Air Compressors Info

Compressed air is expensive to produce. Because compressed air is also clean, readily available, and simple to use, it is often chosen for applications in which other methods or sources of air are more economical. To reduce compressed air energy costs, alternative methods of supplying low-pressure end uses should be considered before using compressed air in such applications. Many alternative methods of supplying low-pressure end uses can allow a plant to achieve its production requirements effectively. Before deciding to replace a low-pressure end use with an alternative source , it is important to determine the minimum practical pressure level required for the application. Alternative Applications to Low-Pressure End Uses Existing Low-Pressure End Use: Open blowing, mixing Potential Alternatives: Fans, blower, mixers, nozzles Reasoning: Open-blowing applications waste compressed air. For existing open-blowing applications, high efficiency nozzles could be applied, or if...

Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20%-30% of the compressor’s output. Compressed air leaks can also contribute to problems with system operations, including: Fluctuating system pressure, which can cause air tools and other air-operated equipment to function less efficiently, possibly affecting production Excess compressor capacity, resulting in higher than necessary costs Decreased service life and increased maintenance of supply equipment (includ-ing the compressor package) due to unnecessary cycling and increased run time. Although leaks can occur in any part of the system, the most common problem areas are couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, and lubricator), condensate traps, valves, flanges, packings, thread seal-ants, and point-of-use devices. Leakage rates are a function of the supply pressure in an uncontrolled system and increase with higher system pre...

Variable Speed Compressors are also know as variable speed drive compressors, and are air compressors that take advantage of variable speed drive technology. They employ a special drive which controls the RPM (Revolutions Per Minute) speed of the compressor, and this in turn saves energy when compared to its fixed speed equivalent. The most common form used in the air compressor industry uses a variable-frequency drive , and this is used to convert the AC input power to DC and then back to a quasi-sinusoidal AC power, with the use of an inverter switching circuit. The main benefits are, reduced power cost, reduced power surges, and the delivery of more constant pressure. The downside is the heavy expense of the drive and their sensitivity to heat and moisture. They combine a speed inverter, which converts the AC signal to DC and speeds up or slows down the motor, with a pressure transducer to precisely match the compressed air output to demand. The energy efficiency of these co...

The power consumed by a compressor is proportional to the specific volume, which is proportional to the absolute temperature of the gas at a given pressure. It is also clear that the compressor work is directly proportional to the inlet temperature of air. Therefore, the lower the inlet temperature of the air, the smaller the compressor work. Then the power reduction factor, which is the fraction of compressor power reduced as a result of taking intake air from the outside, becomes f reduction = (W comp, inside - W comp, outside ) / W comp, inside f reduction = (T inside - T outside ) / T inside f reduction = 1 - (T outside /T inside ) where T inside and T outside are the absolute tempertaure (in K or R) of the ambient air inside and outside the facility, respectively. Thus reducing the absolute inlet temperature by 5%, for example, will reduce the compressor power input by 5%. As a rule of thumb, for a specified amount of compressed air, the power consumption of the compressor ...

The electric power required for the air compressor can be expressed as, We can see that the electric power depends on the efficiency of the electric motor, thus, to install high efficiency motor we can save the energy as shown in the following equations, where: rated power = nominal power of the motor listed on its label (the power the motor delivers at full load) load factor = the fraction of rate power at which the motor normally operates The energy saving by replacing a motor by a high-efficiency motor can be calculated from, Normally, the efficiency of a motor ranges between 70% to 96%. The loss is usually in the form of heat. Load factor also plays an important part in heat generation. Normally, high heat level is generated during part loading of a compressor. Important considerations in the selection of a motor for a compressor Operating profile of a compressor i.e. load vs time Efficiency of the motor at part-load conditions Efficiency of the motor at full-load conditions One i...

What is the results of air leaks on compressed air lines? An air compressor works harder An air compressor works longer The above undesireable results make the compressor consumes more energy. Eventhough air leaks is unavoidable, but with good house-keeping factory, the level of air leaks of 10% is acceptable. Most of the factories have air leaks far beyond that what mentioned. Air leaks normally occur at the joints, flange connections, elbows, valves, filters, hoses, etc. as a result of thermal cycling and vibration. How to detect air leaks? Listen for hissing sound -- in some factories, even when in production process, we can still hear this sound if the leakage rate is high Apply soap water at the location where the air leaks may present Using an acoustic leak detector Pressure drop test Mechanical energy wasted caused by air leaks The following equation expresses the actual mechanical energy wasted due to air leaks where: 1 < n < 1.4 (isentropic) and 0.7 < h comp < 0....

The electric motor is usually the prime mover of the air compressors. Therefore, to save the energy of compressed air system is to save the energy consumption of the electric motor. Energy saving of the electric motor can be written as shown in the following formula Thus, Cost savings = Energy savings x Unit cost of energy

"We are quick to identify energy losses from hot surfaces and to insulate those surfaces. But we are not so sensitive when it comes to saving compressed air, fixing air leask for instance, because most of the people think that the air is free-of-charge, but they don't reallize that to get the air at higher pressure than the atmospheric pressure requires considerable amount of work (energy)" "The cost of electricity to operates the air compressor for one year can exceed the purchase price of the compressor" In the next section we will see the cost of compressed air as well as the amount of energy wasted through the air leaks and so on.

We know from the previous section that the minimum air compressor work is achieved with isothermal compression. In practical way, we try to achieve that by involving some cooling during compression process that leads to Polytropic compression process. Normally, this can be achieved by dividing air compression into 2 stages. The first stage builds up the pressure from P1 to Px then the compressed air is cooled by the intercooler and the second stage compressor builds up the pressure again from Px to the final pressure P2. See the following figures to understand how the energy can be saved by using intercooling between each stage. Fig.1 P-v diagram of polytropic compression process with intercooling Fig.2 T-s diagram of polytropic compression process with intercooling We can see from Fig. 1 that the amount of compressor work saved is related to the pressure Px. What is the optimal value of Px that yields maximum compressor work saved? The total compressor work, for this case, is the s...