I am designing a 3" line to supply raw water. The line is about 750 m long. The inlet pressure of the line is about 900 kPa(g) (9 atm) and the source is an open dam (thus the temperature is ambient temperature, between 5 and 30 deg C). The line can be isolated at the inlet and outlet. My question is: is it necessary to install a TSV (Temperature Safety Valve)?

I have looked in design manuals: One design manual state: "Relief valves shall not be provided for thermal expansion where piping and equipment can be blocked in between valves expect for liquid lines outside process areas (i.e. off sites). Protection against over pressure will be provided when low boiling liquids can be blocked in and the pressure can be increased due to vaporisation. These criteria should be considered as general rather than specific in regard to both location and application. Certain situations will arise that may require deviation from these norms." According to me, the water in this line will never reach boiling point, thus if I follow these guidelines, a TSV is not necessary.

I could not find anything in API 520 or 521.

I have spoken to my colleagues, but I got differences in opinions and neither of them were 100% sure.

I have also read through thread1203-149006 and thread124-133483: From these threads it is not 100% clear it I need a TSV. These are mainly how to size a TSV. However, from the threads, it seems as if I will need a TSV.

I got the compressibility of water at http://www.ldeo.columbia.edu/~martins/hydro/lectures/proph2o.htm. They specify it as: