200°C Steam System Exhaust: 3100 m3/h at 1280 Pa

Sizing a Hot Gas Blower for a Steam System

An industrial heating maker needed a new boiler induced draft fan. Meanwhile, they use it to pull hot gases out of a steam boiler. Normal heat levels inside the flue stay very high. Therefore, they reach 180°C to 200°C all day.

Standard blowers fail fast in this heat. In practice, high heat travels right down the steel motor shaft. Next, it ruins standard bearing grease. Finally, it melts the copper wire covering.

So, the client needed a special high-temperature build. The system needs exact airflow to keep burning fuel well. Specifically, the blower must move 3100 m3/h of hot air. Also, it must push against a high static pressure of 1280 Pa.

This high pressure forces air past tight boiler tubes. It also pushes gas up the tall exhaust stack. Furthermore, the tight machine space set hard limits. The fan height could not pass 550 mm.

The total length had to stay under 505 mm. Also, the local power grid supplies 3-phase 415V at 50 Hz. This is not the standard 380V supply. Therefore, we had to match this higher voltage.

A bad voltage match causes extra heat inside the coils. We had to stop extra heat in this hot system. Finally, the fan had to spin fast at 2800 RPM. This high speed meets the pressure target within the tight space limit.

Cooling the Boiler Induced Draft Fan Motor

Engineers look at two main choices for a boiler induced draft fan moving 200°C air. First, they can pick a belt-driven fan. A belt drive keeps the hot casing far away from the motor. However, we rejected a belt drive for this specific project.

Belt drives take up too much room. They also need frequent checks to keep belts tight. Plus, they cause more shaking and noise. Instead, we chose a direct-drive layout.

This setup uses a special heat block between the parts. We put a connecting seat right between the hot wind case and the motor face. This seat holds internal cooling vanes.

How the Cooling Vanes Work

The cooling vanes act like a small extra fan. They spin on the main drive shaft. As they spin, they pull fresh room air over the metal shaft. Therefore, they cool the steel before heat reaches the front motor bearing.

Consequently, the motor handles extreme heat without using a large belt system. However, spinning these extra vanes takes some power. It lowers the total air output just a little bit. Even so, we accepted this small cost. The system must not break down at 200°C.

Material Choices for the Heat Sink

Next, we upgraded the inside parts to handle the stress. We picked high-temperature bearings for the main shaft. We also added special grease that will not turn to liquid. By contrast, a standard motor seizes fast at 200°C.

We also changed the wire wrapping to block heat damage. Weight was another big problem here. Heavy cast-iron parts bend the thin metal on the boiler walls. Therefore, we made the motor casing out of Y2 aluminum alloy.

We die-cast this metal to cut the total weight a lot. Also, aluminum throws off heat much better than rolled steel. This keeps the inner copper wires cooler during long runs.

Final Dimensions and Power Draw

Every choice changes the final size. Adding the cooling seat makes the blower exactly 505 mm long. This length perfectly fits the client space limit. The fan hits the hard 1280 Pa pressure target easily.

Also, the LW5-47-2.2KW-003 model draws 2200 W on the 415V supply. We custom-wound the copper coils for 415V. As a result, the motor avoids the current spikes that hurt 380V motors on 415V lines.

Technical Specifications

The static pressure and heat rows drive this whole design. Pushing 1280 Pa takes a fast 2800 RPM speed. That fast speed makes extra motor heat. Therefore, the aluminum case and cooling seat are strictly needed to survive.

Reference: AMCA 210 covers the test method behind these figures.

Technical Documentation

This sheet shows the specs for the boiler induced draft fan. It lists the strong materials and exact air numbers. Project managers use this file to check the limits.

Download LW5-47-2.2KW-003 Dimensional Drawing
This PDF shows all the exact measurements. Mechanical teams use it to plan the boiler mount. It shows the 11-hole bolt circle and the 505 mm length limit.

How to Specify a Hot Gas Exhaust Blower

Follow these steps if you face a similar heat problem. Getting the numbers right stops early motor failure. * First, check the true air heat exactly at the fan inlet. Do not just read the boiler core heat.

Hot gas cools down as it travels through pipes. So, guessing the heat too high just adds useless cost to the fan. * Next, find the exact static pressure drop. Adding up the drag from all pipes and tight baffles is key for any boiler induced draft fan.

Your fan must push past this full drag limit. If it fails, dangerous fumes will stay inside your building. * Also, check your exact site voltage before you order. Many sites use 400V or 415V power.

A standard 380V motor runs very hot on a 415V grid. This extra heat kills a high-temperature system very fast. * Finally, trust only real test data. We test to exact AMCA 210-16 rules.

As a result, the air volume you plan for matches the real output perfectly. Related:

Blowers.

Common Questions About a Boiler Induced Draft Fan

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