PSSR 2000 · Pressure systems

Cryogenic and Nitrogen System Thorough Examination

Independent examination of your cryogenic and nitrogen system under a Written Scheme of Examination, by a competent person under PSSR.

A vacuum insulated nitrogen tank holds an inner vessel you can never open and a fluid that expands almost seven hundred times as it boils. We carry out PSSR examination and certification of cryogenic and liquid nitrogen systems, working to the written scheme that makes a sealed vessel examinable.

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  • Independent and impartial
  • Competent engineer surveyors
  • Reports issued promptly
Written schemeA cryogenic system cannot be examined without a scheme under PSSR Reg 8
No internal accessThe inner vessel is sealed inside a vacuum jacket, so the scheme sets the method
700 to 1Liquid nitrogen expands roughly 700 times on boiling, which is why relief devices matter
28 daysThe report of examination follows within the statutory period
Pressure equipment we examine

Why your cryogenic and nitrogen system needs PSSR examination

A static cryogenic system stores nitrogen, argon or oxygen as a refrigerated liquid: an inner pressure vessel holds the liquid, an outer jacket maintains the insulating vacuum, and a vaporiser and pipework deliver gas to the point of use. The inner vessel is the pressure vessel in law, yet it is sealed permanently inside the jacket, which is precisely the difficulty a written scheme of examination exists to resolve.

Because no competent person can open the inner vessel, the scheme decides what can be examined and how: the relief valves and bursting discs that guard against overpressure, the vaporiser and its pipework, the vacuum integrity that keeps the whole thing cold, and the external condition of a vessel that spends its life at temperatures cold enough to embrittle the wrong steel. Nitrogen adds an asphyxiation hazard to the pressure one, so the examination reads the installation as well as the vessel.

Vacuum insulated storage tanks
Liquid nitrogen dewars
Micro bulk vessels
Ambient vaporisers
Pressure building coils
Relief valves and bursting discs
Vacuum jacketed pipework
Fill and withdrawal lines
How it works

How we examine your cryogenic and nitrogen system

Working to the written scheme, our competent person examines the relief valves and bursting discs and their set pressures, the vaporiser and its pipework for icing damage and integrity, the vacuum annulus condition through its indicators, the outer jacket and supports for cold damage and corrosion, and the fill, withdrawal and pressure building circuits, then certifies the system against the scheme.

  • 1

    Work to the scheme, not around it

    The written scheme names what is examined and how on a sealed vessel. We examine to it and, where a scheme is missing or thin, we say so before we start.

  • 2

    Prove the protective devices

    Relief valves and bursting discs are the whole defence against a 700 to 1 expansion. Their condition, setting and discharge routing are examined as the priority.

  • 3

    Certify within 28 days

    The report of examination states the condition, any actions and the next examination date, issued inside the statutory period and filed in your SEIS portal.

Why businesses choose SEIS

  • Competent persons who understand vacuum insulated vessels and their limits
  • The written scheme reviewed as well as followed, not taken on trust
  • Relief device and vaporiser condition examined, not just paperwork checked
  • Certificates and due dates managed through the SEIS client portal
What we examine

Cryogenic and nitrogen system: what a thorough examination covers

Relief valves and bursting discs

The only defence against boil off overpressure. Set pressures, condition and clear discharge routing are examined as the heart of the scheme.

Vaporiser icing

Ambient vaporisers ice up and the ice cracks fins and pipework as it grows and sheds. Frost damage and pipework integrity are examined across the vaporiser bank.

Vacuum integrity

Lose the vacuum and the tank boils off in hours and sweats frost. Vacuum indicators and any loss of insulation performance are assessed against the scheme.

Cold embrittlement

Steel that is fine at room temperature can fracture at cryogenic temperatures. The outer jacket, supports and cold end fittings are examined for cold damage.

Asphyxiation risk

Nitrogen displaces air silently. The installation, ventilation and any oxygen monitoring are read as part of judging the system safe, not just the vessel.

Pipework and joints

Vacuum jacketed and bare cryogenic lines contract hard on cool down. Joints, bellows and supports are examined for the movement the cold imposes.

Scheme and certification

How it works, and what you receive

Every cryogenic and nitrogen system is certified with a report of examination under PSSR, drawn up against its written scheme of examination and issued within 28 days. It records the condition of the vessel, vaporiser, pipework and protective devices, any repairs or limits on use, and the date the next examination falls due. Where the competent person judges a risk of imminent danger the system is taken out of use at once. All certificates live in your SEIS client portal for audits and insurers.

Step oneA Written Scheme of Examination, certified before use
To schemeExamined to the intervals the scheme sets
28 daysA written report, issued within the statutory window
IndependentWe examine it, we do not supply it

You receive a report on the condition of the system and its safety devices, with any actions and timescales set out clearly.

Full statutory cover

Part of our full PSSR inspection service

Cryogenic and nitrogen system is one of the many kinds of equipment we cover. We inspect the full range, across every sector, as an independent provider, one item or a whole site, anywhere in the UK.

See our full PSSR inspection service
Other services

Other statutory inspections we carry out

Many sites run more than one regime. We can examine all of it, under one independent provider.

LOLER inspectionThorough examination and certification of lifting equipment and accessories. PUWER inspectionInspection of work equipment against the five PUWER duties, with a written record. LEV testingLEV thorough examination and test of your extraction systems.
PSSR FAQs

Cryogenic and nitrogen system examination: common questions

Does a liquid nitrogen tank need a PSSR examination?
Yes. A static vacuum insulated nitrogen or cryogenic tank is a pressure system under PSSR 2000, and it must be examined by a competent person to a written scheme of examination, then certified. Mechanical vapour compression plant is a different system with its own page, our refrigeration equipment thorough examination.
How can a sealed inner vessel be examined at all?
Through the written scheme, which sets out what can be examined on a vessel with no internal access: the protective devices, vaporiser, pipework, vacuum integrity and external condition. The scheme is what makes a cryogenic system examinable in the first place.
What is the biggest hazard the examination targets?
Overpressure from boil off. Liquid nitrogen expands roughly 700 times as it becomes gas, so the relief valves and bursting discs are the priority of every examination, alongside the asphyxiation risk nitrogen brings.
Do we need a written scheme before you attend?
You need one to be examined lawfully, and we can help put one in place if it is missing or inadequate. Examining a cryogenic vessel without a scheme is not possible, because the scheme defines the method.
How is this different from our gas supplier's service visit?
A supplier service keeps the tank delivering gas. The PSSR examination is an independent statutory judgement of integrity against the written scheme, ending in a certificate, and the two do not replace one another.
Does the vaporiser and pipework get examined too?
Yes. The vaporiser, its pipework and the fill and withdrawal lines are part of the system and part of the scheme, with icing damage and cold contraction given particular attention.
Where do these duties come from?
From the Pressure Systems Safety Regulations 2000, with the written scheme duty in Regulation 8. HSE guidance on pressure systems sets out the framework, and our PSSR regulations guide explains the scheme, the examination and the report.
How do I book a cryogenic or nitrogen system examination?
Call 0330 043 8191 or use the contact form with the vessel details. If you also run compressed gas receivers or steam plant, our steam boiler thorough examination and wider PSSR service can be scheduled together.

Is your cryogenic and nitrogen system due an examination?

Talk to an engineer surveyor, get a quote and book your inspection anywhere in the UK.

0330 043 8191 Request a quote