Early on in my experience with steam boilers I found out making sure that steam always has a place to go is pretty important if you enjoy the surrounding area being kept intact. But with my usage varying due to simply generating power when I have storage available, it was common that my boiler would heat completely up and then suddenly I don't need any steam anymore. That caused me to start making these regularly:

It's a makeshift safety valve. If the boiler were to fill completely with steam, the steam trap on top would start venting, avoiding dangerous pressure and explosion. I was wondering if you'd consider it worth it to make a smaller, single block "safety valve" that would act the same, venting steam only if a boiler is full. As for a recipe, I was thinking a manual steam trap on top, redstone in the middle, and iron on bottom in a vertical stack, like shown.

The iron would be forced up by pressure into the redstone, triggering the trap. Though really it's final form is up to you. I'm nearly providing my thoughts.

Boilers don't explode when they fill up with stream. They only explode if the water tank is empty and you then put water in while it is above 300 degrees.

Yeah... The only thing you'll loose when the tank overflows is energy.

Huh, could of sworn they did. Well consider this irrelevant then.