6 replies to this topic

[icingrock]

There is a need to increase unloading capacity of one chemical(amine) to one tank in our plant.

There is still free nozzle available on the tank top and the decision wad made to add additional unload pump and related piping system to the existing tank so that tow unloading pump can unload at same time to the tank.

So my question is if is it ok to connect the new pipe to the nozzle without a submerged pipe inside the tank extending close to bottom of the tank, just as the existing pipe design.

My understanding is it should be done to prevent chemical splashing inside the tank and to some degree to prevent static electric accumulation and potential risk for explosion.

But is there any standard covering this requirement? it's "must to have" to "recommended to have" pipe design (I mean submerged pipe for unloading pipe to the tank)

Then tank is about 10 meters high and also nitrogen blanketed with a small overpressure than atmosphere.

[fallah]

Do you know you are increasing max in-flow rate to the tank by adding one more input stream to the tank?
If so,you should modify nitrogen blanketing system accordingly.

About the new line the pipe should be extended till near the tank bottom.

[Art Montemayor]

Icing:

When you solicit advice or recommendations from our forum members, we take on the responsibility of not furnishing information that could be erroneous, bad, hazardous, or totally wrong. In order to avoid all of that, it is imperative that you, as the requestor of the advice, make sure that YOU ARE FURNISHING ACCURATE, CLEAR, CONCISE, AND DETAILED INFORMATION. If you fail to do that, you could be the original cause of wrong and erroneous advice being received by you. For example, you state: “There is a need to increase unloading capacity of one chemical(amine) to one tank in our plant”. This can be easily interpreted in one of two ways:

• You want to transfer amine from one vessel into a tank in your plant.
• You want to transfer amine from the tank in your plant to another vessel.

Which one is it? It makes a BIG difference in understanding your query. This confusion could easily be avoided if you simple create and furnish a detailed drawing or sketch of the operation. That way you avoid any confusion or wrong interpretation.

Because of a lack of a drawing, how are we supposed to understand what you mean by “so that tow unloading pump can unload at same time to the tank”?? Do you mean TWO unloading pumpS or THE unloading pump???

You state “I mean submerged pipe for unloading pipe to the tank”. Do you mean “I MEAN A SUBMERGED TANK FILL LINE”?

Please funish a detailed sketch of what you have and what you propose if you don’t have a complete dominance of the English language. An engineering sketch does not require a translation and is a universal language.

Thank you.

[icingrock]

The explanation for unloading is http://www.merriam-w...onary/unloading :
(1) : to take off : deliver (2) : to take the cargo from <unload the truck>

So I always thought that "unloading" means transfer something from a truck/car to a vessel/tank. Sorry for the confusion. I am aware now that "unloading" can be used in other circumstances.

Maybe I make situation too complicated.
The simple question is: what standard cover submerged pipe design in a vessel or tank.

Thanks.

Attached Files

•  dipin pipe in tank.pdf   257.05KB   62 downloads

[Art Montemayor]

Icing:

You still fail to answer the listed questions I asked in my first reply. So I will forget about giving any help in that area.

You also ask various different questions scattered within your post and in your "sketch". Which ones you want (or need answered) is anyone's guess. I will address some as I recall them (since you have not organized your query, there is no need for me to organize my response).

The only "standards" that exist regarding the transfer of liquid fluids from one vessel into another are company standards. For example, DuPont Chemicals had (& probably still has) their standard for using dip pipes as fill lines. They clearly explained their reason: some liquids generate static electricity when allowed to free-fall into a pool of liquid within a vessel. This can cause a spontaneous combustion (explosion). You can fill a tank at the bottom, but there are safety hazards involved with return-drainage. A dip pipe is used with a vent hole as shown by you in the sketch. I always use a generous 3/8" hole just below the tank's roof line. This hole is to prevent a back-syphon effect of the liquid in the tank.

I always welded an impact plate directly below the end of the dip pipe to absorb the momentum force of the liquid as it exited the dip pipe. We don't know your truck's unloading rate - nor the liquid velocity in the dip pipe, so I can't offer any more on this.

[siddhartha]

Personally, given the quality of the question I would say that Art's answer is the best under these circumstances.
I would not only follow Art's advice but also suggest that if simultaneous loading from two different sources are contemplated, it is a good idea to check that the existing tank vent system (breather/outbreather valve or blanketing system) can cope with the additional vapour displacement output. This is to ensure that we do not overpressure the tank during such simultaneous loading. Again, without any more information on the subject, it is better not to say anymore.

[icingrock]

The comments from Art Montemayor and siddhartha are highly valuable. So I would like to improve my questions.

Let me start from the beginning:

2 unloading pumps(No.1 and 2) can unload trucks to two tanks (tank A and tank B) respectively. Pump 1 can go to tank A or B. pump 2 can also go to tank A or B. These two tanks are for storage of raw materials.

Due to increased production capacity, the decision was made to add another unloading pump (pump 3). There are basically two ways to realize it:

1) use the existing pipes for unloading, which means two of the three pumps must use same pipe for transferring materials. this limit transfer flow rate and also raise the risk of back flow from pump discharge side to unloading truck of another pump

2) add unloading pump 3 and its dedicated unloading pipe ( refer to sketch). But since the pipe should be dipin pipe, it requires longer shutdown time to clean the tanks to remove all the chemicals so that hot work can be done inside the tank(welding work to fix the dip in pipe on the tank wall).

So my question about dipin pipe has been answered.
My remaining question is which options you would prefer. I personally prefer to option 2. My dislike of option 1 is that there is no effective way to prevent back flow and with operation for 3 pumps at the same time with cross piping, there is alway risk of opening the wrong valves.

Attached Files

•  unloading pumps.pdf   335.33KB   34 downloads