Section 123. Jurisdiction of board to be continuing

The  power  and
  jurisdiction of the board over each case shall  be  continuing,  and  it
  may, from time to time, make such modification or change with respect to
  former findings, awards, decisions or orders relating thereto, as in its
  opinion  may  be  just,  except that, where the employer has secured the
  payment of compensation in accordance with  the  provisions  of  section
  fifty  of  this chapter, no claim for compensation or for death benefits
  that has been disallowed after a trial on the merits, or that  has  been
  otherwise  disposed  of  without  an award after the parties in interest
  have been given due notice of hearing or hearings and opportunity to  be
  heard  and  for  which no determination was made on the merits, shall be
  reopened after a lapse of seven years from the date of the  accident  or
  death.  Nor  shall  any  award of compensation or death benefits be made
  against the special fund  provided  in  section  twenty-five-a  of  this
  chapter or against an employer or an insurance carrier where application
  therefor  is  made  after a lapse of eighteen years from the date of the
  injury or death and also a lapse of eight years from  the  date  of  the
  last payment of compensation.