Theoretical Stage This stage is created when vapor and liquid mix perfectly and then separate without entraining any drops of liquid into the vapor or retaining any foam in the liquid. Tray Efficiency A tray in a distillation tower will work at some percentage of efficiency compared to a theoretical stage. This is mostly a function of how well the vapor and liquid are mixed on the tray deck, and how well they are then separated. Gauge This is the thickness of metal. The smaller the gauge, the thicker the metal. Twelve gauge is about 0.1 in thick. Mesh This is the number of wires in a filter screen. The bigger the mesh, the finer the filter.
Flange I worked at Amoco Oil for nine years before I found out what is meant by a flange. It's the flat end of a pipe that is used to bolt up to a flange on another piece of piping. Bolts, with nuts at each end, are used to force the flanges together.
Expansion Loop Piping thermally expands as it gets hot. Allowance must be made for the growth in pipe length otherwise the pipe will break by cracking at its welds. We burned down a fractionator at the Good Hope Refinery because of such an omission. Spool Piece Piping is made in sections with flanges at each end.
This makes it easier to replace bad sections of pipe than if the piping sections were welded together though welded pipe is cheaper. Flange Rating Connections on vessels, spool pieces and valves have a pressure rating called a flange rating. This rating can be confusing—for example, a 150 psig flange rating is actually good for about 230 psig design.
