Question 1

Can a biogas membrane leak at the edge?

Accepted Answer

Yes, a biogas membrane can leak at the edge, because it is one of the most difficult points of the entire sealing system.

Leaks usually occur at the junction of the membrane, the gasket, the clamping profile and the substrate. The cause may be uneven or insufficient clamping pressure, a damaged gasket, corrosion of the fixing elements, material fatigue from repeated movement of the membrane, or workmanship errors at corners and joints. The edge is also exposed to condensate, temperature fluctuations and wind loads. For this reason, the fixing points should be covered by regular leak checks (gas detector, visual inspection) in accordance with the manufacturer's instructions and the plant documentation. Repairs in explosion hazard zones are carried out only in line with safety procedures and by suitably authorised personnel.

Sources: Polski Komitet Normalizacyjny — normy i wyroby normalizacyjne; IEA Bioenergy Task 37 — Energy from Biogas

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Question 2

Does every biogas membrane have a keder?

Accepted Answer

No, not every biogas membrane has a keder, because the edges are fixed using different systems.

A keder, i.e. a bead or cord sewn into the edge of the membrane and locked in a profile, is one solution. Fixing with clamping strips bolted to the wall or rim of the tank, wedge profiles, anchor ring systems and pneumatic clamps are also used. The choice depends on the tank design, the type of membrane (single- or multi-layer), the expected loads and the manufacturer's recommendations. When replacing or repairing, the fixing system should not be changed to another without confirmation of suitability by the designer and in the design documentation.

Sources: Polski Komitet Normalizacyjny — normy i wyroby normalizacyjne; IEA Bioenergy Task 37 — Energy from Biogas

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Question 3

Is a pressure test needed to check tightness?

Accepted Answer

Not always. Pressure tests are carried out at acceptance and after significant changes, according to the design and regulations. For routine checks in operation, non-invasive methods are better suited, as they do not require shutting down the installation or raising the pressure.

Question 4

Is the smell of biogas enough to detect leaks?

Accepted Answer

No. The smell comes mainly from H₂S and other trace components, not from methane, and depends on the gas composition and the wind. With a low H₂S concentration or after desulphurisation, a leak may be undetectable by smell, so measuring instruments are needed.