12 replies to this topic

[Rahul Maurya]

Can anybody give me the answer of this que?

 

if height and dia (mm) will be: 6300 (mm) X 4900 (mm) for conical head Storage tank..

 

1. What will be the HHLL, HLL, LLLL and LLL ?? 

 

2. How its decided??

 

3. Its came from API 650?

 

4. Head type affects on it or not?? (Conical head, flat head etc. )

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[fallah]

Rahul,

 

In brief:

 

1,2) Process and safety requirements will dictate the values

 

3) No

 

4) No

[Chemitofreak]

Rahul,

 

1.

a) Distance between Tank bottom and LLLL is based on the NPSH requirement of the pump.

 

b  ) Distance between LLLL to LLL is based on the time required by the operator to take corrective action against low level in the tank (generally 1 to 3 min, based on the philosophy that the project has).

 

c) Distance between LLL to HLL is based on the residence time required for storage of the raw material / finished product / intermediate (generally 7 days for offsite tanks and 1 day for tanks inside the battery limit).

 

d) HLL to HHLL is same as b  ) i.e. time required for the operator to take corrective action.

 

2. Refer 1)

 

3. API has nothing to do with residence time and time required to take corrective action. It is project specific.

 

4. NO. The fundamentals do not change for cone roof, dome roof and flat roof etc.

 

Revert in case of any query.  

Edited by Chemitofreak, 15 March 2016 - 10:52 PM.

[Rahul Maurya]

If its given to you, that a tank size

 

6300 (mm) X 4900 (mm)ID

 

How can you calculate the levels?

 

Can you show me the calculation according to you?

 

So I can identify in my way..

[Chemitofreak]

Rahul,

 

Can I know what is your purpose of doing reverse engineering?

[samayaraj]

Dear Rahul,

 

Are you a student? Chemitofreak has given the required input. Now you have to start the work. And more over, you did not furnish the details about your product that you going to store in the tank, etc.

 

1. For LLLL level:

 

For Atm tank, based on the vapor pressure of product stored in the tank, suction head & pressure drop for a required flow, find NPSH for the pump. The calculated NPSH (A) available should be at least 1m above the NPSH ( R ) required by the pump. Let the NPSH(A) be 2m, LLLL level should be 2m above the pump center line.

 

2. For LLL level:

 

It the time factor. In how many minutes/ seconds the level will fall from LLL to LLLL. Let the cross section of tank be A m², flow rate be Q m³/sec and residence time for manual action be S sec. LLL level = LLLL level + (Q x S)/A

 

3. HLL Level:

 

Required volume of product to be stored. LLL Level + Volume of product/ Area of tank

 

4. HLLL Level:

 

Time required for manual action. HLLL Level = HLL + (Q_in - Q x S)/A

Edited by samayaraj, 16 March 2016 - 03:13 AM.

[fallah]

 

1. For LLLL level:

 

Let the NPSH(A) be 2m, LLLL level should be 2m above the pump center line.

 

 

samayarj,

 

Not always; just when the liquid inside the tank is in saturated condition and the friction loss along the suction line is neglected...
 

[Rahul Maurya]

Rahul,

 

Can I know what is your purpose of doing reverse engineering?

Dear Chemitofreak,

 

This calculations is done by other, and I captured it, But I don't know perfectly how can I do it by me own.

 

I want to check weather it is ok or not for my knowledge.

[Rahul Maurya]

Samayaraj:

 

As I am not too experienced, I have lots of doubts.  So I want to clear it up right now.  Otherwise I will be confused  in the future at a point.

[Chemitofreak]

Rahul,

 

As I said in my earlier post LLLL is calculated based on pump NPSH requirement.

 

I don't know the pump flowrate, the pumped fluid, the suction line size etc...etc..., how can one calculate the NPSH.

 

Since, NPSH is not know, how can one finalise the LLLL.

 

We also do not know the time required for the operator to take corrective action, also we don't know what is the residence time for storage i.e. between LLL to HLL.

 

Once can find the levels only if he has the aforementioned details, which we do not.

[samayaraj]

 

 

1. For LLLL level:

 

Let the NPSH(A) be 2m, LLLL level should be 2m above the pump center line.

 

 

samayarj,

 

Not always; just when the liquid inside the tank is in saturated condition and the friction loss along the suction line is neglected...
 

 

 

Thanks for your comments Mr. Fallah. May I know the reason?

 

Samayaraj:

 

As I am not too experienced, I have lots of doubts.  So I want to clear it up right now.  Otherwise I will be confused  in the future at a point.

 

We have given you the inputs. Now its your turn to collect the required data, apply it and calculate the various level. Submit your calculation and we will help you if you have any doubts further.

[Chemitofreak]

@ Samayaraj:

 

NPSH(A) = Static Head + (System Pressure-Vapour Pressure) - Friction Loss

 

In saturated fluid the system pressure & vapour pressure is equal, hence it cancels out.

 

If frictional losses are neglected, the NPSH(A) is equal to the static head.

 

That is what Mr. Fallah is trying to say.

 

Revert in case of any doubt.

[fallah]

 

 

 

1. For LLLL level:

 

Let the NPSH(A) be 2m, LLLL level should be 2m above the pump center line.

 

 

samayarj,

 

Not always; just when the liquid inside the tank is in saturated condition and the friction loss along the suction line is neglected...
 

 

 

Thanks for your comments Mr. Fallah. May I know the reason?

 

 

samayaraj,

 

Simply because in NPSHA calculation for saturated liquids the pressure above the liquid in the tank being offset by vapor pressure of the liquid at operating temperature...