The valve is equipped with an ON/OFF actuator, and there are two lines connected to this actuator.
It is installed on lines that can be used in the two directions, so I think small ball valves 1 and 2 are used depending on the flow direction.
I have no more information than the PID...
The 25mm lines Could be pilot lines used to increase the response of the valve which is used as a Pressure regulating device 
The valves are what I would call semi-manual. There is a box with two levers (open and close), admitting instrument air to the actuator.
The two 25mm lines are used to provide additionnal driving force (valve is DN600, so instrument air is not strong enough). Only the one at higher pressure (depending on the flow direction) is open when the valve needs to be actuated.

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