Steam functions overview
- Last UpdatedSep 17, 2025
- 2 minute read
- PI System
- PI Server 2023
- PI Server
The PI Performance Equation (PE) Steam Functions Module (PI Steam) makes available functions that calculate the thermodynamic properties of steam within Performance Equations.
For each steam function, there are two function calls: One in English units, and one in SI units. The following tables list the engineering units for the variables in the steam functions and the supported functions in English units. See Learn about steam functions in asset and tag-based analytics.
Engineering Units
|
Variable |
English Unit |
SI Unit |
Conversion Factor (Eng to SI) |
|---|---|---|---|
|
Temperature |
degree F |
degree C |
(T - 32) / 1.8 |
|
Pressure |
psia |
KPa |
6.894757 |
|
Volume |
ft3/lbm |
cc/g |
62.42796 |
|
Enthalpy |
BTU/lbm |
J/g |
2.326 |
|
Entropy |
BTU/lbm/R |
J/g/K |
4.1868 |
Supported Functions
|
Name |
Function Description |
|---|---|
|
StmEng_tsatp |
Saturation temperature as a function of pressure. |
|
StmEng_hsatp |
Saturation enthalpy as a function of pressure. |
|
StmEng_ssatp |
Saturation entropy as a function of pressure. |
|
StmEng_vsatp |
Saturation vapor specific volume as a function of pressure. |
|
StmEng_psatt |
Saturation pressure as a function of temperature. |
|
StmEng_hsatt |
Saturation enthalpy as a function of temperature. |
|
StmEng_ssatt |
Saturation entropy as a function of temperature. |
|
StmEng_vsatt |
Saturation vapor specific volume as a function of temperature. |
|
StmEng_vpt |
Vapor specific volume as a function of pressure and temperature. (For saturated and super-heated steam.) |
|
StmEng_vptl |
Water specific volume as a function of pressure and temperature. |
|
StmEng_vph |
Vapor specific volume as a function of pressure and enthalpy. (For wet and dry steam.) |
|
StmEng_vps |
Vapor specific volume as a function of pressure and entropy. (For wet and dry steam.) |
|
StmEng_hpt |
Enthalpy as a function of pressure and temperature. (For saturated and super-heated steam.) |
|
StmEng_hptl |
Liquid enthalpy as a function of pressure and temperature. (For water.) |
|
StmEng_hps |
Enthalpy as a function of pressure and entropy. (For wet and dry steam.) |
|
StmEng_spt |
Entropy as a function of pressure and temperature. (For saturated and super-heated steam.) |
|
StmEng_sptl |
Liquid entropy is a function of pressure and temperature. (For water.) |
|
StmEng_sph |
Entropy as a function of pressure and enthalpy. (For wet and dry steam.) |
|
StmEng_tph |
Temperature as a function of enthalpy and pressure. (For wet and dry steam.) |
|
StmEng_tps |
Temperature as a function of entropy and pressure. (For wet and dry steam.) |
|
StmEng_xph |
Steam quality (vapor fraction) as a function of enthalpy and pressure. (For wet steam.) |
|
StmEng_xps |
Steam quality (vapor fraction) as a function of entropy and pressure. (For wet steam.) |
|
StmEng_hpx |
Enthalpy as a function of pressure and steam quality. (For wet steam.) |
|
StmEng_spx |
Entropy as a function of pressure and steam quality. (For wet steam.) |