I'm assuming that this is about valves for a pump used for the dam project. I wouldn't use the term liquid because the valves can also use gas and steam.
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Special valves
More than 50% of co-ax valves that have been sold are designed and developed in close relationship with the customer. Because of its flexibility and quick response to every days changing technologies, müller co-ax has proven to be a very reliable partner for the automotive, process and fluid power industry as well as in environmental process applications.

la rapida apertura e chiusura creano nel filtro / recipiente un picco di pressione unitamente ad una tenuta ermetica all'esterno e da una sede valvola estremamente resistente all'usura
fluidi - gas caldo, per es. azoto, gas sintetico, vapore

fast opening and closing in order to create a pressure surge the filter/pressure vessel; hermetically sealed to the outside;

equipped with extremely wear-resistant valve seats
media - hot gas, e.g. nitrogen, synthetic gas, steam

riempimento gas
applicazioni speciali tecnologia del riempimento gas

special application gas filling technology

The valve is connected in parallel in the bypass line (between supply pump and fluid outlet).

http://www.co-ax.de/us/sortiment_spezial.html

SAFETY RELIEF VALVES SERIES SMU-7000
Flanged, spring loaded, direct acting, full nozzle safety relief valves (ASME Sect.VIII).
Media: gas, steam and liquid

http://www.astspa.it/GENERAL CATALOGUE_11_1999.PDF