I have compacted the grain bed before from pumping too fast. It's really not a big deal, just lost time. Stir the grain bed up again and reset it. What you can get away with will depend on your system and the grist. Installing a vacuum gauge on the outlet of the mash tun would help you see how fast you can pump. Or 2 sight glasses...one with the inlet above the false bottom and one below, then compare the levels while you're recirculating. Rice hulls and malt conditioning will also help you get a higher flow rate before compaction happens.
Fermenting: Egregious-ish, Barrel Fermented Dreg DelcoLambic, Sacch Trois Helles
Drinking: Pre-Prohibition Pilsner, 11 day Oat Pilsner, RIS v7, Doppelbock, RIS v6, Carrot Blossom Cedar Mead, Sauerkraut Fermented Gose, Gueuze, Brett Blonde, Kriek, Saison, Sour Blonde
Barrel aged: Rye Barleywine, Tripel, Wee-Heavy