Do you have vessels that for some reason you either can’t get physical access to the internals to fully inspect them, or you have a vessel that will cause needless and major unplanned costs should it be opened?

You won’t necessarily be surprised to hear that you’re not the only one. However, you may be surprised to hear that there may be an alternative for you and this may be Non-Intrusive Inspection.

The two methods that spring to mind are the API methodology API 510 6.5.2 or HOIS-G-103.

Each call for a number of requirements to be met before the vessel can be accepted for a Non-Intrusive Inspection. Such as known low corrosion rates, vessel remaining life >10 years, known corrosive character of the process fluid and more. All depending on the complexity of the process operation.

The external inspection and extent of NDT required for the vessel has to be such that it can find the known degradation mechanisms, that access can be established at the likely areas of degradation and that the level of coverage combine to give the required level of confidence in the examination.

One area where this has been used very successfully is with the management of Vapour Recovery Units. A number of owners are finding that life of their very expensive adsorbent is outlasting the intervals established by the Written schemes of Examination. This may be 20 to 25 years with Written Schemes of Examination prescribing a 10 to 15 years interval between internal inspections.

Using the principles of NII we have been able to establish levels of external examinations within the WSE that will maintain a satisfactory level of confidence in the vessels integrity until the adsorbent is spent and an opportune internal examination can be carried out.

This methodology has given the client total flexibility in the running of their Vapour Recovery Unit and huge savings.

Could this be done with your plant?