In the day-to-day running of industries, asset inspection is of paramount importance for checking the current state of structures, in order to discover any non-conformities and failures before they can cause catastrophic accidents, production stoppages and similar inconveniences.

When inspecting assets in the field, it is essential to carefully analyze the entire structure in order to identify existing pathologies. A detailed and methodical analysis makes it possible to identify non-conformities and risks, identify possible possibilities and causes, and predict possible solutions. 

Why carry out a visual inspection?

In the national industrial park, various structures have supported process assets, and their Structural Integrity that the production process runs smoothly and mitigate the risk of undesirable events involving employees. Looking at the mineral process, for example, structural failures in equipment such as belt conveyors, transfer houses, process buildings, yard machines, car dumpers, and ship loaders are vitally important for the production process to take place. Therefore, any structural failures in this equipment can be catastrophic.

In many situations in industry, due to various factors, the integrity of structural assets is not given due importance. Because of the immediate impact on production, failures in electrical and mechanical systems deserve immediate attention. However, the consequences of a catastrophic failure in a structure are unpredictable and can lead to expensive and prolonged maintenance and undesirable fatal accidents. 

Kot considers Structural Inspection an indispensable part of the journey to promote the integrity of its clients' assets. Structural Inspection the second step in the CARE Methodology – Asset Control for Structural Revitalization. This methodology was developed in order to offer an engineering solution aimed at promoting the care of its clients' assets. As the name implies, the focus is on caring for assets by promoting structured control and mitigating the risks associated with the use of equipment and structures.

In addition to the good training and preparation of those carrying out the test, the success of the visual structural inspection will depend on a number of important factors: the tools, equipment and instruments that will be used, the characteristics of the object under analysis and the available lighting. 

Therefore, visual inspection is the lowest-cost method that can be used in Structural Integrity journey. The method is not and should not be the only one used in this journey, but its use will highlight the need for other forms of assessment, as shown in Figure 1. It can be followed by:

• Non-destructive testing (NDT), such as ultrasound, liquid penetrant, magnetic particles and x-ray;
• Verification by finite element method; 
• Active instrumentation using extensometry and accelerometry; 
• Risk Assessment. 

Figure 1: Liquid penetrant test - SOURCE: Kot Collection.

In addition, tools such as drones, scaffolding, platforms, industrial mountaineering devices, borescopes and more can be used to support the visual inspection.

The main causes of damage to structures

To start the Structural Inspection it is recommended that you know the causes of damage to structures. The metal structures of industrial assets are generally affected by the climate, the environment, and their use. Based on this knowledge, it is possible to establish which inspection techniques are applicable. 

Research on this subject is extensive. For example, according to the technical study by OEHME (1989) considered by the EUROCODE standard commission, the causes of damage to metal structures of buildings and conveyors can be grouped as shown in Graph 1.

Gráfico 1: Distribuição percentual das causas de danos em estruturas
de prédios e transportadores – FONTE: OEHME, 1989.

In the national park, small to large metal and concrete structures, such as piers, tunnels, OAEs (Special Works of Art, such as viaducts, bridges, pontoons and footbridges), buildings, etc. suffer from the weather and corrosive atmosphere. Factors such as high rainfall and the deposition of chlorides and particulates favor the appearance of pathologies and failures. 

Temperature variations, heavy rainfall, pollution and a highly aggressive environment cause pathologies related to forms of structural deterioration. According to HENRIQUES (2001), the causes of pathologies in civil construction assets (in general) can be seen in Graph 2.

Graph 2: Causes of pathologies in civil construction assets (in general) - SOURCE: HENRIQUES, 2001.

Segundo o exposto por HENRIQUES (2001) e as experiências do dia a dia de campo, pode-se dizer que grande parte das falhas estruturais são derivadas de equívocos durante a fase de projeto, falhas durante a montagem e não conformidades na fabricação e questões de uso do ativo (condições de operação e manutenção). Em prol de detalhar as patologias estruturais mais frequentes em estruturas metálicas e as suas respectivas principais causas, foi proposto por PRAVIA e BETINELLI (2016) um entendimento interessante. Este entendimento pode ser visualizado na Tabela 1.

Pathologies in metal structures	Main causes
Localized corrosion	Deficiency caused by inadequate drainage of rainwater and errors in construction details, resulting in puddles, accumulation of moisture and aggressive agents such as deposition of chlorides and particulates (ore, pollution, soot, etc.).
Generalized corrosion	Deficiency caused by inadequate protection against different corrosion processes.
Excessive deformations	Deficiency caused by overloads and/or thermal effects that were not considered premises in the original project (supply specifications, conceptual, basic and detailed drawings).
Global or local buckling	Deficiency caused by the use of structural models that are not correct and do not reproduce reality and/or do not comply with the standards for verifying stability and rigidity.

Table 1: The most frequent structural pathologies and their main causes - SOURCE: PRAVIA and BETINELLI (2016).

Thus, there can be several causes of structural non-conformities. Possible design flaws can have their risks minimized by carrying out a structural asset audit. Also known as a design review or double check, the following activities are carried out: 

• Support in drawing up technical specifications; 
• Technical Evaluation bidders; 
• Suggestions for basic design; 
• Equipment verification using the finite element method; 
• Proposing solutions and any reinforcements for non-conformities found.

 

How to carry out the visual inspection

The visual inspection test can be divided into two forms: direct and indirect. In the direct form, the naked eye and auxiliary optical equipment such as magnifying glasses, microscopes, borescopes and binoculars can be used. Indirect inspection requires the use of auxiliary vision tools, through the use of an artificial vision method. 

Basically, visual inspection comprises the following steps:

1. Evaluation of the structure in conjunction with the evaluation of technical design drawings. To this end, visual inspection of the structure aims to identify the absence of bolts in connections, corrosion points in assets, visible plastic deformation of plates and profiles, visible cracks and other detectable non-conformities. Photos and videos can be used to record the faults found;

Figure 2: Evaluation of corrosion points on bolts and connecting elements - SOURCE: Kot Collection.

2. Classification of non-conformities and deviations found in terms of criticality and indication of actions;
3. Preparation of Technical Report, highlighting the checks carried out and indicating any non-conformities detected. The detail of the report will vary depending on the complexity of the document or the customer's requirements. Often, the inspection of the object may be governed by specific standards, designated laws, or the customer's own procedures;
4. Finally, suggest actions to mitigate the problems detected.

Main advantages and limitations

The advantages of using the visual test methodology are its low cost, the quick way in which the test can be carried out, the simpler interpretation when compared to other test methods and the ease with which it can be carried out. 

On the other hand, there are some limitations. These include the possibility of detecting discontinuities only on the surface of the structural element, limiting the detection of internal cracks. It is also necessary to ensure good visual acuity on the part of the tester and prior knowledge of the object under analysis. 

For the future, it is important to pay attention to what is recommended by CHA (2018) for OAEs, but which also applies to other structural assets. In the understanding presented, visual changes in civil infrastructures, such as cracks or corrosion, are very important to warn about structural health conditions. Despite the critical role of bridges in public safety and the economy, inspection based on human vision has the limitations and disadvantages already mentioned. Therefore, engineering will increasingly look to the automation of visual inspections to solve the limitations of the common human visual approach. Researchers and companies are increasingly attracted to the development of computer vision-based methods for detecting structural damage.

Kot can provide its customers with visual inspection options through human intervention, as well as computer vision methods to promote the integrity of its customers' assets, using, for example, image processing. Consult our team for more information!

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FAQ

1. Qual é o papel da inspeção visual no gerenciamento de ativos industriais?

A inspeção visual é o ensaio preliminar mais ágil e econômico para avaliar o estado de conservação de estruturas como pontes rolantes, transportadores de correia, prédios de processo, viradores de vagão e máquinas de pátio. Sua função primária é rastrear não conformidades e patologias em estágio inicial, permitindo prever soluções antes que ocorram falhas operacionais ou acidentes graves.

2. Por que os ativos estruturais por vezes recebem menos atenção preventiva do que sistemas mecânicos ou elétricos?

Em ambientes industriais, falhas elétricas ou mecânicas paralisam a produção de forma imediata e visível, exigindo reparos instantâneos. As estruturas metálicas e de concreto, por sua vez, costumam sofrer um processo de degradação silencioso e contínuo. Entretanto, quando uma falha estrutural finalmente ocorre, suas consequências são imprevisíveis, resultando em paradas prolongadas, custos altíssimos de reconstrução e riscos fatais à segurança dos colaboradores.

3. Como a inspeção visual se conecta com a Metodologia CARE da Kot Engenharia?

A Metodologia CARE (Controle de Ativo para a Revitalização Estrutural) foi desenvolvida para promover o cuidado metódico com os ativos industriais. A inspeção visual estrutural representa a segunda etapa dessa jornada de integridade, fornecendo o diagnóstico de campo que fundamentará as tomadas de decisão técnicas e as intervenções de engenharia.

4. A inspeção visual é suficiente por si só ou exige exames complementares?

A inspeção visual é o ponto de partida. Por estar limitada à superfície visível do componente, ela frequentemente indica a necessidade de etapas analíticas e experimentais mais aprofundadas, tais como:

• Ensaios Não Destrutivos (ENDs): Ultrassom, líquido penetrante, partículas magnéticas e radiografia (Raio-X);

• Análise Numérica: Modelação e simulação pelo Método dos Elementos Finitos (FEM);

• Instrumentação de Campo: Medição de deformações e vibrações via extensometria e acelerometria;

• Avaliação de Riscos (Risk Assessment): Matriz de criticidade e priorização de manutenção.

5. Quais são as principais causas de danos e patologias em estruturas metálicas?

Segundo estudos normativos (como Oehme, 1989 e Pravia & Betinelli, 2016), os danos estruturais decorrem do clima, do ambiente agressivo e do modo de operação. As patologias mais frequentes incluem:

Patologia Estrutural	Principal Causa de Origem
Corrosão Localizada	Drenagem inadequada de água pluvial e detalhes construtivos que geram acúmulo de umidade, poças e depósitos de cloretos ou particulados (minério, fuligem).
Corrosão Generalizada	Deficiência ou ausência de sistemas de proteção anticorrosiva (pintura, galvanização) adequados ao meio agressivo.
Deformações Excessivas	Sobrecargas operacionais ou efeitos térmicos não previstos nas premissas originais de projeto.
Flambagem Global ou Local	Utilização de modelos estruturais incorretos no projeto ou descumprimento de normas de estabilidade e rigidez.

6. Quais recursos de acesso e ferramentas podem dar suporte à inspeção visual em campo?

Para alcançar locais de difícil acesso e manter a segurança dos inspetores, utilizam-se recursos como:

• Drones (VANTs) para inspeção aérea em grandes alturas;

• Boroscópios e microscópios óticos para cavidades internas e detalhes micrométricos;

• Dispositivos de alpinismo industrial, plataformas elevatórias e andaimes;

• Instrumentos de apoio ótico direto, como lupas e binóculos de alta precisão.

7. Quais são as limitações da inspeção humana e qual é a tendência futura para a área?

A inspeção visual humana depende fortemente da acuidade visual, experiência do inspetor e condições de iluminação, além de estar limitada a descontinuidades superficiais (sem detectar trincas internas). O futuro da gestão de ativos está voltado para a automação via Visão Computacional e Inteligência Artificial (conforme Cha et al., 2018), utilizando processamento digital de imagens capturadas por drones e robôs para a detecção autônoma de fissuras, trincas e focos de corrosão com elevada precisão.

References:

OEHME, Peter. Analyse von Schäden an Stahltragwerken aus ingenieurwissenschaftlicher Sicht und unter Beachtung juristischer Aspekte. 1989.

HENRIQUES, F. M. A. Notion of Quality in Buildings. Communication to the National Construction Congress. Lisbon, 2001.

PRAVIA, ZMC; BETINELLI, E. A. Failures in metal structures: Concepts and case studies. Civil Engineering Course Civil Engineering FEAR–UPF, 2016.

CHA, Young Jin et al. Autonomous structural visual inspection using region-based deep learning for detecting multiple damage types. Computer-Aided Civil and Infrastructure Engineering, v. 33, n. 9, p. 731-747, 2018.