Thermal relief general

For liquid-packed vessels, thermal relief valves are generally characterized by the relatively small size of valve necessary to provide protection from excess pressure caused by thermal expansion. In this case, a small valve is adequate because most liquids are nearly incompressible, and so a relatively small amount of fluid discharged through the relief valve will produce a substantial reduction in pressure. 

Full liquid containers require protection from thermal expansion. Such relief valves are generally quite small. Two examples are... 

In general, if process fluid cooling temperature difference is larger than IdO T, U-tube, split header, or other means may be required to relief the thermal expansion. 

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