Comprehensive investigation of the corrosion state of the heat exchanger tubes of steam generators. Part I. General corrosion state and morphology (original) (raw)
Related papers
Corrosion Science, 2009
At some VVER-type pressurized water nuclear reactors (Russian-type PWR) different versions of the so-called AP-CITROX method have been widely used for the chemical decontamination of the heat exchanger tubes of steam generators. In the period of 2000–2007, within the frame of a joint-project dealing with the comprehensive investigation of the corrosion state of the steam generators of the Paks Nuclear Power Plant, Hungary, effects of the AP-CITROX chemical decontamination procedure on the corrosion and surface characteristics of the heat exchanger tubes have been studied. These studies provide evidences that some adverse features (formation of a “hybrid” layer with accelerated corrosion rate and great mobility) can be detected after 1–3years of applying the AP-CITROX procedure. The present work is a continuation of the above program and focused on the long-term trends in the corrosion state and structure of protective oxide-layer grown on the decontaminated surfaces. The results of electrochemical (voltammetric), surface analytical (SEM–EDX, CEMS) and mobility (ICP–OES) studies have revealed that (1) some beneficial changes in the corrosion characteristics, mobility and chemical composition of the inner surfaces of decontaminated heat exchanger tubes can be observed in the long run, and (2) the passivity of the oxide-layers formed on decontaminated surfaces of steel tubes exhibits favorable tendency after 4–7years under normal operation conditions.
2004
Steam generators (SGs) are crucial components of pressurized water reactors. The failure of the steam generator as a result of tube degradation by corrosion has been a major cause of Pressurized Water Reactor (PWR) plant unavailability. Steam generator problems have caused major economic losses in terms of lost electricity production through forced unit outages and, in cases of extreme damage, as additional direct cost for large-scale repair or replacement of steam generators. Steam generator tubes are susceptible to failure by a variety of mechanisms, the vast majority of which are related a corrosion. The feedwater that enters into the steam generators under normal operating conditions is extremely pure, but nevertheless contains low levels (generally in the μg/l concentration range) of impurities such as iron, chloride, sulphate, silicate, etc. When water is converted to steam and exits the steam generator, the non-volatile impurities are left behind. As a result, their concentra...
Bio-corrosion Phenomenon of Titanium Grade 2 Tubes in Condenser of a Steam Power Plant
Devotion Journal of Community Service
Titanium is widely applied for the tube condenser in Indonesia’s powerplant especially those that use seawater for the cooling system, because it has excellent properties both mechanical and physical. Leak in titanium in seawater environment occurred, but on the contrary, the leak of titanium tube in the brackish environment frequently occurs. Many defense tasks such as plugging, cleaning, and adjusting operations have taken, but the result remains the same. Until it was decided to perform an overhaul for the condenser and tube mapping using ECT. It was discovered that 80% of the total tube have been wall lost thickness so that total retubing must be conducted. Chemical elements consist of oxygen (O), sulfur (S), and chlor (Cl) were found during DT and NDT. This study aims to analyze the factors causing this severe titanium tube leak in the condenser. This case is like previous research even though it occurred in different equipment and water feed. Sulfur elements came from the excr...
A Case Study: Pitting Corrosion of 316L Stainless Steel Tubes Used in Heat Exchangers
corrosion of 316L stainless steel tubes in heat exchanger, 2023
Heat exchangers are one of the urgent and vital needs of the petrochemical industry, which perform the heat exchange between one fluid and another. Shell and Tube Heat Exchanger are used in process industries in a large number, much more than any other type of exchanger. More than 90% of the heat exchangers used in the industry are shell and tube type. In this research, the cause of corrosion in the pipes of one of the heat exchangers in Mahshahr Fanavaran Petrochemical was investigated. According to the conducted studies, it was found that the percentage of chlorine in the cooling system and improper alloy design in the construction of these types of pipes were the biggest causes of their corrosion.
Thermal-Power-Plant Condenser-Tube Corrosion Analysis
Materiali in tehnologije
The thermal-power-plant condenser tubes, conducting cooling seawater, experienced frequent leakages, prompting the hereby presented failure analysis. Visual inspection of the corroded/ruptured tube segments revealed that localized corrosion may be linked to seawater sediments and thick layers of corrosion products at the tube water side. Sediments were found along the tube bottom and thick corrosion products were found adjacent to the point of contact between the baffle plates and the exterior tube walls. Underdeposit corrosion, accelerated due to sulphate-reducing bacteria, was diagnosed based on the excess sulphur found at the pit bottom using EDX, the FT-IR spectrum indicating the presence of biofilm and SEM determining the featuring corrosion products based on the biofilm. It was proposed that the corrosion initiating deposits were linked to the condenser shutdown and startup periods. Results showed that pitting corrosion occurred under the influence of biofilm microorganisms to...
Corrosion and deposition on the secondary circuit of steam generators
Journal of Nuclear Science and Technology, 2016
This study conducts a critical review on the studies of material corrosion and deposition on the secondary circuit of a pressurized water reactor, especially on the steam generators (SGs). Available knowledge has shown that the structural materials in the environment of the secondary circuit are susceptible to flow-accelerated corrosion and deposition-induced degradation. The deposition of the non-volatile impurities, especially the corrosion products, on the SG surfaces can be a primary cause of material degradations, including stress corrosion cracking. The review will analyze the fouling mechanisms and behaviors, the source of impurities, corrosion mechanisms, and the factors that affect the deposition and corrosion behaviors.
Applied Engineering Letters, 2021
The study on the tubes (made of CuZn36 material) of a condenser used in petrochemical industry revealed that thickness reduction by corrosion is the main factor causing the decrease of the equipment service life. The present paper aims to study, from the experimental point of view, the behavior of the heat exchanger tubes, in the presence of different environments. The experimental program conducted in the article included two directions: evaluation of technical condition of in-service brass tubes after a certain period of operation for a condenser used in petrochemical industry in order to see how the working conditions affect the brass tubes and an experimental study based on simulation of exposure to extreme corrosive environments for samples taken from new CuZn36 tubes. The goal is to establish their influence on the tubes degradations by determining the corrosion rate. The analyzed samples were immersed in different corrosive solutions for 21 days. Another sample was boiled in water and cooled in air in order to simulate the working environment of the tubes in the condenser. All the samples were weighted before and after the exposure in the aggressive environment, thus establishing the corrosion rate for each of them. In order to analyze from mechanical point of view the influence of the environment on the brass tubes, the flattening test was made, comparing the behavior of the exposed samples with that of the unexposed sample.