Remote Visual Inspection (RVI) is a key element of plant maintenance, preventing leaks or other accidents than can result in significant losses

Plant shutdowns are expensive, which means that fast, efficient inspections that do not compromise on reliability are highly beneficial for plant profitability. Although other inspection technologies exist, RVI extends the reach of the human eye into areas that would otherwise be invisible or require dismantling to view, therefore RVI is the only method that provides instant true-tolife images for confident decision-making.

Plants are interesting for RVI inspection due to the wide range of equipment that needs to be inspected. Each piece of plant equipment comes with its own specific inspection challenges. These challenges can relate to the shape of the component (small holes, tight spaces) or to its condition (damage, fouling).

To tackle these complex inspection challenges, the latest generation of videoscopes is equipped with innovative features that are specifically designed to address these tasks. These videoscopes provide high return on investment due to faster inspections and better informed decision making.

CASE STUDY – In-service inspection of corrosion in trunnion supports
A recent article from HSE in England and Wales raised a specific concern relating to the inspection of trunnions or trunnion supports.

Trunnions are welded to the process pipe carrying oil, gas or chemicals in plant locations, power stations and oil and gas facilities and form the support structure for this network of pipes.

There is a critical inspection requirement for trunnion reports, more critical following an HSE (Health and Safety Executive) report highlighting the condition of a number of inspected supports following failure due to corrosion.

The Action required by the HSE at the time following Bulletin Number: HID1-2013 is as follows: “Operators of plant with pipework containing hazardous substances should ensure that their inspection regime includes suitable examination of supports. In particular, where tubular trunnions are installed with an end cap that prevents visual examination, other means should be employed to ensure the integrity of the system, where there is a possibility of moisture ingress. Note that permanent removal of the end cap is not recommended without further design work, as the cap may be required for additional stiffness.”

Historic inspection method and associated challenges
Historically, based on this advice trunnion supports have been inspected using industrial radiography, a non-destructive inspection technique using radioactive isotopes that is both costly, time consuming and carries a number of critical safety challenges.

Due to the nature of this type of inspection, there is generally a requirement to stop works at the specific plant location and evacuate personnel to a designated safety zone. Naturally, efforts have been made to look into new and innovative ways to inspect these trunnion supports.

A new method for inspection trunnion supports ‘in-service’
Remote visual inspection, by default, extends the reach of the human eye into areas otherwise unable to be seen without disassembly or sometimes destructive testing.

As such this scenario is a truly ‘non-destructive’ technique where no disassembly or dismantling is required and inspections can take place in situ. During the trial, the access point for the videoscope was the weep holes found in the support structure of the trunnion. These weep-holes exist so as to allow pressure release during the high temperatures hit whilst welding.

It is possible to pass a videoscope through this inspection port of 6mm or less and take both images to assess the condition, or to take measurements where necessary to map this corrosion if evident.

A number of trunnion samples have been inspected in England and Scotland and in some trunnion samples, the level of corrosion was so high that it was deemed fruitless to take measurements. Equally, in other trunnion samples there was no evident corrosion and again, no measurements needed to be taken.

Conclusion and Olympus recommendation Regular trunnion inspections are a cost-effective way to ensure low downtime and potential catastrophic failure of these process pipe supports allowing operators to make informed decisions when minor faults are identified which left undetected would result in costly replacements.

For more information on the equipment used, please visit: www.olympus-ims.com