How to Calculate Air Consumption of Workshop Equipment and Select Air Compressor

To select the appropriate air compressor for the workshop equipment, it is necessary to scientifically calculate the total air consumption and consider the actual working conditions. The following are the specific steps and key points:

1. calculation of total air consumption of workshop equipment

1. List of statistical equipment

list all gas-using equipment (e. g., pneumatic tools, spray guns, cylinders, CNC machines, etc.) and specify rated air consumption (unit: m & sup3;/min or L/s) and working pressure (in bar or MPa).

• Example:
  • pneumatic wrench: 0.5 m & sup3;/min @ 6 bar
  • spraying equipment: 2.0 m & sup3;/min @ 7 bar
  • cylinders (10): 0.1 m & sup3;/min @ 6 bar & rarr; total 1.0 m & sup3;/min

2. Calculation of theoretical total gas consumption

add the rated gas consumption of all equipment to obtain theoretical total gas consumption (Q theory).

• Example:
  Q theory = 0.5+2.0+1.0=3.5m & sup3;/min

3. Consider the simultaneous use factor (K)

in actual operation, the equipment will not work at full capacity at the same time and needs to be introduced. Coefficient of simultaneous use (K) correction of theoretical values.

• K value range:
  • light load workshop (e. g. electronic assembly):K = 0.6~0.7
  • medium load workshop (such as machining):K = 0.7~0.8
  • heavy duty workshop (such as automobile manufacturing):K = 0.8~0.9
• example:
  if the workshop is medium load, taking K = 0.75, the actual air consumption:
  Q actual = Q theory×K = 3.5 × 0.75=2.625m & sup3;/min

4. Consider leakage and loss

the system has pipeline leakage, valve loss, etc., which need to be added additionally. 5% to 10% of the margin.

• Example:
  after adding 10% margin:
  Q final = Q actual × 1.1=2.625 × 1.1 & asymp;2.89m & sup3;/min

2. selection of air compressor parameters

1. Determine the displacement (capacity)

air compressor rated displacement (unit: m & sup3;/min) it needs to be slightly larger than the calculated final gas consumption.

• Example:
  select the displacement 3.0 m³/min the air compressor can meet the demand of 2.89 m & sup3;/min.

2. Determine the working pressure

air compressor rated pressure (in bar) need to be higher than the maximum working pressure of the equipment, and consider the pipeline pressure drop (usually 0.1~0.3 bar/10 meters).

• Example:
  the maximum pressure of the equipment is 7 bar, the total length of the pipeline is 30 meters, and the pressure drop is about 0.3~0.9 bar, then the pressure of the air compressor should be ≥ 7.9 bar, which is recommended. 8 bar model.

3. Consider power and energy efficiency

• power matching: Calculate the required power according to the displacement and pressure (formula: P = 60 × & eta;Q×P work, where & eta; is the energy efficiency coefficient, usually 0.7~0.85).
• Energy efficiency grade: Give priority to the first level of energy efficiency models, long-term operation can save electricity. For example, the permanent magnet variable frequency air compressor is 10% to 15% more energy-saving than ordinary models.

3. optimization selection scheme

1. Single and multiple combinations

• single large aircraft: Suitable for workshops with stable air consumption and small fluctuations, simple maintenance but poor flexibility.
• Multiple small models: It is suitable for the situation of large fluctuation of gas consumption or standby, and can be rotated to reduce energy consumption.
  • Example:
    if the total air consumption is 5.0 m & sup3;/min, two 3.0 m & sup3;/min models can be selected, one for operation and one for standby.

2. Frequency conversion and fixed frequency selection

• variable frequency air compressor: Automatically adjust the speed according to the air consumption, and the energy saving effect is remarkable (especially suitable for part-load operation scenarios).
• fixed frequency air compressor: Low price, but high energy consumption for long-term part-load operation.
  • Recommendations: If the fluctuation of gas consumption is more than 30%, frequency conversion model is preferred.

3. Oil-free and oil-free options

• oil-free air compressor: Suitable for food, medicine, electronics and other industries with high air quality requirements, the output air oil content ≤ 0.01 mg/m & sup3;.
• Oil air compressor suitable for ordinary industrial scenarios, low cost but need post-processing equipment (such as cold dryer, filter) to remove oil.

4. actual case reference

case: a mechanical processing workshop

• equipment List:
  • pneumatic tapping machines (5 units): 0.3 m & sup3;/min @ 6 bar each
  • sandblasting machine (1 unit):1.5 m & sup3;/min @ 7 bar
  • cylinders (20 pts): 0.08 m & sup3;/min @ 6 bar each
• calculation process:
  1. theoretical total gas consumption:
     Q theory = 5 × 0.3+1.5+20 × 0.08=1.5+1.5+1.6=4.6m & sup3;/min
  2. coefficient of simultaneous use (medium load, K = 0.75):
     Q actual = 4.6 × 0.75=3.45m & sup3;/min
  3. add 10% margin:
     Q final = 3.45 × 1.1 & asymp;3.8m & sup3;/min
• selection results:
  select displacement 4.0 m³/min pressure 8 bar the permanent magnet variable frequency air compressor, taking into account energy saving and standby needs.

5. considerations

1. future Expansion: Reserve a margin of 10% ~ 20% to avoid replacing the air compressor when adding equipment in the later period.
2. Pipeline Design: Reasonably plan the pipe diameter and layout to reduce the pressure drop (the main pipe diameter is recommended to be ≥ DN50).
3. Post-processing equipment: According to the air quality requirements, configure the cold dryer, filter, etc. to ensure that the output air meets the standard.
4. Maintenance Plan regularly check for leaks and replace the filter element to keep the system running efficiently.