Surge in centrifugal fans for sewage tanks
Thread Content
I would like to ask the experts: when two centrifugal variable-frequency fans for sewage tanks are operated in parallel, the fan that starts later experiences significant surge phenomena, along with high vibration and noise. Moreover, the outlet check valve opens only at the highest frequency. What could be the reason? Is it due to too high back pressure?
What is the diameter of the fan outlet pipe? What will be the diameter of the main pipe after parallel connection?
Both the outlet diameter and the main pipe diameter are 200; the outlet pressure is 0.7 MPa
Both the outlet diameter and the main pipe diameter are 200; the outlet pressure is 0.7 MPa
Both the outlet diameter and the main pipe diameter are 200; the outlet pressure is 0.7 MPa
Now that the outlet pressure is known, the cause can be determined by comparing it with the fan’s operating conditions. The outlet pressure must not be higher than the design pressure. If it gets too high, it must be released by opening the relief valve. If it is variable frequency, the speed must be reduced. Also, is this fan suitable for blowing air or sucking in air? If it is suction, the suction pressure must also meet the requirements for using the equipment. For reference.
The design of the main outlet pipe is too detailed; air cannot be blown out from one of the units
You can measure the current to determine it
Regarding the issue with the check valve, check whether its lifting force exceeds the outlet pressure
Estimate the check valve issue. What kind of check valve is it? How is it installed? Photos would be ideal.
1. Was it there before or only now? 2. What Senior Shiraishi said is quite important – it’s a matter of whether it’s suction or ventilation; if it’s suction, there’s likely an element of competing for volume involved.