Hello Twan,
X11 is not an interface for digital In/Outputs. It's for Safety In/Outputs.
You need an external IO modules (such as Beckhoff EK1100 + EL1809 / EL2809 as how KUKA provides on demand) to use digital in/outs.
Or if you don't want to use extra modules,
Try use MediaFlange's interface instead. If your valves are too big, there are so called 'mini valves' which you can install on a tool.
Both would cost extra, so it's up to you.