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[shadow13]

Hi everyone,

This is about a multistage centrifugal blower that is to be used for WWTP applications. It is a fixed speed unit, no VFD and we use an inlet throttle valve. Blower is controlled by the pressure in the header going to the basins. Inlet throttle valve will modulate depending on the pressure requirements.

We asked the vendor to provide us the surge line in the blower curve that they sent to us but they say that they cannot provide this because "this blower operates at a single RPM where you have a single surge point and the blowers are controlled by the inlet throttle valve". Moreover, they also add that if the blower's speed is being adjusted to different values (as if it had a VFD) then we will be able to create this surge line, when the blower operates essentially at different curves and hence you can be able to create a surge line from the each individual surge point of each curve. And also, is it the case that surge lines are most common for positive displacement rather than multistage centrifugal types?

Can anyone please confirm if our vendor's statement is correct for multistage blowers? Is it correct that you cannot get a surge line but just a surge point?

Thank you everyone in advance.