Thermoplastic Pipes - Temperature and Strength Derating
Increased temperature derates the strength of thermoplastic piping materials
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Thermoplastic materials loose their 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 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
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