7.5KW 304 Stainless Steel High-Temperature,High-Pressure Induced Draft Fan

This article's table of contents introduction:

1. Decoding the Specifications
2. Key Engineering Questions for the Manufacturer
3. Expected Design (Typical Configuration)
4. Estimated Pricing & Sourcing (2024-2025)
5. Critical Warning: 304 vs. 316 in High Temp
6. Final Summary / Recommendation

Based on your query, you are looking for a specific industrial fan: a 5 KW, 304 Stainless Steel, High-Temperature, High-Pressure Induced Draft Fan.

This is a highly specialized piece of equipment used in processes like industrial drying, boilers, fume extraction, or chemical processing where corrosive gases and high temperatures are present.

Here is a breakdown of what this specification means and the key factors you need to consider before sourcing or ordering this fan.

Decoding the Specifications

• 5 KW (Motor Power):

  • This is the power of the electric motor.
  • In a high-pressure, high-temperature scenario, this power is typically coupled with a 4-pole (1450-1500 RPM) or a 2-pole (2900-3000 RPM) motor. A 2-pole motor at 7.5KW will generate much higher pressure than a 4-pole at the same power, but with lower volume.
  • Expected Flow/Pressure: A 7.5KW high-pressure fan might move between 1,500 m³/hr to 5,000 m³/hr depending on the impeller design, with a static pressure typically between 2000 Pa to 6000 Pa.

• 304 Stainless Steel:

  • Material: This is the "corrosion-resistant" element. 304 SS is good for damp, mildly acidic gases, steam, and general food-grade or chemical environments.
  • Limitation: It is not resistant to chlorides (saltwater, bleach, PVC combustion fumes). If your gas has high chloride content, you must upgrade to 316L Stainless Steel or Dual-Phase SS.
  • Construction: All wetted parts (impeller, housing, inlet cone) should be 304 SS. The shaft can be 304 SS or 45# steel with a 304 SS sleeve (common in cheaper models).

• High-Temperature:

  • This implies a design for continuous operation at 150°C to 300°C+ .
  • Critical Design Feature: The motor must be mounted outside the airstream (C-face or foot-mounted on a pedestal). The shaft must pass through a cooling fan or a cooling housing to prevent heat transfer to the motor bearings.
  • Bearing Selection: Standard grease will fail. Need High-Temperature Grease (e.g., Mobil XHP 222) or an oil mist system.
  • Expansion: The housing must have expansion joints or flexible couplings to handle thermal expansion of the metal.

• Induced Draft (ID):

  • This means the fan is placed after the furnace or boiler.
  • Problem: The fan must handle hot, dirty, and potentially wet gases. The pressure is often negative (suction side), which requires a fully welded, airtight housing.
  • Trick: ID fans are prone to corrosion if the gas temperature drops below the acid dew point. The 304 SS helps mitigate this.

• High-Pressure:

  • This requires a Forward-Curved (Sirocco) or Radial Blade (Paddlewheel) impeller.
  • Radial Blade is best for dirty, high-temp gases as it is self-cleaning. It is noisier but more robust.
  • Forward-Curved is more efficient for clean air but prone to dust buildup.

Key Engineering Questions for the Manufacturer

To get the right fan, you cannot just say "7.5KW, 304, High Temp, High Pressure." You must ask:

1. What is the exact gas temperature? (e.g., "Continuous 250°C, Peak 300°C for 15 min")
2. What gas is being moved? (Must specify: "Industrial steam + NOx fumes" vs. "Dry hot air from an oven"). This affects material choice.
3. What is the flow rate (m³/hr) and static pressure (Pa)? (The fan curve defines the KW. A 7.5KW fan can be tuned for high flow/low pressure or low flow/high pressure).
4. What is the altitude/air density? (High altitude reduces motor power output).
5. Is the motor required to be explosion-proof? (If combustibles are present).

Expected Design (Typical Configuration)

If you are ordering this in Southeast Asia (China, Taiwan) or India (common sourcing hubs), the typical construction will be:

• Type: Single Inlet, Single Width (SISW) Centrifugal Fan.
• Housing: Scroll type, made of 4mm-6mm 304 SS, fully welded.
• Impeller: 12-blade Radial or Forward-Curved, made of 3mm-5mm 304 SS. Dynamically balanced to ISO 1940 G6.3 or better.
• Inlet Cone: 304 SS, bolted and aligned to impeller.
• Motor: Standard 7.5KW 2/4 pole, TEFV (Totally Enclosed Fan Ventilated) or IC411. Mounted on a sub-base with belt drive (V-belt) or direct drive (Coupling).
  • Recommendation: Belt drive is better for high-temp. It allows you to change pressure/flow by changing pulleys, and the motor is away from the heat.
• Bearing Assembly: Plummer blocks with cast iron housings, fitted with high-temp spherical roller bearings (e.g., SKF FY series or equivalent). Fitted with a remote grease line.
• Shaft Seal: A labyrinth seal or packing gland to prevent hot air leakage.
• Cooling Fan: A separate cooling fan mounted on the shaft between the housing and the bearing to blow cold air over the shaft.

Estimated Pricing & Sourcing (2024-2025)

• Price Range: For a 5KW 304 SS High-Temp ID fan (not just a basic fan), expect a price of $1,800 - $4,000 USD, depending on:
  • Brand (US/European vs. Chinese/Indian)
  • Certification (ATEX, CE, UL)
  • Impeller class (Class I, II, III - Class II is minimum for this duty).
• Sourcing Options:
  • China: Guangdong or Shandong provinces. (e.g., Yilida, S&F, Nanfang) - Good for volume, check material thickness.
  • India: Ahmedabad (Gujarat) - Good for custom fabrication.
  • Europe: Ziehl-Abegg, FläktGroup, Rosenberg - Expensive but high efficiency.

Critical Warning: 304 vs. 316 in High Temp

Do not use 304 Stainless Steel if the temperature is above 800°F (425°C) or if the gas contains chlorides.

• At high temperatures, 304 becomes prone to sensitization (carbide precipitation at grain boundaries), making it brittle and corrosion-prone.
• If >450°C, you need 310S Stainless Steel (high-temp grade).

Final Summary / Recommendation

To proceed:

1. Confirm your exact duty point: Airflow (m³/s or CFM) and Pressure (Pa or inWG).
2. Confirm max gas temperature (not just working temp).
3. Ask the supplier for a fan curve and a material certificate (MTC) for the 304 SS.
4. Specify a bearing cooling feature (cooling fan on shaft).
5. Consider 316L if the gas is acidic or humid.

If you need a quotation, you must provide the actual flow rate and pressure. A "7.5KW" fan is meaningless without the fan curve. A poorly matched 7.5KW motor will either burn out (undersized for the pressure) or over-speed (dangerous vibration).

Would you like me to calculate a typical pressure range for a 7.5KW 2-pole 304 fan based on standard impeller diameter?