why did unit trip on low total air flow?

[chumet1]

i am doing incident investigations on old trips and one of my bottlenecks is lack of information...
attached is a trend of what happened. the right hand (RH) air flow measurement shoots up without any increase in load or vane position. this led to a chain of reaction shown on the trends until the unit tripped on low total air flow.
from my analysis, the possibility is loose vanes that get opened on their own and let in an in rush of air. there has been a history of piezzo rings getting blocked distorting the air flow measurement.
my questions are:
1. from your wealth of experience, can the vanes get loose and let an inrush of air through like this?
2. can a blockage of the piezzo rings cause a reading of an increase in air flow. (i know blockage causing a decrease)
THANK YOU

 

[ivymike]

sorry, what kind of equipment are you talking about?

 

[chumet1]

forced draught fans for the power generation boilers

 

[byrdj]

is there a windbox pressure trace for the left side? the two on the trace are both marked RH. would the lower, red, trace be LH?

cursory review to me indicates false signal. but don't know if any of the trace values are used for fan control or just indication. based upon sudden, significant change in RH flow, but nothing change on windbox. if the red is the LH, then it does show it responding to the LH fan response, where as the RH windbox does not respond.

But, I tried to avoid the boiler side of plants, so I am just guessing!

 

[hacksaw]

you need to be looking at the boiler/firing controls to sort this out

 

[MintJulep]

What type of fan?