Thermal annealing for polyethylene items is not unusual. Some production cycle (i.e. extrusion) after the forming phase foresee the use of a rapid cooling procedure during which the molecules of plastic are “frozen” in their position and residual tension can arise. Annealing process relaxes residual tensions through heat application (around 100 °C) improving mechanical properties. Annealing also contributes to minimize shrinkage phenomena during service.
That depends on its pressure at minimum temperature, the fluid's maximum temperature and the bulk modulus of the fluid within. If the line (assume longitudinally restrained) is closed off near its maximum pressure rating and the fluid heats up for any reason, pressure will increase, regardless of how low its Young's modulus may be. A low E value would simply mean that the pressure increase caused by fluid volume expansion due to temperature change would be LESS than if it were steel, but it would still increase. If the increase in pressure is great enough to put it over its maximum pressure rating, you would need to have thermal relief.
95C is a common maximum temperature rating for HDPE. Melt is 210 C.
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"The problem isn't working out the equation,
its finding the answer to the real question." BigInch
I'm just doing some work with HDPE. Looking at the Georg Fischer catalogue, allowable pressures for PE80 and PE100 drop off to practically nothing at 60 deg C. Melting point is 130 and 131 deg C respectively. My concern about 83 deg. C is that is is probably well into the creep range.
A very low E mod. at 900 MPa means that fluid thermal expansion is absorbed by the pipe for very little force. Remember that the HDPE has a high expansion rate too.
Agree both with C2it and dcasto. Mechanical properties of HDPE decay as service temperature increases. Take a look at the attached paper (especially page 5).
