Tank Internal Inspections - Is there a better way ?

As an Integrity Team Leader , every time you mention or add into the planned look ahead that one of your storage or separation tank requires its API 653 inspection you get a sideways glance from the people "on high" before they get around to ask " Can we inspect the tank without going inside?" and come to mention it we get this question asked about most critical vessels due an internal inspection as we know taking any equipment out of service comes at a cost.

The simple answer in my opinion for Tanks is "No" you need to take the tank out of service to enable a complete and thorough inspection , where as with pressure vessels there are many combinations of modern NDT methods that can allow most of the pressure envelope to be inspected to ascertain its integrity and comply with API standards. In saying that for any vessel over 5 years old without any inspection or operating history I would suggest that a full internal visual inspection be carried out not only for mechanical integrity reasons but also because process engineering should know what is happening inside their vessels in regards to debris collection, internals integrity and process flow assurance. I am not here to comment on your own RBI system or pressure equipment inspection frequency as this depends on many factors specific to your business.

Before I go on I must say that I have organised, planned , and inspected many tanks over the years and none of them are identical when it comes to inspection findings , even though some might be identical in design ! I must also say that when I talk about being involved in projects over the years I have not done this single handed and I have had the absolute pleasure of having some excellent Senior Inspection, Mechanical engineers and Inspectors in my teams from all over the world who have thrown in valuable ideas.

The picture above illustrates what we found inside a large Separation Tank during an inspection where basically all of the distribution pipework had failed and collapsed to the floor , what you don't know though is that we knew it had failed prior to the opening of the man ways because we had completed some "off the wall" inspections prior to the tank being taken out of service.

I had previously used Sonar technology extensively in Sub Sea work and discussed with a reputable Inspection Company the option of using a Sonar inside of our tank as a preliminary check prior to entry and to allow further planning, as the theory on how the Sonar would operate in the fluid level should in principle work the same and offer me some imagery of both the tank internals and also the sludge profile should it not ?

We designed and tested a Sonar specifically for this work , and our clever inspection contractor designed the snubber box system for inserting the Sonar probe into the "on line" tank which was approved by the MOC committee . The results spoke for themselves as we moved the Sonar up and down the fluid column we received results that indicated we had problems with our internal pipework which in itself added further justification for an internal entry. It also allowed for the fabrication of new pipework and allow for critical repair materials to be located.

The debris profile illustrated we had significant sludge build up inside the tank , reaching up to 1m deep towards the center, strike two ! another justification for tank entry which would allow for the planning of a significant sludge removal program saving valuable time reduce costs.

The moral of the story here is that despite my statement that Internal inspections are a critical aspect to our business, there are many pro active inspections that can be done prior to any tank or equipment being taken out of service , some of which will prove invaluable towards helping your preparation as you should never enter into an internal inspection scenario unprepared and without the ability to remedy anything you may find. "Always expect the unexpected".

The use of FLIR gas detection cameras as per the above video can allow you to further ascertain if you have any fugitive emissions , especially relating to Floating roof tanks and this would allow you to incorporate a possible seal change out during your internal outage . I strongly recommend that for floating tanks the roof drain joints gets checked thoroughly after I have seen them fail several times when put back into service after an outage.

To assist with modern day storage Tank inspections I would suggest the additional use of UAV craft fitted with LIDAR surface profile systems which can save a huge amount of time and effort and give you a full tank internal surface profile which can be used for comparison in years to come and also allow you to focus your valuable resources and attention to specific areas highlighted as a potential problem , the use of innovative equipment can significantly reduce the time a tank is out of service and the need for access. I have worked with a company who offer the UAV services with both LIDAR and Gas detection system capability noting that the new FLIR GF x 320 gas detection camera is intrinsically safe and fresh into the market this year.

Modern NDT and the new improved PEC system can assist you with assessing the condition of your annular ring prior to entry , another of your key areas covered . So what are you waiting for ? Yes I know it is not that easy and there are many bases to cover ..... I hope this helps.

For all of your integrity needs , contact me directly in total confidence.