I'm probably not the first one to write you about this, but in Ian Verhappen's "Basics of Analyzer Sample Systems, Part 2" in the August 2011 issue, it says, "675 psi to move a column of water up at 25-ft rack…" Six hundred and seventy-five psi would move it OK—it would move it up at 309 ft/sec; i.e, a sample of it would get up there in 81 milliseconds, including initial acceleration and friction losses. In fact, a 2-in. Schedule 40 pipe with 27-ft head pressure at the bottom of the rack would get 50 gpm up the rack. Even 675 in WC would get water up that rack at > 42 ft per second.
W. Brown, C. Eng. MIET
Katy, Texas
Editor’s note: You’re right. You're not the only one who pointed this out. The correct wording should have been, "Remember, it takes 10.84 psig to move a column of water up a 25-foot pipe rack. Conversely, and more likely, a water stream gains 10.84 psig on its way down from the same pipe rack." We regret the error.
