Problems that occur when blowers are operated in parallel.

Also, sometimes during operation, the inlet pipeline pressure becomes negative pressure, or the inlet pressure does not rise and is only more than 100 PA. Why does this phenomenon occur? Are there any problems with fan selection?

=================================================== Possibly the same model from the same manufacturer. It feels like the problem occurs in the pipeline, but I can't come up with a theory. Asking everyone for advice!

================================================================================ I forgot to mention that the booster station was originally designed for one use and one standby. With the expansion, the flow rate of one machine could no longer meet the user's production, so another unit was ordered from the original manufacturer. Now it is used for both uses and one standby. However, when the blower was installed, the pipeline was not modified accordingly, so the current problem occurred. When a machine is running, the flow rate and pressure are normal.

Then calculate the pipeline resistance and see what the flow rate is at the maximum flow rate and whether it exceeds the appropriate flow rate.

It depends on whether the air is being pumped. A slight negative pressure at the air inlet should be normal. From your question, it seems that the inlet pipe is small and can only provide the capacity of one fan. If you open two fans, the inlet will have negative pressure, so you need to add an inlet pipe.

That is, the pipeline resistance has increased and cannot meet the current needs. It is necessary to thicken the pipeline.

================================================================== How to calculate it? I determined the outlet pressure as 12000Pa and the outlet flow rate as 60000 cubic meters or how to calculate it (the question is too urgent, I made a mistake in one parameter, the conveying capacity of a single unit should be 30000 cubic meters per hour, please forgive me! )? According to the industry's flow rate table, the maximum flow rate of an 800 mm diameter pipe can only be 19 meters, and the flow rate is only 35,060 cubic meters. The outlet pipe diameter cannot transport such a large flow at all. Increasing the rotation speed and increasing the pressure are unbearable for both the pipe material and the user. The only option is to reconfigure the outlet pipe. Could it be that the diameter of the inlet and outlet pipes has been doubled?

===================================================================================================================== When transporting highly toxic and explosive gases, the oxygen content cannot exceed 0.6%. I think not only the inlet pipe is small, but also the outlet pipe.

Quote: The original post was posted by my sister at 2009-2-22 18:30. Then calculate the pipeline resistance and see what the flow rate is at the maximum flow rate. Is it an appropriate flow rate? ================================================================== How to calculate it? I determined the outlet pressure as 12000Pa and the outlet flow rate as 60000 cubic meters or how to calculate it (the question is too urgent, I made a mistake in one parameter, the conveying capacity of a single unit should be 30000 cubic meters per hour, please forgive me! )? According to the industry's flow rate table, the maximum flow rate of an 800 mm diameter pipe can only be 19 meters, and the flow rate is only 35,060 cubic meters. The outlet pipe diameter cannot transport such a large flow at all. Increasing the rotation speed and increasing the pressure are unbearable for both the pipe material and the user. The only option is to reconfigure the outlet pipe. Could it be that the diameter of the inlet and outlet pipes has been doubled? ========================================== Sorry, I got too confused and something went wrong. Should it be "double the diameter of the import and export main pipes"?

================================================= Because according to the flow rate table, the maximum allowable flow rate of an 800 mm diameter pipe is 19 meters per second, and the maximum flow rate is 35,060 cubic hours. If two blowers are connected in parallel, the flow rate reaches 60,000 cubic hours, and the 800 mm diameter pipe cannot bear it. The blower inlet pressure is 2000Pa. When the thin-walled pressure vessel delivers gas to the blower inlet, the maximum pressure in the vessel is only 3200Pa. The 800mm inlet pipe cannot meet the flow rate of 60,000 cubic meters per hour. So the inlet and outlet pipes are small. Am I right to understand this? Newbies don’t understand, so I hope you can give me more advice.

According to the above statement, your air volume has doubled, and the pipe diameter should also be increased accordingly. Calculated based on the air volume of 60,000, the wind speed of the 800 pipe reaches 33. In this case, your wind pressure may be several times higher than before. You definitely can't get out of your current situation. The pipes should not be added just at the inlet and outlet of the fan, but should be added from the source to the outlet. Ensure the diameter of the entire piping system. (Either two 800 pipes, or all modifications, using one 1100~1150 pipe,)

I think this is due to the small diameter of the inlet and outlet pipes. You should appropriately modify the pipes to the diameter you need and determine the diameter requirements based on the flow rate of your extension.

============================================== Also, I’m so happy to be encouraged by my “sister” who is a college student in Haichuan. While I was happy, I couldn't help but think of another question. When increasing the pipe diameter, for economic reasons, what is the reasonable pipe diameter? When two machines are connected in parallel, according to the description in the centrifugal compressor principle, the pressure is constant and the flow rate increases, but the flow rate of the single machine is not multiplied by 2, but slightly decreases. How to calculate the specific flow value of the outlet after parallel connection? Only by knowing the outlet flow rate after parallel connection can we reasonably arrange the inlet and outlet pipes. The meaning of the performance curve is really difficult to understand. Can my sister give me some tips?

================================= grateful!

=================================================== The inlet is a constant pressure vessel, and the maximum design pressure can only reach 3200pa. To make the 800mm pipe reach a flow rate of 60,000 cubic hours, all processes upstream of the vessel must be changed, which is unrealistic. It is also impossible to achieve such a large flow rate at the outlet, unless the blower is replaced by a steam turbine and the cost is huge. The main problem now is that the pipeline configuration in the booster station is unreasonable. Under large consumption, the flow and pressure cannot meet user requirements. Based on user feedback, if targeted production services are provided to a single user, it can satisfy any user in the pipeline network system. Therefore, the pipeline network system other than the booster station is still reasonable and meets actual production needs. Of course, this is only the current situation. With the expansion, the distance between users and booster stations increases. In the future, the booster stations will be arranged in series, and the pipeline network system will also change. Can you tell me how the 1100-1150 in "(either two 800 pipes, or all modifications, using one 1100~1150 pipe)" is calculated? Ask for advice! !

=================================================== Thanks for the reply! Everyone has reached a consensus on the transformation of the inlet and outlet pipelines of the booster station. What I am currently concerned about is the specific diameter of the pipe for economic reasons during renovation. Looking forward to your reply again!