【Haichuan Safety Discussion】The summer maintenance period is approaching – how does your organization manage corrosion issues?

Many corrosive substances exist and are generated during chemical production processes. The type, chemical composition, concentration, pH value, impurities, moisture content, and oxygen level of these substances are all external factors that contribute to corrosion. The faster the flow velocity of the medium, the greater the likelihood of corrosion, as the flowing medium erodes the protective film, creating vortices, turbulence, and bubbles that lead to severe impact wear and cavitation corrosion. Furthermore, improper material selection can also lead to corrosion; for example, if the surface of the equipment comes into contact with corrosive substances and the equipment itself is not resistant to corrosion, surface corrosion will occur. The rougher the surface, the more prone it is to corrosion, with symptoms such as leakage, premature wear, damage, and noise. Uniform surface corrosion can occur in two forms: with film formation and without film formation. Corrosion without film formation is very dangerous, and the corrosion process proceeds at a certain rate; this is mainly caused by incorrect material selection. 「\"Micro-Class\": During major overhauls of chemical plant equipment, corrosion inspection must be thorough! Lack of anti-corrosion measures or poor construction quality create an environment conducive to corrosion damage. During the production of equipment, it is often not possible to ensure both the suitability of the materials used and resistance to environmental corrosion. Differences in temperature, concentration, and pressure lead to different material choices and varying levels of corrosion. In addition, inadequate quality control during construction and poor construction standards further contribute to the inevitability of corrosion problems. Over-temperature and over-pressure during operation, inadequate equipment management, and a lack of attention from relevant personnel are also causes of corrosion damage. Generally, the higher the temperature and pressure of the medium, the faster the corrosion occurs. This is because corrosion is a chemical reaction, and for every 10°C increase in temperature, the corrosion rate increases by 1 to 3 times. Why is corrosion inspection necessary? Corrosion inspection involves using various instruments, tools, and analysis methods to determine the rate of corrosion of materials in specific process media environments. It provides engineering technicians with information regarding equipment corrosion, enabling them to take effective measures promptly to slow down corrosion and prevent accidents caused by it. During the major overhaul of the facility, companies must pay attention to corrosion inspection. They need to develop a corrosion inspection plan tailored to the specific conditions of the facility, and assign specialized teams to examine the equipment and pipelines for signs of corrosion as well as their current state of corrosion. Based on this information, they can analyze the mechanisms behind corrosion, calculate its rate of occurrence, determine the extent of damage, and assess the effectiveness of the anti-corrosion measures that have been implemented on the equipment and processes over the course of this period. This assessment provides a basis and guidance for determining the anti-corrosion measures that should be adopted in the next period.

The main contents of corrosion inspection: Pay attention to collecting relevant data. The data that should be collected includes the plant process flow diagram, operating procedures for the plant, detailed lists and individual drawings of equipment and pipelines, the plant’s major maintenance plan, inspection plans for pressure vessels and pressure pipelines, historical thickness measurement records, historical maintenance and inspection records, and historical laboratory test records (including data on crude oil evaluation, analysis data, data on electrodialysis results, and data on triple-top condensate analysis, etc.). To develop a corrosion inspection plan, it is necessary to take into account the actual conditions of the facility, such as the process flow, process parameters, equipment characteristics, and results of risk assessments. Based on this information, it is possible to identify the corrosive agents acting on different parts of the facility, the mechanisms of corrosion, the ways in which these mechanisms can lead to failures, as well as the appropriate testing methods. This allows for the determination of the key areas that need to be inspected, thereby enabling the formulation of an effective corrosion inspection plan. On-site corrosion inspection shall be carried out in accordance with the corrosion inspection plan, to analyze the corrosion status and mechanisms of the equipment and facilities, prepare a report containing recommendations for corrosion protection, and compile a detailed on-site corrosion inspection report. Comprehensive report on the situation

Comprehensive report: The content of the report should include an introduction to the facility, an analysis of corrosion conditions over the years, as well as information on the operation of the facility during the previous cycle along with relevant analyses. It should also cover inspections of equipment that requires major repairs, the details of those repairs, data analysis related to the inspection of pressure vessels and pipelines, data analysis from thickness measurements taken during facility repairs, data analysis from non-destructive testing conducted during repairs, detailed information on corrosion inspections of equipment and pipelines, analysis of typical corrosion cases and their underlying mechanisms, plans for online corrosion monitoring including the locations and types of monitoring points, analysis of plans for thickness measurement at specific locations, analysis of plans for ongoing inspection and testing, details on sampling points and testing procedures, an overall analysis of the facility’s corrosion status, an analysis of the current state of corrosion prevention measures in the process systems along with optimization suggestions, and an analysis of the current state of corrosion prevention measures for equipment along with optimization suggestions. Device safety assessment: Evaluates whether the corrosion rate of the device, under the existing material conditions and process anti-corrosion measures, remains within acceptable limits. Determine the measures that can be taken to reduce the corrosion rate if it exceeds the allowable range. Weak link assessment: Generally, if the actual corrosion rate is greater than 0.25 mm/a (millimeters per year), it indicates that the material grade used in that area is insufficient, and an upgrade of the material is necessary. The areas where the corrosion rate is above the acceptable level and thus have a higher risk of failure are the weak points of the device; it is necessary to develop a plan for material upgrades for the next cycle as soon as possible. Process adaptability assessment: In petrochemical companies, it is common for the properties of raw materials to change, which in turn leads to changes in process conditions. Especially during each major maintenance of the facility, there are always some process modifications. It is necessary to clarify what impacts these modifications will have on the equipment and pipelines, whether any new problems will arise, and what measures need to be taken to prevent them.

I’m very interested in learning how corrosion should be managed. Your sharing has given me some insights. In reality, the best approach is probably regular anti-corrosion treatment. Investigations into other types of corrosion and corresponding countermeasures are relatively rare; perhaps such management practices have been used for individual or specific equipment, but in most cases, the approach taken is to simply replace the damaged parts as they arise

You can take a look at this plan and then manage things in categories; there are many aspects that can be managed more specifically. For example, there’s the management of paint on the outer surface of pipes, the corrosion prevention of stainless steel pipes, the corrosion management of supports, the corrosion that occurs beneath insulation layers, the corrosion on the outer surface of equipment, and the management of test plates attached to equipment

This post was last edited by wc475511 on 2022-9-15 at 15:08. Contact me at 13839970606 if you have waste catalysts that need to be disposed of