SaniForce 1590 Double Diaphragm Explosion Proof Pump. 

Graco’s SaniForce 1590 air-operated double diaphragm sanitary pumps have one of the best, most durable, lube-free air valves in the industry. Ideal for applications requiring high flow rates and portability.  These Pumps are great for distilleries and breweries.  These pumps will handle thick corn mash no problem.  They are also great for high proof spirits.  The pump is explosion proof but the air compressor that powers the pump isn't, so the compressor needs to be in another room.  These pumps will move heavy grain mashes no problem.  You can empty out a 500 gallon fermenter in as little as 5.5 minutes.  Air valve adjustment gives you control over pumping speed up to 100 gallons per minute.