Question:  This question relates to tank re-testing requirements. How often and what are the procedures for retesting an ISO container. (Pressure and thickness)”  Tank Guru:  Hazardous materials may only be carried in tank containers (ISO tanks) that have a valid, current 5-year or 2.5-year test certificate.

A 5-year periodic test is required 60 months after the date of the original hydrostatic test, or the most recent subsequent 5-year test.  The scope of the test must include a hydrostatic pressure test at the tank’s full Test Pressure, usually 150% of the Maximum Allowable Working Pressure.  It will also include a visual interior inspection of the tank barrel, and exterior inspection of the container to ensure structural integrity of the frame and safety items such as the catwalk.  A bench test of the safety relief valve is required along with a final leakage test (after the water has been drained and the relief valve re-installed), to ensure satisfactory operation of all service valves and equipment.  All of these tests are carried out under the witness of a surveyor/inspector for a third party agency or Class Society, which will issue the test certificate and stamp the new test date on the tank’s data plate.

A 5-year test is also required at any time when welding operations have been conducted on the shell.

At the midpoint between each 5-year test interval, a 2.5-year test is required 30 months after the most recent hydrostatic test.  This will include the exact same scope of testing/inspection as the 5-year test, except that the tank will not be hydrostatically tested.  Instead only the leakage test (pneumatic) is conducted at normal operating pressure.  Again all testing is carried out under the witness of the third party surveyor, and after successful completion the data plate is stamped and a test certificate is issued by the Class Society or competent authority.

There are no specific requirements for checking the thickness of the tank shell.  However, the thickness should be checked by using a UT meter whenever there is reason for concern that the thickness may have been compromised by corrosion, or repairs to the pitting such as excessive grinding, etc.


20 thoughts on “Tank Guru Q&A: TANK RE-TESTING REQUIREMENTS”

  1. Pingback: ISO Tank Container Retesting requirements « Tank Service Inc- ISO Tank/Offshore Tank Blog

  2. A ISO tank container is repaired by replacing the inlet and outlet pipes
    of the vaporizer. After this type of repair does the tank container requires inspection and certification as per IMDG Rules.


    1. Not sure what you are referring to as the vaporizer, but the short answer is YES if the piping is considered a pressure-retaining part of the vessel. Repairs involving pressure-retaining components should be inspected and pressure tested. Re-certification would depend on the nature of the repairs.

    1. The best way to find qualified facilities for repair and testing abroad is to check the ITCO website (www.itco.be) and search under ‘members’ to find service providers in different parts of the world. I don’t see anybody in Qatar or the middle east, but several in India.

  3. Dear Sir

    Understand that there are several requirements for ISO Tank that need to be complied such as ADR/RID, IM101 (US) DOT, (UK) DOT, IMO Type 1, UIC, TIR, CSC, AAR 600, TC Impact Approved, FRA, BAM, DOT51.

    I would like to know if the ISO tank is going to be used in Asia Pacific Country and middle east, which are the requirements it shall comply

  4. Dear Sir,
    Good day.

    My name is Ganesan fm Greenearth Tank Hub Pte Ltd (GETH) Singapore.
    We are basically an Isotank cleaning and repair depot.Pls do guide the procedures for upgrade a non food grade tank (base oil) to Food Grade std (say Palm oil, Propylene Glycol USP grade and etc)..

    Hear fm you,
    Ganesan, Singapore

  5. if the tank is due for 2.5 year or 5 year perodic test , but can we use the tank to load with non haz commoidity & if the test due date is over still how many months we can use the tank to load non haz tank

  6. Do I have to perform a 2.5 year test on a brand new tank manufactured in 2010, which is about 30 months old.

    From my understanding, the first 2.5 year test on a tank is only required between the first 5 year test and the next.

    Please advise.

    From: Oletank

    1. Yes, you need to perform a 2.5 year test when the tank is 2.5 years old. The CSC Safety Inspection is only required once the tank is 5 years old, but the periodic test on the vessel is not exempted.

  7. A hydro is required at regular 5-year intervals or “…in all cases where cutting, burning or welding operations on the shell of the tank have been effected, a hydrostatic test to at least the original test pressure should be carried out.”

    So while grinding and buffing create some heat, they do not fall under the definition of “hot work” above found in 49 CFR 178.270-13. So as long as you are not welding pits first, for instance, before grinding, then NO you would not need to hydro test after grinding and buffing.

    1. The regulations don’t specifically address this to my knowledge, but yes it is standard practice to test the steam system when testing the barrel. If the steam system is found to be leaking, then normally the steam caps would be welded into place (or cut off and blanked permanently) as an indication to future users that the system is inoperable.

  8. Francisco V.Pelino

    After hydro test of piping line the contractor did the repair by cutting and grinding again ,it is required to re-hydro and if required can you give me reference ,it can be Aramco Engineering Standard or international code and standard.

  9. DOT 51 Testing Requirements

    What kind of certification does one require to hydro test DOT 51 tanks ?



  10. After 2.5yr expiration date, how many months may pass to perform the test? Is there a limit after which the hydro is compulsory?
    Also, is there a regulation which bars an empty clean isotank from being shipped for the purpose of testing at destination, providing that it’s structurally sound?

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