1 reply to this topic

[rocky]

Hello,

I am working with a petrochemical plant. We are currently storing our product in a tank designed for "Atmospheric" pressure. Now we want to give a PVRV with Nitrogen blanketing in this tank to avoid moisture ingressment.

Can anybody tell me, whether is it possible.
If that is so, which are the design parameter I need to check out?
Also guide me to decide the pressure that has to be kept in tank?

Data:-
1. Tank Service:- Acetonitrile
2. Sp. Gravity:- 0.78
3. Tank Volume:- 150 m3
4. Tank pressure: - ATM

[Art Montemayor]

Rocky:

The tank you are working with requires that there be detailed calculations and fabrication - as-built quality - drawings on file in your company's engineering department. You should also have a complete report on the ACTUAL physical condition of the tank -as inspected by an experienced inspector, complete with a complete analysis of the welds and any corrosion. With the detailed information, the engineering department than "rates" the present condition of the tank as to its Maximum Allowable Working Pressure (MAWP). You need this value before you proceed any further in your attempts to modify and employ this tank in a potential hazardous application.

You should already have the LATEST edition of API 350 and should have read it and studied it throughout. If you have mechanical engineers in your company's engineeering department, then they should have fulfilled this function. API 350 has all the instructions and examples that it takes to evaluate and rate an API storage tank.

Next, download the various Excel files I have posted on our Forums for designing a storage tank to withstand pressure and vacuum. I don't show you how to mechanically design the tank; I show you how to process design it.

Yes, you can convert a conventional "atmospheric" storage tank into an API design with the capability of withstanding the necessary blanketing pressure in a closed environment. I have done this in the past and converted so-called "atmospheric" tanks to 1.0 psig blanketing service - successfully and safely. However, you have to have FULL engineering knowledge of ALL the tanks critical details. I am sure that in India, as in many USA companies, the company management is lazy, dis-interested, or simply ignorant of what it takes to operate an efficient and SAFE production company. This is why they go out and purchase so-called "atmospheric" tanks without specifying the maximum and minimum working conditions the tank will be under. They also don't obtain the calculations and drawings - and if they do, they throw these away instead of archiving them for ready future access. This is flawed and ignorant engineering and, unfortunately, is prevalent in most all countries I have worked in. I suspect you find yourself in these conditions and will have to do a LOT of engineering work to produce a SAFE, modified storage tank.

Do not settle for anything less than what I have detailed above. To do so will lead you to a potentially UNSAFE application and a failed project.