10 Factors to take into consideration when choosing air compressor

10 Factors to take into consideration when choosing air compressor
 
        Cost, energy saving, machine lifespan extension, pressure stability preservation, contamination and sound reduction, and suitable initial machines are all important factor to take into. These below are 10 factors that should be taken into consideration.
  
1. Air compression objective : Only few customers would actually be factoring in air compression when considering air compressor: power exchange system, parameter, machine cooling system, usage measurement, and different compression method. Initially, factory planners create as much as usage as pressure substitute resulting wasting the system electricity.
  
2. Pressure : Users should first understand the maximum and minimum air usage of each section before adding more pipes or purifying area as these factors will require to lower full load and unload pressure of the compressor. This can alter the amount of pressure from the compressor.
 
Normally, pipe pressure loss rate is at 0.5 kg/cm2. Mandatorily, air compression requires air purification and air drying through pipes or filter which can lower pressure by approximately 0.3-0.5 kg/cm2 (filter + air dryer).
 
3. Air volume : Users often choose compressors by specifying the “horsepower” but specifying “air volume” is more holistically correct. Air volume should be referenced from maximum load to incur different type and size. Try to match the waste air in different period of time to the discharge amount then choose compressor depending on the initial and final “base load” changing whether to use screw or centrifugal type.

"Inverse Load" utilize many screws along with frequency changer.

"Spontaneous Load" respond by utilizing high pressure compressor and large air tank.
 
Choosing the air discharge volume should consider the following factors:
         (A) Current need
         (B) Possible pipe flow volume
         (C) Possible future plans
         (D) Usage range
 
4. Quality indicator : Just like how we have different water for washing and drinking, compression also has different usages. We separated air usages into a few things like air for production (PA), air for instrument (IA), air for breathing (BA), and other special usages (SPA). These usages are often determined by the quality of air according to ISO 8573-1 standard. If the quality is too good for the usage, energy will be wasted. If the quality is too low, it might affect the production line, so meticulous and precise planning is required.

Oil-free type: Parts that are made from special lubricant material don’t require the need of oil to lubricate while still achieving the compression resulting in oil-free air. This can meet the demand of oil-free air in some industries that require extreme precision: medical, food, semiconductor, and coating.

Oil compressors often come with oil waste, oil contamination, and oil in discharged water problem which all need to be properly disposed according to environmental law.

  
5. Control techniques : At first, compressors only have “mechanical pressure switch” and “air power control type” to turn the machine on or off since 1980. With the increase of PLC program controller, “sequential control” but only stop at air compressor electricity. During the end of 1990 has entered PC-based “multiple devices chain control”. After 2000, some technology had also become popular like “frequency change control”, “multiple devices chain control”, “electronics control”, “frequency and velocity change”, and “remote control” with capability of efficiently preventing wasted working hours (around 25-40% of overall electricity cost), helping similar machine get to maximum load and achieve stability (± 0.1 bar), and attaining up to 30% energy saving from just controlling alone.
  
6. Machine running efficacy ：When the machine is running in its designed position, it retains its maximum efficacy, but when the position is altered – therefore the efficacy. Choosing the right compressors can retrospectively save money from future operational cost.
 
7. Air discharge installation : Compared to air conditioning equipment, air compressors price can be on the lower price albeit tough and undemanding. Compressors then was often placed in the worse environment with hazardous conditions: oil leak, air leak, water leak, high temperature, sunlight, dust, humidity, bad insulation, or bad airflow. These are debilitating conditions that will affect both production and energy saving capability. Others affecting conditions are heat waste, water waste recycling, and sound proofing. Lastly, “centric” installation has lower cost than “scatter” and can reduce other instruments cost.
 
8. Cooling system : Air compressors have two types of cooling system: air cooling system and water-cooling system with exception of certain environment. If the horsepower is 200 or lower, air cooling is recommended; higher then water cooling is recommended. Using air cooling will save you from buying cooling tower and water pump but need great air flow while water cooling won’t be affected by outside factors which is beneficial for the machine longevity; the downside is that there might be cracks from ice and blockage.
  
9. Power supply : Every country has their own power supply, voltage, and frequency. These elements and electric phase must be specified so that suppliers can assemble the compressors correctly. Voltage specification and reduced voltage stability will determine different motor, one phase or three phases.
One phase: Normal voltage are 110V and 220V for convenience and safety. If it’s less than 1hp, 110V will be used and 220V otherwise. 5hp or more is not suitable for one phase.
Three phase: Often used with high hp machines. Uses low voltage (usually 380V-460V), but for 600hp or more high voltage is recommended (3kV-10kV).
  
10. Maintenance and repair ：Usage hours and factory guaranteed requirements are to be emphasized for maintenance and repair to avoid low quality parts from repair organizations. As for the energy saving, the priority should be air compressor management. The room containing the machine should be suitably maintained and convenient for getting in or out. The operators and the repairers should also be specially trained for energy saving and maintenance.
  
Reference documents : Air compressor energy saving manual by Energy Regulatory Commission and Ministry of Economy.