A common question when looking at optimization of a compressed air system is; How much air am I wasting? Often, inappropriate uses consume significant amounts of flow, and savings can be gained if the operation can be supplied more efficiently through optimization measures. To be able to initiate improvement projects, we must first calculate how much air we are wasting. When we know the answer we can make a business case to determine if the expense and effort in correcting the problem is worthwhile.
An example might be a blow wand that is permanently fixed to a device to blow dust or debris from a conveyor line. We can try to estimate the flow if we know the hose size and pressure applied, but this estimating method is full of flaws, the best way to measure the load is with a flow meter.
A handy device to have in your test instrument arsenal is a pipe mounted thermal mass meter like in the photograph at the beginning of the blog. This meter (www.cdimeters.com) tells us exactly what flow is being consumed and with the result, knowing the number of hours of operation, and the compressor specific power (kW per 100 cfm), we can calculate the equivalent energy consumption.
This particular blowing device consumes about 83 cfm for 8,000 hours per year. Our compressors produce compressed air at 20 kW per 100 cfm. Therefore 132,800 kWh are used. At 10 cents per kWh, this would eat $13,300 per year in equivalent electricity costs.
If we can reduce the flow by 50% using engineered nozzles, and reduce the duty cycle by 70% by applying sensing eyes to the blow, thus ensuring no flow unless there is something to clean, we can achieve an 85% savings in energy consumption.
It’s easy when you know how!