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Reduce cost by measuring compressed air system



The consistent monitoring of compressor’s power consumption and discharge flow is key for maintaining efficiency. Hidhay shows how WiseAir 4.0 Smart Monitoring System from Systel helps reduce up to 30 per cent of the compressed air costs.
 
Compressed air isn’t as expensive as its mismanagement can make it to be. In a compressor’s life cycle cost more than 85 per cent of the costs are spent on its energy whereas the capital and maintenance costs just constitute to the remaining 15 per cent. Surprisingly, during a new system purchase the focus is always on the capital costs with only theoretical considerations of the specific energy consumption. Specific energy consumption is a term used to define the amount of power a compressor consumes to deliver an output unit of compressed air. While most of the end users measure the compressor’s power consumption, the compressor’s output flow remains unmeasured leading to factual errors in their assumptions about their compressor’s specific energy consumption. The ambient conditions coupled with the inefficiency and tolerance factors that are built into a compressor can take a toll on its energy consumption and in times may increase the specific energy consumption even upto 30 per cent of the compressor’s claimed efficiency. Hence consistent monitoring of a compressor’s power consumption and discharge flow will form a key to maintain the supply side efficiency.
 
Further, a well designed system should define the key performance indicators like flow, power, pressure, and dew point and should be measured at the right locations to understand the overall system dynamics (as shown in Figure 1).
 
The supply side of the system when improperly aligned with the demand side will result in over compensation of system pressures  and will increase artificial demand and related problems like,
  • Higher Air Demand
  • Higher Leak Rate
  • Higher Repair Intervals and Costs
  • Higher Energy Bills
  • Higher Cost Per Product Produced
  • Less Profits
Case Study
An automotive component manufacturing plant in the capital city of Tamil Nadu was consuming close to 1300 CFM from two of their rotary screw compressors of capacity 850 CFM and 450 CFM respectively. The compressors came with an installed motor capacity of 132 kw and 75 kw respectively. On papers, these compressors were showcasing a specific energy consumption of 0.16 kw/CFM which appears acceptable. The factory had set itself an ambitious target of reducing their consumption to 600 CFM but were clueless of where to start with. With consultations from Systel Energy Solutions (India) Pvt Ltd, Coimbatore, the factory installed a smart monitoring system to measure the total volume of compressed air generated and consumed at different production departments. The WiseAir Monitoring System when installed revealed that both the compressors put together were generating only 1120 CFM as against their rated capacity of 1300 CFM, but were consuming close to 220 kW put together. Hence the real specific energy consumption of these compressors were at 0.196 kw/CFM – an increase of over 18 per cent from the manufacturer’s claims. Extensive service and maintenance were carried out at these compressors and the result was that the specific energy consumption was reduced to 0.17 kw/CFM, and the factory was able to realise a power savings of over 537 kWH per day or Rs 12.56 lakh per annum. 
 
On the demand side
The measurements also revealed that the assembly and curing departments were consuming close to 800 CFM as against their actual demand of nearly 300 CFM. The painting booth was also consuming close to 320 CFM as against the actual demand of only 50 CFM. With these data in hand, the factory optimised the operating pressures of the machines thereby eliminating artificial demand and saved close to 150 CFM and further reduced a volume of 350 CFM by repairing leakages. The project resulted in savings of upto 500 CFM and at a power cost of Rs 6.5/kWH the realised annual savings was Rs 47.73 lakh.
 
Consistency of savings
The factory in the past has carried out periodical leak surveys with both internal maintenance teams and external agencies. While there have been reductions posts the leak repair projects in the past, there has been no consistency in the savings as new leaks do occur soon, and it turned out to be a tedious effort to locate and fix them. But with the present WiseAir Monitoring System, the consumption of each departments are monitored on a daily basis and any rise in consumptions are immediately addressed. This has resulted in reduced and easy maintenance. The WiseAir Monitoring System was installed at this factory in 2015 and even after 4 years, the factory continues to maintain the savings achieved and even has lowered their consumption to 560 CFM as against the post project consumption of 620 CFM. The factory also saved close to 60 per cent in their spares costs since it avoided the purchase of huge spares, which are usually listed out by external leak survey agencies during their surveys.
 
Return on investments
The return on investments for this project including WiseAir Monitoring System and the spares that were utilised was just under 6 months.
 
About the author
Hidhay is the Managing Director of Systel Energy Solutions (India) Pvt Ltd. He can be contacted on email: hidhay@systel.asia

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