PSSR 2000 · Pressure systems

Biogas and Biomethane System Thorough Examination

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

A biogas plant turns waste into a flammable gas and then compresses it, which puts pressure and methane in the same pipe. We carry out PSSR examination and certification of biogas and biomethane systems, from the upgrader and its vessels to the compression that pushes gas to grid.

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  • Independent and impartial
  • Competent engineer surveyors
  • Reports issued promptly
Written schemeUpgraders, compressors and receivers are examined under a PSSR Reg 8 scheme
6 to 250 barUpgrading runs at modest pressure; grid and bio CNG compression reaches far higher
Corrosive feedHydrogen sulphide and moisture attack vessels the scheme must track
28 daysThe report of examination follows within the statutory period
Pressure equipment we examine

Why your biogas and biomethane system needs PSSR examination

A biogas installation takes raw gas from anaerobic digestion, roughly half methane, and upgrades it to pipeline biomethane by stripping out carbon dioxide, hydrogen sulphide and moisture. Water scrubbing, pressure swing adsorption and membrane systems all do this under pressure, typically several bar through the upgrader, and grid injection or bio CNG then compresses the clean gas far higher, into the hundreds of bar. Every one of those pressure stages is a pressure system under PSSR.

The chemistry makes it harder than ordinary compressed gas. Raw biogas carries hydrogen sulphide and water that corrode vessels and pipework from the inside, and the product is flammable methane, so a leak is an ignition risk as much as a pressure one. The written scheme has to cover the upgrader columns and vessels, the buffer and gas holders, the compressors and their receivers, and the relief devices across the lot, tracking a corrosive process that ages plant faster than clean service does.

Upgrader columns and vessels
Water scrubbing systems
PSA and membrane skids
Biomethane buffer vessels
Gas holders and domes
Compressors and receivers
Grid injection skids
Relief valves and PRVs
How it works

How we examine your biogas and biomethane system

Working to the written scheme, our competent person examines the upgrader vessels and columns for internal corrosion, the buffer and holder integrity, the compressors and their air and gas receivers, the pipework at the pressure transitions, and the relief valves, bursting discs and PRVs across the system, with hydrogen sulphide attack and moisture given the weight the feed gas demands.

  • 1

    Map the pressure stages

    Upgrading, buffering and compression each sit at different pressures. We confirm the scheme covers every stage, from a few bar to bio CNG's hundreds.

  • 2

    Examine for corrosive attack

    Hydrogen sulphide and moisture thin vessels from within. The examination targets the wetted, sour parts of the system where the feed does its damage.

  • 3

    Certify within 28 days

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

Why businesses choose SEIS

  • Competent persons comfortable with upgrading and compression plant
  • The corrosive feed gas treated as the ageing mechanism it is
  • Every pressure stage, from scrubber to grid skid, brought under one scheme
  • Certificates and due dates managed through the SEIS client portal
What we examine

Biogas and biomethane system: what a thorough examination covers

Hydrogen sulphide corrosion

Sour raw gas thins vessel walls and pits pipework from the inside. Wetted upgrader vessels and pre treatment plant are examined where the attack concentrates.

Compressor receivers

Grid and bio CNG compression drives pressures into the hundreds of bar. The receivers, coolers and their relief devices carry the highest energy on site and are examined accordingly.

Gas holders and domes

Low pressure holders fail in different ways to vessels, through membranes, seals and structure. Their integrity is examined to the scheme's method for the type fitted.

Relief and PRV coverage

Each pressure stage needs its own overpressure protection, correctly set and routed. Set pressures and discharge routing are examined across every stage.

Moisture and condensate

Water carried from the process pools and freezes, corroding low points and blocking reliefs. Drains, traps and low points are examined for the damage moisture leaves.

Pressure transition pipework

The joints between low and high pressure stages take fatigue and thermal cycling. Pipework, flanges and supports at the transitions are examined for that duty.

Scheme and certification

How it works, and what you receive

Every biogas and biomethane system is certified with a report of examination under PSSR, drawn up against its written scheme and issued within 28 days. It records the condition of the upgrader, holders, compressors, receivers and protective devices, any repairs or operating limits, and the next examination date. Where imminent danger is found the affected plant is taken out of use immediately and the enforcing authority notified. Certificates are held in your SEIS client portal.

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

Biogas and biomethane 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

Biogas and biomethane system examination: common questions

Is a biogas or biomethane plant covered by PSSR?
Yes, wherever it holds gas under pressure, which covers the upgrader, buffer vessels, gas holders, compressors and receivers. Each is a pressure system under PSSR 2000 and is examined to a written scheme, then certified.
Does the upgrader itself need examining, or just the compressor?
Both. Water scrubbing, PSA and membrane upgraders run under pressure and their vessels are in scope, alongside the higher pressure compression for grid injection or bio CNG. The scheme should cover every stage.
Why does the corrosive gas matter to the examination?
Raw biogas carries hydrogen sulphide and moisture that corrode vessels and pipework from the inside far faster than clean gas, so the examination concentrates on the wetted, sour parts of the plant where walls thin first.
What pressures are involved?
Upgrading typically runs at a few bar up to around ten, while grid injection and bio CNG compression reach into the hundreds of bar. The higher the pressure, the more energy stored, and the examination weights its attention accordingly.
Do gas holders count as pressure systems?
Low pressure holders are examined to the scheme's method for their type, covering membranes, seals and structure rather than a thick walled vessel. They fail differently, and the scheme reflects that.
Is this separate from our maintenance contract?
Yes. Maintenance keeps the plant producing; the PSSR examination is an independent statutory judgement of integrity ending in a certificate. One does not satisfy the legal duty of the other.
Where are the duties set out?
In the Pressure Systems Safety Regulations 2000, with the written scheme in Regulation 8. HSE guidance on pressure systems covers the framework, and our PSSR regulations guide explains the scheme, examination and report.
How do I book a biogas system examination?
Call 0330 043 8191 or use the contact form with the plant details. Compression sites usually run air receivers and boilers too, which our wider PSSR examination services can cover on the same visit.

Is your biogas and biomethane 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