Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

Meg Transfer Iso Tank To Storage Tank (Offshore Platform)


This topic has been archived. This means that you cannot reply to this topic.
4 replies to this topic
Share this topic:
| More

#1 grax213

grax213

    Brand New Member

  • Members
  • 3 posts

Posted 19 November 2015 - 09:57 AM

Hello,

 

We are currently preparing to fill an offshore platform MEG storage tank and the MEG will be transported by 24kL ISO tanks. The tanks will be loaded onto a work barge before we pump MEG into the storage tank. 

 

As the MEG is 99%, the ISO tanks and the storage tank will nitrogen-blanketed to prevent water/oxygen contamination. The limiting factor will be dissolved oxygen limit of 50ppb.

 

A couple of questions and hope to get advice:

 

As the MEG transfer has to be performed in a closed system, a nitrogen source will be needed which we are thinking of using liquid nitrogen. With transfer hose length ~ 100m, can we commence transfer of MEG to storage tank without purging the hose without introducing dissolved oxygen into MEG? Can we assume that oxygen is not soluble in MEG and only soluble in water (~12ppm)? Otherwise, what is the best method to purge the hose before each transfer?

 

With closed system, the MEG discharge rate from the ISO and the nitrogen inlet rate into the ISO will have to be comparable and we plan to maintain that by controlling the pump output. Is this safe?

 

Thank you



#2 Art Montemayor

Art Montemayor

    Gold Member

  • Admin
  • 5,780 posts

Posted 19 November 2015 - 12:02 PM

Grax213:

 

Your post is difficult to understand because of the composition and the grammar.  You also fail to tell us all the details and furnish a detailed sketch of the proposed operation.  Correct me if I am wrong in my interpretation of your query:

 

You are proposing to transfer MEG from a 24,000 liter tank on a barge into a MEG storage tank located on an offshore platform using one transfer hose.  Both the storage tank and the barge tanks are inerted with nitrogen gas and you are going to transfer the MEG using a pump located on the floating barge.  You must avoid any contamination of the MEG with water or air.

The transfer hose(s) is 100 meters long.  If my description is correct, then my response to your questions is:


Can we commence transfer of MEG to storage tank without purging the hose without introducing dissolved oxygen into MEG?
The existence of liquid nitrogen is of little or no importance.  You must have GASEOUS nitrogen available (presumably on the platform) and this can be obtained by vaporizing the liquid nitrogen.  No, you should not connect the transfer hose(s)and proceed to pump the MEG without first evacuating the air from the hose(s) by either using a vacuum pump with subsequent gaseous nitrogen, or by purging the air out of the hose(s) using gaseous nitrogen in a continuous flow for an appropriate time period.
Can we assume that oxygen is not soluble in MEG and only soluble in water (~12ppm)?
No, you cannot.  You must not expose the MEG to the oxygen in the air.
The MEG discharge rate from the ISO and the nitrogen inlet rate into the ISO will have to be comparable and we plan to maintain that by controlling the pump output.  Is this safe?
That is not the simple, safest way to effect a transfer.  You should start with the storage tank already inerted with nitrogen (which I assume is the case) and use a vapor balance system of transfer.  This means you should use TWO hoses - one to transfer the liquid MEG and the other to equalize the nitrogen vapor space in the storage tank with the nitrogen vapor space in the ISO barge tank(s) - which I also assume is the case.  After making the two inerted hose connections between both tanks, you can operate the transfer pump to your heart’s delight until the storage is filled - without any flow control other than a manual throttle valve to obtain a decent filling rate relative to the level in the storage tank.

 

I don’t understand the idea of trying to continuously feed gaseous nitrogen to the ISO barge tank vapor space due to the liquid pump out.  All you have to do is EQUALIZE BOTH TANKS’ VAPOR SPACES.  Transferring from a barge to an offshore platform is a risky and potentially hazardous job and you should keep the operation as simple and risk-free as possible.  Always use level controls or human continuous monitoring and communications of the levels on BOTH tanks in question with quick or automatic shutoff valves and alarms on the transfer lines and the pump.  You must avoid a potential overflow of the target tank. 

 

That is basically how I recommend to carry out the operation safely.



#3 grax213

grax213

    Brand New Member

  • Members
  • 3 posts

Posted 19 November 2015 - 08:07 PM

Hi Art, thank you for the detailed explanation and guidance. My apology for the bad composition. However, you interpreted my query perfectly.

 

Once we connect the hose from the ISO tank to the pump and another hose from the pump to the storage tank, how do we purge the hose off the air pocket that is present in the hose? We have never done nitrogen-inerted chemical transfer, so please pardon the simple question. Thank you.



#4 Art Montemayor

Art Montemayor

    Gold Member

  • Admin
  • 5,780 posts

Posted 20 November 2015 - 10:49 AM

Grax213:

 

I’m still having to do a lot of guessing with your query because of a lack of basic data and information from you.  I don’t mind guessing except that it creates a lot of lost time, more questions, speculation, the inability of other members to contribute meaningful recommendations, and confusion.

 

If you are having MEG transporting an ISO container that is on a barge, I have to assume that the transfer pump is already installed on the barge and has already been piped (or hosed) up to the pump suction.  Additionally, it would be normal procedure to contract for the MEG supplier to furnish the ISO MEG container already inerted with nitrogen.  This is a normal purchasing procedure for a platform operator in order to ensure that the MEG is delivered in pure and uncontaminated condition.  This would be carefully inspected and checked at the platform before taking custody of the MEG transfer.  I’ve done this before with methanol and other similar chemicals and have prepared written procedures for this operation, so I’m speaking with experience.

 

This leads to the platform operator making sure that all the barge/ISO container equipment and piping is inerted and prepared to be hooked up to the transfer hoses.  There are two hoses: the liquid transfer product hose and the vapor balance hose.  Each of these hoses has a Tee or a convenient nozzle that allows for either vacuum pull + nitrogen purge or for a nitrogen purge procedure.  This procedure allows for making sure that both hoses have a nitrogen atmosphere prior to starting the equalization (first) and the subsequent transfer operation.  During the transfer, the ISO container and the platform storage tank vapor spaces are equalized to facilitate the transfer without any pressurization issue in either tank.

 

The step-by-step written procedure must be prepared very carefully and subjected to both engineering design approval as well as platform operations approval in order to ensure complete safe operation.  Lines and demarcations of responsibility must be accurately and clearly drawn and defined in order to have a safe transfer of product and responsibility.  These procedures incorporate the clear and accurate labeling of all valves, piping, instruments, and alarms incorporated in the transfer operation as well as a detailed definition of the operators involved and their work description.  Obviously, it requires a complete and detailed definition of the scope of work, the accurate definition of the type of purchase agreement together with the conditions of delivery and custody, and all this is subjected to a detailed hazop.

 

The careful and safe purging of all equipment and piping is defined in the procedure and is subject to the normal project engineering design, checking, and approvals.  Your question on how to purge and/or inert the equipment and piping cannot be answered here in this Forum.  We don’t have an iota of basic data or required details to even start on that.  All we can do is outline the concept and overview of what is normally required.  The details are left to you.

 

 



#5 grax213

grax213

    Brand New Member

  • Members
  • 3 posts

Posted 05 December 2015 - 09:57 PM

Hi Art, all your explanation are spot on. Thank you for your advice.






Similar Topics