Description

Product Overview

A PP air duct flange is an injection-moulded polypropylene fitting that joins two duct sections with a bolted, removable connection. It is used where a PP duct run needs to be opened later – for maintenance, inspection, filter changes or equipment access – and it matches the round PP duct range from φ110mm to φ1200mm.

The flange is welded to the end of each duct section by hot air welding, and the two flanges are then joined with screws, so the connection can be opened and re-closed without cutting the duct. It is injection moulded in PP or flame retardant PPs, in beige or grey. For the straight duct the flange connects to, see Polypropylene Round Ducts.

A duct flange is one part of a ventilation system: it provides removable joints at the points that need access, while the rest of the run is welded as one sealed system, and matching fittings are available from the same supplier so a complete PP duct line can be specified from one source.

Product Selection Summary

Good Fit

• Duct connections that need to be opened for maintenance, inspection or filter changes
• Equipment access points – at fans, scrubbers, dampers and inspection openings
• Large-diameter main runs from φ110mm to φ1200mm
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ110mm to φ1200mm, 21 standard sizes) and quantity
• Material grade: PP or flame retardant PPs
• Bolted joint details where high-sealing duty or repeated opening is required
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, flexible connectors or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Parameter	Value
Product Type	PP Air Duct Flange (polypropylene duct flange)
Material	PP (polypropylene) or PPs flame retardant grade
Size Range	φ110-1200mm – 21 standard sizes
Connection	Hot air weld to duct; bolted between flanged sections
Fabrication	Injection molding
Color	Beige / Grey
Working Temperature	-15℃ to 80℃
Chemical Resistance	pH 1-14 (acid and alkali)
Certification	ISO9001, ISO14001, RoHS

Available Sizes (φ)

Diameter	Diameter
φ110mm	φ630mm
φ160mm	φ650mm
φ200mm	φ700mm
φ250mm	φ750mm
φ315mm	φ800mm
φ355mm	φ850mm
φ400mm	φ900mm
φ450mm	φ950mm
φ500mm	φ1000mm
φ550mm	φ1200mm
φ600mm

Material & Performance

Because round fittings are injection moulded rather than welded from sheet, the flange keeps the same corrosion resistance as the welded duct while offering consistent moulded dimensions, smooth surfaces and a shorter production time for standard sizes.

PP air duct flanges are injection moulded from polypropylene, chosen for corrosive fume handling in ductwork:

• Acid and alkali resistance: PP withstands corrosion by high-concentration acids and alkalis across a wide pH range (pH 1-14).
• Sound insulation: PP reduces vibration and noise transmitted through the joint.
• Light weight: moulded PP fittings are light and easy to handle and weld on site.
• Consistent moulded dimensions: each size is produced to a standard mould, giving uniform dimensions and wall thickness across batches.
• Long service life: PP duct systems offer a service life of up to 50 years under specified operating conditions.
• Anti-condensation: PP conducts heat poorly, reducing condensation and heat loss at the fitting.
• Wear resistance: the smooth surface resists scaling and deposit buildup at the joint, keeping the connection area clean through service.

Flame retardant PPs is available where fire-rated ductwork is required; specify the required flame retardant grade when inquiring. The material grade applies to the whole fitting, so a single grade can be specified across the duct, fittings and accessories in the run.

Applications

Removable Connection Points

Flanges are used at the points in a duct run that need to be opened without cutting the duct:

• Maintenance and inspection points – opening sections for cleaning and inspection
• Equipment access – at fans, scrubbers, dampers and filter housings that need regular service
• Large-diameter main runs – the 21 sizes from φ110mm to φ1200mm cover main duct connections
• Section joins where sealing matters – bolted flange joints for connections that must hold a seal

In a typical run, most joints are welded for a permanent seal, and flanges are fitted only at the access points – so the system keeps one continuous sealed duct while allowing maintenance where it is needed. When a section is opened and re-closed, the bolted flange joint is simply re-tightened, avoiding the need to cut and re-weld the duct.

Selection Notes & Quotation Information

Flange or Welded Joint?

Welded joints are permanent, sealed connections used along the run. Flange joints are bolted and can be opened, which suits maintenance points and equipment access. Use flanges where the run will need to be opened during service; use welded joints elsewhere for a continuous seal. The two methods work together in most systems.

To Quote PP Air Duct Flange

Provide: duct diameter (φ110-1200mm), quantity, material grade (PP or flame retardant PPs), color (beige or grey), application, destination port, and your duct schedule or drawings.

MOQ and lead time are confirmed per project. Request a quote via WhatsApp or email using the contact block below.

Installation & System Integration

PP air duct flanges are welded to the end of each duct section by hot air welding, then joined to the mating flange with screws. The joint can be opened and re-closed during service, and re-sealed each time it is bolted back together. Bolting is done from outside the duct, so no tools or hands are required inside the run.

Complete systems combine flanges with straight duct, tees, elbows and reducers. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• PP Air Duct Coupling
• PP 90° Elbow
• PP Air Duct Tee
• PP Concentric Reducer
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a PP air duct flange?

It is an injection-moulded polypropylene fitting that joins two duct sections with a bolted, removable connection, used where a run needs to be opened for maintenance, inspection or equipment access.

What sizes are available?

21 standard sizes from φ110mm to φ1200mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500, φ550, φ600, φ630, φ650, φ700, φ750, φ800, φ850, φ900, φ950, φ1000 and φ1200mm.

Flange or welded joint – which should I choose?

Welded joints are permanent and sealed, used along the run. Flange joints are bolted and can be opened, which suits maintenance points and equipment access.

How is it connected?

The flange is welded to the end of each duct section by hot air welding, then the two flanges are joined with screws – the connection can be opened and re-closed without cutting the duct.

Is flame retardant PP available?

Yes. The flange is available in standard PP or flame retardant PPs; specify the required flame retardant grade when inquiring.

What do I need to provide for a quote?

Duct diameter, quantity, material grade, color, application, destination port, and your duct schedule or drawings.