Steam Condenser Back Pressure

[dshauck]

How is Back Pressure measured properly in the condenser for a steam turbine? Is it simply an absolute measurement of condenser pressure in inches of mercury (inhg)? Or is it the difference between this measurement and barometric pressure?

 

[RossABQ]

The gauges I've seen in powerhouses were referenced to atmospheric.

 

[byrdj]

Here is a good description

http://www.heatexchange.org/pub/pdf/edu/Vacuum and Vacuum Equipment Edcational Primer.pdf

 

[rmw]

Condenser back pressure measurement is most often stated as absolute pressure as in 3" hg which is 3 inches of manometer reading above a perfect vacuum.

But the same vacuum could and by some is stated as 27 inches (hg) of vacuum (rounded off for clarity). That is referenced from atmospheric meaning 27 inches below atmospheric pressure.

In the case of condensers operating in their normal range it is pretty obvious whether absolute or atmospheric reference is being used. Anything less than 5-10" hg is absolute.

However, there are processes and even some condensers that operate in the middle of the range so one has to be careful what is being stated.

rmw