Fan matching
Outlet size, airflow, static pressure and pressure direction help determine whether the body can be collapsible, requires continuous helix support, or needs a short reinforced transition at the machine.
Custom industrial airflow assemblies
Built Around Your Fan, Route & Connection
Custom Large Diameter Ducting
Large-bore flexible duct assemblies configured for high-volume air supply, extraction, temporary HVAC, mining, tunneling, industrial shutdowns and blower OEM programs.
DERFLEX can review non-standard diameter, section length, coated-textile construction, reinforcement, cuffs, zippers, rings, fan transitions, suspension and project identification as one finished ducting specification. Final performance depends on the approved construction, airflow direction, pressure, environment and test requirements.
Custom IDMetric or imperial
Custom EndsCuffs & adapters
OEM SupplyMarks & packing
Pressure direction first
Positive-pressure supply and negative-pressure extraction do not require the same duct architecture.
Interface dimensions matter
Fan outlet OD/ID, flange geometry and cuff style should be confirmed before production.
Large size changes handling
Section weight, bend behavior, packing diameter and lifting method become part of the design.
Claims follow the specification
Fire, static, temperature and pressure values should be tied to the selected construction and test route.
Why “Custom” Matters
A 48-inch duct is not simply a larger version of a portable hose
As diameter grows, the duct wall carries more area, the joint circumference increases, the fan connection becomes less forgiving, and every bend or handling point affects the installed system. A useful custom large diameter ducting specification therefore starts with the equipment and site—not with a catalog diameter alone.
Geometry matching
A non-standard fan outlet, limited headroom, tight bend or offset connection may call for a reducer, enlarger, tapered transition, elbow, branch or custom cuff rather than a straight tube.
Handling matching
Oversized duct sections should be planned around installation labor, relocation frequency, suspension points, storage space, packed dimensions and the method used to replace damaged sections.
From Requirement to Finished Assembly
Define the installed connection before defining the duct
“Custom large diameter ducting” usually means more than changing the bore. The finished product may need to mate with an axial fan, temporary air handler, mine ventilation line, dehumidifier, portable heater, extraction unit or an existing duct network. DERFLEX can review the body and interface together so the quotation reflects how the product will actually be used.
For replacement projects, a dimensioned drawing is ideal. When one is not available, clear photographs with reference measurements can help identify cuff geometry, clamp zones, zipper position, suspension spacing and the transition required at the equipment.
- Internal diameter / nominal bore
- Section and total line length
- Fan outlet ID / OD
- Positive or negative pressure
- Connection and sealing style
- Bends and route clearance
- Suspension or floor handling
- Required test documentation
Three Build Paths
Choose a duct architecture that fits the pressure behavior
Large-diameter airflow products can share the same nominal size while behaving very differently in service. The first selection is structural: does the duct rely on internal pressure to stay open, or must it retain its shape mechanically?
Positive Pressure
Layflat Large-Bore Duct
A coated-textile tube that inflates under forced air and packs flat when the fan stops. It can be practical for long temporary supply lines where low packed volume is important.
- Fresh-air supply and temporary cooling
- Long suspended ventilation routes
- Reduced reinforcement weight
- Custom zippers, rings or soft cuffs
Suction / Extraction
Spiral-Reinforced Large Duct
A flexible wall supported by continuous wire helix so the bore remains open under suction, at bends and near equipment connections.
- Fume and exhaust extraction
- Negative-pressure ventilation
- Portable blower connections
- Optional external wear protection
Interface Geometry
Transitions & Special Sections
Reducers, enlargers, elbows, offset pieces, Y-branches and equipment adapters can connect large duct sections where the machine outlet or site route is not a simple straight cylinder.
- Fan outlet transitions
- Large-to-small diameter reducers
- Branches and directional changes
- Replacement interfaces from drawings
Custom Connection Matrix
Specify the ends so installation does not depend on improvised site modifications
Connection choice affects installation speed, leakage control, replacement and compatibility with the fan or adjoining duct. Final construction should be confirmed against actual dimensions and pressure conditions.
| Connection option | Typical use | What to define in the inquiry | Procurement note |
|---|---|---|---|
| Soft cuff / belted cuff | Portable fans, heaters, chillers and temporary ventilation equipment | Equipment OD, cuff overlap, belt width and fastening method | Useful when the duct must be installed and removed repeatedly. |
| Zipper connection | Modular long-run duct lines and underground ventilation sections | Zipper type, sealing flap, orientation and section identification | Allows repeatable section-to-section connection when matched as one system. |
| Steel ring end | Large project duct sections, suspended lines and custom mechanical joining | Ring diameter, rod section, overlap and joining hardware | Ring design should be reviewed with duct size and joint loading. |
| Hook-and-loop sleeve | Fast temporary connections and equipment sleeves | Overlap length, closure width and sealing expectation | Convenient where frequent access is required. |
| Clamp interface | Fan spigots, rigid pipe interfaces and short transition pieces | ID/OD, clamp zone, reinforcement and surface geometry | Actual interface dimensions are more useful than nominal fan size alone. |
| Reducer / custom adapter | Different fan and line diameters, offset connections or equipment replacement | Both end dimensions, transition length, centerline offset and pressure direction | A drawing is recommended for non-concentric or multi-axis transitions. |
Reference Specification Envelope
Custom large diameter flexible ducting for project and OEM purchasing
The table below is an RFQ planning reference rather than a universal guaranteed datasheet. Final size, material, pressure capability, temperature range and functional treatments are confirmed against the approved order specification and applicable test method.
| Product form | Finished custom large diameter ducting assembly for air supply, extraction or equipment connection. |
|---|---|
| Body material | PVC-coated high-tenacity polyester technical textile; fabric weight and formulation selected by duty. |
| Diameter | Common large-project discussions can include 600, 750, 900, 1000, 1200 and 1500 mm. Larger project sizes may be reviewed in suitable constructions after pressure, handling and logistics checks. |
| Imperial reference | 30 in, 36 in, 42 in and 48 in are common inquiry sizes; non-standard imperial dimensions can also be discussed. |
| Section length | 5 m, 10 m or custom. Very large diameters may use shorter sections to simplify lifting, bends, packing and replacement. |
| Structural options | Layflat positive-pressure body, continuous spiral wire reinforcement, ring reinforcement and localized support. |
| Connections | Soft cuff, drawstring, belt end, zipper, steel ring, hook-and-loop, clamp interface, reducer, enlarger or custom adapter. |
| Suspension / handling | Eyelets, webbing loops, continuous hanging fin, reinforced patches, lifting aids or buyer-defined arrangement. |
| Functional options | Flame-retardant, antistatic, abrasion-focused, moisture-resistant or cold-weather variants when a target and test route are specified. |
| Color / identification | Yellow, orange, black and project colors subject to material availability; OEM logo, section numbers and packing marks can be discussed. |
| Supply scope | Straight sections, bends, reducers, branches, fan transitions, spare cuffs, repair material and storage solutions as agreed. |
Project Workflow
Turn operating data into a repeatable custom duct specification
A repeat-order program is easier to control when the duct is identified by an approved drawing or specification rather than only by “diameter × length.”
Define airflow duty
Fresh-air supply, local extraction, exhaust, reversible service or a custom equipment interface.
Collect fan data
Outlet dimensions, airflow, static pressure, operating mode and available installation clearance.
Build the geometry
Diameter, length, bends, transitions, reinforcement, hanging system and connection details.
Confirm material & tests
Coating, fabric weight, flame/static route, temperature exposure, abrasion and chemical environment.
Lock repeat-order details
Drawing revision, section ID, logo, packing, inspection points and replacement-part reference.
Where Custom Large-Bore Ducts Are Specified
Application environments where standard hose sizes can become the wrong starting point
The same diameter can require different wall, reinforcement and connection details depending on the air stream, pressure direction, installation route and how often the duct is moved.
Mining & tunneling
Long supply or extraction routes where diameter, suspension, section connection and safety documentation must be reviewed together.
Temporary HVAC
Large heaters, chillers and air-handling units for construction, events, shutdowns and temporary climate control.
Industrial shutdown ventilation
Temporary fresh-air routing, hot-air removal and local extraction during maintenance or plant modification.
Shipyard & vessel work
Portable ventilation and extraction for tanks, hulls, confined zones and changing access routes.
Drying & dehumidification
High-volume conditioned-air delivery for coating, curing, water-damage recovery and large enclosed work zones.
Fume & exhaust routing
Wire-supported ducting can be reviewed where the bore must remain open during negative-pressure extraction.
Warehouse air movement
Temporary or semi-permanent airflow lines where rigid duct erection would be slow or difficult to relocate.
Fan / blower OEM programs
Private-label duct assemblies matched to equipment outlets, color systems, labeling and repeat-order packaging.
DERFLEX Supply Approach
Coated-textile knowledge plus finished duct fabrication
For oversized flexible ducting, the wall material and the fabricated assembly should be considered together. DERFLEX can review PVC-coated technical textile, welded seams, reinforcement, cuffs, suspension and packing within one project specification.
This approach is particularly useful for contractors, equipment brands, distributors and replacement programs that need a repeatable construction rather than an improvised one-off hose.
Custom dimensions
Metric and imperial diameters, project section lengths and non-standard fan interfaces can be reviewed from drawings or measured data.
Pressure-specific construction
Layflat and reinforced structures are treated as different engineering choices rather than one universal duct.
Accessory integration
Reducers, bends, branches, adapters, cuffs, suspension components and repair items can be quoted with the main duct line.
OEM specification control
Approved dimensions, connection details, color, identification and packing can support later replenishment and replacement orders.
Procurement Guide
What to send for a useful custom large diameter ducting quotation
A concise technical RFQ usually produces a more relevant proposal than a long inquiry that omits fan pressure, connection geometry or the intended airflow direction.
- Application: mine, tunnel, factory, temporary HVAC, drying, shipyard, OEM equipment or another use.
- Airflow direction: positive-pressure supply, negative-pressure extraction or reversible duty.
- Fan / blower data: model, airflow, static pressure and outlet drawing or measured ID/OD.
- Required duct diameter: inside diameter in mm or inches, including any non-standard interface size.
- Line layout: total length, preferred section length, number of bends, bend radius and elevation changes.
- Connection details: soft cuff, belt, zipper, steel ring, hook-and-loop, clamp, reducer or custom adapter.
- Handling method: suspended, floor-laid, frequently relocated, vehicle-mounted or equipment-mounted.
- Air-stream conditions: temperature, moisture, dust, mist, fumes and known chemical exposure.
- Required tests: named flame-retardant, antistatic or other performance standard and target value.
- Commercial data: quantity, project destination, packaging, labels, OEM marks and required delivery sequence.
Related DERFLEX Engineering Pages
Continue the selection with the duct page that matches your operating condition
Use these related resources to compare general flexible air ducting, pressure-specific structures, industrial exhaust and confined-space applications.
Large Diameter Flexible Ducting Guide
General large-bore sizing, airflow and project-selection overview.
Industrial Ventilation Ducting
Compare supply, extraction and air-distribution architectures.
Spiral Wire-Reinforced Ventilation Duct
Shape-retaining construction for suction, exhaust and bends.
Flexible Ventilation Duct Range
Finished duct category for mine, tunnel and industrial airflow.
Confined Space Ventilation Duct
Portable blower ducting for tanks, vessels and controlled-entry work.
Industrial Exhaust Hose
Flexible fume and process-air routing for extraction systems.
FAQ
Custom large diameter ducting purchasing questions
What is considered custom large diameter ducting?
There is no universal diameter threshold. In industrial projects, “large diameter” normally describes ducting that is large enough for fan matching, reinforcement, handling, section weight and connection geometry to require project review. “Custom” can refer to the bore, length, body construction, reinforcement, cuff, zipper, ring, reducer, color, suspension or OEM identification.
Can DERFLEX review 30, 36, 42 and 48 inch ducting?
These are common large-diameter inquiry sizes and can be reviewed together with metric or non-standard dimensions. Feasibility and final construction depend on pressure direction, reinforcement, section length, fan interface, route geometry and packing requirements.
Can custom large diame, ter flexible ducting be used for suction?
Yes, when the structure is designed to resist collapse under negative pressure. A spiral wire-reinforced or otherwise supported construction is normally evaluated for extraction. A plain layflat duct that depends on positive pressure to stay open should not be assumed suitable for suction.
What information is needed for a custom fan adapter?
Provide the fan outlet ID/OD, flange or spigot geometry, available clamp zone, required duct ID, pressure direction and any offset between the equipment centerline and the duct route. A dimensioned drawing is preferred for reducers, enlargers or non-concentric transitions.
Can flame-retardant or antistatic options be supplied?
Such options can be discussed when the inquiry states the relevant test method, target value and market requirement. The result applies to the confirmed material and finished construction; it should not be assumed from a generic product name.
How should section length be chosen for oversized ducting?
Longer sections reduce joint count, while shorter sections can be easier to lift, route, store and replace. The practical choice depends on diameter, reinforcement weight, available crew, bends, suspension, leakage strategy and transport or storage space.
Project-Based Quotation
Specify the duct around the equipment—not around a generic catalog size
Send your fan outlet, airflow direction, pressure, required diameter, line length, bends, connection style, environment and quantity. DERFLEX can review a suitable custom large diameter ducting construction and quotation scope.
Reference ranges and application descriptions are for product-selection discussion only.
Final product data, test values and compliance statements should follow the approved DERFLEX quotation,
technical specification and applicable project requirements.