7 replies to this topic

[vikramltv]

Dear all

I am quite confused about the nominal capacity of tank.
As per my understanding its the maximum liquid holdup volume (i.e. From Tank Bottom to HLL).
But while reviewing some lisencer data sheets I come across HLL - LLL (i.e working volume) as nominal tank capacity.
Now I want to know the exact definition of nominal volume backed up by some standard.

Thanks in advance.

[Vignesh S]

Vikram,

1. Nominal Capacity is the Full Tank capacity. (For Example: Tank Size is 10m Dia (D) x 10m height (H), then nominal capacity is 785.3 Cu.m (π/4*D^2x H)
2. Gross capacity is the capacity is from tank bottom to bottom of overflow (or HLL)
3. Net/Effective capacity is between HLL to LLL.

Also note that the net capacity is the working volume.

Hope it clarifies your topic.

Regards,
Vignesh.

[jrtailor09]

Vikram ltv,

If you are from india then request you to go through OISD standard.

OISD-RP-108 Recommended Practices on Oil Storage and Handling.

Regards,

[vikramltv]

Hi jrtailor09

I am from India but neither my company nor the client is from india so I need any international standard for reference.
I searched API-650 and API-2000 but cant find.
By the way I want to take a look of OISD-RP-108 but cant find on internet. if you could please upload any link for that it will be better for me.

Dear Vignesh

I think you interchanged the definition of gross capacity with Nominal capacity.

Edited by vikramltv, 01 August 2012 - 06:49 PM.

[Art Montemayor]

Vikramitv:

You state: "I want to know the exact definition of nominal volume backed up by some standard. You seem to looking for the Holy Grail - which doesn't exist. And what's more, there doesn't seem to be any need for its existance.

The confusion starts with engineers who don't have English as their first language. The use of the noun, "nominal" is to give a value a name - and that is all it is. It comes from the Latin, nomen, which means "of a name". There is no standard - international or whatever - that sets a definition for it. If you want to identify a specific tank capacity, call it what it is: Total working capacity, maximum filling capacity, etc. etc. But be SPECIFIC. Just as is the case for Normal Cubic Meters and Standard Cubic Feet of gas, we all get into trouble when we start believing that we are backed up, supported, and defended by some international code or "standard". There is no such animal. We engineers simply have to be specific in our communications, that is all.

When I was a young grad out of university, I couldn't understand why I had to identify pipe with a "nominal" size. The size designation had absolutely nothing to do with the pipe's OD or its ID. So, why not just call it by its OD? The answer from my mentor was: "Forget it; all they are trying to do is to give that pipe size a NAME - that's all". And that is what is happening here - an effort to get away from being specific.

[vikramltv]

Art Montemayor

Sir
What you said is right and there may not be standard definitions for everything.
But while talking about any specific term we have to be on a common ground.
^{All i need is that common ground to communicate.}

Edited by vikramltv, 01 August 2012 - 08:37 PM.

[Vignesh S]

Vikram,

Please, see the below definition from OISD 108 (RECOMMENDED PRACTICES ON OIL STORAGE AND HANDLING)

TANK CAPACITY
3.4.1 Nominal Capacity of a Tank
Nominal capacity shall mean the geometric volume of the tank from bottom upto curb angle in case of fixed roof tank sand the underside of roof deck upto the maximum floating position of floating roof incase of floating roof tanks.

3.4.2 Gross Capacity of a Tank
Gross capacity (stored volume) is thecapacity of the tank upto the maximumsafe filling height of the tank.

3.4.3 Net Capacity
Net capacity is the net pumpable capacity of the tank during operation after subtracting the volume of tank bottom contents up to the top of normal pumpout nozzle from safe filling capacity of the tank.


Regards,
Vignesh

Edited by Vignesh S, 02 August 2012 - 04:36 AM.

[vikramltv]

Thanks Vignesh S