By Steve Fiscor, Editor-in-Chief
A little more than nine months after the explosion occurred at Massey Energy’s Upper Big Branch (UBB) mine, officials from the Mine Safety and Health Administration (MSHA) provided the families of fallen miners with an update on its investigation into the tragedy. During a press conference the following day, MSHA outlined a number of factors it believes at this time in the investigation caused the explosion. Investigators said a gas ignition from a small methane cloud on the longwall face near the tailgate propagated into an explosion fueled by non-compliant coal dust accumulations throughout the mine. Investigators attached a high pressure water line to the shearing machine and demonstrated that the water sprays were not working properly and noted the bits were not properly maintained.
MSHA Director Joe Main said he had hoped to hold this briefing in early December, but the investigation had been delayed. Water had to be pumped from two sections of the mine involved in the explosion so investigators could enter those areas. A second problem was encountered installing the water lines to the shearer to test the sprays. “We also had to issue an impeding violation to Massey Energy to help move the investigation along,” Main said.
Post explosion conditions in the mine at the time made it unsafe for investigators to enter certain areas and remedying the situation took considerable time. Investigators were unable to begin work until late June. “Other things occurred that do not normally occur with investigations of this type,” Main said. “From the outset, there was a legal challenge to investigative procedures, which turned the process into one that engaged the courts. Additionally, the president had asked the Department of Justice (DoJ) to get involved early in the investigation.” More recently, the DoJ asked MSHA to delay public hearings and the release of transcripts that would interfere with its investigation.
The investigation into the UBB explosion is not complete and it continues. “We informed the families last night during a lengthy meeting,” Main said. “We are going to try to put together the issues to explain the technical parts of what caused the UBB explosion. I have asked the investigative team to complete that within the next 60 to 90 days.”
Kevin Strickland, MSHA’s administrator for coal mine safety, walked journalists through the same presentation the agency shared with the families, which is available on the MSHA Web site (www.msha.gov).
The UBB explosion took place April 5, 2010, at the end of the day shift. The accident investigation began April 12, 2010. The underground physical investigation began June 25, 2010.
MSHA investigators interviewed 261 people as of January 18, 2011. A total of 18 individuals have exercised their 5th Amendment rights. “The majority of the continuing interviews will be call backs,” Strickland said. “Now that we have been underground, there are specific questions we need to ask people that have already been interviewed.”
More than 100 MSHA personnel have been used during the on-site investigation. An additional 45 technical support personnel were performing tests and other technical activities. “We asked them to look at 250 electrical components gathered from the explosion,” Strickland said. “We have also manned the portals 24-7 with field service personnel to make sure everything was guarded during the investigation.”
Events Leading to the Accident
The 1 North Development was the headgate and tailgate entries for the longwall panel that was mining at the UBB mine at the time of the explosion. “Initially this area was developed for room-and-pillar mining,” Strickland said. “There was problem with this longwall at another Massey Energy mine. A decision was made to bring the longwall from that mine to the UBB mine and convert this section into a longwall panel. There were some ground control issues that occurred in the headgate entries, and now we have some issues in the tailgate entries as well. Floor heave, water, rib spalling created issues with ventilation system.”
On the weekend prior to the explosion, the continuous miner sections did not cut coal, but the longwall produced coal on Saturday (April 3, 2010). The entire mine sat idle Easter Sunday (April 4, 2010). On the shift prior to the explosion, the longwall third shift (midnight shift) was a maintenance shift (no production). Some welding and cutting activities took place and various items remain under investigation.
The first call out from underground on the longwall day shift (April 5, 2010) occurred at 7:30 a.m. The longwall ran until 11:00 a.m. and had made two passes. The longwall was down from 11:00 a.m. to 2:15 p.m. The last call out was at 2:30 p.m. from longwall face personnel saying the shearer was located at shield 115 going toward the tailgate. This longwall had 176 shields on the face. So between 2:30 until the time of the explosion, shortly after 3:00, the longwall crew had mined to shield 176 or the tailgate.
In addition to the 2:30 p.m. call out, there was a pre-shift report called out at 2:40 p.m. That call indicated 56,000 cubic feet per minute (cfm) of air entering the longwall face with the velocity entering the headgate of approximately 700 fpm and a tailgate air velocity of 513 fpm. The report also indicated 0% methane.
Methane Ignition & Dust Accumulations
Part of the investigation involves simulating the ventilation conditions just prior to the explosion. That will be more difficult because mine maps were not up to date. During the investigation, underground mapping teams were asked to inspect the perimeter of the mine entries, looking for remnants of concrete, Strickland explained. “That would tells us that at one time there was a stopping or a regulator at that location,” Strickland said. Determining which ones exactly were in place at the time of the explosion will be difficult.
An examination of the belt conveyors included a number of notations indicating that belt entries needed to be rock dusted. MSHA took 1,800 dust samples underground. Approximately 80% of the samples were noncompliant.
“It appears—in MSHA’s opinion—a low volume of methane and/or methane from natural gas provided the fuel for the initial ignition on or near the face of the tailgate end of the longwall,” Strickland said. “In the investigation team’s opinion, the body of methane that provided the initial fuel for the ignition was as small as 13 cu ft.”
The investigators do not believe an explosion occurred immediately. “The personnel operating the shearer when the ignition occurred had the time to move from that location to mid-face where we found all of the bodies,” Strickland said. Investigators believe it would have taken the miners 70 to 90 seconds to scramble 400 to 500 ft through the longwall system.
“There is no evidence to date of flame on the tailgate end of the longwall face,” Strickland said. “There is no evidence to date of coking on the tailgate end of the longwall face.” These two facts build a case for a small of amount of methane being ignited, Strickland explained.
“To date, the analysis of the evidence shows that a small methane/methane from natural gas ignition transitioned into a massive coal dust explosion,” Strickland said. “This was not a massive methane explosion.”
Looking for a possible ignition source, investigators collected and inspected 250 pieces of electrical components. “We did not find any electrical ignition sources that could have created this explosion,” Strickland said.
Without an electrical ignition source, investigators turned their attention to potential frictional ignition sources. “Right now, we think the most likely source was the longwall shearer,” Strickland said. “Although we haven’t ruled out roof falls or the panline chain conveyor, the most likely source, according to the investigative team, is the longwall shearer. A couple of factors led us in that direction: worn bits and missing water sprays.”
Investigators plumbed 150 psi water to the tailgate drum. Strickland showed a video of the UBB shearer with high pressure water connected to it (www.msha.gov). “That would be enough for each of the 48 sprays to reach 90 psi, the minimum required by the plan,” Strickland said. The video shows a number of sprays missing. The flow coming from a couple of the sprays looks like a garden hose while several of the sprays are clearly not working.
Sprays serve two purposes: dust control and to quench the frictional ignition sources. The bits were extremely worn. “It’s important to have well maintained bits and water sprays,” Strickland said. “Ignitions do occur. Fortunately in most cases there are safety mechanisms in place to prevent the ignitions from becoming an explosions.”