Sometimes in compressed air systems there will be “high flow, short duration demands” consuming large gulps of compressed air for short periods of time. This could be a dust collector, a drain, a compressed air blowing device, a large cylinder, or a material transport system — just about anything can happen.
When high flow demands hit the system, this can cause havoc with air compressor control, reducing the pressure to low levels and causing pressure sensitive devices like clamps and clutches to malfunction. Typically, an attempt to fix this problem causes an increase in the air pressure, often to extremely high levels. But high air pressure causes more energy consumption and sometimes exceeds the capability of air compressors.
If the transient air demand is of short duration (like a few minutes or shorter), instead of increasing system pressure, or running another compressor, you may be able to use stored air to feed the high flow demand instead. The storage receiver in the photo, a tank sized at 2,000-gal is doing just that.
A tank of 2,000-gal size contains about 1,850 cubic feet of compressed air at 100 psi. It is connected to a cleaning operation that blows for 5 seconds every 10 minutes at a rate of 2,000 cfm to blast large debris from a press. The cleaning pulse uses about 165 cubic feet in 5 seconds every time it pulses.
If you work it out, the average air demand is only 16.5 cubic feet per minute, however, before it was installed, this manufacturing plant had to run 200 hp in extra air compressor capacity to maintain adequate pressure.
This tank is installed with a flow restrictor on its inlet; when the cleaning pulse fires, 165 cubic feet (at a flow rate of 2,000 cfm for 5 seconds) of compressed air is taken from the tank, reducing its pressure by about 9 psi. However, due to the flow restriction, only about 20 cfm of compressed air flows into the tank to replenish the pressure between cycles. Due to this large receiver capacity, and the designed in flow restriction, the 200 hp of running compressors is now not required, saving the plant $52,000 per year in wasted compressor electrical costs. You will notice the air receiver does not have any large electrical cables running to it; it uses no electricity so it is a one-time cost.
“Tanks” for the savings, design engineer!
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