Tank Guru blog

Question:  “Could you tell me the service life of an ISO tank? Do you know if tank companies keep a record of the services and repairs performed on the tanks??” 

Tank Guru:  The first question is one I get asked a lot, and unfortunately the answer is not simple because it depends on too many factors – and it depends also one what type of tank you are referring to… T11’s? T50’s? T75’s?

We have refurbished some of the first ISO tanks ever built from the late 1960’s (liquid products, not gas products) and lots of units from the 1970’s and 1980’s, and they left our shop ready for another 40 or 50 years of service. 

For liquid tanks, the stainless steel was just better back then (many older tanks were built from 316LN or 316Ti instead of 316L) and the tank shells were a little thicker.  Newer tanks are built with the thinnest possible 316L material and very little corrosion allowance, in order to minimize the amount of stainless used – which keeps tare weights low and new tank prices down as cheap as they are.  

On the contrary, we’ve also seen brand new tanks that were declared a total loss before their first 2.5-year test, due to being loaded with a corrosive product in tanks without an interior lining.

The service environment also matters. Tanks operating in the Caribbean (or other saltwater areas) that don’t get regular exterior washes will have frame corrosion problems early on, whereas tanks operating strictly on land don’t experience that same corrosion.

With T50 tank barrels made of carbon steel instead of stainless steel, it makes a huge difference whether the interiors are always kept dry (free from moisture) by maintaining an inert environment, or not.

The second question is much easier. All of the large leasing companies and tank operators have very sophisticated computer systems that can track work that was done on their equipment. One of our customers bases their decisions about disposal of old equipment based exclusively on how much they’ve spent on M&R feach asset, rather than the age of the asset.

Question:  “Our office in Japan will be sending a gas tank to the USA with class 2.2 Non-toxic/Non-flammable. The tank will be gas free when offhire. Does the tank needs to be cleaned in order to prep the tank for the next loading?” 

Tank Guru:  I suppose it depends on what mean when you say ‘gas free’ and also what you mean by ‘next loading.’  

In my mind, gas-free means ‘safe for fire, safe for man,’ or in other words, the tank is safe to enter when you check the LEL and O2 levels and there is no risk of fire.  This definition of gas-free also includes nitrogen as a gas, meaning that the O2 level is high enough that a worker entering the tank can safely breathe without special PPE. 

If the tank is truly gas-free to this standard, then it should be good enough to meet the offhire requirements of most lessors since an interior inspection would normally be performed in the process of writing the offhire estimate. 

But if by ‘next loading’ you mean that it is going to be reloaded immediately upon arrival to the U.S. instead of off-hired and then loaded at some future date, then I don’t think the tank would necessarily need to be safe to enter.  So long as all residue of the previous gas has been purged from the tank and the atmosphere inside is completely inert (for example a nitrogen atmosphere), then I think that is normally more than good enough for loading the next cargo.

Question:  “ISO Tanks are assigned a six-digit serial numbers by an international body. Can we label a tank with a different serial number?  The six-digit serial number remains on the tank.  For example, we have a tank with a serial number 117003.  We labeled the tank as AH-1.  This is how the tank is identified on a BOL.  Is this authorized?  Can we do this legally?” 

Tank Guru:  Absolutely, provided you are talking about transportation domestically.  If the tank were traveling internationally and going on a container ship, you would want to refer to it by the container number (the six digits you refer to above, preceded by the 4 alpha characters and then followed by the check-digit).  For more information on that numbering system, please see this link:  https://www.bic-code.org/bic-codes/

But if the tank stays on a chassis and you’re just referring to trucking the tank container from A to B, then you can call it whatever you want on the BOL.  Hope that helps.  Great question!

Question:  “Is there anything in CFR about pressure-testing lined tanks?” 

Tank Guru:  Not that I’m aware of. All tanks have to be pressure tested, regardless of whether they are lined.  Additionally, the lining should be inspected visually as you would perform an interior inspection at the 2.5 and 5-year periodic anyway; and if the visual raises cause for concern then a spark test (or other type of additional inspection) may be warranted.

There is the IMDG language about waiver of the interior inspection during 2.5 year test for tanks in dedicated service (as I suppose that many lined tanks are), but as a tank owner you certainly wouldn’t want to skip something so important as a chance to ensure that your lining is holding up against the cargo!

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