14 replies to this topic

[Nilesh Ambuskar]

Hi,

 

I want to know the applicable scenarios for spherical storage tank for mixed C4 to size the PSVs.

 

Please reply, its urgent

 

Regards,

Nilesh

[fallah]

Nilesh,

 

With such limited info it isn't possible to specify the applicable and then the credible overpressure scenarios of a spherical storage tank system...

Edited by fallah, 21 November 2013 - 02:21 PM.

[Nilesh Ambuskar]

Fallah,

 

I mean, which are possible scenarios generally we consider for spherical storage tank.

 

I am little bit confused for overfilling scenario. Are we consider overfilling in sphere? if yes, then how?

 

I am probably consider following scenarios: 

 

1) External fire - (which considerations would required for wetted area viz. 55% of surface area of sphere or 30 ft or if horizontal dia is greater than 30 ft)

 

2) Liquid Blocked outlet (Overfilling, is it possible to consider this scenario in spherical, how? please share any example regarding the operation of the tank)

 

4) Inbreathing (Since, there are five PSVs out of which one is vacuum vent).... (Also I would like to know whether outbreathing scenario is considered in this case???)

 

5) Failure of automatic controls....

 

 

Hope you are satisfied with the given inputs, kindly expecting your positive response soon....

 

have a nice day!

 

Regards,

Nilesh

[Grish]

Hi Nilesh

 

I am having same query regarding the spherical tank overpressure scenario analysis.

 

Also whether overfilling scenario is applicable for spherical tanks? If yes, kindly share the operational guidelines for the same.

 

Also let me know what wetted surface area to be considered for such case.

 

Warm Regards,

Grishma

[fallah]

Nilesh,

 

You didn't provide required info/sketch. You did submit your estimation on applicable overpressure/undervacuum scenarios for the system you just yourself have its info in hand...  

 

All scenarios you mentioned could be applicable for a spherical storage tank, but it might just some of them be credible...HAZOP review followed by a LOPA study will determine which applicable scenarios can be credible...

[curious_cat]

Out of curiosity, I see a fire water line connection to two nozzles on the tank: What's the protocol on using those? Are they used selectively in certain fire / leak scenarios?

 

I'm assuming the intent is to flood the tank internally? Or am I misreading the drawing. 

[Nilesh Ambuskar]

Hi Fallah,

 

I am waiting for your response....

 

 

Curious_Cat: I appreciate your point of view but I am not able to define anything please anyone suggest the methodology....

 

 

Regards,

Nilesh

[fallah]

_Nilesh,

 

All mentioned scenarios could be possible, but the main point is if a scenario could move to a credible scenario. To specify credability of a scenario it should be investigated if maximum pressure can be developed by a possible scenario would be greater than MAWP of the spherical tank. Then adequate protection layers to be provided to prevent an overpressure event following that credible scenario. As you can see it's not a simple matter to be performed by such limited info and needs to be investigated in depth along with adequate relevant info and documents...

 

Has a HAZOP meeting been done for that spherical storage tank system? If so, relevant report would help you out in this regard...

[Nilesh Ambuskar]

Hi Fallah,

 

Thanks for the reply, but still I am not convinced with the overfilling and external fire scenarios..... Can you share some operational guidelines or SOP for spherical storage tank which help me to find the outputs....

 

 

thanks

 

 

- Nilesh 

[Nilesh Ambuskar]

Hi Fallah,

 

Gentle reminder!!!

 

 

-Nilesh Ambuskar

[YNC]

here are the any possible scenarios I consider during relief load calculations. 

 

Case #

Case Description

Case Validity

Comments

1

Block Valve Mis-operation

2

Check Valve Failure

3

Control Valve Mis-operation

4

Exchanger Tube Rupture

5

Blocked Exits

6

Fire

7

Instrument Air failure

8

Instrument Power Failure

 

9

Individual Electric Power Failure

10

Individual Steam Failure

11

Cooling Water Failure

12

Air Fan Cooler Failure

13

Condensing Duty Failure

14

Reflux Failure

15

Accumulation of Non-condensable

16

Abnormal Heat Input

17

Abnormal Vapor Input

18

Abnormal Chemical Reaction

19

Equipment Shutdown

20

Hydraulic Expansion

21

Entrance of Volatile Liquid

22

Other

 

 

If you can add any to these then please welcome.

 

I recently published my paper titled: "Discussion of Over pressure Scenarios & its Mitigation by Proper    Relief Valve Sizing Techniques",  also present this paper in MEPEC 2013 (Middle East Process Engineering Conference & Exhibition), held in Bahrain during 29th September to 2nd October. if anyone want paper or presentation, you are welcome.

 

for any further details, kindly advise.

Edited by YNC, 28 November 2013 - 05:41 AM.

[josh68]

If possible can you send the paper for me please jove_gem@yahoo.com

[breizh]

YNC ,

For the benefit of the community can you post your paper/presentation?

Thanks

Breizh

[S.AHMAD]

Hi

1. The fire water connected to the nozzle is for filling the sphere in a situation of leakage at the sphere bottom section. By filling with water then the LPG will be displaced (LPG is lighter than water) and hence the leakage shall be water rather than LPG. This is called FLOOD Line.

2. Liquid over-filling is one scenario due to failure of level control (filling operation) since the sphere is normally has a maximum ALLOWABLE level for safe operations.. However, if you installed an independent high level alarm that gives enough time for operator to response, then this overfilling may not be credible case. Independent high alarm means, the connection point is not the same point as the level control point. This shall increase SIL (Safety Integrity Level).

3. My advise is for you to consider overfilling. You may find that the currently installed PSV capacity is enough to cater for the liquid overfilling. In that case no further action required.

Edited by S.AHMAD, 10 December 2013 - 05:02 AM.

[YNC]

Thanks fellows,

 

Kindly find the attached file of my paper.

 

if you need, I can also share the presentation, I presented in MEPEC 2013, for this paper.

 

Hope you will let me know about your feed backs in details, any suggestions or correction will be welcomed.

 

REGARDS,

 

YNC

Attached Files

•  Paper - Final.pdf   216.4KB   76 downloads