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Non-intrusive inspection is a growing trend in many asset-intensive industries.

The traditional approach of confined space entry where personnel would need to enter the vessel to gain the internal condition of said pressure vessel. This approach presents itself as a severe risk to personnel, and production loss with vessel closure is outstanding.

This is due that the process of internal inspection includes a shutdown, inventory purging, and cleaning before personnel can enter the process vessel for inspection.

 Confined spaces are dangerous due to several characteristics (1) not made for human occupation, (2) may contain a hazardous atmosphere, (3) a material that may engulf the entrant, (4) has an internal condition that may cause an entrant to be trapped or asphyxiated, and (5) any other severe or health hazards.

Other potential hazards include: biological contaminants, flammable gases, toxic gases, low oxygen levels, and elevated temperatures.

Hence, there will always be a risk to personnel entering a confined space as a harmful environment may be present in addition to cramped and uncomfortable working conditions

Non-intrusive inspection (NII) on the other hand allows internal inspection of a process vessel from the external surfaces utilizing non-destructive testing (NDT) techniques. This method eliminates the risk of sending personnel into a confined space – where inspections may be conducted online without taking the process vessel out of service.  

There are several benefits to non-intrusive inspection:

  1. Reduction of production losses due to shut down for confined space entry
  2. Reduction of workforce requirements- as the shut-down cost and shorter overall shut-down times since a more substantial capacity is available in other tasks
  3. Removal of hazards linked to man entry of vessels
  4. Removal of the need for internal vessel cleaning
  5. Targeted and concise inspection planning and reporting
  6. Reduced hydrocarbon damage potential

However, before a non-intrusive inspection is to be executed,  a detailed corrosion risk assessment of the vessel should be conducted to obtain a defined work scope for non-intrusive inspection effectiveness and coverage.

Cygnus Asset Solutions approach to NII is tailored to DNVGL-RP-G103 (Non-intrusive inspection) and industry experience.

Our sequential methodology to conduct a NII assessment : 

Stage 1: Integrity Review

Reviewing construction history, operating profile, damage mechanisms, flaw types, locations, growth rates, and associated risks. Furthermore, we aim for a CRA Type IV Assessment following the DNVGL RP G103 guidelines. Cygnus Asset Solutions are highly experienced in executing Corrosion Risk Assessments (CRA) and Risk-Based Inspection Assessments (RBI).

Stage 2: Decision Process

 The pressure vessel is then determined if it is suited for non-intrusive inspection and the required inspection extent. This procedure follows the DNVGL RP G103 with its decision-making process- taking into account different factors of the degradation process. An NII decision record is then produced.

Stage 3: NII Planning process

The main objective of this process is to develop an efficient strategy for pressure vessel inspection to ensure that the vessel is safe and functional until it’s next inspection.

Cygnus runs simulations using CIVA software, which is developed explicitly for non-destructive testing applications.

Stage 4: Inspection

On-site inspection activities which involves preparation for inspection, performing the examination, dealing with non-conformances, reporting of results, and demobilization.

Stage 5: Evaluation

Reviewing the work carried out by the contractor to ensure that the requirements of the work order are met is imperative. Cygnus’ evaluation covers five main elements (1) method, (2) procedure, (3) data quality, and (4) location.

Cygnus’ consultants has experience across a range of disciplines combining skills and knowledge in materials and corrosion engineering, metallurgical failure analysis, Risk-Based Inspection (RBI), condition assessment, and inspection engineering.