Our double membranes are made of a PVC-coated polyester fabric that was specifically designed and produced for use in the biogas sector. The material is flame retardant in accordance with DIN 4102 B1 and it is UV-resistant. We use materials with a grammage ranging from 800 g/m² to 1,500 g/m². Our standard colours for this are agate grey as per TRAS-120 (similar to RAL 7038) or moss green (similar to RAL 6005), but other colours are also available on request, such as silver grey (similar to RAL 7001).  The gas permeability of the membranes ranges from <200 cm³/(m² d bar) to <500 cm³/(m² d bar). 

The material is welded together in our two factories in Düren using the high-frequency welding method. The outer membrane has built-in air inlets and outlets and condensate drain plugs. Hemstitch seams or flaps are worked into the inner membrane as guides for the fill level measuring equipment. If desired or depending on individual needs, we can also integrate viewing windows, service platforms or other built-in parts in our double membranes. For profiles up to the size of the hemisphere, we employ parallel cutting with material webs arranged in parallel to prevent concentrations of tension in the pole area.

Double membranes for bolted fastening systems feature a reinforced piping edge to guarantee the best possible durability at the clamping edge even under unusually high pressure or extreme weather conditions.

The TRAS-120 regulations define the technical requirements for biogas plants to minimise dangers such as fire, explosions and other safety-related risks. They include design requirements such as materials, sealing systems, tank and piping dimensions, and safety equipment. In addition, they contain operational specifications for monitoring gases and temperatures, handling substrates, pressure-relief systems and guidelines on what to do in the event of malfunctions or emergencies. Furthermore, the TRAS-120 guidelines specify regular inspection, maintenance and servicing of plant sections to ensure safe operation and avoid dangers.

For more information and editions, consult, for example, the Commission on Process Safety (KAS) at the German Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection.

You can download the technical rules for plant safety (TRAS 120) – technical safety requirements for biogas plants (unofficial version from 15.03.2019, official version of TRAS-120 published in the Federal Gazette) here.

Below is a list of the most important points required to comply with TRAS-120 that we at dbds cover. We will be happy to inform you about additional measures.

The question of energy efficiency and thermal efficiency is becoming more and more important, including in the biogas sector. To achieve significant reductions in the demand for heating and thus improve the energy efficiency of biogas plants, dbds – Deutsche Biogas Dach-Systeme GmbH uses patented Low Emissivity Technology (LowE). This involves a coating of aluminium particles applied to the PVC membranes in the factory on the outer face of the inner membrane or the inner face of the outer membrane. The principle of applying a coating with a low emmisivity is familiar from thermal insulation glazing, where it has become a tried and tested, state-of-the-art method.

• Energy savings from reducing the annual heating demand (by up to -20%)
• Reduction of gas or volume losses by reflecting heat in summer and thus preventing excessive expansion
• No additional insulation in the roof system and thus no additional load on the substructure or additional work and expense during installation
• Attractive funding options from the KfW national development bank possible thanks to process-related savings for conventionally generated energy