The single-layer EPDM rubber gasholder stores biogas and covers circular digesters, filtrate tanks and liquid manure tanks. No external protective dome or support-air blower is required: elastic membrane tension creates the gas pressure. The membrane rises during filling and lowers during gas withdrawal, buffering changes in gas production and consumption. EPDM is resistant to hydrogen sulfide in biogas. Suitable for new tanks and replacement of existing covers.

Circular membrane, clearly defined dimensions

The gas-retaining element is a flat circular membrane made of black EPDM rubber with a nominal thickness of 2.0 mm. The catalogue size refers to the tank diameter, from 10 to 40 m in 2 m steps. The membrane diameter is listed separately. For this range, the calculation uses a membrane diameter 1.5 m larger than the tank, corresponding to a radial allowance of 0.75 m. Final manufacturing dimensions, edge tabs and the fixing arrangement are agreed from the tank drawing.

Elastic material for changing gas volumes

EPDM is an elastomer that changes shape as the gas space fills and empties. The material data sheet gives a tensile strength of at least 8 MPa and elongation at break of at least 400%; measured values are 10.5 MPa and 500%. These are material test results, not permissible operating strain. The working shape and membrane movement are selected for the tank, the required storage duty and the fixing system. Tank diameter alone does not define usable gas capacity.

Material properties and gas retention

For the 2.0 mm membrane, the reported methane permeability is 480 cm³/(m²·day·bar), measured at 23 °C according to ISO 15105-1. This is a material permeability value, not a measured leakage rate for a complete installed gasholder. The material has a density of 1.22 kg/l and a measured hardness of 66 Shore A. Tear resistance is at least 10 N/mm, with a measured value of 12 N/mm. The data sheet records cold bending at ≤ −45 °C and no cracking in the specified ozone test.

UV, frost and repeated flexing

EPDM resists UV radiation, ozone and weathering. Its elasticity allows repeated changes of shape during filling and gas withdrawal. Cold flexibility is supported by a cold-bending test result of ≤ −45 °C (EN 495-5); this is not the operating temperature limit of the complete gasholder. No rated number of bending cycles is specified. After 12 weeks at 80 °C, hardness changed by +3 Shore A, tensile strength by −2% and elongation at break by −15%. These laboratory results do not establish a guaranteed service life.

Fixing and sealing around the tank

A continuous perimeter connection secures and seals the membrane to the tank. A suitable system may comprise a fixing profile, clamping pressure hose, stainless-steel connectors, seals and mounting accessories. Its configuration depends on the tank rim and membrane edge. The profile and clamping components are selected together, so that the connection suits the membrane and the loads for the installation. These fixing components are optional and are not included in the membrane price.

Protection, monitoring and project selection

Pressure/vacuum protection and suitable monitoring are specified for the complete gas system. A safety valve, its connection parts and level measurement can be supplied at additional cost. Membrane height provides a visible indication of filling; an optional sensor can support continuous monitoring. Permissible operating pressure, protection settings, support arrangements and wind or snow loads are checked for the actual installation. Material test values do not replace the design of the assembled system. Generally suitable for wind zone 4; suitability must be confirmed for each project.

Scope and price list

The base item is one circular EPDM membrane, 2.0 mm thick, in the selected size. The catalogue lists tank diameter, membrane diameter, flat membrane area and price. Fixing systems, pressure/vacuum protection, level sensors, transport packaging, delivery and installation are offered separately on request. An alternative 1.5 mm membrane may be specified separately; its price is not included in this 2.0 mm range. For selection, provide the tank drawing, rim details, existing fixing system and required operating conditions.