DMeier5950
Industrial
- Aug 8, 2024
- 1
Good evening,
I am writing a procedure for operation of a steam system at a combined utility plant. I am working on a cold iron start-up procedure, whereas they will pressurize the steam header through an 18 inch carbon steel pipe through approximately 2 miles of steam tunnel at 175 psig and will use that pressurize a 24 inch by 20 foot header, which then branches off into multiple 6 - 8 inch runs to different reducing stations.
I am trying to figure out the proper pressurization/heat up rate limit for bringing steam into the tunnel and then into the header. The tunnel I think is more critical due to the amount of piping. Unfortunately none of the available drawings provides me any more information on the piping system aside from the pipe O.D., so I was attempting to use the most limiting stress factors I could find for the system and apply them throughout.
The individual headers are equipped with 1 inch warm up lines, so I assume that over-stressing the header isn't plausible if they simply use the warm-up line. However I cannot verify that the tunnel valves have warmup valves installed, so I want to provide a pressurization rate.
When I was an operator, we had pressurization rates for our steam header (1.45 hrs from ambient to 0 psi, 1 hr from 0 - 100 psi, etc.,). Our system was much higher pressure and more complex, but I imagine it is still an important factor. Am I overthinking this?
Is there a way to use the Tensile and Yield stresses from ASME B.31.1 to calculate the maximum allowable thermal stress due to rate of change? Or at least in the ballpark? Or is it not as important as I think it is?
Thanks!
I am writing a procedure for operation of a steam system at a combined utility plant. I am working on a cold iron start-up procedure, whereas they will pressurize the steam header through an 18 inch carbon steel pipe through approximately 2 miles of steam tunnel at 175 psig and will use that pressurize a 24 inch by 20 foot header, which then branches off into multiple 6 - 8 inch runs to different reducing stations.
I am trying to figure out the proper pressurization/heat up rate limit for bringing steam into the tunnel and then into the header. The tunnel I think is more critical due to the amount of piping. Unfortunately none of the available drawings provides me any more information on the piping system aside from the pipe O.D., so I was attempting to use the most limiting stress factors I could find for the system and apply them throughout.
The individual headers are equipped with 1 inch warm up lines, so I assume that over-stressing the header isn't plausible if they simply use the warm-up line. However I cannot verify that the tunnel valves have warmup valves installed, so I want to provide a pressurization rate.
When I was an operator, we had pressurization rates for our steam header (1.45 hrs from ambient to 0 psi, 1 hr from 0 - 100 psi, etc.,). Our system was much higher pressure and more complex, but I imagine it is still an important factor. Am I overthinking this?
Is there a way to use the Tensile and Yield stresses from ASME B.31.1 to calculate the maximum allowable thermal stress due to rate of change? Or at least in the ballpark? Or is it not as important as I think it is?
Thanks!
