Slashing Compressed Air System Costs

Taking a step-by-step approach

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Are the controls obsolete? Many systems currently are operating with obsolete controls that cannot achieve the savings of today's microcontroller-based control systems.

Master control systems can save large amounts of energy. For example, a chemical company in the Southeastern United States ran a quick test to see how much energy the new master control system was saving its facility. They recorded motor amps with the master system engaged, and then recorded the amps with the system disengaged. At the same system demand, the master control system was saving them approximately 800 kW, which amounted to $238,000 per year. This translated into a three-month payback on a less-than-$50,000 master control system.

Another chemical company was able to shut off a 1,250 hp compressor when it installed a master control system. This system paid for itself in one year.

Identify equipment needs

After the team makes all possible minor improvements identified under the first step, it then must consider what major improvements really are necessary. It should carefully examine the equipment and control options currently available.

If the compressor equipment itself is not performing efficiently, it might be time to consider some capital expenditures in this area. To do this, it is helpful to take a look at the types of compressors and related equipment currently available. Some examples include:

The addition of new aerodynamic hardware to existing machines. In some cases, the hardware brings about an 8 percent to 10 percent efficiency improvement over older compressors.

Newer air dryer technologies, which might offer significant reductions in purge rates and energy consumption over existing air dryers.

Better inlet filtration, which might reduce the contaminants entering the machine, thereby decreasing the frequency of overhauls.

The addition of high-quality condensate traps. Some systems operate with a continuous blowdown of condensate through v-notch ball valves. High-quality condensate traps can significantly reduce air and energy loss through the condensate system.

Variable-speed drives, which might offer large energy savings on systems using rotary screw compressors.

In addition, if production demands have changed over time, the compressors might be oversized. In cases such as this, a smaller trim compressor or additional compressed air storage might be needed to reduce energy consumption.

If the plant has unused steam that is either being blown off or let down stations, a steam-turbine-driven compressor might allow a motor-driven compressor to be shut down. If the steam pressure is being reduced through a valve, the team might want to consider using a turbine-driven compressor as the reducing station. Or perhaps the team might want to evaluate the feasibility of a gas-engine-driven compressor that uses natural or landfill gases to slash energy costs.

 

Justify the project

After the team identifies energy-savings opportunities, performs minor adjustments and determines equipment- and control-related needs, it must justify all capital expenditures, making sure they bring to the table a timely payback within the company's return-on-invested-capital guidelines.

If the team determines it can make the designated improvements and still achieve the desired payback, great. If the payback period is too lengthy, however, it might want to consider alternatives to capital purchases. Even if the payback period is acceptable, the team will want to evaluate its purchasing scenario against other alternatives, as detailed in the next step.

Consider alternatives

Customized energy solutions are available that allow chemical and other facilities to lease the desired equipment, with the turnkey design, installation and startup provided by the supplier. Some programs include an extended warranty package that provides preventive maintenance inspections and warranty throughout the contract period.*

These types of programs might require no capital investment on the part of the customer, and allow a positive cash flow in the first month of operation. The sidebar provides one real-life example of how this type of program can benefit chemical-industry customers.

Verify results

Once the team has installed the new equipment or entered into an equipment-related lease agreement, it should begin tracking its savings. The best way to verify results is by installing flow and kW monitoring equipment as part of the project. This allows the team to monitor demand and energy consumption over time. After all, the use of this expensive utility cannot be managed unless the team knows how much is being used and what it costs the plant each month.

Conclusion

When it comes to cutting compressor-related energy costs, no one solution fits all chemical facilities. By following the five-step approach detailed here, however, the plant can identify and implement the solution(s) that will work best for its individual needs and capital budget.

Watson and Scutella work in Ingersoll-Rand Co.'s HIS Air Solutions Group, Davidson, N.C. Contact them at larry_watson@irco.com and kristen_ scutella@irco.com, respectively.

*Ingersoll-Rand is one company that offers such a program.

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