Which of the following is NOT a method for re-qualifying DOT cylinders?

The option that is not a recognized method for re-qualifying DOT cylinders is ultrasonic testing. Re-qualification of DOT cylinders ensures that they remain safe for continued use, and it typically involves methods that evaluate the structural integrity and performance of the cylinders.

Visual inspection is a commonly used method that involves examining the cylinder for any notable damage, corrosion, or other issues that could compromise safety. Hydrostatic testing is another widely accepted technique where the cylinder is filled with water and pressurized to check for leaks and measure expansion. The water jacket method involves placing the cylinder in a water bath to monitor for any leaks while it is under pressure.

Ultrasonic testing, while a valuable non-destructive testing method for other applications, is not standard for the re-qualification of DOT cylinders. This method uses high-frequency sound waves to detect flaws within a material but does not specifically meet the regulatory requirements set forth by the Department of Transportation for cylinder re-qualification. Understanding these distinctions ensures proper adherence to safety regulations and protocol.