19 replies to this topic

[navneet2109]

Liquid propane storage tank is provided with 10" of inlet nozzle. And inside storage tank Distributor is provided with 20" of holes!!!!!  this is just little information.

 

I just wanted to know that what is the basis of deciding

- nozzle size

- inlet distributor size

- If propane is flows from distributor there is chances of splashing of liquid propane? will it cause phase change???

 

Is there any calculation for this?

or any reference??

 

Note:- I don't have any any simulation software. i am doing all calculation manually because its only LPG storage system.

 

Please need help

 

thanks

[Art Montemayor]

Navneet2109:

 

You cannot expect a rational, engineering response to your query when you haven't given any specific and detailed information of what your application is.  For example, just ask yourself if anyone reading this is capable of guessing or speculating accurately what it is you have when you haven't defined the following:

• Is your saturated liquid propane storage at atmospheric temperature or is it refrigerated (for a lower storage pressure)?
• What is the specific meaning of "provided with 20" of holes"?  This doesn't make any sense.  Are you trying to say you have an internal liquid propane distributor with 20 holes?  Or are you stating that holes are distributed through a length of 20"?  No one is going to figure out what it is that you mean to state.
• What is the "distributor" used for?  There is normally no need to "distribute" liquid propane while transferring it into a storage tank - UNLESS you have a specific process requirement for it (such as a refrigeration cycle).  Please explain this need and USE A DETAILED SKETCH to show our members exactly what you have or are proposing - complete with fluid temperatures and pressures.
• You normally cannot cause a phase change in the liquid propane fed into a storage tank by a pump unless you are expanding a liquid feed that is at a higher pressure than the tank's vapor pressure.  This is sometimes a technique used to refrigerate the tank contents.  Is this what you mean?  Please explain with a detailed sketch.

You don't need a silly simulation to calculate the correct tank nozzle sizes.  What you need is common sense to identify the conditions and flowrates of the flow stream(s) you are dealing with before attempting to size the correct piping and nozzle sizes.

[navneet2109]

 

Respected Art Montemayor,

 

 Sorry for the inconvenience, My reason of not attaching of data is only that i did not want to disclose. Though i have uploaded Sphere data sheet. This propane liquid storage. Here at inlet nozzle distributor is given.

 

questions:

 

1. Why distributor is necessary ??

2. How to calculate distributor size??? Is there any reference?? any formula???

Attached Files

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[Bobby Strain]

Is there some problem with the installation?

 

Bobby

[navneet2109]

Bobby Strain:

 

Not yet, But i wanted to know the basis of providing of distributor. and how we design it !!!! 

distributor was propose to me by mechanical engineer because he did the same in previous job. but when i asked the reason they just told me they had done this in previous job. seriously ..

so i wanted a genuine reason by the experienced person which i think i can get in this site...!!!

[fallah]

navneet,

 

No need to consider distributor inside the tank and over the liquid surface due to splash and subsequent vaporization increment; normal practice in such cases is considering a dip pipe to release the propane below the normal liquid surface...

[Art Montemayor]

Navneet2109:

 

Once you give our members the needed and important details on your application, you find that you start to obtain expert and experienced advice from them.

 

Your data starts to tell us most of the vital details (although not all of them).  I fail to see what you are "giving up" by simply disclosing what you are trying to do.  Our members need this information to accurately and clearly furnish help.  By using your common sense and knowledge of your application you can easily arrive at what would be considered necessary dimensions for your inlet and outlet liquid propane nozzles for your spherical storage tank.

Firstly, you are storing a fairly large amount and you require large filling flow rates.  If you are a chemical engineer, you will recognize that you are dealing with saturated, atmospheric temperature liquid propane and, as such, you are not depending on having to refrigerate the contents.  You merely are required to transfer the liquid from supply sources (ships, tank cars, rail cars, etc.) into the tank for storage.  Common sense should tell you that all that is required is knowledge of how you propose to make the transfer: by pump, compressor displacement, or other means.  That should specify to you what are the critical flow criteria you must take into consideration - such as the pressure drops involved or allowed.  This should indicate to you, complete with the design flow velocity you want (or need) to use in the associated piping and nozzles.  Your data sheet, for example cites 500 m³/hr (= 2,200 gpm = 4.9 ft³/sec) of inlet flow rate and using a 10", sch 60 pipe nozzle yields an average flow velocity of 9.5 ft/sec.  This is a normal, conventional flow velocity used in most applications.  HOWEVER, we don't know if this suits your transfer piping requirements.  You have to do the necessary piping calculations to ensure you get the proper pressure drop and flow rate with your supplied driving force.  The same logic applies to the outlet nozzle, where you might have to satisfy a NPSH requirement for a transfer pump if you are feeding a system above the storage pressure conditions.

 

You failed to tell us if your query is regarding an existing, planned, proposed, or designed installation and that is essentially what Bobby is trying to get across to you: you have to take all of your project's scope of work into consideration and ensure you comply with what you have available and what you additionally need to conform to the needs.  That is why he asks if you have any existing problems.  He doesn't know if the installation exists or is being proposed or designed.  He needs more information in order to help out.

 

Fallah is precisely correct also.  With data sheet information he also now knows what you are trying to design and that you require no refrigeration.  (I assume you are aware of what type of refrigeration we refer to with propane storage and transfer operations).  His recommendation of employing a dip pipe to fill the tank is a normal, valid one.  This is done to avoid the generation of static electrical charges when dealing with hydrocarbon liquids free-falling into a tank.  In this case, the tank is a closed system and the hazard of having oxygen present is not there; however, the dip pipe serves as a means also to avoid any splashing and contents' movement and agitation which could affect steady level readings in your level control instruments.  I consider it good practice; others may not care to use the dip pipe.  (Don't forget to use a small, drilled hole at the top of the dip pipe to break a potential syphon action)

 

Answers I offer to your specific questions are:

 

1. Why distributor is necessary ??  In your application there seems to be no logical reason to use a distributor inside the tank.  I don't recognize any reason for it.  If you are a chemical engineer, that is YOUR process decision to make and specify to the mechanical engineer that will mechanically design the tank.  It is not the other way around, where the mechanical engineer is making process decisions.  That is also why YOU have to specify the size of the nozzles.
2. How to calculate distributor size???  Is there any reference?? any formula???  There is no such "formula" - just common fluid mechanics sense.  Since you don't specify how you intend to transfer the propane and the allowable pressure drop as well as other constraints in the fill piping, there isn't much more to add.

[navneet2109]

Wow, Tank you all of you for giving valuable information. I am glad that you all replied.

 

To,

Art montemayor sir

 

According to your given point i got confidence so i am going to have a meeting with my senior and others.

Dip pipe with hole is totally new point for me.. 

 

I will keep in mind to give proper information with sketch in the future so that i can get a good answer

 

With regards

Navneet

[Swapnil Sabu]

Navneet ,

For this we can used tapered nozzle inside tank through which liquid material fall in tank along with surface of tank and provide extra thickness to that part so we can avoid corrosion and erosion of tank...due to this we can avoid turbulence in tank...vapor loss, environmental loss

[farid.k]

navneet2109:

 

this has been discussed before. refer link below on how to specify the hole diameter and number of holes

 

http://www.cheresour...g-calculations/

 

for further info, just Google "perforated pipe distributor" or some other call pipe sparger. I did have spreadsheet and will share once I found it.

 

It is not mandatory to have that in the tank but by having that will slowdown the pressure build up in tank and minimize the splash in the tank too.

 

when you take your shower, which one that you prefer, the one that have many small holes that create smaller and uniform droplet to your body or the one that come from single piping which the liquid straight forward hit your body? both can but I trust many people love the first one.

 

any further comment is welcomed

[breizh]

hi ,

about distributor ,good reference.

Good luck,

 

Breizh

[farid.k]

Breizh:

 

Agreed..i used this document also as reference. Additionally, you may use aft fathom software to calculate the sparger.

[Art Montemayor]

farid.k:

 

You requested comments and I would add that Chemical Engineers are traditionally the "caretakers" or "champions" of the process in a project or design.  The reason for this being that it is they who are held accountable for the process working correctly and according to the scope and design basis of the project.  That is why it is Chemical Engineers who are responsible for generating the Process Flow Diagrams and the P&IDs as well as the mass and heat balances.  Mechanical, Electrical, Civil, and Instrumentation Engineers are contributors to such basic documents but they do not have ownership of them.  The reason for this is very simple:  It is the Chemical Engineer who has to determine if the process is Safe, Workable, Operational, and Reliable with the design being implemented.

 

That is why I would not recommend a refrigeration type distributor being implemented inside what seems to be an ambient-temperature design for a liquid propane storage tank - especially one as large as the one specified.  If a high-discharge pressure pump is used together with a liquid propane distributor in this application, a refrigeration effect can be obtained and that will drop the temperature of the stored liquid and associated vapor.  That does not seem to be what is called for in the tank Data Sheet.  Correct me if I am wrong because what I read is that the tank is designed for "ambient" temperature with a max. of 50 ^oC.   One should always respect Data Sheet Specifications because they reflect the basis of the process design for operation and safety.

 

If Navneet2109 imposes a refrigeration effect on the tank, this will lower the storage pressure and temperature, causing probable atmospheric condensation of water on the exterior of the carbon steel, un-insulated spherical tank ---- something that could cause major problems for the operator due to exterior corrosion with deterioration of paint and metal.  Additionally, you are advocating refrigeration in a process when it is not specified nor requested.  Whoever specified ambient temperature storage design must have considered alternatives such as refrigerated storage, but chose instead ambient, pressurized storage for a reason.  That decision should be respected and obeyed by the design engineers who are responsible for following the process specifications.

 

Insulating such a spherical tank and furnishing the necessary pumps and distributors to apply a refrigerating effect adds capital and operating costs that must be specified and justified.  I believe that stage of the design has already been surpassed in this application and the Data Sheet specification must be followed.

 

I would simply follow Fallah's recommendation and size the nozzle for minimum pressure drop, using a simple transfer pump with a discharge pressure slightly above the tank's operating pressure.  No refrigeration effect is asked for; none is applied.

[farid.k]

Dear Sir,

 

I do respect on your point and do correct me if I were wrong.

 

sorry to ask as I don't get you what is mean by refrigeration type distributor.

 

what has been proposed by me previously is actually based on what has been practiced here and also clearly stated in typical LPG storage tank design standard. based on the standard, for sphere, it is recommended to install top spray filling ring (typically piping (ring) in the sphere tank 1 size smaller of the inlet piping & equipped with spray) and for bullet type storage is recommended with a straight piping with has holes.

 

the intention of having that kind of inlet is to minimize the back pressure build up during filling operation. the pressure drop across the ring also should be 1 bar (max) based on inlet rated capacity. but this is just recommendation only and it is not mandatory. inlet as simple as 1 single piping for me will work too.

 

I still cannot see the refrigeration effect or flashing of the LPG happened at the spray/piping with holes especially during transfer.

[Bobby Strain]

I have experienced in major engineering companies that "experienced" engineers have provided unnecessary equipment. These companies have experienced process engineers who review and approve such designs. Not just a measly $200 piece of pipe. This spray looks to be in the same category. But your are the only one who has all the information. You shared only part of what you know about the intended operation of the storage tank and associated facilities. None the less we are always happy to solve problems for others; we can't be held accountable.

 

Bobby

[farid.k]

thanks sir for comment

 

as I said, it is just recommendation and not mandatory. if not happy with that design can go for simpler one. on how to calculate I already shared the link that has been posted by mr ankur which is for me is very detail explanation.

 

incase to use spray can communicate with vendor directly.

[Napo]

Dear Farid K,

 

Maybe you can share your information about the design standard. I can´t find information about this practice.

 

I was working in some gas plants and the connections are always in the bottom (in sphere).

 

Many Thanks.

 

Napo.

[Benigno Ramos]

Dear colleagues,

 

Would you kindly help me to find some information, about calculating the loads on the columns and foundations of a sphere of LPG?.

I am interested in literature or even a post graduate course.

thank you in advance,

 

Benigno Ramos

[mohamedellejmi]

Gents,

I have experience with LPG facilities.

These spargers are particularly important on bullets receiving heavy loads in a short time like in Import terminals where the LPG ship and the port authorities want to unload within the shortest period possible.

The spargers will make the "hot" vapor phase to get in intimate contact with the incoming "cool" liquid phase and get close to the theoretical equilibrium at the bulk average temperature. This prevents the pressure surge that we observe in the bullet being filled from the bottom or from the top with a downcomer and that makes liquid to act as a piston and compresses the "hot" vapor until the PSVs pop-off.

This phenomenon normally cannot be seen on LPG production facilities.

[navneet2109]

Gents,

I have experience with LPG facilities.

These spargers are particularly important on bullets receiving heavy loads in a short time like in Import terminals where the LPG ship and the port authorities want to unload within the shortest period possible.

The spargers will make the "hot" vapor phase to get in intimate contact with the incoming "cool" liquid phase and get close to the theoretical equilibrium at the bulk average temperature. This prevents the pressure surge that we observe in the bullet being filled from the bottom or from the top with a downcomer and that makes liquid to act as a piston and compresses the "hot" vapor until the PSVs pop-off.

This phenomenon normally cannot be seen on LPG production facilities.

Thanks To @mohamedellejmi

I also thought of this before not exactly but nearly to this. I was not confident at that time. You gave me the confidence.

Concept getting clear after so long time. Thanks once again.