Fan Not Responding to Increase in Static Pressure

[RJB32482]

Hi,
If a industrial fan inlet is blocked by a damper, will the flow decrease even if it is controlled to increase when it sees a spike in static pressure in the duct before the damper? Our fan is controlled by static pressure. We see that it is not responding to an increase in pressure (it usually speeds up). If the damper after the pressure element but before the fan is not fully open could this cause this effect (fan slowing down)?

Thank You

 

[MariusChE]

Your question is vague and therefore it raises more questions.
Is the fan on an electrical drive?
How far above its surge point is the fan operated?
Have you checked the control system?
Is the control system over-damped?
Do you have anti-surge control in place?
Is the valve drifting? and have you checked it?
When was the last time you checked the link and link update between the DCS and the fan?

The "spike" would worry me a bit. What in the process would cause this?

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