Topic:

Optimization of compressed air system – Air blow guns

Synopsis:

Compressed air costs a lot of money. In fact, a poorly managed/ operated compressed air system can cost more than water, electricity, steam or natural gas. Analysis of the required amount of air for a process is an essential part of a compressed air management system. One of the major air consumption point in an industry has been studied and presented in this article.

Article:

Air Blow guns: 

We use air blow guns at many points in our industry. Nevertheless, we were unaware of the amount of air used by the guns and if the impinging pressure was equal to or more than the requirement. We conducted a test to quantify the amount of air used by the guns. The test was carried out with various air guns (different makes) and a variety of nozzles. The idea was to find the consumption with the currently installed air guns and their respective nozzles and the difference when compared to a standard air gun with minimum leak. The energy efficient nozzle which uses atmospheric air in addition to the compressed air was also included in the test. The below results were obtained from the test 

The test was conducted at various operating pressures from 6 bar down to 2 bar and the respective flow rates and impinging pressure were recorded. Figure 1 shows the comparison of flow rates of various nozzles. It is evident from the figure that the currently installed air gun and nozzle had a higher flow rate of 215 l/m compared to the energy efficient nozzles which had 53 l/m at 6 bar pressures. The results had a similar trend at lower operating pressure too. 

The impinging pressure comparison in figure 2 shows that the energy efficient nozzles’ (1 mm diameter) impinging pressure is 0.024 kPa compared to our current 0.16 kPa. 

The energy efficient nozzles were tested for practical application of blowing dust and minute plastic particles. Surprisingly the energy efficient nozzle’s impinging pressure seemed to do the job for us. This means that we achieve the same result with one fourth the amount of air which also equated to a much lower cost involved. The data from the compressor manufacturer helped us to quantify the savings as shown below. 

Figure 3 shows the volumetric flow rate and the power consumed thereof for the GA90VSDFF type compressor which is part of our asset. As per the manufacturer specification, the variable speed drive runs at 90% on average. Figure 3 shows 96.9 kW of power consumption for a flow rate 257.2 l/m (taking close values of approximation). As mentioned earlier, the energy efficient air blow guns consumed air at 53 l/m compared to 215 l/m (currently installed air guns 2.5 mm diameter). For calculation purpose we considered our air guns to work 1 hour in a day. The performance data of the 

compressor helped us to correlate the energy consumed by the VSD compressor to match the load created by the air consumption by the air guns. It was evident from the calculations that our previous air guns consumed 797.5 kWh per day vs 237 kWh per day while using the energy efficient nozzle fitted blow gun. That is a reduction of 70.2 % in terms of energy consumption. The savings seemed to be directly proportional to the number of air guns installed. Nevertheless, these energy efficient nozzles would not be suitable for hard applications like oil, grease blow off in a tool room environment which require higher impinging pressure. Thus, we standardized the VMBg11 blow gun with energy efficient nozzle KNH-R02-100 from SMC all over our plant but normal nozzles of diameter 2 mm were used for tool room environment alone. This is to ensure that we not only save cost but also meet our internal requirements. 

About Vivek Raman: