This part of IEC 60609 serves as a basis for the formulation of guarantees on cavitation pitting on Pelton turbine runners and also for the measurement and evaluation of the amount of cavitation pitting on Pelton turbine runners of a given turbine, which is defined in the contract by power, specific hydraulic energy of machine (head), rotational speed, material, operation, etc. The sequence of clauses in this part of IEC 60609 is the same as in IEC 60609 (1978). The clauses on measurements and evaluation of the amount of cavitation pitting are practically identical to those of IEC 60609. Evaluation has to be based on the loss of material during a given time and under accurately defined operating conditions. Guarantees which restrict the extent of cavitation pitting and drop erosion on Pelton turbines at the end of an operating period specified in the contract are necessary when cavitation pitting is expected in all or in some operating ranges. Such guarantees should include limits for operation which are consistent with specified operating conditions.