How to read a marine cylinder before hydrotesting

Build a complete photograph set

Start with one full-length photograph showing the cylinder, valve and any protective boot or guard. Then photograph the permanent marks around the neck, shoulder or label area in overlapping frames so no part of the marking string is cut off. Use even light and take a second angle when curved metal creates glare.

Keep the photographs grouped per cylinder. For a large batch, place a removable numbered tag beside the cylinder and use the same reference in the equipment list. Do not stamp a new number, grind the surface or remove paint to make a mark easier to read.

Separate cylinder identity from test history

The original marking set commonly identifies the manufacturing specification or approval, manufacturer, serial number, service or working pressure and initial test information. Later requalification marks record inspection or test events under the applicable scheme. Their layout can differ, so do not assume every pair of digits is a month and year or that the newest-looking stamp is valid for the cylinder.

Copy each character exactly as it appears, including prefixes, suffixes and symbols. If a mark is unclear, label it unreadable in the request instead of completing it from another cylinder in the batch. The station needs the photograph because a transcription can lose the order and position of the marks.

Connect the cylinder to its onboard purpose

Tell the station whether the cylinder belongs to self-contained breathing apparatus, a fire extinguisher, a fixed suppression system, diving equipment or another installation. Include the contents or extinguishing agent where known, the cylinder material if documented and the equipment manufacturer and model.

This context matters because a similar-looking cylinder may follow a different inspection standard or service route. UK marine guidance, for example, separates recommendations for seamless steel, aluminium, composite and certain gas services. The correct route begins with the exact cylinder, not with a generic hydrotest interval.

Breathing apparatus: Dräger identification and service guide →

Show condition before deciding to move it

Photograph corrosion, dents, cuts, gouges, heat exposure, bulges, damaged threads, a questionable valve or deterioration of a composite wrap. Include the base and any surface normally hidden by a boot, harness or clamp. A photograph cannot prove internal condition, but it can reveal a reason for the station to ask for different handling or decline intake.

Organise a mixed batch before handover

Group cylinders by purpose and identical marking set, but keep an individual serial-number list. Record which complete equipment set each cylinder came from, particularly for SCBA units or fixed-system banks. Send the current service report or certificate and identify any unit that does not appear on it.

State the quantity, vessel, current location and required return date. If cylinders are part of an operational fire-suppression or breathing-air arrangement, plan how that capability will be maintained while the equipment is ashore.

Confirm the test route before transport

Send the photographs and register before moving the batch. The station will use the markings, material, use and condition to assess whether the cylinder falls within its capability and which inspection or test route may apply. A request is not an acceptance decision, and an old test mark does not guarantee that a cylinder can be requalified again.

Pressure cylinders and their contents can be regulated as dangerous goods during transport. Confirm the cylinder state, valve protection, packaging, carrier and route with the party responsible for transport. The station's service assessment does not replace those transport obligations.