This International Standard provides a standard procedure for assessing and modifying performance of solids control equipment systems commonly used in the field in petroleum and natural gas drilling fluids processing.This procedure is not intended for the comparison of similar types of individual pieces of equipment.This Standard specifies a different labelling requirement for shale shaker screens that will be permanently attached to the screen. It also covers the marking of shipping containers for shale shaker screens.This International Standard provides a standard procedure for quick assessment of a solids control screen sizing. The method can be used in the field or laboratory for identification of an unknown screen approximate size rangeThis edition of RP 13C is the modified national adoption of ISO 13501, Drilling fluids processing equipment evaluation.