API 2000 Tank P/V Vent Sizing Causes List

Posted on 2021/07/15 by admin

The standard API 2000 discusses Pressure/Vacuum (P/V) vents. These special safety vents can automatically open to release tank vapor if the tank pressure increases, or open to allow atmospheric air inside if the pressure decreases. This helps prevent the tank from bursting due to high pressure, or sucking in like a crushed soda can due to vacuum. Remember that tanks tend to have surprisingly low design pressures, so it is deceptively easy to break a tank if you don’t have a proper P/V Vent. A little vacuum, and they can start to resemble a crushed soda can!

API 2000 lists a number of different conditions to consider and gives guidance on them:

  • Liquid movement in/out: use the API 2000 equations
  • Weather change: pressure (usually only a concern refrigerated tanks)
  • Weather change: temperature
  • External Fire Exposure

However, you should also use your judgement to consider any extra cases. Here are some examples: Continue reading →

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Designing Heat Exchangers to Prevent Fouling

Posted on 2019/06/12 by admin

Hey all, just an update to mention I found an aged but excellent article about designing heat exchangers to prevent fouling:

Coal Furnace
(Photo credit: William Warby)

No Fooling – No Fouling,  by Charles H. Gilmour. Chemical Engineering Progress Magazine July 1965; Volume 61, No. 7. (Transcribed by Art Montemayor August 21, 2009)

See also this discussion on it: https://www.eng-tips.com/viewthread.cfm?qid=251669

I decided to add this to the article Fouling Factors for Heat Exchanger Design so that all the information is in one place. If you haven’t done so, check that article out for more background on why you’d want to design exchangers this way.

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How to Invert a Matrix

Posted on 2019/05/31 by admin
Let’s review my Matrix Inversion cheat-sheet, for those times you need to do it by hand:

For a 2x2 Matrix:

a b
c d

Then the inverse is 1/(ad-cb) * d -b
                                -c a


For a 3x3 matrix:
  a b c
  d e f
  g h i

The Inverse is 

        1                           (ei-fh)   (bi-ch)   (bf-ce)
-----------------------------   *   (fg-di)   (ai-cg)   (cd-af)
a(ei-fh) - b(di-fg) + c(dh-eg)      (dh-eg)   (bg-ah)   (ae-bd)

Continue reading →

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HYSYS Shortcuts for Stream Flags / Labels

Posted on 2017/10/20 by admin
Another tip for Aspentech’s HYSYS process simulator today. At the simulation PFD, streams by default are labeled with their stream name. However, you can change the stream flag to show different info, which can help you get a quick visual overview of the system. Learn these hotkeys:

  • Displays Inlet Nozzle Elevation           SHIFT I
  • Displays Stream Mass Flow Rates       SHIFT M
  • Displays Stream Molar Flow Rates     SHIFT F
  • Displays Stream Names (Default)       SHIFT N
  • Displays Object Description                  SHIFT R
  • Displays Outlet Nozzle Elevation         SHIFT O
  • Displays Stream Pressures                     SHIFT P
  • Displays Stream Temperatures             SHIFT T
  • Pan Display:                                               Arrow keys
  • Pan Display Further:                                SHIFT+Arrow Keys
  • Rotate Objects:                                          1 (90°), 2 (180°), 3 (270°), N (return to default orientation)
  • Mirror Objects:                                           X (X-axis mirror), Y (Y-axis mirror), N (return to default orientation)
  • Selecti Object Label (to move, etc.)         L
  • Break Stream Connection                         B (Hold B and left-click)
  • Undo                                                              CTRL Z

These are especially useful for troubleshooting Dynamic Simulations, where you want to monitor what the file is doing over time.

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Value Improvement Practices (VIP) Guide Words

Posted on 2017/08/02 by admin
Brainstorming around a table

Brainstorming around a table

A Value Improvement Process (VIP) session, also known as Value Engineering, is a meeting that tries to analyze a design and find ways to improve the “value” the project provides to those undertaking it. This usually means saving money, but it can also mean saving time, reducing maintenance, increasing profit margins, etc.

Value improvement meetings are often run using methods similar to safety meetings like HAZOPs:

  1. A facilitator leads the meeting, keeping the group on track. A scribe takes notes. Members of the project team and others (operations, clients, valued equipment vendors, etc.) may participate
  2. Break the process broken down into “nodes,” sub-divisions that make a logical sense to review at the same time. (Ex: truck unloading, the crude unit, the diesel tank farm, the pig launchers and receivers, the chiller unit, etc)
  3. For each note, brainstorm for ideas that may generate value
  4. The ideas are ranked for their value: how much money could be saved, and at what cost (in time/schedule/safety etc.). Generally it’s enough to categorize ideas into Implement, Maybe, and Reject piles, depending on how promising the idea appears.
  5. A list of recommendations are created, for the project team to follow up on.

Also like safety meetings, several VIPs can be taken over the life-cycle of a project.

Much like having a list of HAZOP guidewords, a VIP list of guidewords, ideas, or prompts can help you have a better session. For any given situation, the majority of guidewords won’t apply, but flipping through the list may occasionally spark an idea. You may also get value reviewing previous articles on brainstorming and TRIZ.

Guidewords/ideas/prompts for VIP brainstorming:

Continue reading →

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Posted in Brainstorming & Idea Generation, Business / Finance, Chemical Engineering General, Consulting, Cost Estimation, Economics / Equipment Costing | Tagged , , , , | Leave a comment