Valve see-through

This is a view at an automatic valve that regulates the amount of water to the shaftseals of the main feedwater pump of unit EC 20.
The pump operates at a pressure between 120 bar and 200 bar (1 740.452 856 1 and 2 900.754 760 1 pound/square inch) so normal shaftseals are not applicable. (graphite blockpacking and so on) .
The pump has a max. output of 500kg/sec (we now only use 428 kg/sec= 1540 ton/hour))
The handwheel in front is belonging to the idling system, this is used during start-up when only a little bit of water is flowing to the boiler.
The pump needs a minimum flow and by using the idling system a minimum flow is pumped back to the feedwater tank.
The idling system consists of sevaral valves, flow is regulated by an aircontrolled valve.
The valve that belongs to the handwheel is used to block the system during maintenance.

Here in LARGE...