This article's table of contents introduction:
- What is a Double Suction Centrifugal Fan?
- The Role: Primary Air Fan (PA Fan) in a Boiler
- Why "Blue"? (Color Code)
- Key Features of a Double Suction Centrifugal PA Fan
- Typical Specifications (Example)
- Common Manufacturers (often seen in Blue)
- Common Issues & Maintenance
- Summary
It seems you are referring to a Double Suction Centrifugal Fan used as a Primary Air Fan in a boiler system, likely in a thermal power plant or industrial boiler. The phrase "Blue" likely refers to the color of the fan casing or impeller, which is common for industrial equipment.
Here is a detailed breakdown of this equipment, its application, and specifications.
What is a Double Suction Centrifugal Fan?
A Double Suction (Double Inlet) Centrifugal Fan draws air from both sides of the impeller. This design allows for higher flow rates (CFM/m³/h) compared to a single suction fan of the same diameter, while maintaining a relatively compact footprint and balanced axial thrust.
The Role: Primary Air Fan (PA Fan) in a Boiler
In a coal-fired or biomass boiler, the Primary Air Fan serves two critical functions:
- Drying the Fuel: Hot primary air dries the coal in the pulverizer (mill).
- Transporting the Fuel: It carries the pulverized coal from the mill to the burners.
Therefore, the PA Fan must be highly reliable, capable of handling high temperatures (preheated air) and often slightly dirty air.
Why "Blue"? (Color Code)
- Standard Industrial Color: Many industrial fan manufacturers, especially in Asia (e.g., Howden, TLT-Babcock, or local Chinese brands), paint their PA fans blue (RAL 5010, RAL 5012, or dark navy). This is a standard protective coating against corrosion and wear.
- Not a Technical Specification: "Blue" is just the paint color. It does not indicate a specific technical feature.
Key Features of a Double Suction Centrifugal PA Fan
| Feature | Benefit |
|---|---|
| Double Inlet / Double Suction | High volume airflow required for coal transport. |
| Centrifugal Design | High pressure rise needed to overcome system resistance (mills, ductwork, burners). |
| Backward Curved / Airfoil Blades | High efficiency (up to 85-88%), lower noise, stable operation. |
| Robust Casing (Blue Paint) | Resists abrasion from dust and thermal stress. |
| Inlet Guide Vanes (IGV) | Variable control of airflow for load following (power generation). |
| Hollow Shaft / Shaft Cooling | Prevents heat transfer from the hot air to bearings. |
Typical Specifications (Example)
- Application: Primary Air for 300 MW or 600 MW coal-fired boiler.
- Fan Type: Double Suction, Single Stage, Centrifugal.
- Flow Rate: 150,000 – 400,000 m³/h (depending on boiler size).
- Total Pressure: 5,000 – 12,000 Pa (0.7 – 1.75 psi).
- Operating Temperature: 20°C (cold start) to 350°C (after air preheater).
- Drive: Motor + Coupling + Bearings (or direct drive).
- Material: Casing: Carbon Steel (Q235/SS400); Impeller: Corten or High Tensile Steel.
Common Manufacturers (often seen in Blue)
- Howden (Renowned for heavy-duty fans)
- TLT-Turbo GmbH (German engineering, often blue-gray)
- FLSmidth
- Sichuan Milectric (Chinese OEM, blue is standard)
- Shenyang Blower Works
Common Issues & Maintenance
- Bearing Vibration: Due to rotor imbalance from dust buildup.
- Erosion/Wear: On the impeller blades and volute tongue (from coal dust).
- Overload: If the mill system clogs or the air heater is blocked.
- Hot Bearing Failure: Insufficient shaft cooling or lubrication.
Summary
A "Double Suction Centrifugal Fan Primary Air Fan In Boiler Blue" is simply a standard, high-reliability industrial fan designed to move large volumes of hot, slightly dusty air for drying and transporting coal. The blue color is cosmetic, but indicates a standard industrial finish (often epoxy or polyester powder coating). If you are looking to purchase, replace, or repair one, you will need to specify the flow, pressure, temperature, and motor power rather than the color.
