I made this in well under one evening, and it can direct lava at a rate of about one layer of volcano per 2 or 3 seconds @ 300 FPS. Enough to launch lava 8-10 blocks out off a flat cliff face.
It's pretty easy to set up. All there is to it is what you see here for the main level (which can all be dug out first, including those channels). Then on the level below, there is simply a series of rooms going all around, with a door in between where each pump is above. The channels from above break into each of those rooms. Then I simply used Dwarf therapist to assign only one miner job in the fortress to a peasant, and had him dig into the volcano in Room #1. Then assign a miner job to peasant #2 and have him dig into the volcano in room #2. Forbid the doors each time as they dig, so they dont run around and open the doors while on fire.
The room above this one just has gears and axles to power the pumps (from a few water wheels elsewhere).
This is also really good at draining the volcano if you want to build stuff in it (make sure you have a lot of fortifications in a row on the edge of the map, because I think stuff has to drain at a natural pace off the map, it can't be forced out)
If I were to build it again now that I have the design, it could probably be done in about 1.5 hours. Hopefully that is useful to some people.
In image:
LEFT: Drain off edge of map. If you want to drain the volcano. Next to that is the stairway and water stack (unrelated) and power line from elsewhere.
MIDDLE LEFT: a bunch of switches and floodgates already built in, which can later on be hooked up safely to whatever project you desire.
RIGHT: Obviously, a volcano, with 20 pumps tapping into it.