To add two noise level values in decibel can be used the following formula or the graph shown on side. Sum dBA = 10 Log (10 dBA /10 + 10 dBA /10) A B In the graph the abscissa axis represents the arithmetic difference between the values to be added dBA - dBA , the ordinate axis shows the value to be A B added to the greater of the two values dBA to obtain A the sum of dBA. 3.5 3.0 2.5 .2.0 1.5 1.0 0.5 0.0 0 1 2 3 4 5 6 7 8 9 10 Sum of noise levels of multiple pumps Difference values dBA - dBA A B Value to be added to the greater Example: Pump type: ELI2-D-14.0/9.6 Rotation speed = 1500 rpm Operating pressure front element = 250 bar Operating pressure rear element = 150 bar Noise level front element dBA = 56 dBA (graphs page 19) A Noise level rear element dBA = 53 dBA B Difference between the values to be added dBA - dBA = 3 A B Value to be added to dBA = 1.8 A Noise level multiple pump = 56 + 1.8 = 57.8 dBA In the case in which the double pump have two stages of equal displacement, operating at the same pressure, just add to the noise single value 3 dBA. Verification of the limit of transmitted torque The maximum transmissible torque between the elements is 100 Nm; therefore in the case of double pumps there are no restrictions on configurations. It is still need to check the resistance of the front shaft. Must verify that the total torque to be transmitted will be less tan the upper limit of the shaft (pag. 14, 15). For each stage, calculate the maximum torque with the formula (3) or from the graphs on pag. 17, 18. Add the values obtained and to verify if they fare lower than the maximum defined for the shaft chose. Example: Pump type: ELI2-D-14.0/9.6—T0 Operating pressure front element = 250 bar Operating pressure rear element = 150 bar Torque front element = 60 Nm (graphs page 17, 18) Torque rear element = 26 Nm (<100Nm) Maximum torque transmitted from front shaft = 60 + 27 =87 Nm Maximum torque shaft type T0 = 145 Nm > 87 Nm Shaft checked ® Low Noise, Low Pulsation Gear Pump Elika Sum of Multiple Pump Noise Level 49 www.jbj.co.uk/ELIKA_gearpumps.html #DriveLineHarmony
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