Custom PP duct sections are polypropylene ventilation pipes made to order for projects that need non-standard sizes, lengths, colors or connections. They are produced from PP sheet welding with flange reinforcement, in standard polypropylene (PP) or flame retardant PPs, in beige or grey. Sizes are customized to your duct schedule, and sections are supplied in 3 m lengths or in lengths confirmed per project.

Because the duct is made to order, it is a good fit when a standard catalog size does not match the duct run, or when material grade, color or connection detail must be specified for a particular project. The XICHENG standard range covers sizes from φ20 mm to φ500 mm; custom ducts extend that range with dimensions confirmed against your drawings. For standard sizes within the catalog range, see Polypropylene Round Ducts.

A custom duct is one part of a ventilation system: it connects to fans, fittings and airflow dampers rather than replacing them, and matching elbows, tees, reducers, flanges and dampers are available from the same supplier, so a complete PP duct line can be specified from one source.

Product Selection Summary

Good Fit

• Projects needing non-standard duct diameters, wall thicknesses or section lengths
• Specific material (PP or flame retardant PPs) or color (beige, grey) requirements
• Duct runs calling for collar or flange connections
• Engineering and OEM projects where dimensions are confirmed from drawings before manufacture

Conditions To Confirm

• Gas composition, concentration, temperature and moisture at the actual operating point
• Required diameter, wall thickness, section length and quantity
• Material grade: PP or flame retardant PPs (specify grade when fire-rated ductwork is required)
• Color (beige or grey) and connection method (collar or flange) for each joint
• Available static pressure and airflow schedule

Not a Replacement For

• Fans, airflow balancing devices, room controls or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Because every section is made to order, all dimensions above are confirmed per project – see Customization Options below for what can be specified, and the selection notes for the information to include with your inquiry.

Customization Options

What Can Be Customized

• Size: diameter, wall thickness and section length are confirmed per project against your duct schedule and drawings. Non-standard sizes are the main reason customers choose a custom duct over a catalog section.
• Material: standard PP or PPs flame retardant grade. Specify the required flame retardant grade when fire-rated ductwork is needed.
• Color: beige or grey, selected per project.
• Connection: collar connection or flange connection, selected per joint to match the rest of the duct run.
• Reinforcement: flange welding is applied where the duct body needs extra support, including large-diameter sections.

Why Order Custom

Catalog sizes do not always match an existing duct layout or a retrofit run. A custom duct lets the section dimensions, material grade, color and connection detail be specified to the project – engineering and OEM projects often supply their own drawings and require ducts made to those drawings. Custom sections also let a facility standardize on one non-catalog diameter across a complete system.

How Custom Orders Are Confirmed

Send your duct schedule and drawings with the inquiry. Each section is confirmed with approved dimensions, wall thickness and connection detail before manufacture, so the delivered duct matches the design. MOQ and lead time are confirmed per project.

Material & Performance

Custom PP round ducts are made from polypropylene, a lightweight thermoplastic synthetic resin with strong corrosion resistance, high-strength mechanical properties and good processing performance. The properties that matter in ventilation ductwork include:

• Acid and alkali resistance: PP withstands corrosion by high-concentration acids and alkalis across a wide pH range (pH 1-14) and a wide temperature range, preventing secondary chemical reactions between the medium and the pipe body.
• Smooth wall, low flow resistance: the smooth, uniform wall of the pipe and its fittings gives low flow resistance and resists scaling and deposit buildup.
• Sound insulation: PP has sound insulation performance that significantly reduces vibration and noise caused by air flow.
• Anti-condensation and low heat loss: PP is a poor thermal conductor, reducing condensation and heat loss along the run.
• Anti-freeze cracking: PP’s elasticity lets the pipe section expand with frost-heaving liquid without bursting.
• Light weight and easy installation: PP duct is light, easy to install and operate, and has excellent weldability – which also helps when custom sections must be handled and joined on site.
• Long service life: PP duct systems offer a service life of up to 50 years under specified operating conditions.

Flame retardant PPs is available where fire-rated ductwork is required; specify the required flame retardant grade when inquiring.

Applications

Custom PP round ducts are used wherever a tailored duct run is required for air movement and corrosive fume handling:

• Laboratory ventilation with non-standard duct layouts, where hood and bench positions fix the duct route.
• Workshop ventilation for corrosive gas treatment at normal temperature conditions.
• Chemical and plating process exhaust where dimensions follow the equipment layout and pipe runs.
• Warehouse ventilation and general air movement.
• Retrofit and replacement runs where existing duct sizes must be matched to extend or repair a system.

PP resists acid and alkali attack (pH 1-14), insulates sound, prevents condensation and stays light and easy to install – properties that apply equally to standard and custom sections.

Selection Notes & Quotation Information

To quote a custom PP round duct, provide: required diameter(s), wall thickness, section length and quantity, material grade (PP or flame retardant PPs), color, connection method (collar or flange), application, destination port, and your duct schedule or drawings. Gas composition, temperature and available static pressure help confirm wall thickness and reinforcement for the actual duty.

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

Installation & System Integration

Custom PP round ducts are connected with collar or flange joints:

• Collar connection: a collar at the section end receives the next section for a stable joint – fast field installation.
• Flange connection: flanges are welded to the duct and joined with screws – suited to high-sealing working conditions and allows maintenance disassembly.
• Hot-air welding: available where a continuous sealed run is preferred.

Large-diameter sections are reinforced with flange welding during production to prevent deformation. Complete systems combine custom ducts with matching accessories: PP 90° elbows, tees, reducers and flanges. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• PP Air Duct
• PP Exhaust Duct
• Flame Retardant PP Duct
• PP 90° Duct Elbow
• PP Duct Flange
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a custom PP round duct?

A custom PP round duct is a polypropylene ventilation pipe made to order: diameter, wall thickness, length, color and connection are confirmed per project instead of taken from a catalog. It is produced by PP sheet welding with flange reinforcement.

What can be customized?

Diameter, wall thickness, section length, material (standard PP or flame retardant PPs), color (beige or grey) and connection method (collar or flange).

What is the standard length?

Custom PP round ducts are supplied in 3 m sections or in lengths confirmed per project.

Is flame retardant PP available?

Yes. PPs flame retardant grade is available; specify the required flame retardant grade when inquiring.

How are custom ducts connected?

Two standard methods are offered: collar connection (a collar at the section end receives the next section) and flange connection (screwed flanges for high-sealing duties). Hot-air welding is available for continuous sealed runs.

How are custom orders confirmed?

Send your duct schedule and drawings with the inquiry. Each section is confirmed with approved dimensions, wall thickness and connection detail before manufacture. MOQ and lead time are confirmed per project.

A manual volume damper, also called a manual air damper valve, is an injection-moulded polypropylene or PVC damper fitted into a PP duct run. The opening is adjusted by hand at the valve, giving local control of airflow volume without an actuator or control signal, and the valve matches the round PP duct range from φ63mm to φ500mm.

The valve is injection moulded in PP or PVC, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Standard sizes cover φ63mm to φ500mm, and custom sizes are made to order. For the straight duct this damper is fitted into, see Polypropylene Round Ducts.

A manual damper valve is one part of a ventilation system: it regulates airflow volume in the run rather than connecting or branching it, 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 runs where airflow volume is set once and adjusted on site
• Branch lines that need local balancing without remote control
• Systems where manual access to the valve position is available
• Projects needing simple, reliable volume control without actuators

Conditions To Confirm

• Duct diameter (φ63mm to φ500mm, 12 standard sizes or custom) and quantity
• Material grade: PP or PVC
• Where the valve will sit in the run and how it will be reached for adjustment
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, back draft dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

For sizes outside the standard range, custom valves are made to order – confirm the required diameter with the project.

Material & Performance

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

Manual volume dampers are injection moulded from PP or PVC, both chosen for corrosive fume handling in ductwork:

• Acid and alkali resistance: the valve body withstands corrosion by acids and alkalis across a wide pH range (pH 1-14).
• Sound insulation: PP and PVC reduce vibration and noise transmitted through the fitting.
• Light weight: moulded 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: plastic duct systems offer a long service life under specified operating conditions; limits depend on the material grade selected.
• Anti-condensation: the material conducts heat poorly, reducing condensation and heat loss at the fitting.

Working temperature and service limits follow the material grade selected – PP or PVC – and are confirmed against the operating conditions when quoting. 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

Manual Balancing

Manual damper valves are fitted where airflow volume is set and adjusted by hand:

• Branch balancing – trimming the volume of each branch to match the design
• Fan outlet control – adjusting flow at the fan discharge
• Terminal volume setting – setting the flow to a hood, hood filter or outlet
• Simple on-site adjustment – re-balancing a run when loads change

The valve is set by hand at the fitting: the opening is adjusted to the required position and left in place, so the volume stays at the set point until the run is re-balanced. With no actuator or control wiring, the manual damper is a simple, low-maintenance option for local flow control.

Selection Notes & Quotation Information

Manual or Electric Damper?

A manual volume damper is adjusted by hand at the valve. An electric air damper valve is driven by an actuator, so it can be adjusted remotely, automatically or from a control system. Choose the manual version where a hand adjustment at the duct is sufficient; choose the electric version where the damper must respond to a controller.

Back Draft or Manual Damper?

A back draft damper is an automatic one-way valve that stops backflow but does not regulate volume. A manual damper valve regulates airflow volume by adjusting the opening. The two serve different functions and can both appear in one system.

To Quote Manual Volume Damper for PP/PVC Duct

Provide: duct diameter (φ63-500mm or custom), quantity, material grade (PP or PVC), 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

Manual volume dampers are joined to the duct run by hot air welding, and the joint is reinforced with a socket connection. The valve is positioned where the opening can be reached for adjustment, then set to the required position after the run is installed. The same joining method applies to straight duct and other fittings, so the valve becomes part of one welded, sealed system.

Complete systems combine manual damper valves with straight duct, rain caps, elbows and couplings. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• Motorized Duct Damper for PP/PVC Duct
• PP Backdraft Damper
• PP Duct Rain Cap
• PP 90° Duct Elbow
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a manual volume damper?

It is an injection-moulded PP or PVC damper fitted into a duct run – the opening is adjusted by hand at the valve, giving local control of airflow volume without an actuator.

How does it work?

The valve is set by hand at the fitting: the opening is adjusted to the required position and left in place, so the volume stays at the set point until the run is re-balanced.

What sizes are available?

12 standard sizes from φ63mm to φ500mm: φ63, φ75, φ90, φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450 and φ500mm – plus custom sizes made to order.

Manual or electric damper – which should I choose?

A manual volume damper is adjusted by hand at the valve. An electric air damper valve is driven by an actuator for remote or automatic adjustment. Choose manual where hand adjustment is sufficient.

What material is it made from?

The valve is injection moulded in PP (polypropylene) or PVC, in beige or grey. Working temperature and service limits follow the material grade selected.

What do I need to provide for a quote?

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

A motorized duct damper, also called an electric air damper valve, is an injection-moulded polypropylene or PVC damper fitted into a PP duct run. An actuator drives the blade to adjust the opening, so airflow volume can be controlled remotely or automatically, and the valve matches the round PP duct range from φ110mm to φ550mm.

The valve is injection moulded in PP or PVC, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Standard sizes cover φ110mm to φ550mm, and custom sizes are made to order. For the straight duct this damper is fitted into, see Polypropylene Round Ducts.

An electric damper valve is one part of a ventilation system: it regulates airflow volume in the run rather than connecting or branching it, 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 runs that need airflow volume adjusted from a control point
• Automated systems that link dampers to fans, fume hoods or room pressure control
• Ducts where manual access to the damper position is impractical
• Projects needing remote or automatic airflow regulation

Conditions To Confirm

• Duct diameter (φ110mm to φ550mm, 10 standard sizes or custom) and quantity
• Material grade: PP or PVC
• Actuator requirements – supply, control signal and mounting are confirmed per project
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, back draft dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

For sizes outside the standard range, custom valves are made to order – confirm the required diameter with the project.

Material & Performance

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

Motorized duct dampers are injection moulded from PP or PVC, both chosen for corrosive fume handling in ductwork:

• Acid and alkali resistance: the valve body withstands corrosion by acids and alkalis across a wide pH range (pH 1-14).
• Sound insulation: PP and PVC reduce vibration and noise transmitted through the fitting.
• Light weight: moulded 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: plastic duct systems offer a long service life under specified operating conditions; limits depend on the material grade selected.
• Anti-condensation: the material conducts heat poorly, reducing condensation and heat loss at the fitting.

Working temperature and service limits follow the material grade selected – PP or PVC – and are confirmed against the operating conditions when quoting. 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

Automated Flow Control

Electric damper valves are fitted where airflow volume must be regulated by a control system rather than by hand:

• Fume hood control – adjusting exhaust volume with the hood in use
• Fan and system coordination – opening or closing with fan start and stop
• Room pressure control – trimming supply or exhaust to hold the room balance
• Central control points – adjusting branch volumes from a panel or controller

The actuator rotates the blade to a set opening, so the valve can be opened, closed or held at an intermediate position for volume control. Because the actuator moves the blade, the damper can be adjusted without entering the duct and without manual access to the valve position.

Selection Notes & Quotation Information

Electric or Manual Damper?

An manual air damper valve is adjusted by hand at the damper. An electric damper valve is driven by an actuator, so it can be adjusted remotely, automatically or from a control system. Choose the electric version where the damper must respond to a controller, a schedule or a linked device; choose the manual version where a hand adjustment at the duct is sufficient.

Back Draft or Electric Damper?

A back draft damper is an automatic one-way valve that stops backflow but does not regulate volume. An electric damper valve regulates airflow volume by adjusting the opening. The two serve different functions and can both appear in one system.

To Quote Motorized Duct Damper for PP/PVC Duct

Provide: duct diameter (φ110-550mm or custom), quantity, material grade (PP or PVC), color (beige or grey), actuator requirements, 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

Motorized duct dampers are joined to the duct run by hot air welding, and the joint is reinforced with a socket connection. The actuator is mounted on the valve and connected to the control supply according to the project specification, so the actuator details are confirmed before production. The same joining method applies to straight duct and other fittings, so the valve becomes part of one welded, sealed system.

Complete systems combine electric damper valves with straight duct, rain caps, elbows and couplings. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• Manual Volume Damper for PP/PVC Duct
• PP Backdraft Damper
• PP Duct Rain Cap
• PP 90° Duct Elbow
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a motorized duct damper?

It is an injection-moulded PP or PVC damper fitted into a duct run – an actuator drives the blade to adjust the opening, giving remote or automatic control of airflow volume.

How does it work?

The actuator rotates the blade to a set opening, so the valve can be opened, closed or held at an intermediate position. Because the actuator moves the blade, the damper can be adjusted without manual access to the valve.

What sizes are available?

10 standard sizes from φ110mm to φ550mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500 and φ550mm – plus custom sizes made to order.

Electric or manual damper – which should I choose?

An electric damper valve is driven by an actuator for remote, automatic or control-system adjustment. A manual air damper valve is adjusted by hand at the duct. Choose electric where the damper must respond to a controller.

What material is it made from?

The valve is injection moulded in PP (polypropylene) or PVC, in beige or grey. Working temperature and service limits follow the material grade selected.

What do I need to provide for a quote?

Duct diameter, quantity, material grade (PP or PVC), color, actuator requirements, application, destination port, and your duct schedule or drawings.

A PP square duct elbow is an injection-moulded polypropylene 90° fitting that turns a rectangular PP duct run through 90° in one corner. It is the fitting used where square ductwork changes direction – along walls, across ceilings or around obstacles – and it is custom-made to match the dimensions of the rectangular duct sections it connects to.

The elbow is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Because each elbow is made to order, dimensions, wall thickness and corner radius are confirmed with the project before production. For the straight duct this elbow connects to, see Polypropylene Rectangular Ducts.

A square duct elbow is one part of a ventilation system: it changes the direction of the run rather than connecting or branching it, 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

• Turning a rectangular PP duct run through 90° at a wall or ceiling corner
• Routing square ductwork around obstacles, columns or equipment
• Building long main lines that follow the building structure
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Rectangular duct section dimensions (width, height) for the custom elbow
• Material grade: PP or flame retardant PPs
• Gas composition, concentration, temperature and moisture at the operating point
• Whether the run needs removable access at the change of direction (use flanges there instead)

Not a Replacement For

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

Technical Specifications

Confirmed Product Parameters

Because this elbow is made to order, there is no standard size list: the width and height of the duct section, the corner radius and the quantity are confirmed per project before production.

Material & Performance

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

PP square duct elbows 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 fitting.
• Light weight: moulded PP fittings are light and easy to handle and weld on site.
• Consistent moulded dimensions: each elbow is produced to a standard mould, giving uniform dimensions and wall thickness.
• 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.

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

90° Direction Changes in Rectangular Systems

Square duct elbows are used at the points where a rectangular duct run changes direction by 90°:

• Wall and ceiling corners – turning the run to follow the building structure
• Obstacle bypass – routing around columns, beams and equipment
• Main line routing – changing the direction of long square mains
• Branch take-offs – connecting a branch line at right angles to the main

Each elbow adds one corner to the run. Because the fitting is made to the same section size as the duct, the change of direction keeps one continuous cross-section, and the joint is sealed by the same hot air welding used for the rest of the square duct run.

Selection Notes & Quotation Information

Square or Round Elbow?

A square duct elbow is used in rectangular duct systems and is custom-made to match the duct section. A round PP elbow is a standard moulded fitting used in round duct systems, with 17 standard sizes from φ20mm to φ500mm. Choose the square elbow where the system uses rectangular duct, typically for space-efficient runs along walls and ceilings; choose the round elbow where the run uses round duct with standard sections.

To Quote PP Square Duct 90° Elbow

Provide: rectangular duct section dimensions (width and height), 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 square duct elbows are joined to the duct run by hot air welding, and each joint is reinforced with a socket connection. The same joining method applies to straight square duct and other rectangular fittings, so the run is welded and sealed as one continuous system.

Because the elbow is made to order, its dimensions are confirmed against your duct schedule before production, so the fitting arrives sized to the run and is welded on site with the same tools used for the straight sections.

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

Related Products

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

FAQ

What is a PP square duct 90° elbow?

It is an injection-moulded polypropylene fitting that turns a rectangular PP duct run through 90° in one corner, used where square ductwork changes direction along walls, across ceilings or around obstacles.

What sizes are available?

The elbow is custom-made to match your rectangular duct section dimensions – width and height are confirmed per project, so there is no standard size list.

Square or round elbow – which should I choose?

A square duct elbow is used in rectangular duct systems and is custom-made to match the duct section. A round PP elbow is a standard fitting used in round duct systems with 17 standard sizes.

How is it connected?

By hot air welding to the duct sections, with socket connection reinforcement at the joint – the same method used for straight square duct and other rectangular fittings.

Is flame retardant PP available?

Yes. The elbow 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?

Rectangular duct section dimensions (width and height), quantity, material grade, color, application, destination port, and your duct schedule or drawings.

A PP backdraft damper is an injection-moulded polypropylene one-way valve fitted into a PP duct run. It opens with forward airflow and closes when airflow stops, so air, fumes and odours cannot move back into the duct, and it matches the round PP duct range from φ110mm to φ600mm.

The damper is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Standard sizes cover φ110mm to φ600mm, and custom sizes are made to order. For the straight duct this damper is fitted into, see Polypropylene Round Ducts.

A backdraft damper is one part of a ventilation system: it controls flow direction in the run rather than connecting or branching it, 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 runs that must not allow backflow when the fan is off
• Exhaust lines where fumes or odours could return into the space
• Outlet protection combined with a rain cap or wall terminal
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ110mm to φ600mm, 11 standard sizes or custom) and quantity
• Material grade: PP or flame retardant PPs
• The intended airflow direction through the damper
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, rain caps, motorised control dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

For sizes outside the standard range, custom dampers are made to order – confirm the required diameter with the project.

Material & Performance

Because round fittings are injection moulded rather than welded from sheet, the damper 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 backdraft dampers 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 fitting.
• 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.

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

One-Way Flow Control

Backdraft dampers are fitted at the points in a duct run where airflow must move in one direction only:

• After the fan – preventing air moving back through the fan when it is off
• Before the outlet – stopping fumes and odours returning into the building through the exhaust
• On branch lines – isolating a branch so air does not flow back from the main line
• At outdoor terminals – combined with a rain cap to keep backflow and weather out of the duct

With forward airflow the damper opens and the run flows freely; when the fan stops or pressure reverses, the damper closes and seals the run. This is automatic – no actuator or operator is needed for the one-way function.

Selection Notes & Quotation Information

Back Draft Damper or Control Damper?

A backdraft damper is an automatic one-way valve: it opens and closes by itself to stop backflow. A control damper – such as an electric damper valve or manual air damper valve – regulates airflow volume by adjusting the opening. Use a backdraft damper where backflow protection is the need; use a control damper where airflow must be adjusted or shut off.

To Quote PP Backdraft Damper

Provide: duct diameter (φ110-600mm or custom), quantity, material grade (PP or flame retardant PPs), color (beige or grey), airflow direction, 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 backdraft dampers are joined to the duct run by hot air welding, and the joint is reinforced with a socket connection. The damper is installed in the direction of intended airflow, so the flow direction is confirmed before fitting. The same joining method applies to straight duct and other fittings, so the damper becomes part of one welded, sealed system.

Complete systems combine backdraft dampers with straight duct, rain caps, elbows and couplings. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• PP Duct Rain Cap
• Motorized Duct Damper for PP/PVC Duct
• Manual Volume Damper for PP/PVC Duct
• PP 90° Duct Elbow
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a PP backdraft damper?

It is an injection-moulded polypropylene one-way valve fitted into a PP duct run – it opens with forward airflow and closes when airflow stops, so air, fumes and odours cannot move back into the duct.

How does it work?

With forward airflow the damper opens and the run flows freely; when the fan stops or pressure reverses, the damper closes and seals the run. The one-way function is automatic, with no actuator or operator.

What sizes are available?

11 standard sizes from φ110mm to φ600mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500, φ550 and φ600mm – plus custom sizes made to order.

Backdraft damper or control damper – which should I choose?

A backdraft damper is an automatic one-way valve for backflow protection. A control damper – electric or manual – regulates airflow volume by adjusting the opening. Use each where its function is needed.

Is flame retardant PP available?

Yes. The damper 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, airflow direction, application, destination port, and your duct schedule or drawings.

A PP duct rain cap is an injection-moulded polypropylene terminal fitting that fits over the outlet of a PP exhaust duct run. It shields the opening so rain, snow and debris stay out of the duct, and it matches the round PP duct range from φ110mm to φ600mm.

The rain cap is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. It is fitted as the last part of the run, over the outlet of a roof or wall exhaust duct. For the straight duct this rain cap is fitted to, see Polypropylene Round Ducts.

A duct rain cap is one part of a ventilation system: it protects the outlet of the run rather than connecting or branching it, 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

• Roof and wall exhaust outlets that must stay clear of rain and snow
• Exhaust runs where debris could enter the open duct end
• Terminal protection for the outlet of a PP fume or ventilation line
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ110mm to φ600mm, 11 standard sizes) and quantity
• Material grade: PP or flame retardant PPs
• Gas composition, concentration, temperature and moisture at the operating point
• Whether the outlet also needs airflow backflow protection (use a back draft damper there)

Not a Replacement For

• Fans, airflow balancing devices, back draft dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

Material & Performance

Because round fittings are injection moulded rather than welded from sheet, the rain cap 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 duct rain caps 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 fitting.
• 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 moulded surface resists scaling and deposit buildup, keeping the outlet 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

Terminal Protection for Exhaust Outlets

Rain caps are fitted over the open outlet at the end of an exhaust duct run, where the duct passes through a roof or an outside wall:

• Roof exhaust outlets – protecting the vertical outlet from rain and snow
• Wall exhaust outlets – shielding the horizontal outlet at the building face
• Fume and ventilation terminals – keeping debris out of the last section of the run
• Outdoor duct ends – reducing water entry where the duct is exposed to weather

The rain cap is the last part of the run, so it does not affect airflow balance inside the duct: it protects the opening while the exhaust stream continues to leave through the outlet.

For an exhaust outlet, the rain cap is welded over the end of the duct after the run is complete, so the fitting is added as the final step of installation. Because the cap is made to the same standard sizes as the round duct range, it can be ordered with the rest of the run and welded on site with the same tools.

Selection Notes & Quotation Information

Rain Cap or Back Draft Damper?

A rain cap protects the outlet of the run from rain, snow and debris entering through the open end. A back draft damper stops airflow moving back into the duct when the system is off. The two protect the outlet in different ways and can be used together: the damper stops backflow inside the duct, and the rain cap shields the opening from weather.

To Quote PP Duct Rain Cap

Provide: duct diameter (φ110-600mm), 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 duct rain caps are joined to the outlet of the duct run by hot air welding, and the joint is reinforced with a socket connection. The same joining method applies to straight duct and other fittings, so the rain cap becomes part of the same welded, sealed system.

Complete systems combine rain caps with straight duct, flanges, couplings and elbows. See the full range of PP duct systems.

Related Products

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

FAQ

What is a PP duct rain cap?

It is an injection-moulded polypropylene terminal fitting that fits over the outlet of a PP exhaust duct run, shielding the opening so rain, snow and debris stay out of the duct.

What sizes are available?

11 standard sizes from φ110mm to φ600mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500, φ550 and φ600mm.

Rain cap or back draft damper – which should I choose?

A rain cap protects the outlet from rain and debris entering through the open end. A back draft damper stops airflow moving back into the duct when the system is off. They can be used together.

How is it connected?

By hot air welding to the outlet of the duct run, with socket connection reinforcement at the joint – the same method used for straight duct and other round fittings.

Is flame retardant PP available?

Yes. The rain cap 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.

A PP duct coupling is an injection-moulded polypropylene fitting that joins two duct sections end to end, making a long run one continuous line. It is the fitting used where a PP duct is extended, repaired or connected section to section, and it matches the round PP duct range from φ110mm to φ600mm.

The coupling is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Being a moulded fitting, each size has consistent dimensions and wall thickness across batches. For the straight duct the coupling connects to, see Polypropylene Round Ducts.

A duct coupling is one part of a ventilation system: it connects straight duct sections together rather than replacing them, 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

• Extending a PP duct run with additional straight sections
• Repairing or re-joining a cut duct section in place
• Building long main lines from standard duct sections
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ110mm to φ600mm, 11 standard sizes) and quantity
• Material grade: PP or flame retardant PPs
• Gas composition, concentration, temperature and moisture at the operating point
• Where the run needs removable access (use flanges there instead)

Not a Replacement For

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

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

Material & Performance

Because round fittings are injection moulded rather than welded from sheet, the coupling 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 couplings 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 moulded surface resists scaling and deposit buildup, keeping the joint 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

Extending and Repairing Duct Runs

Couplings connect straight duct sections end to end, which is how a long main line is built from standard sections and how a damaged section is replaced:

• Run extension – adding straight sections to reach new equipment or extend the line
• Section replacement – cutting out a damaged section and coupling a new one into the run
• Standard-section building – assembling long mains from factory duct lengths
• Joint reinforcement – the socket connection reinforces each end-to-end joint

Each coupling adds one welded joint to the run. Along a straight line, the joint is sealed by the same hot air welding used for the rest of the duct, so the extended run keeps one continuous corrosion-resistant interior.

For a run extension, the new straight section is aligned with the existing line, the coupling is welded over the joint, and the socket connection reinforces the join before the next section continues. This keeps later adjustments simple: a section can be cut out and a new one coupled in without replacing the whole run.

Selection Notes & Quotation Information

Coupling or Flange?

A coupling makes a permanent welded joint that extends the run as one continuous line. A duct flange makes a bolted joint that can be opened later. Use couplings along the run for permanent connection; use flanges at maintenance points and equipment access.

To Quote PP Duct Coupling

Provide: duct diameter (φ110-600mm), 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 couplings are joined to the duct run by hot air welding, and each joint is reinforced with a socket connection. The same joining method applies to straight duct and other fittings, so the extended run is welded and sealed as one continuous system.

The socket connection is formed as part of the moulded coupling, so the joint is reinforced by a sleeve of the same material rather than relying on the weld seam alone. This gives the end-to-end connection additional stiffness at the joint while keeping the interior smooth for airflow.

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

Related Products

• Polypropylene Round Ducts
• PP Duct Flange
• PP 90° Duct Elbow
• PP Duct Tee
• PP Duct Reducer (Concentric)
• 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 coupling?

It is an injection-moulded polypropylene fitting that joins two duct sections end to end, making a long run one continuous line – used to extend, repair or connect PP duct runs.

What sizes are available?

11 standard sizes from φ110mm to φ600mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500, φ550 and φ600mm.

Coupling or flange – which should I choose?

A coupling makes a permanent welded joint that extends the run as one continuous line. A flange makes a bolted joint that can be opened later, used at maintenance points.

How is it connected?

By hot air welding to the duct sections, with socket connection reinforcement at the joint – the same method used for straight duct and other round fittings.

Is flame retardant PP available?

Yes. The coupling 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.

A PP 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

Available Sizes (φ)

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 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 Duct Coupling
• PP 90° Duct Elbow
• PP Duct Tee
• PP Duct Reducer (Concentric)
• 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.

A PP duct reducer is an injection-moulded polypropylene fitting that connects two duct sections of different diameters. It is the fitting used where a PP duct run changes size – at equipment connections, where a main duct steps down to a branch, or where airflow is rebalanced along the run – and it matches the round PP duct range.

Concentric means both ends share the same centre line, so the transition is symmetrical around the duct axis. The reducer is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joints. For the straight duct the reducer connects to, see Polypropylene Round Ducts.

A duct reducer is one part of a ventilation system: it connects to straight duct, tees, elbows and other fittings rather than replacing them, 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

• PP duct runs that change diameter between two sections or at equipment connections
• Connecting equipment outlets or fan connections to the main duct size
• Corrosive exhaust and ventilation systems using the round PP duct range
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Inlet and outlet diameters (the two sizes being connected)
• Material grade: PP or flame retardant PPs
• Gas composition, concentration, temperature and moisture at the operating point
• Whether a standard size (φ20-500mm) covers the transition or a custom size is needed

Not a Replacement For

• Fans, airflow balancing devices, dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Standard sizes cover φ20mm to φ500mm. A transition to a larger diameter, such as φ600mm, or a non-standard pair of inlet and outlet sizes is made to order – confirm the two diameters against your duct schedule when inquiring.

Material & Performance

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

PP concentric reducers 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 caused by air flow through the size change.
• 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.

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

When a Duct Run Uses a Reducer

A reducer is used wherever the duct diameter changes along the run:

• Equipment connections – matching a fan, hood or scrubber outlet to the main duct size
• Main to branch steps – where a distribution main reduces before feeding smaller branch lines
• Flow adjustment – stepping the duct size to suit the airflow carried by each section
• Existing system modifications – joining new duct of a different size into an existing run

Because the concentric reducer keeps both ends on a common centre line, it is suited to vertical runs and installations where the duct axis must stay aligned through the size change. On horizontal runs the same fitting is used where alignment is not a constraint, and the welded transition keeps the whole section sealed as part of the continuous duct.

Selection Notes & Quotation Information

Inlet and Outlet Diameters

Confirm both diameters when ordering: the larger end and the smaller end of the transition. If one end falls outside the standard φ20-500mm range – for example a φ600mm connection – the reducer is made to order and the size pair is confirmed against your duct schedule and drawings.

To Quote PP Duct Reducer (Concentric)

Provide: inlet diameter, outlet diameter, 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 concentric reducers are joined to the duct run by hot air welding, and each joint is reinforced with a socket connection. The same joining method applies to straight duct, elbows and tees, so the reducer can be welded into the run as part of one continuous sealed system.

Where a run will be disassembled later for maintenance, flange connections are used at those points instead, so the reducer can be bolted between flanged sections.

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

Related Products

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

FAQ

What is a PP concentric reducer?

It is an injection-moulded polypropylene fitting that connects two duct sections of different diameters, with both ends on a common centre line, used where a run changes size.

What sizes are available?

Standard sizes cover φ20mm to φ500mm. Larger transitions, such as φ600mm, or non-standard inlet-outlet pairs are made to order against your duct schedule and drawings.

Concentric or eccentric – what is the difference?

Concentric reducers keep both ends on the same centre line, suited to vertical runs and aligned connections. The XICHENG range offers concentric reducers as the standard fitting.

How is it connected?

By hot air welding to the duct run, with socket connection reinforcement at each joint – the same method used for straight duct and other round fittings.

Is flame retardant PP available?

Yes. The reducer 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?

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

A PP duct tee is an injection-moulded polypropylene fitting with three openings that branches a ventilation run into two directions. It is the fitting used where a main duct distributes airflow to a branch line, or where two branch lines join back into a main run, and it matches the round PP duct range from φ20mm to φ500mm.

The tee is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joints. Being a moulded fitting, each size has consistent dimensions and wall thickness across batches. For the straight duct the tee connects to, see Polypropylene Round Ducts.

A duct tee is one part of a ventilation system: it connects to straight duct, elbows, reducers and other fittings rather than replacing them, 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

• PP duct runs that need to branch a main line into one or more branch lines
• Distribution systems feeding multiple exhaust points, hoods or workstations
• Corrosive exhaust and ventilation systems using the round PP duct range
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ20mm to φ500mm, 17 standard sizes) and quantity
• Material grade: PP or flame retardant PPs
• Branch position and the number of branch points in the run
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Available Sizes (φ)

Material & Performance

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

PP duct tees 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 caused by air flow through the branch point.
• 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.

Flame retardant PPs is available where fire-rated ductwork is required; specify the required flame retardant grade when inquiring.

Applications

Main and Branch Duct Structure

In a ventilation system, the tee is the connection point where ducting splits: a main duct carries the airflow along the run, and at each tee a branch duct leads off to an exhaust point, hood, bench or workstation. The same fitting also works in reverse, joining branch lines back into the main return run.

• Distribution runs – one main line feeding several branch lines
• Multi-point exhaust – fume hoods, benches and cabinets connected along one main duct
• Collection runs – branch lines merging into a main line to the fan or scrubber
• Exhaust and ventilation systems – the same fitting serves laboratory, workshop and chemical exhaust runs built from round PP duct

A typical branch layout runs the main duct along the length of the room or building, with a tee at each distribution point and a short branch duct leading to the exhaust point. This lets one main line serve several hoods or benches from a single fan and control setup, which is why tees are among the most common fittings in a multi-point PP duct system. Each branch can be fitted with its own damper or valve where individual airflow control is needed at the exhaust point.

Selection Notes & Quotation Information

Equal-Size Tees and Diameter Changes

The standard tee has three equal openings of the same diameter, matching the duct size at the branch point. Where the branch line uses a smaller diameter than the main line, add a concentric reducer at the branch opening so both sides weld to matching diameters.

To Quote PP Duct Tee

Provide: duct diameter (φ20-500mm), 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 duct tees are joined to the duct run by hot air welding, and each joint is reinforced with a socket connection. The same joining method applies to straight duct, elbows and reducers, so the whole main and branch structure can be welded and sealed as one continuous system, with no mechanical clamps required along the welded joints.

Where a run will be disassembled later for maintenance, flange connections are used at those points instead, so the tee can be bolted between flanged sections.

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

Related Products

• Polypropylene Round Ducts
• PP 90° Duct Elbow
• PP 45° Duct Elbow
• PP Duct Reducer (Concentric)
• PP Duct Flange
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a PP duct tee?

It is an injection-moulded polypropylene fitting with three openings that branches a round PP duct run into two directions, connecting main and branch duct at the distribution point.

What sizes are available?

17 standard sizes from φ20mm to φ500mm: φ20, φ25, φ32, φ40, φ50, φ63, φ75, φ90, φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450 and φ500mm.

Can the branch be a different size from the main duct?

The standard tee has three equal openings. For a smaller branch, add a concentric reducer at the branch opening so both sides weld to matching diameters.

How is it connected?

By hot air welding to the duct run, with socket connection reinforcement at each joint – the same method used for straight duct and other round fittings.

Is flame retardant PP available?

Yes. The tee 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.