibly bent.

8. STRESS DUE TO INTERNAL PRESSURE: The thickness of the fitting wall, where it broke, was 0.11 inches and the inside diameter was 0.95 inches. The stresses on this area of the fitting due to the normal 4,400 psi internal working pressure were calculated. The tensile load on the fitting in the longitudinal direction due to the internal pressure was 8,400 psi and the tensile load in the circumferential direction was 18,700 psi. The 8,400 psi tensile load in the longitudinal direction (this is the direction in which the fitting failed) was well below the 78,000 psi tensile strength of the fitting.

9. SUPPORT METHOD FOR THE BACKFLUSH FILTER: In the mine, the backflush filter, shutoff valve, and series of fittings were supported with chains attached to the underside of the No. 74 support shield. The two chain loops were approximately 36 inches apart where they were attached to the shield. One chain loop supported the inlet side of the assembly and a second chain loop supported the outlet end of the assembly. The chain loops were free to slide back and forth on the assembly. This arrangement had reportedly been in place for approximately a month, having been installed on November 7, 2000, and the accident occurred on December 4, 2000. The inlet and outlet of the assembly were connected to 1�-inch hydraulic hoses that draped down on both sides. This allowed bending loads to be applied to the assembly when the hoses moved or forces were applied to the hoses such as: hose flexing due to normal pressure fluctuations, a downward force applied to the hose due to a falling object, a downward force applied to the fittings due to the weight of the hose, hose movements caused by relative movement between the shields and the conveyor, and manually operating the handles of the shutoff valve and backflush filter.

   The cumulative effect of these repetitive forces and motions eventually caused the fitting to fail.

10. BACKFLUSH FILTER: The backflush filter was a Unitech Model 4UC 3070 004 filter. According to the DBT Operating Manual for this longwall, one of these filters is to be installed on each shield to provide filtration for the hydraulic fluid used by a single shield. As installed in the tailgate pressure feed line, it was filtering fluid for multiple shields. The maximum rated flow rate for the backflush filter was 52 GPM and the total flow rate from the two hydraulic pumps supplying the longwall was 164 GPM. (The 164 GPM flow rate would be divided between the headgate pressure feed line and the tailgate pressure feed line.) According to the longwall manufacturer, DBT, the backflush filter may have created a flow restriction, however this would not result in any kind of structural failure of the filter. A specification sheet for the filter states that its maximum working pressure is 5,075 psi and its maximum rated flow rate is 52 GPM.

   The Unitech Model 4UC 3070 004 backflush filter had a 1-inch inlet size requiring the 1�-inch hydraulic hose from the ring main to be attached through reducers. The �-inch fitting that broke was the most restrictive fitting in the series entering the backflush filter. The pump circuit was provided with a pressure switch, in the pump station manifold outlet, that cuts power to the electric pump motors when a large pressure drop occurs, such as when a line breaks. Witnesses to the accident stated that after the fitting broke, the hose whipped for three to four seconds, before the pressure bled off and the pressure cut-out switch shut down the main hydraulic pumps.

11. The fitting that failed was located at No. 74 shield approximately 6 feet above the walkway. After the failure, approximately 15 feet of 1�-inch high pressure hydraulic hose became loose and whipped around in the walkway area. A combination of fittings on the end of the loose hose weighed approximately 15 pounds.

12. After the accident, all high pressure hydraulic emulsion hoses, running from shield to shield, were placed in protective boots and were secured to other hoses with plastic tie wraps. At the headgate and tailgate where the high pressure hydraulic emulsion hose crossed over the longwall walkway, special bretby was installed over these hoses and secured with large plastic tie wraps. The entire unit was chained securely to the underside of the shield canopy.

   The ends of these hoses, where they joined the main line, were secured with special double chain hose clamps to keep the hose from whipping out of control in the event that another fitting failed.

CONCLUSION


The direct cause of the accident was the failure of a �-inch female by 1-inch male Dayco staple lock fitting in the tailgate high pressure emulsion feed hose. This fitting failed due to faulty support of the high pressure emulsion hose, fittings, backflush filter, and shutoff valve located over the walkway at the No. 74 shield in the longwall tailgate. The method of routing and supporting the hose allowed an excessive external bending load to be applied to the fittings. The cumulative effect of repetitive internal and external forces and motions due to this method of installation eventually caused the fitting to fail. The absence of any clamps or restraints on the pressurized emulsion hose allowed it to break free and whip violently, resulting in the fatal injury. A metallurgical evaluation of the failed fitting by an independent testing laboratory did not detect any material defects.

ENFORCEMENT ACTIONS


1. A Section 103(k) Order (No. 7267103) was issued to the mine operator on December 4, 2000, to ensure the safety of all persons in the mine until an investigation could be completed and the mine deemed safe. This order was terminated on December 6, 2000, at 11:00 p.m.

2. A 104(a) Citation (No. 7615244) was issued to the operator for a violation of 30 CFR 75.1725(a). The citation stated, "The high pressure emulsion hose, backflush filter, shutoff valve, and fittings at the tailgate of the 12 North longwall were not installed and maintained in safe operating condition. The method of routing and supporting this equipment over the walkway at the No. 74 shield allowed an excessive external bending load to be applied. This equipment was installed near the center of the walkway about head high and was hung loosely from the bottom of the shield by two �-inch chain slings. The cumulative effect of repetitive internal and external forces and motions, due to this method of installation, eventually caused one of the fittings, a �-inch female by 1-inch male Dayco staple lock, to fail. The absence of any clamps or restraints on the pressurized emulsion hose allowed it and a series of fittings weighing about 15 pounds to break free and whip violently, resulting in a fatal injury to the tailgate shearer operator on December 4, 2000."

Appendix E

Related Fatal Alert Bulletin:
 FAB00C34




APPENDIX A


OXBOW MINING, INCORPORATED OFFICIALS
James Cooper .......... Vice-President of Operations
Randy Litwiller .......... Superintendent
Joseph Ternyik .......... Longwall Coordinator
Robert Koch .......... Chief Engineer
Kevin L. Lee .......... Longwall Maintenance Foreman
Terrance Hayes .......... Safety Director
Kevin Swisher .......... Longwall Supervisor
Peter Darland .......... Longwall Supervisor
Fred English .......... Assistant Safety Director
OXBOW MINING, INCORPORATED EMPLOYEES
Donald McGovern .......... Longwall Faceman
Robert Geisler .......... Longwall Faceman
Ray Kennedy .......... Crib Setter
Brandon Lindsey .......... Longwall Tailpiece Operator
William Chesnik .......... Longwall Headgate Operator
James Blue .......... Longwall Shearer Operator (Headgate)
Rick Gentzler .......... Crib Setter
Joseph White .......... Longwall Faceman
STATE OF COLORADO, MINE SAFETY & TRAINING PROGRAM
William C. York-Feirn .......... Program Coordinator
John C. Barton .......... Inspector/Trainer
GUNNISON COUNTY SHERIFF'S DEPARTMENT
Ian Clark .......... Deputy Sheriff
MINE SAFETY AND HEALTH ADMINISTRATION
Jerry O.D. Lemon .......... Coal Mine Safety & Health Inspector Lead Investigator, Price, UT
Sarah A. Perry .......... Coal Mine Safety and Health Specialist, Denver, CO
Ronald Medina .......... Mechanical Engineer, Technical Support Triadelphia, WV
Anita Goodman .......... Training Specialist, Educational Field Services, Delta, CO
APPENDIX B


List of persons interviewed:

OXBOW MINING, INCORPORATED
Joseph Ternyik .......... Longwall Coordinator
Kevin Swisher .......... Longwall Supervisor
Peter Darland .......... Longwall Supervisor
Fred English .......... Assistant Safety Director
Donald McGovern .......... Longwall Faceman
Robert Geisler .......... Longwall Faceman
Ray Kennedy .......... Crib Setter
Brandon Lindsey .......... Longwall Tailpiece Operator
William Chesnik .......... Longwall Headgate Operator
James Blue .......... Longwall Shearer Operator (Headgate)
Rick Gentzler .......... Crib Setter
Joseph White .......... Longwall Faceman