Internal Visual Inspection 

IVIInternal Visual Inspection is the traditional method of inspecting vessels by getting inside and having a look at the condition. It is the opposite of NII – non-invasive inspection. IVI will allow identification of corrosion, erosion and pitting. Where the tank of a vessel has a corrosion-resistant lining or protective layer, then IVI will allow the identification of blistering, breaks and holes in the layer. In certain circumstances, IVI will also be able to detect surface-breaking cracks.
IVI can be applied to all materials and all accessible surfaces. Various aids can be used to assist the inspection including magnifying glasses and profile gauges. The removal of any loose paint or corrosion products is necessary to ensure a reliable inspection.
Although IVI is a simple and effective technique to apply, entry into a vessel poses many safety hazards, with the requirement for consequential safety actions such as cleaning and purging of the vessel, confined space training for the operators, a permit to work system, installation of air sampling apparatus and a safety watch.

For more information on IVI see:
PCN Classroom Training Handbook – Visual Testing available from:

Specific guidance on the inspection of pressure vessels for corrosion and other flaws is given in API Recommended Practice ANSI/API RP 572, Inspection of Pressure Vessels, 2nd Edition, American Petroleum Institute, Feb 2001.

What the hec?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: ndtnews@bindt.org