Engineering Ethics and a Database of Cases

Posted on 2009/12/30 by admin

Let’s have a quick discussion about engineering ethics: what it is, why it’s important, and a database of ethical case rulings. I think this post might help you if you’re ever in an ethical conflict.

In many places around the world, the title of a professional engineer is closely regulated by professional engineering bodies. Much as you cannot practice medicine without a license, or cannot be a lawyer without passing the bar exam, you cannot do some key engineering activities without a license…or at least close supervision by someone with a license. To get your license, the rules vary from place to place. I know that, annoyingly, all the states of the U.S. and provinces of Canada are different. But normally you need to prove your technical and academic skills through schooling and/or competency exams, build some engineering experience in general, get specific experience in the region you are applying, prove a grasp of legal and ethical concerns, show good character, and reach the age of adulthood.

The ethical rules in each jurisdiction are different, and probably you can get the list for free by contacting your local engineering board. But usually the rules revolve around the same priorities and advise you how you must meet them:

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How to be a Star Engineer

Posted on 2009/12/20 by admin

Interesting little article I found: How to be a Star Engineer.

What the [Bell Laboratories] wanted to know was: what separates the star from the average performer? Is it innate or can star performance be learned? Could a program to improve productivity be designed that would help turn average performers into stars?

The article emphasizes making the most of non-technical skills, like building networks of people who know things, avoiding political problems, volunteering ideas and volunteering for tasks, improving themselves.

I showed it around at work: a few people thought it was very helpful.  Others that “this is advice is all good, but pretty obvious.” One woman thought it was all just talking about “a person’s natural charisma, which you either have or you don’t.” (I disagree).

What do you think?

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Posted in Career Advice, General Engineering Topics, General Office, Psychology and People Skills | Tagged | 1 Comment

Aspentech’s Hysys: Fluid Package (Thermodynamics) Notes

Posted on 2009/12/04 by admin

Aspentech’s Hysys is a process simulation tool. You always have to pick a “fluid package” when you use the program: a thermodynamic method it will use to calculate properties, especially vapour-liquid equilibria. I watched an old “webinar” (presentation given through the Internet) on their property packages and took some notes.

You can combine this post with the Hysys manual, the Hysys property package wizard, Aspentech Support’s advice, and books on simulation, and put it all together to choose the best package in each case. If you are in doubt Aspentech Support can always give you personalized advice. They are really quite good at quickly suggesting the best method to use.

One trick to remember is that you can use different fluid packages and different component lists in different parts of the simulation. You can have a Peng-Robinson Package running the calculations for your hydrocarbons, and the ASME Steam Package running the steam and water calculations.

Here are my notes from the webinar:

-Hydrocarbons: normally use an Equation of State method
-Vapour pressure models are OK at low pressures
-Activity coefficient like NRTL is poor model for hydrocarbons

Equations of State:
-Peng-Robinson is most enhanced in Hysys, highest T & P range, has special treatment for key components, largest binary interaction database: good standard for hydrocarbons
-PRSV: extends PR to moderately non-ideal systems and better represents poor components and mixtures. Adds a new parameter to the equation. Slower calculation speeds than Peng-Robinson
-SRK: modified Redlich Kwong model. Similar accuracy/use as Peng Rob, but in Hysys SRK has less enhancements than PR.
-PR-Twu, SR-Twu for hydrogen solutes? In liquid hydrocarbons
-TST: hydrocarbons with non-ideal components (used in glycol package)
-GCEOS: generalized cubic EOS for user to add their own parameters. Use this to build your own model when necessary
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Engcom.net for Engineering News & Trivia

Posted on 2009/12/04 by admin

For some fun, check out Engcom.net. It has engineering news, weekly trivia, humour, and also some interesting articles. You can contribute to the site if you get into it.

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Introduction to Pressure Relief Valve Design Part 3 – Sizing Orifices and Piping

Posted on 2009/11/21 by admin

This is the third in a set of articles introducing the basics of pressure relief valve design from a process designer’s viewpoint. Read Part 1 here and Part 2 here.

Orifice Sizes

Once you have all of the scenarios that can cause your relief valve to open (see Part 2), and all the key fluid data for each scenario, you can size the relief valve orifice. This is the size of the opening that the fluid passes through within your relief valve. In general, a relief valve vendor will have several standard orifice sizes and you will pick the one that best fits your need.

API 520/521 has some equations to determine the minimum orifice size you need, as well as good advice and factors to put into their equations when you don’t have information from the valve manufacturer yet. There are many programs and spreadsheets out there to size the orifice, so find out what your office uses. By carefully reading the standard and an example problem or two done by your office’s methods, you should find the actual “sizing” of the relief valve is relatively easy.

One key factor that any calculation procedure will have you do is check for choked flow / critical flow. Choked flow is when a fluid is going so fast that it reaches sonic velocity: after that, it cannot go any faster no matter what the downstream pressure is.  You should know the approximate inlet and outlet pressures of the relief valve, so you can check if you will reach choked flow. If it is choked, then that changes your results. API discusses this and gives different instructions and equations for chocked vs. non-chocked flow.

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