The siphons, or serpentines, are pressure accessories to be applied between the measuring instrument (pressure gauge or sensor) and the process.
It is mainly used as a heat sink, thus ensuring that the measuring instrument does not deteriorate even at potentially harmful temperatures for the instrument itself.
The pressure gauge valves are used to connect a measuring instrument (pressure gauge or sensor) to the process and, if necessary, to close the main fluid coming from the instrument itself, thus avoiding leaks in the system.
They can be realised as a “two-way” system (process / instrument connection only) or as a “3 way” system with inspection flange (process / instrument / control instrument connection).
The purpose of the control flange is to make it possible for an entity to check the pressure without having to close or disassemble the system.