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: Brown IPA, JeanBeer, Barrel Fermented Dreg Lambic, Brett Trois Helles, Carrot Blossom Cedar Mead
Drinking: RIS, Coffee RIS, Jalapeno RIS, Heavy Hopper v2, Dusseldorf Altbier v5, Oktoberfest v5, Dopplebock v2, Cider, Rye Berliner Weisse, Sauerkraut Fermented Gose, Lambic, Brett Trois IPA, Brett Blonde, Kriek, Saison, Sour Blonde, RIS
Barrel aged: RIS, Rye Barleywine, Tripel, Wee-Heavy