Presumably, you're feeding your valve block with a signal representing the opening of the valve. How is that signal generated?
If it is integrated twice from an acceleration signal, you can use two rate limiter blocks (as you found out) to limit both the acceleration and speed rate before integrating. Note that limiting the speed rate is equivalent to limiting the acceleration, and limiting the acceleration rate is equivalent to limiting the derivative of the acceleration. If you want to limit the speed and acceleration, rather than their respective rates, use Saturation blocks instead.
If your opening signals are generated differently, please provide more details as to how they are generated.
HTH,
Arnaud
