How to Read a Cryogenic Tank Nameplate and Data Sheet

A cryogenic tank nameplate is the stamped or engraved plate on the outer vessel that records manufacturer, serial number, year of manufacture, capacity, maximum allowable working pressure, design temperature, test pressure, the code the vessel was built to and the service fluid. On a used tank it is the first thing to read and the first thing to verify against the documents.

The nameplate is the vessel's identity. Every certificate, every inspection report and every valve schedule in the file should trace back to the serial number on that plate. If they do not match, the paperwork does not belong to the tank in front of you.

This guide walks through the plate field by field, explains what each entry means in practice, and sets out how to cross check it against the document dossier when you are inspecting a second hand unit.

What is a cryogenic tank nameplate and where do you find it?

The nameplate is a metal plate attached to the outer jacket of the vessel, usually near the valve cabinet or on the shell at a readable height. On a vacuum insulated tank the plate must be on the outside, because the inner vessel it describes is sealed inside the vacuum space and cannot be inspected visually.

On transport equipment the arrangement differs. A semi trailer or ISO tank container carries the vessel plate plus transport approval markings, and an ISO container also carries its CSC safety approval plate and the frame identification. On a trailer the vessel data and the road vehicle data are separate records.

• Static tanks: plate on the outer shell or valve cabinet area
• Semi trailers and bobtails: vessel plate plus transport approval and periodic inspection markings
• ISO tank containers: vessel plate, CSC plate and container identification on the frame
• MicroBulk and smaller vessels: plate or engraved data on the jacket, sometimes under a cover

Before anything else, photograph the plate square on and in good light, with the serial number legible. That photograph is what you will compare against every document in the file.

What information is on a cryogenic tank nameplate?

Content varies with the code the vessel was built to, but a cryogenic tank nameplate normally carries the following. Read every line, and note anything that is missing rather than assuming it is unimportant.

• Manufacturer name and works or shop identification
• Serial number or works number, the unique identity of the vessel
• Year of manufacture
• Gross and net or usable capacity, usually in litres or cubic metres
• Maximum allowable working pressure, marked MAWP or PS, for the inner vessel
• Design temperature, minimum and maximum, marked TS on a PED plate
• Test pressure, marked PT, and the date of the pressure test
• The code and standard the vessel was built to, for example PED 2014/68/EU with EN 13458, or ASME Section VIII
• CE marking and the four digit notified body number on PED vessels
• Service fluid or permitted fluids, for example LIN, LOX, LAR, LNG, LCO2
• Empty weight, and on transport equipment the maximum gross weight
• Fluid group or hazard category where the code requires it
• Vacuum space data or annular space information on some designs

Note that the plate describes the vessel as built. It does not tell you the current condition of the vacuum, the valves or the relief devices. Those come from testing and from the maintenance record.

What do MAWP, design temperature and test pressure mean?

MAWP or PS

Maximum allowable working pressure is the highest gauge pressure the inner vessel is designed and certified to hold at its design temperature. It sets the pressure class of the tank and it is the reference for relief valve set pressure. You cannot raise it by changing a valve. If the MAWP is below the pressure your process needs, the tank is the wrong tank, regardless of price. Our guide to cryogenic tank MAWP and pressure class explains how to match it to a duty.

Design temperature or TS

The design temperature range confirms the vessel is qualified for cryogenic service. Low temperature service requires impact testing, normally Charpy V notch testing, of materials used below about minus 150 C, to guard against brittle fracture. A minimum design temperature consistent with the intended product is what tells you the material selection and testing were done for that service.

Test pressure or PT

Test pressure is the pressure applied during the manufacturing acceptance test, higher than MAWP by the factor the code specifies. The plate normally shows the value and the date. On a used vessel, compare this date with the year of manufacture and with any periodic inspection records in the file.

Gross and net capacity

Gross capacity is the geometric volume of the inner vessel. Net or usable capacity is what you can actually store, since a cryogenic tank is filled to a maximum level and leaves vapour space above the liquid. Size your supply against the net figure, not the gross figure. Our cryogenic tank sizing guide covers how that feeds into autonomy days and delivery frequency.

How do you read the code and notified body markings?

The code marking tells you which regulatory system the vessel was certified under, and that determines which markets will accept it. This is a compliance question, not a quality ranking. ASME is the US code, Section VIII. PED 2014/68/EU is the European directive, evidenced by CE marking. EN 13458 is the harmonised standard for static vacuum insulated cryogenic vessels and EN 13530 covers transportable ones.

• CE mark followed by a four digit number: the notified body that carried out the conformity assessment under PED
• PS, TS, PT and V markings: the PED convention for pressure, temperature, test pressure and volume
• EN 13458 reference on a static vacuum insulated vessel, EN 13530 on a transportable one
• ASME U stamp and National Board number on a vessel built to Section VIII
• AD 2000 reference on vessels built to the German technical rules
• Fluid group or category marking, which reflects how the code classifies the stored medium

A vessel built to one code does not automatically qualify in another market. If you are buying for export, establish the required code before you shortlist units. Our comparison of ASME and PED certification and our guide on choosing the code by export market both cover this decision.

For transport equipment there is an additional layer. Road tankers carry ADR related approval and periodic inspection markings, and the validity date of the tank inspection matters as much as the original certificate. See our article on ADR inspection for cryogenic trailers.

How do you cross check the nameplate against the document dossier?

This is the step that separates a real inspection from a walk around. Take the plate photograph and work through the file line by line. The serial number is the key that should appear on every document.

• Serial number on the plate matches the serial number on the manufacturer's data report or declaration of conformity
• Year of manufacture on the plate matches the certificate date and is consistent with the condition of the unit
• MAWP on the plate matches the MAWP in the certificate and matches the set pressure of the fitted relief valves
• Design temperature on the plate is consistent with the material and impact test records
• Test pressure and test date on the plate match the acceptance test record
• Notified body number on the plate matches the body named in the declaration of conformity
• Service fluid on the plate matches the product the tank has actually been used for, and matches the intended future service
• Capacity on the plate matches the general arrangement drawing and the level instrument calibration
• Any repair, modification or re certification record references the same serial number

Two mismatches deserve particular attention. First, relief valves whose set pressure does not correspond to the plate MAWP, which suggests either a substitution or an undocumented change of duty. Second, a service fluid on the plate that differs from the product the seller says it held. Changing service, especially into oxygen from another product, requires cleaning and documentation, not just a repaint.

Our used cryogenic tank safe buying checklist covers the full inspection sequence, and the certifications guide explains each document you should find in the file.

What does a missing or illegible nameplate mean?

A missing, painted over, corroded or replaced nameplate is a serious finding. Without a legible plate you cannot confirm the design pressure, the design temperature, the code or the identity of the vessel, and the pressure vessel documentation cannot be tied to the physical unit.

• Illegible or heavily corroded plate: ask for the manufacturer's records against the works number and for a re marking process through a competent body
• Painted over plate: it may be recoverable, but confirm the data before accepting the unit
• Plate removed or replaced with a non original plate: treat as unverified until traceability is re established
• No serial number anywhere on the unit: the documentation cannot be linked to the vessel
• Plate data that contradicts the certificates: stop and resolve before any commercial commitment

In some cases traceability can be restored. The original manufacturer may still hold records against the works number, and a competent inspection body may be able to re assess and re mark the vessel. That is a process with cost and lead time, and it is the seller's job to complete it, not the buyer's. If nobody can restore the identity, the vessel should be priced and treated as an unverified asset.

This is also why an as is purchase and a refurbished purchase are not the same transaction. Our comparison of refurbished and as is cryogenic equipment explains what each level of preparation actually includes.

What should you record during a used tank inspection?

Build a simple record you can compare against the dossier later, ideally before you leave the yard. Photographs cost nothing and settle most later disagreements.

• Straight on photograph of the full nameplate with the serial number legible
• Close ups of MAWP, design temperature, test pressure and code markings
• Photographs of relief valve tags showing set pressure and any date marking
• The vacuum reading taken at inspection, with the gauge and method noted
• Photographs of the outer shell showing any frost, sweating, dents or corrosion
• Photographs of the valve cabinet, level gauge and pressure gauge
• For transport units, the ADR and periodic inspection markings with their validity dates
• Any second plate, repair plate or re marking plate on the unit

Frost or sweating on the outer shell, a rising boil off rate or faster than normal pressure build all point to vacuum degradation, which the plate will never tell you. Our article on vacuum loss in cryogenic tanks explains the symptoms, and a vacuum reading is recommended every 6 to 12 months in normal service.

How does KAF handle nameplates on certified used tanks?

KAF Cryogenics sells cryogenic equipment through two channels: new units built to specification, and certified second hand units. On the second hand channel, identity and documentation are part of what is being sold, not an afterthought.

• The vessel is inspected, NDT tested, and vacuum and pressure tested before sale
• The nameplate is verified against the certification file and the serial number traced through the documents
• The unit is supplied with a document dossier and a written warranty
• Relief device set pressures are checked against the plate MAWP
• Certification is matched to the destination market: PED 2014/68/EU with CE marking for Europe, ASME where the US code applies
• Units without recoverable traceability are not sold as certified

Lead time is often what brings buyers to the used market in the first place. New fabrication typically takes months, while a certified used unit can ship from stock in weeks. KAF also buys used equipment and accepts trade in against new orders, and applies the same identity checks when purchasing.

If you are comparing suppliers, our guide on how to choose a cryogenic equipment supplier sets out what to ask about documentation and testing before you commit.

Frequently Asked Questions

Related reading

• cryogenic tank MAWP and pressure class
• ASME and PED certification
• used cryogenic tank safe buying checklist
• cryogenic tank certifications explained
• vacuum loss in cryogenic tanks
• how to choose a cryogenic equipment supplier