Kevin - The 473 went through a comprehensive (1472 Service Day) inspection that was completed on August 13, 2014. All tubes were removed, the boiler surveyed and a recalculated Form 4 was done at that time. I am not sure how many service days it has accumulated since, but my guess is around 400 or so. In anycase, it is good until August 2029 or 1472 service days, whichever comes first.
The boys in the shop are probably doing some needed boiler maintenance, which in some cases requires changing out some tubes. Been there, dome that...
MD Ramsey