Existing methods of determining residual working life for vessels and plant usually deal with only some of the relevant factors [1]. Experience over many years of examining hundreds of them in the chemical and petrochemical industries has enabled the Irkutsk Chemical Engineering Research Institute to formulate basic principles for calculating residual life [2] and methods for the purpose, which incorporate the requirements of the regulatory documentation [3].The residual working life is determined from engineering diagnosis (examination). This extends to all the main components of a vessel: cylindrical and spherical bodies, planar and convex end sections, flanges and connections, convex and planar lids, compensators, and reinforcement around holes, for all of which calculations on the strength are performed in accordance with the documentation for the purpose and on the test pressures to be used as appropriate to the actual properties of the material, the wall thicknesses, and the corrosion rates. Calculations are also performed on the stability and on the wind and seismic loadings to be expected, the external pressure, and the supporting loads. If positive results are obtained from the examination and calculations, one can calculate the residual life.The methods of determining the life involve identifying the major damaging factors and evaluating the state of the vessel as affected by them. The working life of a vessel is considered as exhausted when it attains the limiting state defined by the standard criteria.Basic damaging factors:-corrosion and erosion; -cyclic load;-changes in metal characteristics; -creep; -cyclic loading under creep conditions; and -the danger of brittle failure. There may also be other factors such as hydrogen corrosion. We consider methods of calculating the working life subject to those factors. Forecasting Residual Working Life for Plant Subject to Corrosion and Wear (Erosion). The following defines the residual working life of plant subject to corrosion (erosion):Tres.c (Tres.e) = Sa -Sc KI K2"( 1 ) a where S a and S c are the actual and calculated thicknesses in mm of any wall; a is the rate of uniform corrosion (erosion wear) in mm/year; K 1 is a factor that incorporates the difference between the mean expected residual working life and the guaranteed life (with probability y = 0.7-0.95); and K 2 is a factor that incorporates the difference between the residual life defined with linear change in the relevant parameter (wall thickness) and the residual life calculated from a more exact (nonlinear) law for variation in that parameter.