Fan static pressure

[dynamo78]

I have to replace several fans that were installed in the 70s. I don't have any cat sheet or drawings to verify their performance and data, manufacturer closed shop. I know their CFM and actual Hp. I figured out that in order to verify the static pressures of each fan, I have to plot the CFM and horsepower on the curve and take the reading on the Y axis for the static pressures, at this point, I am still plotting it at sea level and .075 air density its a kind of reverse engineering. Is these an accepted procedure? another caveat. this is located around 7000ft. above seal level. when will I include the correction factor? in this case, it is 1.15. Do I have to multiply the CFM with the correction factor before plotting it?
Thank you for all the help.

 

[lukaiENG]

rather than reverse engineer the existing fan performance, is it not better to examine what the required capacity is from an engineering perspective? maybe the old fans were over-sized?

 

[dynamo78]

@Lukai, Thanks for your input. I agree but I have limited resources to investigate the whole building and I got the assurance that ventilation system is ok meets the building requirement. That's why I came up with that simplistic solutions.

 

[EnergyProfessional]

what lukai said.

you could measure static pressure and flow to select new fan.