Sanitary Stainless P/T Relief Valve

[steamdog]

Is there such a thing as a sanitary stainless pressure & temperature relief valve? I have a customer who is circulating hot DI water and asked for this. I have seen commercial sanitary pressure relief valves but not temperature (normally used in domestic hot water heaters).

 

[micalbrch]

Leser (

http://www.leser.com)

have those. Sanitary and up to 250 °C.

 

[steamdog]

Thanks Micalbrch, I checked the Lesser web site and saw pressure only safety relief valves, but not pressure-temperature??

 

[Duwe6]

Keep in mind that water and steam are the same chemical, and that for thermal events you have generated steam. Also, pressure is temperature for steam. I know these are tough to "wrap your head around" when empirically looking at a system. I've got a BUNCH pf PRV's that some engineer rerated to liquid flow, just because they were in process or cooling water service. Except he/she failed to note that the relieving temperature was 300-400°F. No longer a liquid.

The only time you should worry about relieving at a particular temperature [vs. pressure] is if your PRV is too small to vent at a rate sufficient for vapor. Best example are the Pressure /Temp Safety Valves on hot water heaters in the USA. They are small, but they relieve at, or just below the boiling point of water -- temperature-activated vent. So the relieving volume is much smaller -- steam occupies 1600X the volume of liquid water.

 

[steamdog]

Duwe6, I understand what you are saying and it makes sense when the water is above saturation temperature. This DI water is running around 160 def F. Should it get over about 190 Deg F it will ruin other parts of the system. Just like a temperature relief valve in commercial domestic hot water systems, they want one for this sanitary DI water. It will never turn to vapor even under atmospheric conditions.

 

[Duwe6]

Look at thermal fuse plugs. There are several metal alloys that melt below 190°F.