StmSI_XPS
- Last UpdatedSep 17, 2025
- 1 minute read
- PI System
- PI Server 2023
- PI Server
Calculates the steam quality (vapor fraction) as a function of pressure and entropy—all variables expressed in SI units. Use only for wet steam.
Format
StmSI_XPS(P, S)
Arguments
-
P
Pressure of the steam in KPa. The valid range is 0.611213 to 22064 KPa.
-
S
Specific entropy of the steam in J/g/K. The valid range is -0.41868 to 12.5604 J/g/K.
Returns
Computed steam quality (vapor fraction) or Error digital state.
Sample Values
|
Pressure |
Entropy |
Steam Quality |
|
2500. |
5.8837 |
0.9 |
|
5000. |
5.6682 |
0.9 |
|
10000. |
5.3939 |
0.9 |
Note: If the input entropy is greater than that of the saturated vapor, the function returns 1.0 as vapor fraction. If the input entropy is less than that of the saturated liquid, the function would compute negative vapor fraction without setting an error state.