How to read your cylinder’s stamps

The markings on a cylinder’s shoulder are its identity document. Learn to read them and you can verify any cylinder is rated, legal and safe to fill — essential before buying used.

5 min readEN 1964 markings

Key takeaways

The shoulder shows working pressure, test pressure, water capacity, maker/standard and test date.
Test pressure is typically 1.5× working pressure (348 bar for a 232).
An expired hydrostatic test date means a commercial station can’t fill it.
Always read the stamps before buying a used cylinder.

Everything is stamped on the shoulder

Steel cylinders are marked to EN 1964, and that marking is the first thing to check before buying or filling one. It’s stamped into the metal at the shoulder, just below the valve. Here’s what each part means.

Manufacturer & standard — the maker’s mark and EN 1964
Working pressure — the maximum fill pressure (e.g. 232 bar)
Test pressure — the hydraulic test, typically 1.5× working
Water capacity — the volume in litres
Hydro test date — the date of the last hydrostatic test
CE mark — conformity for sale in the EU

Shoulder stamp · decodedEN 1964

Maker / standardCrMo · EN 1964

Water capacity12 L

Working pressure232 bar

Test pressure348 bar 1.5×

Last hydrostamped date

CE marked · retest typically every 5 years

The two numbers that keep you legal

The working pressure tells you how much you can fill the cylinder — and never to exceed it. The test date tells you whether it’s currently within its inspection interval. Steel cylinders are hydrostatically retested on the EN 1964 schedule — typically every five years — with a visual inspection in between. A cylinder past its test date can’t be filled at a commercial station until it’s retested.

Buying used Before you buy a second-hand cylinder, read the stamps: confirm the working pressure matches your fill station, check the last hydro date isn’t expired (and budget for a test if it’s close), and make sure the markings are legible and unpainted. A cheap cylinder that needs an immediate hydro and visual isn’t cheap.

Don’t obscure them

Never paint over, grind or cover the shoulder stamps. They’re the legal record of the cylinder’s rating and test history — an inspector or fill operator needs to read them, and an unreadable cylinder won’t get filled.