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Temperature Derating Factors

Metals lose strength at high temperature

In the metallic hose world, this means that the Maximum Working Pressure (MWP) of a metallic hose must be reduced or “derated” as operating temperature increases.

The degree of strength reduction is predictable, so it is relatively straightforward to determine the combination of temperature and pressure that can be accommodated by a metallic hose.

Some metals are better than others in this respect, so in a particularly demanding application with a combination of sustained high temperature and high pressure, it is often possible to select a more exotic alloy that will meet the demand.

The table below enables easy selection of the correct derating factor for each alloy through a range of temperatures. This table is based on data from ISO 10380:2012.

Here’s a working example;

An engineer needs a 1” (DN25) 316SS hose to accommodate 40 bar MWP at 200°C.

From the table, she finds that the derating factor for 316SS @ 200°C is 0.62. So our engineer needs to select a 1” 316SS hose that has a standard (20°C) rating of at least 40/0.62 = 64.5 bar.

Using our Hose Configurator tool, she searches on 1” (25mm) Size and 64.5 bar Pressure. The Configurator confirms that UFBX2 double braided 316SS hose rated at 76 bar will accommodate the pressure and temperature requirement.

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