Editing Paintball compressed-gas cylinder failures (section)

== Hydrostatic testing and cylinder rejection ==

Hydrostatic testing is a periodic requalification procedure used to determine whether a compressed-gas cylinder remains suitable for service.

The cylinder is subjected to a controlled test pressure, with its expansion and subsequent contraction measured against the applicable specification.[1]

Visual inspection and testing can identify defects including:

* Excessive permanent expansion
* Internal corrosion or pitting
* Cracks, dents or damaged cylinder threads
* Damaged composite fibres
* Leakage through the pressure-containing wall
* Other defects exceeding the applicable rejection limits

A cylinder may be rejected during preliminary inspection without undergoing the full hydrostatic pressure test.

Cylinders that fail requalification or meet condemnation criteria are removed from service. The procedure is a normal part of compressed-gas cylinder maintenance and is not limited to the individual cases described in this article.[1][9]

A cylinder described as '''out of hydro''' has exceeded its applicable requalification interval without passing a subsequent required test.

An expired test date does not itself prove that the cylinder has suffered structural damage. Conversely, a cylinder within its test period may still require removal from service if damage is discovered.

The testing interval depends on the cylinder's specification, approval, manufacturer requirements and jurisdiction.