This document specifies the general requirements, test unit parameter design, operation parameters, water quality and contamination, parameters to be evaluated in pilot test units, design and operation of pilot test device, etc., to be followed in the pilot test evaluation of corrosion and scaling additives in open circulation cooling water systems. This part of ISO 16784 covers the criteria that must be defined and implemented in a pilot scale testing programme to select water treatment programmes for use in specific recirculating cooling wáter systems. This part of ISO 16784 covers only open recirculating cooling water systems. Closed cooling systems and once through cooling water systems are specifically excluded. This part of ISO 16784 applies only to systems incorporating shell and tube heat exchangers with standard uncoated smooth tubes and cooling water on the tube side. Heat exchangers with shell side water, plate and frame and/or spiral heat exchangers, and other heat exchange devices are specifically excluded. However, when the test conditions are properly set up to model the surface temperature and shear stress in more complex heat transfer devices, the test results may predict what may occur in an operating heat exchanger of that design. The test criteria established in this part of ISO 16784 are not intended to govern the type of bench and pilot scale testing normally carried out by water treatment companies as part of their proprietary product development programmes. However, water treatment companies may choose to use the criteria in this part of ISO 16784 as guidelines in the development of their own product development test procedures.