Outer Weather Membrane
Maintains the visible dome profile and is selected around UV exposure, weathering, wind and snow loads, surface durability and long-term outdoor appearance.
Gas-contact membrane · Biogas storage
Inner Membrane for Biogas Holder
DERFLEX supplies inner gas holder membrane material for double-membrane biogas storage systems where the working layer must move with changing gas volume while maintaining a controlled gas barrier and dependable welded seams. Material structure can be matched to gas composition, pressure range, fabrication process and project service conditions.
- Low gas-permeability material direction
- Biogas, moisture and condensate exposure consideration
- Flexible response to repeated inflation and deflation
- HF/RF, hot-air or wedge welding support by formulation
- Custom reinforcement, width, color and coating structure
- OEM supply for gas-holder builders and membrane fabricators
Gas Barrier FirstPermeability requirement should be defined before weight or surface appearance.
Cyclic FlexibilityThe working membrane repeatedly rises and falls as storage volume changes.
Seam ReliabilityFabric and coating must fit the intended welding process and seam design.
Chemical ExposureGas composition, H?S, moisture and condensate should be reviewed by project.
Inner layer engineering
A Gas Holder Inner Membrane Is Not Simply a Lighter Outer Membrane
The outer shell and the inner working layer operate in different environments. The outer membrane faces sunlight, wind, rain, dirt and external loads. The inner layer works against stored biogas and the support-air pressure system. It flexes continuously, experiences pressure cycles, and relies on welded seams to keep the gas envelope intact.
For that reason, a project should not select the gas-tight inner membrane only by GSM, thickness or color. A more useful specification starts with gas permeability, chemical contact, mechanical movement, seam fabrication, dimensional behavior and the way the membrane connects to the gas holder's anchoring or bottom sealing system.
DERFLEX approaches the product as a technical coated-fabric component for gas-holder manufacturers, EPC contractors, membrane converters and replacement projects. The goal is to define a repeatable material specification that can be sampled, welded, inspected and reproduced for future systems.
Layer roles
Three Membranes, Three Different Jobs
Separating the functions early helps buyers avoid over-specifying one layer and under-specifying another.
Inner Gas Holder Membrane
Forms the variable-volume biogas chamber. Its priorities are low gas permeability, chemical resistance, flexible cyclic movement, dimensional control and gas-tight welded fabrication.
Bottom / Sealing Membrane
Used in selected free-standing or dome configurations for base sealing and connection. It must match foundation interface, anchoring, gas tightness and mechanical loading.
System diagram for membrane role identification. The inner membrane is the flexible gas-holding layer inside the air-supported outer shell.
Material anatomy
Build the Inner Layer Around the Gas, Not Around a Generic Tarp Specification
A practical inner membrane structure combines a load-carrying textile reinforcement with coating layers that provide flexibility, weldability and gas-barrier performance. Exact construction depends on the project.
Gas-contact coatingSelected for biogas exposure, moisture, condensate and the required permeability criterion.
Barrier / functional coating buildCoating formula and thickness can be adjusted to balance gas retention, flexibility and processing.
High-strength polyester reinforcementProvides tensile and tear performance while helping control shape during inflation, deflation and handling.
Weldable reverse coatingMust suit the fabricator's HF/RF, hot-air or hot-wedge process and the intended seam geometry.
Performance priorities
What Buyers Should Evaluate in a Gas-Tight Inner Membrane
These are the factors that directly affect material selection, sample approval and fabrication performance.
1. Defined Gas Permeability
Ask for a project-relevant gas permeability criterion and test method rather than relying on the general wording “airtight.” Gas composition, temperature and test conditions can affect the result.
2. Resistance to Biogas Constituents
Methane-rich biogas can also contain CO?, moisture, H?S and other process compounds. Chemical exposure and condensate conditions should be disclosed before the coating system is finalized.
3. Flexibility Under Volume Change
The inner membrane repeatedly moves as storage volume changes. The material should retain useful flexibility without creating excessive stiffness, fold stress or unstable deformation under the project's operating conditions.
4. Weld Seam Compatibility
Gas storage performance depends on the fabricated membrane as a system. Material formulation, surface finish, seam overlap and welding parameters should be verified together through trial welds.
5. Tensile, Tear & Dimensional Control
The textile reinforcement should match panel size, pressure, connection details and handling loads. Higher strength is useful only when it remains compatible with flexibility and fabrication requirements.
6. Batch Repeatability
OEM gas-holder builders need stable coating, base fabric, width, color and welding behavior across repeat orders so fabrication settings and panel patterns do not have to be reinvented for each batch.
Specification framework
Inner Membrane for Biogas Holder — Project Specification Table
This framework is designed for RFQ and engineering review. Final numerical values and tolerances should be confirmed after project data and sample testing are agreed.
| Product role | Inner gas holder membrane / gas-contact working membrane for double-membrane biogas storage systems. |
|---|---|
| Base reinforcement | High-tenacity polyester woven fabric; yarn, weave density and strength direction can be customized by project. |
| Coating direction | PVC coated polyester is a common direction; PVC/PVDF or TPU-related structures can be discussed when project chemistry, durability or fabrication requirements justify them. |
| Gas barrier | Low-permeability structure to be specified by gas type, test method, temperature and acceptance criterion. |
| Chemical environment | Project review can include methane, CO?, H?S, moisture, condensate and other known process compounds. |
| Mechanical properties | Tensile strength, tear strength, elongation and dimensional stability are developed around holder geometry, panel design and operating pressure. |
| Fabric weight / thickness | Project-defined. Select according to membrane role, reinforcement, required strength, handling, flexibility and welding process rather than GSM alone. |
| Welding compatibility | HF/RF, hot-air or hot-wedge welding can be supported depending on material formulation and the fabricator's equipment. |
| Color & surface | Project color and finish can be discussed; functional gas-contact and welding requirements take priority over appearance for the inner layer. |
| Supply form | Roll goods, custom roll width, cut material or fabricated-panel direction subject to project agreement. |
| Optional requirements | Flame-retardant, anti-mildew, anti-wicking, low-temperature flexibility, labeling, batch identification and custom packaging where applicable. |
| Recommended RFQ inputs | Holder type, diameter, storage volume, working/design pressure, gas composition, H?S level if known, temperature, welding method, membrane geometry, quantity and required test criteria. |
Engineering note: This page describes material selection directions, not a completed pressure-vessel or gas-holder design. Structural loads, pressure controls, safety devices, anchoring and local compliance should be confirmed by the gas-holder designer, EPC contractor or responsible project engineer.
Failure-mode thinking
Four Questions to Ask Before Approving the Inner Membrane
A procurement specification becomes stronger when it is written around what could fail in service, not only around nominal material data.
Could gas migration exceed the project's acceptance criterion?
Define permeability by test method and conditions so different samples can be compared consistently.
Could condensate or H?S exposure change the coating over time?
Share gas chemistry and condensate conditions instead of assuming all biogas environments are equivalent.
Could repeated folding and movement concentrate stress?
Balance reinforcement and coating build with the flexibility required by the holder's operating cycle.
Could a good fabric still produce a weak welded seam?
Approve trial welds using the real fabrication process before bulk production whenever practical.
Quality & sample approval
A Practical Test Plan for Inner Gas Holder Membrane Projects
Testing should follow the purchase specification and applicable project standards. Depending on the application, a buyer's approval plan may include the following checks.
Gas permeabilityConfirm the gas, test method, temperature, units and acceptance limit.
Tensile & tearReview warp/weft behavior and values relevant to the panel and attachment design.
Coating adhesionHelps assess coating stability during fabrication, flexing and long-term handling.
Trial weld evaluationUse the selected welding method and representative seam construction before bulk production.
Dimensional / flex behaviorCheck stability, folding response and low-temperature flexibility when project conditions require it.
Batch & visual inspectionVerify width, surface condition, coating uniformity, identification and approved specification.
Procurement workflow
For New Gas Holders and Replacement Inner Membranes
DERFLEX can support both standardized OEM programs and project-by-project material matching.
New System / OEM Program
- Define holder geometry, capacity and membrane position.
- Confirm working pressure, design pressure and pressure-control concept with the system designer.
- Share gas composition and chemical exposure information.
- Choose fabrication method and required roll width.
- Agree test criteria and sample approval process.
- Freeze a repeat-order specification for future gas-holder models.
Replacement Inner Membrane
Replacement work should begin with the existing system data, not only the old membrane's color or thickness.
- Existing membrane datasheet or a verified material sample.
- Holder diameter, usable gas volume and connection geometry.
- Known reason for replacement, if any.
- Current welding / fabrication method and seam configuration.
- Operating temperature and gas chemistry.
- Any changes in pressure, capacity or local project requirements.
Applications
Where the Inner Gas Holder Membrane Is Used
The same basic gas-contact function appears across several biogas and renewable-gas storage configurations.
Agricultural Anaerobic Digestion
Flexible gas storage above or beside digesters treating manure, crop residues and other agricultural feedstocks.
Municipal Wastewater Treatment
Inner gas membranes for digester-gas storage and pressure buffering before CHP, boilers, flares or upgrading equipment.
Food & Organic Waste Projects
Gas holder systems serving industrial digesters where gas production can vary throughout the treatment cycle.
Tank-Mounted Double Membrane Roofs
Inner working layer installed beneath the outer weather membrane on concrete, steel or other engineered tanks.
Free-Standing Gas Holders
Gas-contact membrane inside slab-mounted or ground-mounted holders with a controlled support-air space.
Biomethane / RNG Buffer Storage
Flexible low-pressure storage used as part of biogas handling before or around upgrading and downstream utilization.
DERFLEX material support
Why Material-Focused Buyers Use DERFLEX
DERFLEX's role is to support the coated-fabric layer: specification matching, sample development, weldability review and repeatable supply for companies that design or fabricate the complete gas-holder system.
Layer-Specific Development
Inner, outer and bottom membrane requirements can be treated separately so the gas-contact layer is not forced into a weather-membrane specification.
Coated Fabric Manufacturing Focus
DERFLEX works across PVC coated fabric, PVDF-surface directions, TPU coated materials and industrial membrane applications.
Fabricator-Oriented Coordination
Material selection can be discussed together with HF/RF, hot-air or wedge welding, roll width, panel processing and seam validation.
OEM Repeat Supply
Color, coating, base fabric, width, labeling, packaging and inspection requirements can be standardized for recurring holder models and multi-project programs.
Related DERFLEX resources
Continue Your Biogas Membrane Specification
Six related pages provide adjacent material, system and application information without turning this page into a generic biogas membrane overview.
Biogas Holder MembraneInner, outer and bottom membrane material roles for gas-holder systems.
Double Membrane Biogas HolderSystem-oriented guide to inner and outer membrane functions in low-pressure storage.
Biogas MembraneBroader PVC, TPU and PVDF membrane directions for digesters and gas containment.
PVC / PVDF Coated Fabric for BiogasCoating and surface options for exposed and gas-related membrane applications.
Anaerobic Digester Cover MembraneCover materials for digestion tanks, gas collection and environmental containment.
Gas Storage MembraneMaterial selection for low-pressure gas storage, domes and OEM membrane systems.
FAQ
Inner Membrane for Biogas Holder FAQ
Buyer-focused answers for system builders, EPC contractors, wastewater projects and membrane fabricators.
What is the difference between an inner membrane and an outer membrane in a biogas holder?
The inner membrane forms the variable-volume gas chamber and is selected primarily for gas containment, chemical exposure, flexibility and welded seam performance. The outer membrane protects the system from weather and supports the external dome form, so UV resistance, weathering and external loads are more dominant considerations.
What material is commonly used for an inner gas holder membrane?
Reinforced PVC-coated polyester is a common material direction because it combines textile strength, flexibility and weldability. Other coating structures can be discussed when chemical exposure, permeability targets, temperature or fabrication requirements call for a different solution.
How should gas tightness be specified?
For procurement, it is better to define a gas permeability test method, gas type, temperature, units and acceptance criterion instead of relying only on terms such as airtight or gas-tight. The project engineer or system supplier should confirm the applicable requirement.
Can DERFLEX support replacement inner membranes for existing gas holders?
DERFLEX can review replacement material requirements based on the existing membrane specification or sample, holder geometry, working conditions, gas composition, connection details and welding process. Final compatibility should be verified through project review and sample approval.
Which welding methods can be used?
Depending on the coating formula and fabrication design, high-frequency/radio-frequency welding, hot-air welding or hot-wedge welding may be considered. Trial welding with the fabricator's actual equipment is recommended before bulk production where practical.
What information should I send for an inner membrane quotation?
Please send the gas-holder type, membrane position, diameter, storage volume, working/design pressure, gas composition, H?S level if known, temperature range, welding method, required test criteria, color, roll width, quantity and any available drawings or existing datasheet.
Project-specific quotation
Build the Inner Membrane Specification Before You Lock the Material
Send the operating data first. DERFLEX can then discuss a practical inner membrane direction for sample evaluation, welding trials and project quotation.
Useful files to send
Gas-holder drawing, current membrane TDS, gas composition, pressure data, required permeability test, welding method and expected order quantity.
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