Automation Apps, Gaming Systems and Thermodynamic Steam Quality

Readers Ask for Clarification on Some of Our Latest Articles

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Do We Need an App for That?

I am the recent owner of an iPad, and I am sending this message as advice for you and your magazine.
I am an avid reader of technical and trade magazines. These things help keep me abreast of trends in technology in order to keep my company focused in the right direction. At 55 years old, it did not occur to me that I would ever give up my printed magazines for electronic versions, but it happened.

One of the first things I did with the new iPad was download Zinio, an electronic reader program. I now find it impossible to justify carrying printed magazines while I travel, which can be extensive at times. I read all my magazines, if they are available, on my iPad.

This allows me to keep many magazines with me at all times and past issues of those magazines for reference. I keep 20 or 30 magazines available, all in a package the size of one.

My disappointment is that not enough of my favorite technical magazines are available electronically. Please consider adopting this new technology for distributing Control magazine.

Rick Caldwell
President, SCADAware

[Editor's note: We always strive to deliver content in the most convenient way possible. We are researching this new technology now. To read the magazine online, visit to view all articles or download PDFs to your iPad's library.]

Gaming Systems

It's very interesting what Siemens is trying to do with Plantville (see Walt Boyes' SoundOff! blog post, It is a very tough balance to strike between engaging and real. Personally, as soon as I heard "KPI," I was done.

Autodesk recently launched an iPad app aimed at middle and high school students with the goal of introducing them to engineering and physics (see It is basically a graphical physics engine, plus a 2D Erector set that lets you create all sorts of simulated mechanical contraptions. Though it is aimed at older kids, my six-year-old absolutely loves this thing because to him, he is "making" something. The common refrain now after dinner is "Dad can I make something on your iPad?"

Autodesk has also created a short presentation and series of videos to be used at middle and high school career days. The main purpose is to show all of the amazing things people do with Autodesk software (from video games to process plants), and that it is all based on science, math and engineering. Apparently, the number of kids who "would consider careers in science and engineering" typically starts in the 10% or under range, but then moves to the over 50% range after the presentation.

Robert Shear
Business Line Director, Autodesk Plant Solutions

Missing the Point on Steam

In the April 2011 "Ask the Experts" column ("Measurement of Drift, Stability, Offset, Bias"), there is a question regarding steam quality. Unless I'm missing something, there appears to be a disconnect between the question asked and the answer provided. The question seems to be related to steam quality in the classic thermodynamic sense, i.e. the ratio of the mass of vapor to the total mass at saturation temperature; hence, the mention of a throttling calorimeter. When the term "quality" is used in this sense, it only has meaning when saturated conditions exist. Yet the answer provided speaks of superheated steam and seems to be related to steam purity, i.e. measurement of impurities in the steam.

Carl Foresti
Analyzer Reliability Engineer
ConocoPhillips Bayway Refinery

Béla Lipták's Team of Experts Replies 

I agree with Carl Foresti. "Steam quality" refers to the mass of water vapor at a given temperature compared to the total mass at saturation temperature.

When we talk about steam composition, the words "steam chemistry," and "impurities or contaminants in steam" should be used, especially in steam quality control programs (which actually means steam chemistry, not steam quality).

The following are quotes from "Interim Consensus Guidelines on Fossil Plant Cycle Chemistry," EPRI CS-4629, Project 2712-1, Final Report, June 1986, Sargent & Lundy, Chicago, Illinois:

  • P. S-1, "The Interim Consensus Guidelines contained herein are primarily based on current industry experience and well-established thermodynamic data that pertain to water and steam chemistry."
  • P. S-1, "These Interim Guidelines reflect a consensus of current state-of-art knowledge of International experience with cycle, water and steam chemistry control practices necessary to improve unit availability."
  • P. 3-21, "The target values for steam were derived based on turbine steam purity considerations and the solubility of major impurities in superheated steam near saturation."

Gerald Liu, P.Eng.
Calgary, Alberta, Canada

I used to teach Mollier Diagrams in thermodynamics. We would show an adiabatic process from a steam line with saturated steam that dropped the pressure (through a throttling calorimeter) at constant enthalpy to a superheated state. We located the exit state and traced at constant enthalpy back to the pressure in the saturated region to get the quality. Thus, the responder is sort of correct.

When you use a throttling calorimeter to get the quality of saturated steam, you will exit the calorimeter with superheated steam at a lower pressure.

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