Accepting estimates of electrical output from a welding  machine from experts representing MSHA and a mine  operator, an MSHA judge nevertheless turned to reference  literature to determine if contact with that current was  likely to produce a serious injury.

Administrative Law Judge Priscilla Rae upheld a violation of  MSHA’s electrical standard against River View Coal, LLC at  its mine of the same name in Kentucky.  The citation was  written in August 2012, after an inspector observed bare  wires on the electrode holder of a welder mounted on a  two-person diesel-powered mantrip. A mantrip is a shuttle  for transporting miners underground, and an electrode  holder is an insulated clamp that holds the welding rod in  place during welding. 

In court, MSHA’s expert witness and counsel for River View  jointly calculated the current a miner would experience if  he or she touched the bare electrode.  That calculation, coupled with another offered by River View’s expert, led  both sides to agree the range of the current would be  between 28 and 35 milliamperes (mA).

However, they could not agree on the impact that current  would have on the human body.  MSHA asserted the  shock could affect the heart and/or produce an injury from  a miner's involuntary reaction to being shocked. That conclusion had led the agency to classify the violation as  significant and substantial (S&S), i.e., one likely to produce  serious injury.  Conversely, the operator asserted a miner  would feel only a tingle.

Both parties submitted reference materials. Faced with the  conflicting testimony, ALJ Rae turned to those materials for  guidance.  She noted that 300-500 mA would be needed  to affect the heart. In addition, the so-called let-go  threshold whereby the flexors of the arm contract but still  allow release of the hand from a shock hazard is 75 mA for  a 154-pound male.  Since the estimated 28-35 mA current  fell significantly below either the let-go or heart-damaging  level, Rae determined that serious injury was unlikely and  cut the S&S classification to non-S&S. 

MSHA also had written the ticket as representing  moderate negligence, but Rae said the operator’s safety  requirements and diligence in conducting weekly  examinations of electrical equipment justified only a  finding of a low level of negligence.  As a result, she cut  MSHA’s $687 fine to $125 in a decision released in July.