The Importance of Right-Sizing Mechanical Draft Fans

mechanical draft fans

When it comes to cement production, mechanical draft fans (raw mill fan, preheater ID fan, and kiln baghouse ID fan) put a significant amount of demand on the system. Often, these fans aren’t performing at max capacity, which means it’s essential to consider possibilities to make them more efficient.

How Draft Fans Are Sized

The peak efficiency point on the fan curve of a mechanical draft fan is typically located a little to the right of the peak capacity curve. Normally, the manufacturer will construct the fan in such a way that the performance curve intersects the system resistance curve at a point of efficiency. However, if the system resistance curve isn’t predicted correctly, the efficiency of the fan is probably going to suffer. Because of the way a fan’s performance changes based on the shape of the system resistance curve, the importance of “right-sizing” draft fans is obvious.

There are a few ways to right-size a fan for more optimal performance. These include the following:

  • Tipping and De-tipping – A method of tipping or de-tipping can be used to help performance characteristics better fit the operating system. This method changes the fan impeller’s effective diameter without changing its effective width. A fan that is being dampered by 40% or more at peak loads is an excellent candidate for de-tipping. However, if more capacity is needed, increasing the effective diameter with the addition of tips may be a good option.
  • Upgrade Blades – Sometimes, if the blades were installed a long time ago and there have been changes in the system, the fan may be operated differently than it was meant to be. This may call for a change in blades — for example, going from radial blades to backward curved blades along with a backward curved rotor.
  • Total Replacement – There are times when the best option is to fully replace the fans. If your draft fans are so grossly inefficient that your plant cannot operate properly and a retrofit isn’t possible, this may be the time to consider a replacement. Although the cost can be intimidating up front, the savings later may amount to tens of thousands of dollars per year — plus additional savings in power usage.

ProcessBarron Can Help!

If you’re looking for a company to partner with you in your plant maintenance, contact ProcessBarron today. We have years of experience helping plants just like yours stay up and running, working at maximum efficiency. Contact us to start a conversation!