Calculation method for determining air consumption of air compressor

The traditional method of determining the compressed air requirements of a new plant is to add up the air consumption (m³/min) of all air-consuming equipment, and then consider adding a safety, leakage and development factor.

  In an existing factory, you only need to do some simple tests to know whether the compressed air supply is sufficient. If not, you can estimate how much more needs to be added.

for example:

  The output pressure of the general industrial air compressor is 0.69MPa(G), and the pressure to the point of use of the equipment is at least 0.62MPa. This shows that the typical air compressor we use has an unloading pressure of 0.69MPa(G) and a cylinder loading pressure of 0.62MPa(G), or system pressure. With these numbers (or the unloading and loading values ​​of a certain system) we can determine.

   (1) Test method-check the capacity of the existing air compressor

   Timing pumping test is a relatively easy and accurate method to check the air volume or output of existing air compressors, which will help determine that the shortage of compressed air is not caused by machine wear or failure.

   The following is the procedure for timing pumping test:

  A. Volume of gas storage tank, cubic meter

   B. The volume of the pipeline between the compressor tanks in cubic meters

   C. (A and B) Total volume, cubic meters

  D. Compressor running at full load

  E. Close the air valve between the air tank and the factory air system

  F. The gas storage tank is deflated and the pressure is reduced to 0.48MPa(G)

  G. Close the bleed valve soon

   H. The time required for the gas storage tank to pump gas to 0.69MPa(G) (seconds)

   Now you have the data needed to determine the actual capacity of the existing compressor. The formula is:

  C=V(P2-P1)60/(T)Pa

formula:

  C= compressor displacement, m³/min

  V=volume of gas tank and pipeline, m³ (item C)

  P2=final unloading pressure, MPa(A) (H item + Pa)

  P1=Initial pressure, MPa(A) (F term + Pa)

  Pa=Atmospheric pressure, MPa(A) (0.1MPa at sea level)

  T= time, s

   If the calculated result of the test data is close to the rated air volume of your plant’s air compressor, you can be more certain that the load of your plant’s air system is too high and you need to increase the air supply.

  (2) Estimation method-determine gas consumption

  V=V air consumption of existing equipment + V air consumption of post-processing equipment + V leakage + V reserve

  (3) Determine the additional compressed air required

  According to the air volume to increase the system pressure to the required pressure, the compressed air supply volume that needs to be increased can be determined:

   Required m³/min = existing m³/min (P2/P1)

In    type, required m³/min = required compressed air supply

   Existing m³/min= Existing compressed air supply

  P2=Required system pressure, MPa(A)

  P1=existing system pressure, MPa(A)

  Need to increase m³/min=required m³/min-existing m³/min

  The result will tell you how much gas you need to increase to meet the existing gas demand. It is recommended to increase enough gas volume to not only meet the current gas demand, but also take future demand and leakage factors into consideration.

   (4) The effect of system leakage

   Insufficient air supply is often or definitely due to system leakage. Air system leakage is a continuous source of power loss, so it should be as small as possible. Several small leakage points equivalent to 1/4-inch small holes may leak up to 2.8m³ of compressed air at a pressure of 0.69MPa, which is equivalent to the loss of air volume of an 18.75Kw air compressor, with electricity per degree 0.4 yuan, 8000 hours of operation per year (three shifts) calculation, these leaked air cost you 60,000 yuan in vain.

   Most factories will provide maintenance personnel and parts to plug leaks. Damaged tool. Valves, packing, joints, droppers and hoses should be inspected and repaired in time.

  The leakage of the entire system of the factory can be diagnosed by measuring the time required for the system pressure (on the upper side of the gas cylinder) to drop from 0.69MPa(G) to 0.62MPa(G) without air supply. Using the pumping test, we can calculate the leakage of the entire system:

  Leakage amount m³/min=V(P2-P1)60/90(Pa)

   If the leakage rate exceeds 5% of the total system gas volume, the leakage must be stopped.

  (5)Select the specifications of the compressor

   Once you determine the air volume (m³/min) and pressure (MPa(G)) requirements of the factory, you can choose the air compressor specifications.

   (6) Factors you may consider when choosing include:

   What is the current gas consumption? What is the gas consumption requirement after the factory expansion? Generally speaking, the annual growth rate of gas consumption is 10%. Do you consider using special manufacturing processes and tools in the future?

  The ideal approach is that the screw compressors and centrifugal compressors set specifications should ensure normal operation in the modulation and adjustment control range.

  The specifications determined by the single-acting air-cooled reciprocating air compressor should guarantee a 30-40% unloading time based on the constant speed control system.

   water-cooled reciprocating air compressor can work continuously, but it is best to consider 20-25% buffer or unloading time when selecting specifications.

   Research the performance characteristics of various types of air compressors to estimate power costs, so as to determine which one is the best choice to meet your plant's current and future requirements.