Improper venting of the evaporator tube nests causes either an accumulation of air in the tubes, with a loss of capacity, or an excessive loss of tube nest steam to the distilling condenser, with loss of economy. Troubles of this type usually result from improper operation rather than from material failures.

Scale Deposits on Evaporator Tubes

Until 1958, scale deposits on evaporator tubes had been one of the more serious causes of operating difficulties. In 1958, a new compound was authorized for treatment of evaporator feedwater. The new compound PD-8 evaporator treatment is far superior to the cornstarch-boiler compound formerly used. For details on PD-8 and its use, refer to the applicable chapter in Engineman 3 & 2, NAVEDTRA 10541 (current edition).