Diesel fuel tank question

[Ray Dunakin]

Here's the best photo I could find of an RS-3's fuel tank. I can't quite figure out what the thing is at the bottom of the long tank, that looks like it has an X on it:

 

 

 

 Anybody know? Or have a clearer photo?

[dehusman]

Actually that is the water tank,  the fuel tank is the thing to the right.

[Tugboat Tony]

If it was the Fuel tank I would assume its the condensation/ crud drain.

[dehusman]

The fuel tank is the thing on the right in FRONT of the air tanks, not between them (note the sight glass at the top, right of the tank). 

[BerkshireSteam]

It could be a drain valve. The long tank is actually a water tank to store boiler water for a steam generator. However, the unit may have been rebuilt with the steam generator removed but the water tank left.