The traditional method for determining the compressed air requirements of a new plant is to add up the gas consumption (m3/min) of all gas-using equipment, and then consider adding a safety, leakage and development factor.
In an existing plant, you can know whether the compressed air supply is sufficient by doing some simple tests. If not, you can estimate how much more needs to be added.
For example:
The output pressure of general industrial air compressors is 0.69MPa(G), and the pressure delivered to the equipment use point is at least 0.62MPa. This means that the typical air compressor we use has an unloading pressure of 0.69MPa(G) and a cylinder loading pressure or system pressure of 0.62MPa(G). With these numbers (or the unloading and loading values of a certain system), we can determine.
(1) Test method - check the gas volume of existing air compressors
The timed pump air test is a relatively easy and accurate way to check the gas volume or output of existing air compressors. This will help to determine whether the shortage of compressed air is caused by wear or failure of the machine.
The following is the procedure for conducting a timed pump test:
A. Volume of the air tank, cubic meters
B. Volume of the pipe between the compressor and the air tank, cubic meters
C. Total volume (A and B), cubic meters
D. Full load operation of the compressor
E. Close the air valve between the air tank and the factory air system
F. Deflate the air tank to reduce the pressure to 0.48MPa(G)
G. Close the bleed valve quickly
H. Time (seconds) required for the air tank to pump air to 0.69MPa(G)
Now you have the data needed to determine the actual air volume of the existing compressor, the formula is
C=V(P2-P1)60/(T)Pa
In the formula:
C=compressor exhaust volume, m3/min
V=air tank and pipeline volume, m3 (C item)
P2=final unloading pressure, MPa(A) (H item + Pa)
P1=initial pressure, MPa(A) (F item + 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 factory's air compressor, you can be more certain that the load of your factory's air system is too high, and you need to increase the air supply.
(2) Estimation method - determine the gas consumption
V = V existing equipment gas consumption + V post-processing equipment gas consumption + V leakage + V reserve
(3) Determine the required additional compressed air
Based on the amount of air required to increase the system pressure to the required pressure, the required additional compressed air supply can be determined:
Required m3/min = existing m3/min (P2/P1)
Where, 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)
Required additional m3/min = required m3/min - existing m3/min
The result tells you how much gas volume 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 into account future demand and leakage factors.
(4) Effect of system leakage
Insufficient air supply is often or certainly due to system leakage. Air system leakage is a continuous source of power loss, so it is best to minimize it. Several small leaks equivalent to 1/4 inch holes may leak up to 2.8M3 of compressed air at a pressure of 0.69MPa, which is equivalent to the air volume of an 18.75Kw air compressor. Based on an electricity cost of 0.4 yuan per kilowatt-hour and 8,000 hours of operation per year (three shifts), these leaked air will cause you to lose 60,000 yuan in vain.
Most factories will provide maintenance personnel and parts to plug leaks. Damaged tools. Valves, packings, joints, droppers and hoses should be inspected and repaired in a timely manner.
Leaks in the entire factory system can be diagnosed by measuring the time required for the system pressure (on the upper side of the air storage cylinder) to drop from 0.69MPa(G) to 0.62MPa(G) without air supply. Using the pump air test, we can calculate the leakage of the entire system:
Leakage m3/min = V (P2-P1) 60/90 (Pa)
If the leakage rate exceeds 5% of the total system gas volume, it must be plugged.
(5) Select the specifications of the compressor
Once you have determined the gas volume (m3/min) and pressure (MPa (G)) requirements of the factory, you can select the specifications of the air compressor.
(6) Factors you may want to consider when making a selection 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%. Are you considering using special manufacturing processes and tools in the future?
Ideally, the specifications of screw compressors and centrifugal compressors should ensure normal operation within the modulation and regulation control range.
The specifications of single-acting air-cooled reciprocating air compressors should ensure 30-40% unloading time based on the constant speed control system.
Water-cooled reciprocating air compressors can work continuously, but it is best to consider a 20-25% buffer or unloading time when selecting specifications.
Study the performance characteristics of various models of air compressors to estimate power costs and determine which one is the best choice to meet your factory's current and future requirements.