Letters

Pressure Transmitter Mounting March, Column Instrumentation Basics, p. 48 The illustration in Figure 9 purports to show a flowmeter installation for vapor or gas. In vapor or gas service, the differential pressure and pressure transmitters are always mounted above the process taps, with the impulse tubing sloped from the transmitters to the process taps, without low point or high point pockets. This is done to prevent liquids from accumulating in the impulse lines and causing errors. Pretty art, bad installation engineering. Yours very truly, Douglas J. Morrison Project Manager, WorleyParsons, Deer Park, Tex. Author’s reply: Thank you, great catch! This figure illustrates the opposite of what is in the text. Sincerely, Ruth Sands Senior Consulting Engineer, DuPont Engineering Research & Technology, Wilmington, Del. Correction November, Facts At Your Fingertips — Pump Selection and Specification, p. 29 In the Pump Comparison Chart, under Centrifugal Pumps, Viscosity, it is written that "Efficiency increases with increased viscosity." It should read, "Efficiency decreases with increased viscosity." A more complete comparison of centrifugal and positive displacement pumps, including a discussion of…