Boiler hp related to pressure?

[JNJdropout]

I'm basically a machine design engineer, but have been asked a question re boilers (industrial), namely does boiler HP change with boiler pressure.
If we have a 200 hp, 200 psi boiler and operate it at 20 psi, does the actual hp go down? All the info I have found on the web says pressure has nothing to do with boiler hp.

Also, looking at the steam tables, I notice that the total energy in the steam, whether at 14.7 psi or 214.7 psi does not change very much, only about 4-5%.

I need an Thermodynamics Expert's input.

Thanks very much

 

[quark]

If you bother about useful boiler HP, then it does decrease. You will have more moisture in the steam which is subsequently wasted.

 

[25362]

The specific volume of saturated steam at the lower pressure would be about 8.8 times greater. For an equal volume of saturated steam, the weight rate would drop by the same factor.

Boiler horsepower, abbreviated bhp, is defined as a rate of water evaporation. One bhp is produced when evaporating about 34.5 lb per hour water at 212^oF into steam at the same temperature.

The latent heat (enthalpy) of evaporation at those conditions is 970.3 Btu/lb.
Thus, one bhp equals 33,480 Btu/h (rounded up).

Now, whatever the new conditions are, divide the "new" Btu/h by 33,480 to get the "new" bhp.