High pressure cylinders in a water mist system must be discharged and hydro tested after how many years of continued use?

High pressure cylinders in a water mist system must be discharged and hydro tested after how many years of continued use?

• A. After 5 years
• B. After 10 years
• C. After 12 years
• D. After 15 years

Answer: (C)

Stored-pressure high‑pressure cylinders in water mist systems are kept in service only after periodic requalification testing. The reason for the 12-year interval is that a hydrostatic test checks the cylinder wall for fatigue, corrosion, or thinning that could lead to failure under sustained high pressure. Discharging the cylinder before testing ensures a safe test and allows inspection of the valve and connections. If the cylinder passes the hydro test, it is recharged and placed back in service; if it fails, the cylinder is condemned and replaced. This 12-year interval distinguishes water mist cylinders from some other types of cylinders that have shorter test intervals.

Stored-pressure high‑pressure cylinders in water mist systems are kept in service only after periodic requalification testing. The reason for the 12-year interval is that a hydrostatic test checks the cylinder wall for fatigue, corrosion, or thinning that could lead to failure under sustained high pressure. Discharging the cylinder before testing ensures a safe test and allows inspection of the valve and connections. If the cylinder passes the hydro test, it is recharged and placed back in service; if it fails, the cylinder is condemned and replaced. This 12-year interval distinguishes water mist cylinders from some other types of cylinders that have shorter test intervals.