When is a cylinder considered in service?

A cylinder is considered in service until it has a failed hydrostatic test because the hydrostatic test is a crucial assessment of the cylinder’s structural integrity and capacity to safely contain gases or liquids under pressure. These tests are designed to ensure that the cylinder is free from critical defects or weaknesses that could lead to failure during operation.

If a cylinder passes its hydrostatic test, it demonstrates that it can withstand the required pressure levels safely, making it suitable for continued use. Conversely, a failed test indicates that the cylinder has likely been compromised and is no longer safe for operation, thus removing it from service.

The other options do not address the standardized testing protocols that govern the safety and usability of cylinders. A cylinder that has been used up can still be viable until it is tested, while physical damage may not be immediately indicative of a failure. Similarly, cylinders may be permanently stored for various reasons but are not classified as in service until their integrity can be validated through testing.