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Old March 26th, 2020, 01:35 PM   #1
id10t_error
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What is the opposite of free-board in Process Control terminology?

From what I have read, freeboard (above the waterline) is a nautical term and the opposite is Design Draught (below the waterline), but is there a common term used in process control besides the obvious "Tank Level" or "filled level"?


Tank A
__________
| | <-----+------------+
| | | |
| | FreeBoard??? (ft) |
| | | |
| | <-----+ Total Capacity (ft)
|==========| <-----+ |
|==========| | |
|==========| ???????? (ft) |
|==========| | |
|==========| <-----+------------+

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Old March 26th, 2020, 02:12 PM   #2
kvogel
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The nautical term would be "draft"
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Old March 26th, 2020, 02:22 PM   #3
Bob O
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Ullage
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Old March 26th, 2020, 02:23 PM   #4
Ken Roach
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"Freeboard" is the distance between the nominal "Full" level and the level at which actual overflow or relief flow begins. It's important for sloshing, foaming, and fluid-in-transit purposes (among others).

I don't really think there's an "opposite" to it.

"Fluid level" (replace with fluid of your choice) would be the obvious term for the distance from the tank bottom to the top of the fluid.
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Old March 26th, 2020, 02:25 PM   #5
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Old March 26th, 2020, 02:27 PM   #6
Ken Roach
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Bob, there aren't a lot of days on which my vocabulary expands, but today is one of them. Thanks !

A distinction is that "ullage" is container volume in excess of "full", while "freeboard" is vertical height above "full level".
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Old March 26th, 2020, 02:35 PM   #7
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[quote]Originally posted by id10t_error:

...but is there a common term used in process control besides the obvious "Tank Level" or "filled level"?

Sounding?

But I don't think it is commonly used.

Keith
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Old March 26th, 2020, 02:37 PM   #8
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Old March 26th, 2020, 03:16 PM   #9
drbitboy
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Reserve or level.


TL;DR


Freeboard in the nautical domain is the height of the topsides above the water level <b><i>outside</i></b> the boat, so roughly speaking it is the size of the smallest wave that will wash over the gunwhale into the boat.


In the context of a dam it is the height of the top of the dam and/or spillway above the water level, so it represents the upstream capacity to handle e.g. the next rain storm.


So ullage is more a synonym than an antonym of freeboard.



Inverting that concept in the other direction i.e. how much liquid do I have to e.g. fight a fire, I think the word would be simply reserve (same root as reservoir?) or stored amount, or perhaps level to maintain a one-dimensional term.
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Old March 26th, 2020, 05:01 PM   #10
id10t_error
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Thanks for the excellent responses, reserve and unused might be a winner.

The best thing I could think of is "Dry Level" and "Wet Level." or load, unload, supply, demand...
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Old March 26th, 2020, 05:12 PM   #11
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Available reserve? Current reserve?


There is another word/phrase on the tip of my tongue. "In the tank?" Ooh, how about "IN reserve?" "Fat?"


P.S. Another VMS dinosaur; I miss EDT!

Last edited by drbitboy; March 26th, 2020 at 05:19 PM.
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Old March 27th, 2020, 07:55 AM   #12
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In the water and wastewater it is either "level" or, if the reference is to something in the tank (say a diffuser or sparger) it is "submergence".
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Old March 28th, 2020, 01:28 AM   #13
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When I worked for an oil major (the red & yellow one) some years ago, 'Ullage' was definitely the term used for the remaining capacity or volume between the current level/volume and 'full'. Level High and Level High High alarms were above that again but below the level at which the tank roof was lifted off or lots of hydrocarbon liquid hit the ground!
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Old March 28th, 2020, 10:02 AM   #14
Tom Jenkins
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I looked up ullage. I won't argue with real-world experience, but it looks to me like ullage would be synonymous with freeboard.

"Definition of ullage: the amount that a container (such as a tank or cask) lacks of being full"

https://www.merriam-webster.com/dictionary/ullage
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Old March 28th, 2020, 09:47 PM   #15
IanfromOz
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Quote:
Originally Posted by Tom Jenkins View Post
I looked up ullage. I won't argue with real-world experience, but it looks to me like ullage would be synonymous with freeboard.

"Definition of ullage: the amount that a container (such as a tank or cask) lacks of being full"

https://www.merriam-webster.com/dictionary/ullage
Hi Tom,
I think we're saying the same thing. "lacks of being full" seems to agree with my description that it is the volume remaining between current level and 'full'. Or as another in-line dictionary puts it, "The amount by which a container, such as a bottle, cask, or tank, falls short of being full."
https://www.thefreedictionary.com/ullage
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