Evaluation of the integrity of metallic stuctures

It is well known how corrosion represents the principal threat to the integrity of metallic structures during their operating life. CESCOR supports the operators of complex assets in the evaluation and in the management of integrity and durability.

The evaluations of integrity can be requested for various reasons:
  • They are periodically performed with the purpose to underline possible criticalities in comparison to a previous assessment and allowing the operator to intervene in time avoiding more serious problems:
  • They can be requested as dedicated verifications in case of important changes in the system configuration or in the process and operational parameters.
  • They are mandatory during the processes of requalification of the assets that have reached or overcome their life-cycle with the purpose of getting an extension on their operating life.
The analysis has to necessarily consider of all the operational, inspected project corrosion data, those concerning the fluids treatment in order to get a clear prospect of the integrity and the durability of components.

Cescor long experience is able to supply its customers with the following services:
  • Corrosion Risk Assessment (CRA)
  • Integrity Operating Windows (IOWs)
  • Risk-Based Inspections (RBI)
  • Direct assessment 
  • Fitness for service 
  • Sour service


Drafting of inspection plans and programs according to the RBI methodology


The Corrosion Risk Assessment provides a relative risk ranking of the considered items with respect to the probability of a failure which implies the leakage of the conveyed fluid and the entity of the consequences.

Corrosion analysis is the main activity of the corrosion risk assessment procedure, aimed to calculate or assess, for each item, the likelihood of a corrosion failure, expressed by the corrosion factor, FC.

The main output of the procedure is the risk matrix. The targets of corrosion risk assessment are:
  • to witness the integrity status of the assets
  • to provide input data for risk-based inspections
  • to provide recommendations on actions to be taken for reducing corrosion related risks.
Cescor holds the experience to perform other types of risk assessment such as:
  • FMECA (Failure mode effects and criticality analysis)
  • FTA (Fault tree analysis).


Integrity Operating Windows (IOWs) 

Integrity Operating Windows (IOWs) are established following industry-recommended international standard API RP 584. They are developed to:

  • Establish appropriate limits for process parameters (chemical or physical), called key process variable to prevent excessive facilities degradation and unexpected failures;

  • Provide initial indicators where corrosion threats could become active, setting up IOW levels between "Target, Standard, and Critical";
  • Recommend appropriate actions to restore safe process operation within a given time frame. IOWs shall provide a bridge between the design phase and operational phase to ensure the integrity of oil & gas facilities and maintain safe operations.

CESCOR can join the team as a corrosion and integrity specialist, able to propose tailored and pragmatic solutions suiting the client's requests.


Drafting of inspection plans and programs according to the RBI methodology

CESCOR elaborates inspection plans and programs based on the logic of RBI (Risk Based Inspections). The structures to which the RBI methodology has been broadly applied, with punctual adaptations, are the plants for the treatment of oil and gas of the oil upstream, the plants of oil downstream and the plants of re-gasification.

Activity consists in a detailed risk analysis of all the components with the aim of categorising every component on the basis of the possible mechanisms of degradation and of real corrosion risk.

Starting from the components with the highest risk, some plans of inspection are elaborated in order to define the techniques of inspection for the survey of expected degradation mechanisms, and define, with the support of inspective sketches, the appropriate areas of investigation, their extension, and the necessary detail of investigation.

The elaboration of an inspective program containing inspective frequencies and their management is an integral part of the activities.

The RBI method can be applied both to new plants, planning it since the start of the development phase of the project, and on existing plants.
The first inspective survey is usually carried out in the first year of the operating life of the plants, the collected data constitute the base-line of the plant and have the purpose to confirm that the items lack of constructive defects.

For the working plants, the application of the RBI method consists in the periodic execution and planned frequencies of inspective surveys, the results of which properly filed and analyzed, constitute the starting point for the planning of following inspections.


Direct assessment studies for non-inspectionable plants

CESCOR elaborates integrity studies on the pipes that operate the transportation of hydrocarbons, both onshore and offshore, based on the Direct Assessment method (DA). The Direct Assessment (DA) is a NACE standardised methodology, used to carry out a Corrosion and Integrity Assessment activity in order to support the verification of the corrosion integrity and risk state of a pipe in the absence of inspective data internally acquired. CESCOR applies methodologies for the assessment of the internal (ICDA) and external (ECDA) corrosion. The Direct Assessment is known as a valid methodology for the extension of the operating life of a pipeline with an ISO-12747 standard. The Direct Assessment is made of the following phases:
  • Pre-Assessment: it consists in the collection and categorization of data and in the subdivision in homogeneous sections of the pipeline.
  • Indirect Inspection: It consists in the corrosion analysis finalized to the identification of the most critical areas and the definition of number and position of those points along the layout of the pipeline where non-destructive inspections have to be carried out.
  • Direct Examination: it consists in the execution of non-destructive inspections in the excavation points, in the analysis of the inspected data and in the assessment of congruence between the inspective results and previous forecasts.
  • Post Assessment: is finalized to identify the causes of degradation, the formulation of corrosion mitigation actions, the estimation of residual operating life for the pipeline, the redefinition of inspective intervals and the preparation of a plan for the inspection and maintenance.


Fitness for service assessment of pressure pipelines

The term fitness for service assessment indicates a procedure commonly applied in the oil and petrochemical sector to verify the eligibility of a component in pressure to operate in presence of material defects.

The pressure pipelines are subject to periodical inspections intended to individuate defects and determine their form and dimensions.

Starting from the inspective of the pipeline (ILI - In-Line Inspections), CESCOR applies the methodologies described in ASME B31G and DNV-RP-F101 codes for the analysis of criticality of the defects in comparison to the expected effort conditions. Additionally, CESCOR applies its own competence in the field of the corrosion to foresee a model of growth of the defect which keeps in consideration the real conditions of exercise of pipeline and transported fluids (for internal defects) and the external conditions of protection (for external defects).

Applying once again the mechanical codes it is possible to determine what defects will be critical ones in the future and when, allowing the operator to perform mitigating interventions avoiding the perforation of the pipeline.


Materials evaluation for “Sour” Services

In the past, and today still, plants and pipes originally destined to the treatment of fluid missing H2S (sweet) are built with materials without requirements “sour service”. Nevertheless, it's more frequent now the case in which the treated or produced fluids change in time their chemical composition passing from sweet to sour. This change has catastrophic consequences on the materials that might incur in very severe cracking phenomena. CESCOR, expertly applying the knowledge of the materials and the principles contained in the ISO 15156 / NACE MR 0175, provides the structures operator with a specific evaluation on the adequacy of the components to work in presence of H2S. Verification studies on materials can be provided for:
  • Systems for the collection and injection of oil and gas
  • Plant for the treatment of oil and gas
  • Systems of storage and/or
  • Refineries and plants for the treatment of waters
The detail evaluation is based on the analysis of certificates of materials, on the verification of materials testing performed during construction phase, on the review of welding procedures and specifications and on the evaluation of the fluids corrosiveness.
Cescor Srl - Ingegneria della corrosione e protezione catodica.


Cescor Srl
Via Maniago 12
20134 MILANO (Italy)
Tel +39 02 26412538
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