Thermoplastic Pipes - Strength Derating vs. Temperature
Increased temperatures derates the strength of thermoplastic piping materials.
Thermoplastic materials loose strength to pressure and tension with increasing temperature. The table below can be used as a guide to common thermoplastics and their derated strength with temperature. Manufacturing data should always be consulted.
| Derating Factor | |||||||
|---|---|---|---|---|---|---|---|
| Temperature | PVDF | CPVC | PVC | PB | PEX | PE | |
| (oC) | (oF) | ||||||
| 21 | 70 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| 27 | 80 | 0.9 | 1.0 | 0.9 | 1.0 | 0.9 | 0.9 |
| 32 | 90 | 0.9 | 0.9 | 0.8 | 0.9 | 0.9 | 0.9 |
| 38 | 100 | 0.8 | 0.8 | 0.6 | 0.9 | 0.9 | 0.8 |
| 43 | 110 | 0.8 | 0.8 | 0.5 | 0.8 | 0.8 | 0.8 |
| 49 | 120 | 0.7 | 0.7 | 0.4 | 0.8 | 0.8 | 0.7 |
| 54 | 130 | 0.7 | 0.6 | 0.3 | 0.7 | 0.8 | 0.5 |
| 60 | 140 | 0.6 | 0.5 | 0.2 | 0.7 | 0.7 | 0.4 |
| 66 | 150 | 0.6 | 0.5 | 1) | 0.7 | 0.7 | 0.2 |
| 71 | 160 | 0.5 | 0.4 | 1) | 0.6 | 0.7 | 1) |
| 82 | 180 | 0.5 | 0.3 | 1) | 0.5 | 0.6 | 1) |
| 93 | 200 | 0.4 | 0.2 | 1) | 0.4 | 0.5 | 1) |
| 104 | 220 | 0.4 | 1) | 1) | 1) | 1) | 1) |
| 121 | 250 | 0.4 | 1) | 1) | 1) | 1) | 1) |
| 138 | 280 | 0.3 | 1) | 1) | 1) | 1) | 1) |
1) The thermoplastic is not resistant for long term service at this temperature. Operating conditions should be avoided.
- PVDF - PolyVinylidene Fluoride
- CPVC - Chlorinated Polyvinyl Chloride
- PVC - Polyvinyl Chloride
- PB - Polybutylene
- PEX - Cross Linked Polyethylene
- PE - Polyethylene
Plastic Pipes Temperature Derating Diagram
Example - Higher Temperature and Reduced Strength
If the operating pressure for a 6" Schedule 80 CPVC pipe is 167 psi, the maximum operating pressure at 150 oF (66 oC) is reduced to
(167 psi) 0.5
= 83.5 psi
