A sawmill had a large compressor located in a small outbuilding near their mill. The compressor was moved away from the plant because there was excessive dust inside. But even in a remote location, the sawdust found its way into the compressor intake — and deposited inside the compressor’s air-cooled aftercooler. The restriction caused by excess buildup made the discharge temperatures to rise to 125° F and higher.
Because the compressor was installed remotely, it was a bit of a hike to visit it when it was operating at full capacity. Operational staff did not notice the excessive temperatures, and the condition caused an overload of moisture going into the air dryer. Air dryers are normally rated for 100° F inlet temperatures and not designed to handle higher levels.
Running the dryer intake air at 25° higher than rating more than doubled the amount of water the unit had to process. As a result, the dew point on the dryer showed 10° F rather than the normal rating of -40° F. What was worse, a portable dew point tester was installed on the dryer discharge and measured a dew point of 75° F; the onboard dew point probe had been flooded by excess moisture and had become out of calibration.
The excess dew point and probe failure made the dryer run its heater and blower full time. Rather than turning off on dew point control, the average flow into the dryer was only 25% of its capacity … yet the heaters worked near 100% duty, costing an extra $6,000 per year in electricity costs.
Regularly checking the temperature gauge and then taking action by cleaning out the cooler could have prevented this problem. Additional filtering of the cooling intake air would also help keep the intake free of dust. Repairs are ongoing, with corrections expected to correct air quality and save significant energy.