High Temperature Industrial Fans

High temperature industrial fans in heat treating applications can be designed and fabricated for maximum performance and service life. Knowing the customer’s operation conditions, cycle, and application environment can help Alloy Engineering foreshadow potential failure modes and design-in service life improvements.

In general, there are three key reasons why a high temperature fan might fail: fan vibration, design flaws, and mechanical wear.

Vibration issues that we see frequently occur due to misalignment of the fan shaft with the bearings. Other vibration issues can be caused by structural problems with the fan’s frame housing and its proximity to the furnace wall. If the fan’s plug frame is not engineered or welded properly, vibration often results. The type of bearings used also can be a source of vibration. Fixed inboard bearings are many times the vibration culprit, especially if they are not properly engineered for heat expansion. Replacing fixed inboard bearings with floating bearings can eliminate this vibration problem. An improper packing seal can also cause vibration at the base of the fan (near the fan wheel). Finally, build-up, erosion, or damage to the fan wheel or shaft can cause balance-induced vibration too.

As mentioned above, the fan shaft and bearings require cooling to operate efficiently and effectively in high temperature furnace environments. This cooling is generally provided with air-cooling provisions or water cooling jackets. While water jackets help provide a more rapid or efficient cooling process, sometimes it’s appropriate to move to an air-cooled design from a water-cooled furnace. This is because water cooling requires plumbing circulation lines to/from the furnace, which tend to leak over time. Or, if the water jacket leaks water into the furnace, bad or rejected heat treatment of the furnace product results. Unseen water leaks impact the operating dew point of the furnace and cause maintenance headaches as well.

Even in the optimum running conditions, a high temperature fan may ultimately need service or repair due to mechanical wear over time. When an Alloy Engineering specialized team member looks at fan failure, we search for ways that might extend the life of the fan. In some of our evaluations, we see distortion in fan blades that are a direct result of improperly chosen alloys or materials of construction. Poor welding practices also result in leaks, vibration issues, and structural failures. Proper welding, fabrication, and fan assembly are key, as are choosing the right alloys and materials for the temperature and operating conditions of the furnace.

Preventive maintenance (PM) of the fan and its components is also important throughout the life-cycle of a high temperature fan. Periodic bearing greasing and inspection, for example, can help with less down time. Thermocouples can be used to check and monitor the temperature exposure of the packing seal and head off future fan shaft bearing problems. Fan noise and vibration issues are two key warning signs that there are issues with the fan – and most likely fan failure will soon result.

Whether we are fabricating a new fan, or repairing an existing fan, Alloy Engineering takes the time to listen to our customers and understand the operating conditions in which our fans will be operating. This helps us make design or material changes that will reduce the most common high temperature fan failure reasons.