Determining Long-Term Hydrostatic Strength (LTHS)
When designing a pressurized system, it’s important to understand how a material performs when exposed to constant stress in the presence of water. Data from creep-rupture curves generated at various temperatures can be extrapolated to predict a material’s LTHS for a given set of conditions. These values are then used to determine design stresses, which should include appropriate safety margins.

50-year prediction and lower prediction limit (LPL) Values
ISO 9080 Method 4 |
| |
Radel R-5100
|
Acudel 22000
|
Udel P-1700
|
| Temp., °C |
Time, hours |
Mean, MPa |
LPL, MPa |
Mean, MPa |
LPL, MPa |
Mean, MPa |
LPL, MPa |
| 20 |
438,000 |
41.5 |
36.6 |
39.4 |
33.4 |
13.4 |
– |
| 70 |
438,000 |
25.4 |
21.3 |
18.9 |
15.2 |
5.7 |
– |