Which of the following could cause boiler efficiency to decrease?
A. Blowdown valve is leaking
B. Conductivity setpoint is too low
C. Conductivity sensor measures high
D. Steam flow measurement is low
E. Feedwater flow measurement is nonfunctional
The steam and feedwater flow measurements (Answers D and E) can be used to calculate boiler efficiency, but do not affect the actual efficiency of the operating boiler.
A leaky blowdown valve (Answer A) will continuously cause heat to be lost. Boiler efficiency will decrease when the flow rate through the leaky blowdown valve exceeds the average blowdown flow rate.
Setting the conductivity setpoint too low (Answer B) will cause the blowdown valve to open wider, causing more heat losses than would occur had the setpoint been set correctly (higher), which decreases boiler efficiency. A conductivity sensor (Answer C) that measures high will effectively make the system operate at a lower conductivity and have essentially the same effect.
Additional complicating factors
Numerous other problems can decrease boiler efficiency.
David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes LLC, which offers engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER. He has more than 40 years of experience and has written more than 10 books and 350 articles about flow measurement, instrumentation and process control. Spitzer may be reached at 845-623-1830 or via spitzerandboyes.com. Click on the “Products” tab to find his Consumer Guides to various flow and level measurement technologies.