Also, such end of life techniques do not allow any differentiation between the good tubes. Early detection of underutilized tube life can prevent the lost opportunity on both unrealized production through running them too cool and tube life giveaway if good tubes are discarded prematurely. Tubes in furnaces, reformers, etc. undergo creep strain, in the form of diametrical growth, from the first day that they are fired. The ability to accurately measure and record this growth means that the tubes condition can be monitored from day one. Therefore, not only can individual tubes be retired from service at an appropriate time, but also the component as a whole can be assessed for performance.
Manual measurements are too time consuming to provide more than a few readings per tube.
Furthermore, neither way can provide diametral growth data at or through the furnaces or reformers refractory. External measurements are inherently less precise as they are based on a crude surface rather than the internal surface and do not take into account the effects of oxide shedding. Process plants in New Zealand, South America, Canada, and the United States have successfully used the laser profilometry method. Whenever furnace, reformer, etc. Use of laser profilometry allows mapping and quantification of a tube s ID as several hundred thousand diameter readings can be acquired down its length.