The Role of the DOT in Ultrasonic Examination
DOT Special Permit
Ultrasonic Examination of High Pressure Cylinders is covered under DOT 49 CFR. The DOT requires that you obtain a Special Permit for the Ultrasonic Examination of Cylinders. Through this Special Permitting Process, the DOT sets limits on what defects must be detected by the UE System and what size of defect is acceptable and what must be rejected according to defect sizes and other factors. This is done through the use of Calibration Cylinders.
UE System Calibration
The DOT requires the Ultrasonic Examination System be calibrated at least once every four hours or after 200 cylinders have been tested, and whenever there is a major cylinder-size change. The system is calibrated using DOT approved Calibration Cylinders. Every calibration standard must have a representative flaw against which to assess a thin-wall area, pitting, transverse and longitudinal cracks, and linear defects at the side-to-base transition area (the section at which the side wall grows thicker at the bottom of the cylinder).
System Operator Certification Requirements
The DOT also requires that the system is operated by individuals trained and certified in the use of Ultrasonic Examination equipment. UE System operators are required to have a minimum of an ASNT Level I UT certification. Level I Certified operators must be supervised by a resident ASNT Level II UT Certified individual.
Senior Review Technologist (SRT)
The DOT further requires that each Ultrasonic Examination location be supervised by a Senior Review Technologist (SRT). The SRT is required to be ASNT Level III UT Certified. The SRT may be either an employee, contractor or consultant.
The SRT is responsible for the training and certification of the UE System operators and for ensuring that the Ultrasonic Testing is being carried out in a manner that is consistent with the DOT Special Permit. The SRT is required to make formal submissions to the DOT on an annual basis which details the individual test results of all UE testing.
