Problems with multi-stage centrifugal blowers
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Our company’s wastewater treatment system is equipped with three multi-stage centrifugal blowers; usually two are in use while one serves as a backup. The flow rate is 150 cubic meters per minute, and the outlet pressure is 69.6 kPa. Due to insufficient dissolved oxygen, another unit with a flow rate of 80 cubic meters per minute and the same pressure of 69.6 KPA was recently repaired and put back into use. However, after running the smaller blower for two hours, it was unable to reach sufficient operating pressure – the outlet check valve couldn’t be opened either. The larger blowers had to be turned off for the current on the smaller blower to increase, but this resulted in exceeding the rated current level; moreover, no aeration took place in the biological treatment tank. Here’s the question: Can multi-stage centrifugal blowers with different flow rates but the same outlet air pressure not be used in parallel? Additionally, some colleagues suspect that the outlet check valves used in smaller blowers are the same as those in larger ones, resulting in too much resistance Should the DN300 one be replaced with a DN250 outlet for the smaller fan?
Is the resistance in the outlet pipeline too high?
The outlet pipe is a long-distance pipeline with a DN400 diameter; this possibility cannot be ruled out. For now, a pressure gauge will be installed at the outlet of the small fan to check the wind pressure
The fan outlet pressure refers to the pressure at the diameter of the pipe at the fan’s outlet. If it was originally DN250 and you change it to DN300, then the pressure after the fan’s outlet will definitely decrease. The pressure in the pipeline downstream of the large fan remained unchanged, which prevented the small fan from being put into use