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.