Layflat Positive-Pressure Duct
Collapsible ducting inflated by fan pressure for carrying fresh air toward an advancing tunnel face.
- Compact transport and storage
- Long straight runs
- Fast route extension
Project-configured underground airflow products
China Tunnel Ventilation Duct Supplier for Project Procurement
DERFLEX supplies flexible tunnel ventilation ducting from China for road, rail, metro, hydropower, mining and underground construction projects. Instead of quoting from diameter alone, the duct is configured around airflow direction, fan duty, route length, available clearance, connection method and the project’s written performance requirements.
01 · AirflowSupply, exhaust or combined duty
02 · FanAir volume, static pressure, outlet size
03 · RouteTotal run, bends, branches, elevation
04 · SizeDiameter, section length, clearance
05 · ConnectionsCoupling, suspension, fan interface
06 · SafetyNamed flame / static test requirement
Supplier selection
A supplier quotation should describe the air route—not just “1,000 mm duct price”
Tunnel ventilation is a system problem. Two ducts with the same nominal diameter can behave differently because of fabric construction, seam quality, coupling leakage, section length, reinforcement, suspension and the number of bends in the route.
For an EPC contractor, ventilation equipment manufacturer or project purchasing team, a useful quotation should therefore make the product form explicit: layflat forced-air duct, ring-supported duct, spiral-wire suction duct, low-profile geometry, or a combination of straight sections and fittings. The quote should also identify how the duct connects to the fan, how sections join, how the line is suspended and which performance requirements must be tested.
DERFLEX’s tunnel duct range covers both PVC-coated technical textile and fabricated flexible duct assemblies. That allows material selection, welded fabrication, connection details and order documentation to be discussed in one procurement sequence rather than handled as unrelated components.
Product ranges and performance descriptions on this page are reference configuration fields for procurement. Final values, compliance statements and test documents are subject to the confirmed construction, order specification and agreed test method.
Product architecture
Forced air
Extraction
Shape support
Low headroom
Choose tunnel ventilation ducting by airflow duty and available clearance
The pressure direction determines whether the duct can rely on fan pressure to stay open or needs structural reinforcement to resist collapse.
Spiral-Wire Reinforced Duct
A continuous helix supports the air passage where suction, extraction or tight bends would collapse unsupported ducting.
- Negative-pressure duty
- Equipment connections
- Optional external wear strip
Ring-Supported Flexible Duct
Periodic rings help retain shape while preserving more flexibility and packability than a rigid duct route.
- Partial suction or mixed duty
- Route geometry support
- Project-selected ring spacing
Oval / Custom-Profile Ducting
Alternative profiles can be reviewed where machinery, utilities or tunnel crown clearance limits the space available for round ducting.
- Restricted vertical clearance
- Custom suspension layout
- Geometry reviewed with airflow target
Material & construction
From PVC-coated textile to a finished flexible tunnel air line
Field performance depends on how the duct body, seam, reinforcement, couplings and suspension details work together.
Typical duct wall logic
Outer PVC SurfaceSupports moisture resistance, cleanability and handling protection; formulation can be adjusted by project.
High-Tenacity Polyester ReinforcementCarries tensile load and contributes to tear resistance and dimensional stability.
Inner PVC SurfaceForms a smooth air path and supports welded fabrication for the finished duct body.
Optional Structural SupportRings or continuous spring-steel helix where the duct must retain geometry under suction or through bends.
Construction points to define on the purchase specification
| Seam method | Welded construction selected for the fabric and duct geometry; seam layout should be agreed before production. |
| Couplings | Zipper, ring, clamp, sleeve, hook-and-loop or drawing-based connection. |
| Suspension | Reinforced fin, eyelets, straps, hooks or project-defined hanger spacing. |
| Stress zones | Extra reinforcement can be added around cuffs, hanging points, zipper areas and abrasion-prone contact locations. |
| Safety options | Flame-retardant and antistatic formulations should reference the buyer’s required standard, limit and test method. |
| Identification | Section labeling, diameter/length marks and packing identification can be discussed for staged installation. |
Specification framework
Reference fields for a China tunnel ventilation duct RFQ
These are selection fields used in DERFLEX’s current flexible ventilation duct range. Final construction is confirmed after fan and route review.
| Specification field | Reference project options | Why the buyer should define it |
|---|---|---|
| Product form | Layflat, ring-supported, spiral-wire, oval / low-profile, transitions and branch fittings | Different pressure modes and clearances require different structural behavior. |
| Duct body | PVC-coated high-tenacity polyester technical textile; construction selected by duty | Influences tensile / tear behavior, flexibility, weldability, handling and abrasion resistance. |
| Nominal diameter | Approx. 300–3000 mm reference range; non-standard sizes subject to review | Must be coordinated with required airflow, velocity, pressure loss, fan curve and available space. |
| Section length | Approx. 5–300 m project-configured options depending on product form | Affects handling weight, coupling count, leakage opportunities, storage and route extension rhythm. |
| Reinforcement | None, periodic support rings, continuous steel-wire helix, local wear reinforcement | Controls collapse resistance, bend behavior, weight and durability at contact points. |
| Connection system | Zipper, hook-and-loop, steel ring, clamp, sleeve, soft cuff or project interface | Changes installation speed, seal quality, compatibility and maintenance access. |
| Suspension | Reinforced fin, eyelets, straps, D-rings, hooks or custom spacing | Needs to support long sections without concentrating load into isolated stress points. |
| Performance options | Flame-retardant, antistatic, cold-resistant, abrasion-oriented, high-visibility or custom color by requirement | Acceptance should be tied to a written project specification and an agreed test method. |
| Order documentation | Dimensional, material and agreed inspection / test records by order requirement | Helps procurement teams compare what is actually included in different supplier quotations. |
Quotation comparison
How to compare tunnel ventilation duct supplier offers on an equal basis
A low unit price may represent a different product scope. Procurement teams can reduce ambiguity by checking whether every quotation includes the same construction and test requirements.
Compare this field
Weak quotation
More useful procurement definition
Duct type
“PVC air duct”
Positive-pressure layflat / spiral suction / ring-supported / low-profile, with intended airflow direction.
Material
Only GSM or thickness
Base textile + coating construction + agreed performance options + welding suitability.
Connections
“Standard coupling”
Named zipper / ring / clamp / sleeve, overlap or cuff dimensions, and fan interface.
Safety language
“Fireproof / antistatic”
Specific test standard, acceptance value, sample / finished-product scope and required documentation.
Delivery scope
Duct body only
Clarify suspension, fittings, reducers, branches, repair material, labels and packing in the commercial offer.
Manufacturing & quality gates
A procurement-oriented production sequence
The following checkpoints focus on what can be defined and inspected before a tunnel duct shipment is released.
Step 01Requirement reviewConfirm airflow direction, fan data, route, diameter, fittings, safety and documentation needs.
Step 02Material matchingSelect the coated textile construction, reinforcement and optional surface / safety treatments.
Step 03Cutting & weldingForm straight sections, cuffs, seam geometry, suspension zones and local reinforcements.
Step 04Interface assemblyInstall zippers, rings, sleeves, clamps or drawing-based connection details.
Step 05InspectionCheck dimensions, visible seam quality, hardware details and agreed test items according to the order plan.
Step 06Project packingIdentify sections by size / length / installation sequence when required for site logistics.
Applications
Flexible ventilation ducting for changing underground work zones
The duct format should follow excavation method, available clearance, contaminants, route length and how often the ventilation line must move.
Road & Highway Tunnels
Fresh-air supply and exhaust routing during drill-and-blast or mechanical excavation, with section extension as the heading advances.
Rail & Metro Construction
Temporary airflow through long underground alignments, shafts, cross passages and station excavation zones.
TBM Projects
Flexible duct assemblies and transitions coordinated with confined machinery envelopes, moving equipment and planned ventilation routes.
Hydropower Headings
Fresh-air distribution and localized extraction in access tunnels, caverns and underground construction areas.
Mining & Underground Development
Layflat forced-air ducting for development headings plus supported duct sections for extraction or equipment connections.
Industrial Temporary Ventilation
Portable, reroutable airflow lines for confined maintenance, dust / fume management and temporary work zones.
Why DERFLEX
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One technical conversation from coated duct fabric to finished assemblies
DERFLEX combines PVC-coated textile knowledge with finished flexible duct fabrication, which is useful when a project must coordinate material, seams, fittings and documentation under one purchase specification.
Material Matching
Fabric structure, PVC coating and optional treatments can be reviewed against pressure mode, abrasion exposure and handling conditions.
Finished Duct Supply
Straight sections, reinforced suction duct, cuffs, couplings, branches and transition pieces can be discussed as a complete fabricated scope.
Custom Project Details
Diameter, length, color, suspension, connection geometry, labeling and packing can be specified before production.
Export RFQ Support
Buyers can submit fan curves, route drawings, existing samples and acceptance criteria so the commercial offer reflects the actual project scope.
Related selection resources
Continue the tunnel ventilation duct selection process
These six DERFLEX pages cover adjacent airflow modes, safety-oriented configurations and duct material choices.
Tunnel Ventilation Duct ManufacturerConfigure a finished tunnel air duct around fan, route, pressure and installation details.
Mine Ventilation DuctingCompare underground duct types, fittings, materials and installation factors.
Positive Pressure Ventilation DuctLayflat forced-air ducting for fresh-air supply to advancing headings.
Spiral Wire-Reinforced Ventilation DuctShape-retaining flexible ducting for extraction, suction and equipment connections.
Antistatic Flame-Retardant Mine DuctSelection guidance for project-defined static and flame performance requirements.
PVC Fabric for Tunnel Ventilation DuctReview the coated technical textile that forms the flexible duct wall.
FAQ
China Tunnel Ventilation Duct Supplier FAQ
What information should I send to a tunnel ventilation duct supplier for a quotation?
Send the airflow direction, fan model or airflow/static pressure, outlet size, total duct route, required diameter, section length, bends and branches, connection method, suspension preference, site conditions and any named flame-retardant or antistatic test requirement. Drawings and installation photos are also useful.
What is the difference between layflat and spiral tunnel ventilation ducting?
Layflat ducting relies on positive fan pressure to inflate and is commonly used for fresh-air delivery. Spiral-wire or otherwise supported ducting keeps the air passage open under suction or negative pressure and is often selected for extraction, fan connections and tighter bends.
What tunnel ventilation duct diameter can DERFLEX supply?
DERFLEX’s current flexible ventilation duct range lists approximately 300–3000 mm as a reference nominal diameter range. The selected diameter should be checked against airflow, fan performance, route length, bend losses and available tunnel clearance rather than chosen from diameter alone.
Can flame-retardant and antistatic tunnel ventilation duct be specified?
Project-specific flame-retardant and antistatic configurations can be discussed. The buyer should identify the required standard, test method, acceptance value and documentation before production, because terminology and thresholds vary by market and project type.
How can leakage be controlled on a long tunnel ventilation duct line?
Leakage is affected by seam construction, coupling design, overlap, zipper or ring details, section alignment and installation practice. The preferred section length should balance fewer joints against handling weight, maintenance and the need to extend the duct as excavation progresses.
Can DERFLEX make custom reducers, branches and fan connection cuffs?
Custom reducers, transition sleeves, Y/T branches, soft cuffs and project-defined connection details can be reviewed from fan dimensions, interface drawings and route requirements. Confirming these interfaces before production helps reduce field modification.
Project-based quotation
Send the fan data and tunnel route—not only the duct diameter
Include airflow direction, fan curve or operating point, total run, bends, required diameter, section length, coupling and suspension preferences, safety test requirements and expected quantity. DERFLEX can then review a suitable duct construction for technical and commercial discussion.