Functions using temperature and pressure as independent variables
- Last UpdatedSep 23, 2025
- 2 minute read
- PI System
- PI Server 2023
- PI Server
For the HPT, SPT and VPT functions, the steam has to be superheated or saturated dry. If the temperature and pressure are on the saturated curve, the calculated entropy, enthalpy or volume is the property of saturated vapor. If the input temperature is less than the saturated temperature for the input pressure, an Input Out of Range error is returned (that is, digital state INPOUTRANGE for PI formulas or error code -1 for user-callable functions). Since measurements are not exact, these PT functions can tolerate an error margin:
if (0 > Tsat - Tin > error margin) then saturated steam
The default error margin is 0.5 °F.
Input range for each function
|
Function |
Temp (deg f) |
Pressure (psia) |
Enthalpy |
Entropy |
Quality |
|
StmEng_tsatp |
0.088649 to 3200.112645 |
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|
StmEng_hsatp |
0.088649 to 3200.112645 |
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|
StmEng_ssatp |
0.088649 to 3200.112645 |
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|
StmEng_vsatp |
0.088649 to 3200.112645 |
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|
StmEng_psatt |
32. to 705.1028 |
0.088649 to 3200.112645 |
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|
StmEng_hsatt |
32. to 705.1028 |
0.088649 to 3200.112645 |
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|
StmEng_ssatt |
32. to 705.1028 |
0.088649 to 3200.112645 |
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|
StmEng_vsatt |
32. to 705.1028 |
0.088649 to 3200.112645 |
|||
|
StmEng_vpt, StmEng_vptl High temperature region |
1472 to 3632 |
0.088648951 to 7251.886887 7251.886887 to 14503.77377 |
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|
StmEng_vph |
0.088648951 to 14503.77377 |
-0.017879547 to 1744.60206- |
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|
StmEng_vps |
0.088648951 to 14503.77377 |
-3.691353466E-05 btu/lbm/R to 1.672077738 btu/lbm/R |
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|
StmEng_hpt, StmEng_hptl High Temperature Region |
32 to 1472 |
0.088648951 to 7251.886887 |
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|
StmEng_hps |
0.088648951 to 14503.77377 |
-3.691353466E-05 BTU/lbm/R to 1.672077738 BTU/lbm/R |
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|
StmEng_spt, StmEng_sptl |
32 to 1452 |
0.088648951 to 14503.77377 |
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|
StmEng_spt, StmEng_sptl High Temperature Region |
1472 to 3632 |
0.088648951 to 7251.886887 |
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|
StmEng_sph |
0.088648951 to 14503.77377 |
-0.017879547 to 1744.60206- |
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|
StmEng_tph |
0.088648951 to 14503.77377 |
-0.017879547 to 1744.60206- |
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|
StmEng_tps |
0.088648951 to 14503.77377 |
-3.691353466E -05 to 1.672077738 |
|||
|
StmEng_xph |
0.088649 to 3200.112645 |
-0.017879547 to 1744.60206 |
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|
StmEng_xps |
0.088649 to 3200.112645 |
-3.691353466E -05 to 1.672077738 |
|||
|
StmEng_hpx |
0.088649 to 3200.112645 |
0 to 1 |
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|
StmEng_spx |
0.088649 to 3200.112645 |
0 to 1 |