DP is the pressure difference between beneath the false bottom and upper, as measured by a gauge, and what the pressure would be, and showing if the grain bed offered no restriction to the flow of wort.
For example, say we are sparging a mash and are maintaining a balance between wort flowing out and water spraying on. The height of liquid in the lauter tun, from the bottom (real bottom) to the surface, is steady at 27.7 inches. A one square inch water column, 27.7 inches high, weighs one pound and exerts a pressure of one PSI. It is wrong expressing the differential pressure in PSI. That is not how it is usually done. DP is commonly stated as inches or millimeters of water column. So 0.64 PSI works out to about 17.7 inches, and our differential pressure is 10 inches. This is a crisis. The rule of thumb in commercial breweries is that one to two inches is optimal, four is fine, and six is okay. When you get to eight it's past time to drop the rakes and start backing down the flow rate. As a matter of fact, at Blackstone I start lowering the rakes when the DP hits 3 inches. At 10 we're talking remedial measures -- stop the runoff, do a deep cut with the rakes, maybe underlet to lift the bed.
Edited by Kevin
Email: [email protected]
http://www.brewerybeerequipment.com
.jpg)
.JPG)
Get In Touch