Simple calculation of compressed air pipeline length and pressure loss

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Simple calculation of compressed air pipeline length and pressure loss. The pressure of the compressed air flowing from the air compressor to the equipment that uses it is often not fully utilized, resulting in unnecessary waste of energy. These losses are primarily manifested as resistance losses in gas transmission pipelines, valves, bends, changes in gas flow direction, and throttling. These resistance losses are converted into heat that is released into the atmosphere, resulting in a pressure drop. Therefore, there must be a simple and practical method for calculating pipe length and pressure loss, in order to minimize resistance losses and achieve the most economical investment. We can use the following formula for calculation: Table 1 Equivalent Length Table. Note: The impact of certain pipe fittings and their losses in pipes of different diameters is converted into equivalent lengths, which is equivalent to an increase in the length of the pipeline. When calculating the various components of compressed air pipelines, the values of allowable pressure drop listed in Table 2 can be used as the permitted pressure drop. Table 2 Permitable pressure drop: The pressure drop between the air compressor and the farthest air-consuming equipment should not exceed 0.10 bar. From this, the required pipe lengths for each component of the pipeline (supply pipe, distribution pipe, and vertical pipe) are calculated. The pipe length needs to be corrected by adding the equivalent lengths of valves, elbows, joints, etc. The volumetric flow rate, pressure, allowable pressure drop, and pipe length must already be known at the time of calculation. Then, based on the latest values, a larger standard pipe is selected for the gas transmission system. Example: There is a pipe with a length of 23 m and an inner diameter of 80 mm, through which the volumetric flow rate of compressed air is 140 L/s. There are 8 elbows in the pipeline, with the bend diameter equal to the inner diameter, and the initial absolute pressure is 8 bar. What is the pressure drop across the pipe? Solution: Given: L1=23m ； d=80mm ； q=140L/s ； With p=8 bar, it is first necessary to determine the equivalent length of the 8 elbows. According to the equivalent length table in Table 1, the equivalent length is 1.3 m; therefore, the total pipe length is: L=1.3×8=33.4 m. The resulting total pressure drop across the pipes is 0.0054 bar, which meets the requirements specified in Table 2 for allowable pressure drops