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Hydrostatic test pressure for oxygen cylinders

Aviation Mechanic Airframe (AMA) practice question 15 of 15 on Environmental Systems. ACS element AM.II.G.K10 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA high-pressure oxygen cylinder certified for a rating of 1,800 psi is given a hydrostatic test. To what pressure is the cylinder pressurized during that test?

  1. A3,000 psi
  2. B2,400 psi, the pressure it can hold
  3. C1,800 psi, the rated value
Show the answer and explanation

Correct answer: A. 3,000 psi

  • A — correct A hydrostatic test pressurizes the water-filled cylinder to five-thirds of its certified rating: 1,800 x 5/3 = 3,000 psi.
  • B — incorrect Steel cylinders are capable of maintaining pressure up to 2,400 psi, but the hydrostatic test uses five-thirds of the certified rating instead.
  • C — incorrect Testing only to the rating would prove nothing beyond normal service pressure; the test deliberately exceeds it.

BACKGROUND

Gaseous oxygen is stored in high-pressure cylinders certified to Department of Transportation specifications, traditionally heavy steel tanks rated for 1,800 to 1,850 psi and capable of maintaining pressure up to 2,400 psi. To ensure serviceability, cylinders must be hydrostatically tested periodically, and in general the test consists of filling the container with water and pressurizing it to five-thirds of its certified rating, after which it must not leak, rupture or deform beyond an established limit. Most cylinders also have a limited service life, expressed as a number of filling cycles or a calendar age, after which they must be removed from service. Manufactured dates, certification numbers and subsequent hydrostatic test dates are stamped near the cylinder neck, while composite cylinders carry placards instead. Cylinders approved under DOT-SP-8162 have a five-year interval between hydrostatic tests, extended from the previous three years.

STUDY TIP

Memorize the five-thirds multiplier and practice it on the ratings you are likely to see, such as 1,800 and 1,850 psi. Also be ready for questions on where test dates are recorded, since composite cylinders use placards rather than stamping.

KEY POINTS

  • Hydrostatic test pressure is five-thirds of the cylinder's certified rating.
  • Common aviation cylinders are rated 1,800 to 1,850 psi.
  • Test dates are stamped near the neck, or placarded on composite cylinders.

SOURCES

  • sources/ama-airframe/ch16.txt "Oxygen Storage Cylinders"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.