Stainless steel duct fittings are core components in heating, ventilation, and air conditioning (HVAC) systems, as well as industrial ventilation setups. They ensure airflow efficiency, system integrity, and adaptability to complex installation environments. Below are the key types of stainless steel duct fittings, along with their professional definitions, functional characteristics, and typical applications:  

 

 

1. Bends (Elbows & Long Radius Bends)  

Function: Redirect airflow by changing duct direction while minimizing pressure loss and turbulence.  

Classification:  

- Elbows: Bending radius ≤ 1.5× duct diameter; common angles include 45°, 90°, and 135°. Designed for space-constrained areas.  

- Long Radius Bends: Bending radius ＞ 1.5× duct diameter; reduces airflow resistance and noise, suitable for high-velocity ventilation systems.  

Application: Used in duct routing around structural obstacles (e.g., beams, columns) in commercial buildings, industrial plants, and cleanrooms.  

 

 

2. Tee & Cross Fittings  

Function: Enable airflow diversion (splitting one air stream into multiple) or confluence (merging multiple streams into one) while maintaining pressure stability.  

Classification:  

- Tee Fittings: 3-way connections (one inlet, two outlets or vice versa); available in equal-diameter (same size for all ports) and reducing-diameter (different port sizes) variants.  

- Cross Fittings: 4-way connections (one central port, four branch ports); used for complex airflow distribution.  

Application: Critical in HVAC systems for zone-specific ventilation (e.g., office buildings, shopping malls) and industrial exhaust systems requiring multi-point air collection.  

 

 

3. Reducers (Concentric & Eccentric)  

Function: Transition between ducts of different diameters to adapt to airflow volume changes or equipment interface requirements.  

Classification:  

- Concentric Reducers: Centerlines of inlet/outlet align; ideal for vertical duct runs, ensuring uniform airflow.  

- Eccentric Reducers: Centerlines offset; prevents air pocket formation in horizontal ducts, widely used in fuel gas or exhaust systems.  

Application: Connecting fans, air handlers, or filters to main ductwork; common in power plants, chemical facilities, and HVAC systems.  

 

 

4. Flanges  

Function: Provide rigid, leak-tight connections between duct sections, equipment, or fittings; facilitate assembly, disassembly, and maintenance.  

Features:  

- Manufactured to match duct thickness (e.g., 1.2mm–3.0mm stainless steel) for structural consistency.  

- Sealed with heat-resistant, corrosion-resistant gaskets (e.g., EPDM, silicone) and secured with stainless steel bolts to avoid galvanic corrosion.  

Application: Mandatory in high-pressure duct systems (e.g., industrial dust collection) and environments with corrosive fumes (e.g., chemical processing plants).  

 

 

5. Flexible Connectors  

Function: Absorb vibration from fans or blowers, reduce noise transmission, and compensate for minor installation misalignments.  

Features: Constructed with stainless steel bellows or coated fabric (reinforced with stainless steel wire) for corrosion resistance; short length (typically 150mm–300mm) to maintain rigidity.  

Application: Installed between fans, pumps, or air handlers and rigid ductwork in HVAC systems, power generation facilities, and pharmaceutical cleanrooms.  

 

 

6. Guide Vanes  

Function: Optimize airflow distribution, eliminate dead zones, and reduce turbulence in duct bends or junctions; enhance system energy efficiency.  

Features: Streamlined, aerodynamic blades (stainless steel 304/316) mounted inside ducts; adjustable designs available for fine-tuning airflow direction.  

Application: Critical in precision environments such as semiconductor cleanrooms, laboratory fume hoods, and hospital operating rooms where uniform airflow is required.  

 

 

7. Duct Silencers (Acoustic Attenuators)  

Function: Reduce airborne noise generated by airflow, fans, or equipment within duct systems; comply with occupational noise standards (e.g., OSHA ≤ 85 dB(A)).  

Classification:  

- Resistive Silencers: Use sound-absorbing materials (e.g., glass wool wrapped in stainless steel mesh) to dampen broadband noise.  

- Reactive Silencers: Utilize acoustic chambers and baffles to reflect and cancel low-frequency noise.  

- Combination Silencers: Integrate resistive and reactive mechanisms for full-spectrum noise control.  

Application: Installed in HVAC return/exhaust ducts, industrial exhaust systems, and data center cooling ducts.  

 

 

8. Round-to-Rectangular Transitions  

Function: Facilitate smooth connections between circular and rectangular duct sections; minimize pressure loss and airflow disturbance during shape transitions.  

Features: Gradual, aerodynamic contour design to avoid abrupt airflow changes; welded or flanged ends for secure connection.  

Application: Used where circular equipment (e.g., centrifugal fans) interfaces with rectangular ductwork—common in commercial buildings, food processing plants, and HVAC retrofits.  

 

 

9. Auxiliary Fittings  

- Duct Caps/Plugs: Seal unused duct ends or openings to prevent air leakage, dust ingress, or cross-contamination; available in threaded or welded designs.  

- Duct Hangers & Supports: Secure ductwork to ceilings, walls, or floors; include rod hangers, angle brackets, and floor stands (all stainless steel to match duct corrosion resistance).  

- Duct Access Panels: Provide entry points for inspection, cleaning, or maintenance; equipped with airtight gaskets to maintain system efficiency.  

 

 

Stainless steel duct fittings, with their inherent corrosion resistance, durability, and hygiene (critical for food, pharmaceutical, and medical industries), are preferred over carbon steel alternatives in harsh or sterile environments. The selection of specific fittings depends on system pressure, airflow velocity, medium (e.g., clean air, corrosive fumes), and installation space constraints.