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Quality Control & Asset Integrity Management by Advanced NDT
In this article, S Venkataraman, Director, Sievert India Private Limited, describes how Non-destructive Testing (NDT) is assisting in Quality Control and Quality Assurance, and inherently how NDT is supporting the Integrity Management. Quality control (QC) is a process by which entities review the quality of all factors involved in production. It is a series of analytical measurements used to assess the quality of the analytical data collected during the production of part.

Inspection and testing forms an important part of design and development of individual components or assemblies. Quality Control and Quality Assurance always impinged with ‘standards’ and ‘codes’. NDT itself is carried out following its own codes and standards, ultimately supporting in the Cost Reduction, Rise in Productivity, Quality and Reliability of the Equipment. Integrity Management (IM) is a life cycle application relevant to all phases of an asset’s life. It should be embodied in the conceptual design stage, and only end with decommissioning and abandonment. Integrity is a holistic requirement defined by a philosophy that sets strategies, procedures and management systems that will ensure the safe, cost effective and reliable operation of an asset.

Quality Control is reactive process, where quality is inspected or checked after the product is manufactured with inspection tools like Non-destructive Testing, Destructive Testing, Raw Material Inspection, Microstructural Analysis etc. Quality control maintains proper standards for goods. Quality Control is often done by doing periodic inspections and start from survey services to integrity services after the production.

On the other hand, Quality Assurance is a proactive process and superlative to Quality Control. It guides the Quality Control with respective to standard and safety at each and every step of product manufacturing. Quality Assurance is a fundamental element of commercial success in manufacturing and process industries. It is an overall management plan to build the quality in the product from design stage to final manufacturing of the product, and believes in quality in each and every step of product inspection.

Advanced NDT is used as a tool for Quality Control and Quality Assurance by detecting, locating and sizing of surface and internal discontinuities (in welds, castings, forging, composite materials, raw materials, concrete and many more). Various Advanced NDT methods are applied for preventive maintenance (aircraft, bridge), for the inspection of raw materials, half-finished and finished products, for in-service-inspection and for plant life assessment studies.

Asset Integrity Management (AIM)
AIM outlines the ability of an asset to perform its required function effectively and efficiently whilst protecting health, safety and the environment. AIM system should address the quality at every stage of the asset life cycle, from the design of new facilities to maintenance management to decommissioning.

AIM incorporates with Higher Authorities, Management, Design, Maintenance, and Inspection Process, Customers, Public, Operations and Management Concepts. It magnifies the reliability, maintainability, understanding of asset condition and improving safety in the industry. It optimises the maintenance and inspection costs, and regulates the industry with its best performance.

Best practice facilities have comprehensive, fully integrated systems and a culture directed at gaining greater lifetime effectiveness, value, safety, availability, profitability and return from production and manufacturing assets. Advanced NDT and AIM Process plants & manufacturing plants run on various engineering components like reactors, heat exchangers, pipelines and many more.

These components’ estimated life is designed by considering the physical & chemical properties of material, maximum working temperature and working pressure on the component. These components are designed to last longer, but in actual condition they fall short of their designed life due to different working environment of varying temperature and varying stresses. This makes an AIM team to make a “RUN, REPAIR & REPLACE” decision of the component to avoid unplanned outages. AIM gathers the inspection data from Plant Life Assessment (PLA), Predictive Maintenance and Risk based Analysis in accordance with company’s ethics and policies under the guidance of higher authorities to take “RUN,REPAIR & REPLACE” decisions.

Today many countries in the world follow the trend of PLA for AIM for improving the safety standards and reliability of the industrial manufacturing process. PLA is nothing but a process to calculate the remaining life of the plant. Advanced NDT for plant life assessment deals with application of Advanced NDT techniques to detect discontinuities in an industrial manufacturing process that can affect the mechanical strength of a product and may cause its premature failure.

PLA or inherently, AIM is applied to any kind of processing lines, structures, vessels or pipes which are designed to operate for a specific life time taking account the temperature, corrosion and material. To assess and monitor the quality of the product during its manufacturing and service life without interfering with service performance of the product the NDT techniques provide the best choice. On line and on-site NDT techniques are used for plant life assessment.

Major inputs for assessing the plant life assessment of the components include:
1. Material Properties (mechanical & thermal)
2. Flaw Characteristics (type, location, size & shape)
3. Stresses (residual, service)

Flaw characteristics can be obtained with Advanced NDT techniques like Phased Array, Automated UT, Thermography, Eddy current techniques etc. Stresses induced in the components are inspected with the help of Acoustic Emission and Vibration Analysis while Microstructural analysis and Ultrasonic Testing along with software assistance provides the material properties of the components. These NDT inspection data can be used for assessing the remaining life of the component and the measures required to take for extending the life of the components

Risk Based Inspection (RBI) is a technology process which is used to correctly identify and assess the HSE and Business risk of each equipment or piping in a plant for optimising the inspection interval based on site acceptable risk levels.

It is used to priorities inspection based on Advanced and Conventional Non-destructive Testing tools to outline the type and frequency of inspection for the asset. Tools which are widely used for RBI are Acoustic Emission, Corrosion Mapping, Phased Array UT and Vibration Analysis. Items with high probability and high consequences are given a higher priority for inspection than items with lower probability.

Predictive Maintenance (PdM) helps determine the condition of in-service equipment in order to predict when maintenance should be performed helping cost savings over time based preventive maintenance. PdM helps in increasing the plant availability, increased plant safety & fewer accidents by sifting from unplanned stops to fewer or shorter planned stops. To evaluate the system condition PdM utilises the Advanced NDT technologies such as Airborne Ultrasonics, Thermography, Vibration analysis Acoustical Emission, ACFM, and Corrosion Mapping.

Role of NDT Engineer
Proper application of NDT methods would help to produce valid results applicable for plant integrity. For this reason, NDT Engineers are part of the team responsible for this activity, right from the planning stage to the analysis of data.

The roles of NDT Engineer in this activity include:
  • To advice the plant life assessment team on the selection of an appropriate NDT method or combination of NDT methods applicable for a specific plant component that is/are capable of providing optimum information required for assessing the status of the components
  • To ensure that NDT is always performed by personnel having the right qualification and certification. In cases, where the NDT activity involved the use of sophisticated, nonconventional equipment, the NDT specialist shall be able to organize mockup tests to ensure that the NDT personnel are capable of detecting pre-fabricated defects by using such equipment
  • To provide a continuous supervision and to ensure that all NDT activities are performed in accordance with approved written procedures
  • To and advice the plant life assessment team on the reliability of NDT test results
  • To work together with the PLA team during the analysis of the test results. In cases where defects are detected but still within an acceptable limit, NDT specialists may work together with other PLA members for the planning of inspection program applicable for that particular component

Conclusion
To cope up with growing industry needs of safety, reliability, quality and profit it becomes compulsory for the industries to follow the policies of Asset Integrity Management (AIM), Quality Assurance (QA) & Quality Control (QC). Advanced NDT tools like Phased Array UT, LRUT, MFL Tank floor, AUT, Corrosion mapping, Eddy Current Inspection etc help the industries to satisfy the needs of AIM, QA & QC with reduced amount of human intervention in inspection leading to reduced amount of man made errors and increased probability.