PP Processing Air Valve

Product Model	PP board welded rectangular multi-leaf control valve
Category	PP Machined Products
Reference Price	Price on request

Hot Customizable for Working Conditions 11 Technical Parameters

Product Overview

The PP processed square damper is a plate-welded air volume regulating valve installed in rectangular anti-corrosion air ducts. The valve body is formed by folding and welding PP plates into a square frame, with one or multiple vanes inside. The external handle drives the vanes to rotate synchronously through a link mechanism, changing the cross-sectional ventilation area of the rectangle to achieve air volume regulation and actuation. The square damper matches the cross-section of the rectangular duct and connects via square flanges, making it the primary regulating component for laboratory and workshop rectangular exhaust systems.

For larger rectangular cross-sectional dimensions, a single vane spans a wide area with poor rigidity. Therefore, square dampers typically adopt a multi-vane structure, where multiple narrow vanes are arranged vertically. Each vane is fixed to a small vane shaft, with linkage cranks installed at the end of each shaft. A single link connects all Crank, ensuring that when the handle is turned, all vanes open or close synchronously and at the same angle, providing uniform opening and effortless operation. When the multi-vane damper is closed, the vane edges overlap, offering superior air tightness compared to single large-area dampers.

Xicheng Environmental can plate-weld PP square dampers according to the rectangular duct cross-sectional dimensions. The number of vanes is determined by the valve height, with square flanges matching the square tubes. Sealing strips can be added to the vane edges, and the handle includes an opening scale and lock. The product is widely used for laboratory fume hood exhaust, rectangular ducts in electroplating workshops, and square exhaust pipes in suspended ceilings for air volume balancing.

Working Principle

The multi-vane square damper changes the rectangular flow area by Interconnection vanes. When the external handle is rotated, the active vane shaft rotates, and the Crank at the shaft end transmits the motion synchronously to the remaining vane shafts through a link, causing all vanes to rotate at the same angle. When the vanes are closed, the edges of the blades overlap to seal the cross-section. When open, the blades align parallel to the airflow, forming multiple parallel airflow gaps at intermediate angles. Air flows uniformly through these gaps, with resistance varying continuously with the opening degree.

Compared to single large-area dampers, the multi-vane structure divides the large vane area into multiple narrow blades. Each vane has a small span and strong rigidity, resulting in low aerodynamic torque and minimal vibration. The synchronization of all blades is ensured by the mechanism. The PP material and vanes are acid and alkali resistant. The square valve body is welded or flanged to the rectangular duct using the same material, ensuring continuous corrosion resistance for the system. The Interlocking Pivot and shaft sleeves are made of corrosion-resistant materials to guarantee smooth rotation in corrosive gas environments.

Structural Components

The square damper consists of a rectangular valve body, vanes, vane shafts,Linkage Rod,Crank, handle, and flanges. The valve body is formed by folding and welding four PP plates into a square frame, with square flanges welded at both ends. The vanes are narrow, long PP plate segments arranged parallel along the valve height. Each vane is mounted on a vane shaft, with both ends supported by the valve body side wall shaft holes.

The Crank is installed at the end of the vane shaft on the same side, with all Crank connected by a single vertical link, forming a parallel four-bar Interconnection mechanism. One vane shaft is connected to the external handle and an opening scale. Turning the handle drives all vanes. Sealing strips can be added to the vane edges and ends for sealing when closed. For larger cross-sectional areas,Reinforcement rib are added to the valve body exterior, and the vanes can be designed with Edge folding or arched cross-sections to enhance rigidity.

Specification Model Table

The following table provides the vane configuration and connection details for the square damper, matching the cross-sectional dimensions of the rectangular ducts.

Section Size	Vane Type	Features
Small Section	Single Vane	Simple Structure
Medium-Large Section	Multi-Vane Linkage	Effortless, Uniform Opening
Sealing Type	Multi-Vane with Sealing Strips	More Sealed Closure

Product Features

The PP processed square damper features multi-vane linkage and uniform opening, making it a specialized regulating valve for rectangular anti-corrosion ducts and fume hood exhaust. Key features include:

PP plate-welded rectangular valve body, acid and alkali resistant
Multi-vane linkage ensures consistent actuation and uniform opening
Narrow vanes with small span and strong rigidity, stable under high pressure
Blade overlap for sealed closure, superior to single square dampers
Square flanges for easy installation with rectangular ducts
Customizable section size and vane count to match non-standard ducts
Handle with opening lock, also available with electric actuators

Body Material	PP Sheet
Processing Technology	Panel welding assembly
Section Shape	Rectangle
Valve Leaf Form	Single-piece / Multi-leaf linkage
Drive Type	Hand-operated handle link
Connection Method	Square Flange
Corrosion resistance performance	Acid and Alkali Salt Resistant
Sealing Options	Leaflet edge soft seal
Specifications and Features	Non-standard custom section size
Sheet Thickness	Select according to section size
Electric Options	Support electric actuator retrofitting

Application Industries

Rectangular duct regulating valves for laboratory fume hood exhaust
End damper for laboratory variable air volume exhaust systems
Multi-leaf regulating valves for rectangular exhaust main ducts in electroplating workshops
Square duct air volume balancing dampers for suspended ceilings and interlayers
Rectangular partition dampers for stratified connections in ventilation shafts
Regulating air dampers for large rectangular exhaust equipment inlet and outlet
Non-standard corrosion-resistant duct valves for rectangular cross-section dimensions

Typical Process Locations

Processing dampers are installed on branch ducts, terminations, and main ducts of rectangular ducts. In laboratory fume hood exhaust systems, one square damper is set at the outlet or branch/main duct of each fume hood to adjust the exhaust volume and face velocity of each cabinet. Large-section multi-leaf valves are installed on rectangular main ducts to regulate regional air volume. Valves are connected to square pipes via square flanges, with the operating handle oriented toward maintenance channels. The valve shaft should be installed horizontally to ensure even weight distribution of the valve leaf.

During commissioning, adjust the valve leaf opening and lock the handle in coordination with face velocity or air volume measurements to achieve the designed air volume at each exhaust point. The linkage mechanism of multi-leaf valves is located outside the valve body; sufficient maintenance space must be left to avoid wall-mounted installations that prevent linkage adjustment. For automated control applications, electric actuators can replace handles on the active valve shaft to form electric multi-leaf regulating valves. Before installation, verify the rectangular interface dimensions and flange hole positions. Ensure the valve leaf rotates freely without sticking, and align the valve body with the square pipe before fixing the bracket. During electric retrofitting, match actuator torque with the number of valve leaves, and debug wiring and limit switches in a shutdown state. Regularly inspect linkage pins and seals during operation, and promptly adjust or replace them if Loosen or air leakage is detected.

Rectangular duct sections are typically flat and wide. If a single large vane is used, the vane has a large span and thin plates, which are prone to vibration and distortion under wind pressure, while also exerting significant stress on the shaft, making operation difficult and sealing poor. Multi-leaf valves divide the large section into multiple narrow vanes, each with a small span, high rigidity, and low required torque. Synchronized drive via linkages ensures effortless operation and reduces vibration. Additionally, overlapping adjacent vanes during closure enhances airtightness. Therefore, single-leaf vanes are only used for smaller rectangular sections, while medium and large square sections predominantly employ multi-leaf linkage structures. Multi-leaf valves are also convenient for pairing with electric actuators, where a single active shaft drives all vanes. During selection, the number of vanes is determined based on the rectangular section dimensions and wind pressure. Larger sections and higher wind pressures require correspondingly more vanes and increased shaft rigidity.

Leaf valve leaf synchronization issues are typically caused by loose or Detachment of the coupling pin in the linkage rod, or loose of the crank fixing screw, resulting in some valve leaves not rotating with the main shaft. The machine should be shut down to inspect the linkage rod, crank, and pins. Worn pins should be tightened or replaced, and the fixing screws should be locked. All valve leaves should be manually adjusted to the same angle and the linkage rod repositioned. After the treatment, perform several full-cycle openings and closings to observe whether all leaves open and close consistently, without delay or jamming. During routine inspections, pay attention to the consistency of the opening, ensure the linkage mechanism is not jammed by debris or crystallization, and maintain cleanliness at the pin locations. In corrosive environments, promptly replace rusted metal linkage components or select cranks with corrosion-coated covers. After adjusting the synchronization mechanism, mark it for future reference to check for displacement.

The clearance exists between the vanes of a conventional multi-leaf valve and between the vanes and the valve body, resulting in air leakage even when fully closed. This is a normal characteristic of regulating valves and cannot be measured by the requirements of a sealed valve. If the air leakage increases significantly compared to before, it is necessary to check whether the sealing strips on the vane edges are aging or falling off, whether all vanes are aligned synchronously, whether there are any Miscellaneous Items in the valve body, and whether the vanes are deformed or warped. After cleaning the Miscellaneous Items , aligning the synchronization, and replacing the failed sealing strips, the air leakage generally returns to normal levels. For applications requiring higher gas tightness, an enclosed multi-leaf valve with soft sealing strips on the vanes and side sealing at the ends should be ordered, along with a handle, worm gear, or actuator capable of providing sufficient closing force. When ordering valves for isolation maintenance, the gas tightness specifications must be clearly defined at the time of ordering, and they cannot be replaced with conventional regulating valves afterward.

Cannot directly connect, as the rectangular flange and circular pipe opening have different shapes, making it impossible to achieve a sealed fit. Rectangular square air valves can only be connected to rectangular ducts and rectangular pipe fittings via square flanges. When connecting to round pipes, add square-to-round transition joints at one or both ends of the valve, then connect to round pipes or circular equipment. When ordering, specify whether the valve ends are square or round. If a round-to-square configuration is required, custom-made square-to-round transition air valves can be ordered. One-piece molding results in smoother surfaces and less air leakage compared to on-site assembly. On-site use of diameter reducers or rigid/soft connections for square-to-round cross-sections can cause flow deviation, air leakage, and additional resistance, which is not recommended. When arranging, clearly define the sequence of square-to-round conversions, soft connections, and air valves, and verify the flange standards of each section to ensure a successful one-time connection on-site.

Variable Air Volume Fume Hood System: A standard manual multi-leaf square damper can be installed on the exhaust branch pipe for air volume balancing, and the opening will remain basically fixed after one adjustment. The Variable Air Volume Fume Hood System requires maintaining a constant face velocity when the cabinet door opening changes. An analog electric damper should be equipped at the fume hood outlet, controlled by a face velocity sensor or cabinet door displacement sensor to adjust the actuator and continuously regulate the damper blade opening. Whether an automatic damper is needed depends on the ventilation system type: manual dampers are used for one-time commissioning and balancing, while analog dampers are used for real-time dynamic control. They serve different functions and cannot be mixed. When multiple fume hoods in the same laboratory share a system, each fume hood is typically equipped with one end-of-line control valve, and balancing dampers are installed on the branch pipe. Provide the number of fume hoods, exhaust volume, and face velocity control requirements during selection to ensure the proper matching of manual and automatic dampers.

For custom-made square butterfly valves, the following information is required: the inner cross-sectional dimensions (width x height) of the rectangular valve body, flange outer frame dimensions and hole positions, vane type and quantity requirements, valve body thickness, valve shaft orientation (horizontal or vertical), handle or actuator installation orientation, material (standard PP or flame-retardant PP), whether to add a sealing strip, and pipeline air pressure and medium composition. Providing an air duct cross-sectional drawing and installation space photos helps the manufacturer determine the operating orientation and reinforcement method. Incorrect valve shaft orientation and operating orientation can result in on-site inoperability or maintenance difficulties, so it must be clearly marked on the drawings. For electric control requirements, specify the control signal, power supply, and actuator torque requirements. Complete parameters and clear drawings are essential to ensure the valve matches the air duct, actuator, and on-site space upon arrival, avoiding rework.

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