What are the methods of energy conservation in compressed air systems.
1 Answer

Methods of energy conservation in compressed air systems are as follows:

  1. Ensure air intake to compressor is not warm and humid by locating compressors in well-ventilated area or by drawing cold air from outside. Every 40°C rise in air inlet temperature will increase power consumption by 1 percent.

  2. Clean air-inlet filters regularly. Compressor efficiency will be reduced by 2 percent for every 250 mm WC pressure drop across the filter.

  3. Keep compressor valves in good condition by removing and inspecting them once every six months. Worn-out valves can reduce compressor efficiency by as much as 50 percent.

  4. Install manometers across the filter and monitor the pressure drop.

  5. Minimize low-load compressor operation; if air demand is less than 50 percent of compressor capacity, consider change over to a smaller compressor or reduce compressor speed appropriately (by reducing motor pulley size) in case of belt driven compressors.

  6. Consider the use of regenerative air dryers, which uses the heat of compressed air to remove moisture.

  7. Fouled inter-coolers reduce compressor efficiency and cause more water condensation in air receivers and distribution lines resulting in increased corrosion. Periodic cleaning of inter-coolers must be ensured.

  8. Compressor free air delivery test (FAD) must be done periodically to check the present operating capacity against its design capacity and corrective steps must be taken if required.

  9. If more than one compressor is feeding to a common header, compressors must be operated in such a way that only one small compressor should handle the load variations whereas other compressors will operate at full load.

  10. The possibility of heat recovery from hot compressed air to generate hot air or water for process application must be economically analyzed in case of large compressors.

  11. Consideration should be given to two-stage or multistage compressor as it consumes less power for the same air output than a single stage compressor.

  12. If pressure requirements for processes are widely different (e.g. 3 bar to 7 bar), it is advisable to have two separate compressed air systems.

  13. Reduce compressor delivery pressure, wherever possible, to save energy.

  14. Provide extra air receivers at points of high cyclic-air demand which permits operation without extra compressor capacity.

  15. Retrofit with variable speed drives in big compressors, say over 100 kW, to eliminate the `unloaded’ running condition altogether.

  16. Keep the minimum possible range between load and unload pressure settings.

  17. Automatic timer controlled drain traps waste compressed air every time the valve opens. So frequency of drainage should be optimized.

  18. Check air compressor logs regularly for abnormal readings, especially motor current cooling water flow and temperature, inter-stage and discharge pressures and temperatures and compressor load-cycle.

  19. Compressed air leakage of 40- 50 percent is not uncommon. Carry out periodic leak tests to estimate the quantity of leakage.

  20. Install equipment interlocked solenoid cut-off valves in the air system so that air supply to a machine can be switched off when not in use.

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