Specifies the methods to be applied for the calibration and routine performance checking of ultrasonic flaw detection equipment and lays down the occasions, or intervals, at which these operations shall be performed. Also specifies the levels to which calibration and routine performance checks shall be documented. Applies to ultrasonic equipment used for manual NDT, and purchased to the relevant ESI Standard. Covers single and twin crystal probe of 1-6 MHz nominal frequency, used in conjunction with portable battery or mains powered A-scan flaw detectors. It is primarily intended for application to contact probes, but may also be applied to gap scanning probes subject to some limitations.