Does Increasing PSI on a Boiler Increase its BHP Output?

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Discussion Overview

The discussion revolves around the relationship between the pressure settings on a boiler and its brake horsepower (BHP) output, particularly in the context of an experiment conducted with a Cleaver Brooks boiler. Participants explore the implications of venting steam to the atmosphere at different pressures and the resulting BHP measurements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports an experiment with a Cleaver Brooks 30bhp boiler, noting that at 40 PSI, the boiler produced about 13bhp, but higher pressures were needed to meet work demands.
  • Another participant seeks clarification on the experimental setup and requests a system diagram to better understand the context.
  • A participant questions whether venting steam faster than the boiler can maintain pressure results in a BHP output exceeding the rated capacity, citing specific measurements of steam output at different valve openings.
  • Concerns are raised about discrepancies in BHP calculations, particularly regarding the output observed during the experiment.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the experimental results, particularly regarding the relationship between pressure, valve position, and BHP output. There is no consensus on the calculations or the interpretation of the data presented.

Contextual Notes

Participants note potential limitations in the experimental setup, including the effects of venting steam and the capacity of the custom condenser, which may influence the observed BHP output. The discussion does not resolve these uncertainties.

Gary K
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Just completed an experiment using a Cleaver Brooks 30bhp boiler rated at 140 PSI. At 40 PSI I did a "vent to atmosphere" test with a water meter attached to the boiler feed tank. I was able to find the equilibrium point of the boiler (didn't kick off, pressure remained fairly constant) over the course of an hour. The result of the test showed that the boiler was putting out about 13bhp. During the course of the experiment we found that this setting (40psi with a gate valve opened 1 1/4 turns) was not enough to produce the work we needed. Even with the gate valve opened 100% at 40psi we needed more power. We ended up ramping up the psi to 60, 80, 100 and 120. During all of these tests the gate valve was opened to 100% and of course the boiler could not keep up and lost about 10psi per minute. The steam we used was vented to atmosphere. The question is, when the gate valve was wide open at say 100 psi, were we still using about 13bhp or were we actually using far more than 13bhp as we were exceeding the boiler's capacity to maintain pressure? Thanks in advance.
 
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I can only vaguely guess what this question is about . Please explain more clearly what you are doing and show us a system diagram .
 
The point of the question is, If you vent a boiler to atmosphere faster than it can keep up, are you using more bhp (pounds per hour) than the boiler is rated for a brief period of time. When the gate valve was open about 1/8 we were seeing about 450 pounds per hour coming out of the pipe. When the same valve at the same pressure was opened 100% were we seeing more than 450 pounds per hour? We built a custom condenser that would condense 100% of the steam at 40 psi with the valve 1/8 open. When the valve was at 100% open the condenser could not keep up and copious amounts of steam came out. The boiler had a 2" outlet that was reduced to 1". About 70 feet of non-insulated black pipe lead to the outlet.
 
Gary K said:
a Cleaver Brooks 30bhp boiler rated at 140 PSI. At 40 PSI I did a "vent to atmosphere" ... the boiler was putting out about 13bhp
Why the large discrepancy in bhp? Something seems off in your calculation,
 

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