Boiler steam pressure setting vs. max. capacity 1

[josemg]

Is it true that lowering the set point operation pressure of a boiler will give more efficiency with equal or more than rated capacity in lbs/hr?

What is the difference between lower than design pressure on a water tube and fire tube boiler ?

I have one 39,000 lbs/hr water tube and two 10,350 lbs/hr fire tube boilers and the design operating pressure was 125 psig but now they operate at 90psig. I still can only get about 40% of maximum lbs/hr of these boilers since actually the maximum is 20,000lbs/hr on the water tube and 6,000 on the two fire tubes.

 

[CARF]

Dear Josemg,

It is simply NOT true. Who told you that? Tell him to take a lesson in physics. Go back to the higher set-points again to get higher capacity.

http://www.armstrong-intl.com/products/traps/stbasics.php3

This link may help,
MVD

 

[alexpln]

... try to download Process Control Calculators and run the installation cost on steam

http://www.lavell.lnk.pl/str/soft/soft.html

 

[sabap]

On steam turbine units, operating the unit with lowest possible steam pressure helps in improving heat rate due to following reasons:

1. Lower leakages in the furnace/boiler which means low losses.
2. Turbine governer valves will remain close to full open which will result very low throttling losses and also result in less wear and tear of valves.

Keep in mind, i have said, lowest possible pressure. If you go too low, your steam flow requirements may not be met.

For example, if you can get 400 t/he of steam at 165 kg/cm2 pressure. Then by operating at 170 kg/cm2 will result in poorer efficiency. But def running at 100 kg/cm2 will not give you the same flow rate.