Case Study of Full-Length Tube Coating and Condenser Life Extension

The two most common condenser tube problems faced by chemists are internal tube fouling and tube failure. Fouling can have a major impact on power station generating efficiency and capacity, and tube leaks can seriously impact unit availability and reliability. Fundamental understanding of the root cause(s) of these issues, and their mitigation, is essential to resolving these problems and/or preventing their occurrence.

In early 2005, the 4-unit, 1200 MW Cottonwood Energy facility on the Sabine River in Deweyville, TX experienced a sudden increase in condenser tube failures and eddy current pit indications. Metallurgical analysis of failed tube specimens revealed the presence of a thin, hard manganese-rich coating, with intense pits propagating at breaks in the deposit. Successful mitigation of manganese-induced pitting and repassivation of the condenser tubes requires that the surface and pits first be thoroughly cleaned prior to implementing a manganese deposit control program. This paper reviews the successful cleaning process developed and implemented by Cottonwood Energy to remove manganese deposits from four stainless steel surface condensers. The cleaning procedure employed several novel features to ensure complete manganese removal, minimize environmental impact, reduce costs, control attack on the base tube metal, and ensure personnel safety. The paper also includes a discussion of corrective actions taken to prevent re-occurrence.

Integrity monitoring and flaw diagnostics of flat beams and tubular structures was investigated in this research task using guided acoustic signals. A piezo-sensor suite was deployed to activate and collect Lamb wave signals that propagate along metallic specimens. The dispersion curves of Lamb waves along plate and tubular structures are generated through numerical analysis. Several advanced techniques were explored to extract representative features from acoustic time series. Among them, the Hilbert-Huang transform (HHT) is a recently developed technique for the analysis of non-linear and transient signals. A moving window method was introduced to generate the local peak characters from acoustic time series, and a zooming window technique was developed to localize the structural flaws. The time-frequency analysis and pattern recognition techniques were combined for classifying structural defects in brass tubes. Several types of flaws in brass tubes were tested, both in the air and in water. The techniques also proved to be effective under background/process noise. A detailed theoretical analysis of Lamb wave propagation was performed and simulations were carried out using the finite element software system ABAQUS. This analytical study confirmed the behavior of the acoustic signals acquired from the experimental studies. The report presents the background the analysis of acoustic signals acquired from piezo-electric transducers for structural defect monitoring. A comparison of the use of time-frequency techniques, including the Hilbert-Huang transform, is presented. The report presents the theoretical study of Lamb wave propagation in flat beams and tubular structures, and the need for mode separation in order to effectively perform defect diagnosis. The results of an extensive experimental study of detection, location, and isolation of structural defects in flat aluminum beams and brass tubes are presented. The results of this research show the feasibility of on-line monitoring of small structural flaws by the use of transient and nonlinear acoustic signal analysis, and its implementation by the proper design of a piezo-electric transducer suite.

Life extension of ageing assets is becoming increasingly important for the offshore oil and gas industry. Many pressure vessels in service have reached or are about to reach the end of their design lives, but their continued operation is required until the economic field life is exhausted. Many vessels in-service were designed over 30 years ago, when fatigue assessment was not required by the design standards. Therefore, fatigue reassessment is a critical part of the life extension process. This paper presents reassessment of a benchmark vessel as a case study for life extension of other similar vessels. Life extension assessments are costly and time consuming, often hindered by a lack of information and a lack of access to the vessels. By determining the commonality between a vessel and the benchmark vessel, it may be possible with suitable on-going in-service inspection to justify life extension of the vessel without the need for a full fatigue life extension reassessment in every case. The case study considered in this paper is a condensate flash separator vessel constructed in the early 70s which was in operation for 25 years; and is similar to many pressure vessels still in service on offshore platforms. The fatigue lives of key features of the vessel have been calculated and compared using different modern pressure vessel design codes, supported by finite element analysis.

seriously fouled condenser of the Sakai-Port Power Station which started in 1965 has been renovated by in-situ artificial protective film (APF) coating of the condenser tubes. The condenser of the No.2 unit with a capacity of 250 MW has two-water boxes called A and condensers installed with aluminum -brass tube. The gradual decrease in heat transfer performance of the condenser tubes has been revealed by inspections of removed tubes. Based on measurements carried out in October 1983 for evaluating in-situ APF coating, in march 1984 in-situ APF coating was applied to only condenser being more heavily fouled than B condenser. The comparative measurement conducted in October 1984 proved that the condenser vacuum was improved by about 0.6 kPa. The removed APF coated tubes presented sound coated surfaces, except for some tiny blisters at both ends, and no indication of corrosion after six months duration. In-situ APF coating is concluded as being a good countermeasure against corrosion and fouling.

Controlled additions of chromium to Cu-Ni-Fe base alloys have been shown to enhance tenacity of protective oxide films and provide increased velocity tolerance in flowing sea water systems. An optimized 85 Cu-15 Ni-0.8 Fe-0.5 Cr composition has been developed as alloy C72200. Extensive laboratory and field corrosion studies have been conducted to characterize corrosion behavior with particular emphasis on conditions relating to condenser tubing in sea water service. Results quantify a significant increase in impingement and erosion-corrosion resistance at tube inlets and downstream blockages, major causes of premature corrosion failures of copper alloys subjected to strenuous operating conditions. Although 2-3% Cr additions can effect significant hardening in copper-nickel alloys, the 0.5% addition in C72200 does not affect base metal mechanical properties. Similarly, there are no adverse effects in the important properties of thermal conductivity, fouling resistance, fabricability, tube sheet galvanic compatibility or condensate corrosion resistance.

For the better part of the past 15 years composite materials have been used to repair corrosion in high pressure gas and liquid transmission pipelines. This method of repair is widely accepted throughout the pipeline industry because of the extensive evaluation efforts performed by composite repair manufacturers, operators, and research organizations. Pipeline damage comes in different forms, one of which involves dents that include plain dents, dents in girth welds and dents in seam welds. An extensive study has been performed over the past several years involving multiple composite manufacturers who installed their repair systems on the above mentioned dent types. The primary focus of the current study was to evaluate the level of reinforcement provided by composite materials in repairing dented pipelines. The test samples were pressure cycled to failure to determine the level of life extension provided by the composite materials relative to a set of unrepaired test samples. Several of the repaired dents in the study did not fail even after 250,000 pressure cycles were applied at a range of 72% SMYS. The results of this study clearly demonstrate the significant potential that composite repair systems have, when properly designed and installed, to restore the integrity of damaged pipelines to ensure long-term service.

Shelf life extension of wheat bread by alhydwan flour and Carboxymethylcellulose and improvement of their quality characteristics, dough rheological and microstructure

This article reviews the status and scope of ultraviolet (UV) light technology in food processing industry for control of foodborne pathogens and spoilage organisms for food safety and shelf life extension. The literature suggests that there have been extensive studies on application of ultraviolet light for disinfection of apple ciders. FDA acceptable reduction of pathogens and spoilage organisms were reported by UV treatment of for apple cider. Several recent studies on UV treatment of milk suggest that there is more work needed to improve design of UV reactors for raw milk processing. Fresh produce industry will also benefit from UV processing so that occurrence of frequent outbreaks can be avoided. A brief review of recent applications in produce industry has also been reported. Finally a recommendation was made for future direction of UV application research in food processing industry.

High fatigue reliability is one of the most important design criteria for welded offshore steel structures. Due to repeated wave loading fatigue cracks may initiate and grow in welded joints that are important for the integrity of these structures. The present paper presents the methodology and the practical calculations for risk based inspection planning for fatigue cracks in welded details. Due to the uncertainty in the variables involved in the problem the planning has to be carried out by stochastic modeling and risk based assessments. Scatter in potential crack growth has to be analyzed by applied probabilistic facture mechanics and the uncertainty in the performance of the actual inspection technique has to be determined. With given risk acceptance criteria the practical outcome of the analyses is recommended inspection techniques and associated planned inspection time intervals. The classical theory is outlined and the latest recommendations from a Joint Industry Project recently completed by Det Norske Veritas in Norway are discussed. Discussion on how to model the fatigue process correctly is emphasized, particularly the role of time to crack initiation versus the subsequent crack propagation phase. Proper modeling of these two phases is crucial to get the potential crack path correct and thus obtain a reliable estimate of the probability of crack detection. For the crack propagation phase the selection of geometry functions is addressed. A practical case study for life extension of an offshore oil loading system is finally presented. A structural significant item in the system is the steel gooseneck connection for the sub-sea flexible loading hoses. The case is an interesting one in the way that two similar systems were analyzed independently, one analysis based on the tradition S-N approach and one where the decisions were reliability based by applying the Risk Based Inspection approach.

Dynamic analyses of steel catenary risers (SCRs) suspended from a floating platform usually show that the vicinity of the zone where the riser touches down on the seabed is important to fatigue assessments, and can be critical in realizing an economical SCR design or in assessing SCR design life extension. The motivations of the paper are to advance the understanding of the complex mechanism of SCR-soil interactions in a comprehensive yet efficient way, to supplement the extensive model test-based SCR-soil interaction studies in the literature, and to offer a numerical tool to predict the SCR-soil interaction in different clay types. The objective is to investigate the fundamental mechanism of SCR-soil interactions using advanced finite element (FE) analyses. The FE analysis is conducted in Abaqus using the coupled Euler-Lagrangian (CEL) technique to capture the local large deformation surrounding a riser. A strain-softening soil model for deepwater soft clays subject to cyclic degradation is developed based on cyclic direct simple shear (DSS) tests to avoid cycle-by-cycle simulations. The stress-displacement relations are proposed in the FE analysis to avoid the size effect associated with strain-softening soils. The FE analysis results are compared to the test data from the independently conducted model tests and the established results from the literature. Good agreements among different studies are observed.

Journal of the American Society for Naval EngineersVolume 26, Issue 2 p. 595-602 THE FAILURE OF CONDENSER TUBES* Sir Henry J. Oram K.C.B., F.R.S., &c., Sir Henry J. Oram K.C.B., F.R.S., &c. Engineer-in-Chief of the FleetSearch for more papers by this author Sir Henry J. Oram K.C.B., F.R.S., &c., Sir Henry J. Oram K.C.B., F.R.S., &c. Engineer-in-Chief of the FleetSearch for more papers by this author First published: May 1914 https://doi.org/10.1111/j.1559-3584.1914.tb01141.x * Institute of Metals, Presidential Address. Slightly condensed. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume26, Issue2May 1914Pages 595-602 RelatedInformation

Glass Reinforced Epoxy (GRE) pipes have been extensively used by Petroleum Development Oman (PDO) in pipeline application mainly for oil and water transportation. Though there is no corrosion threat on the GRE pipelines, the integrity of GRE lines may be affected by a number of in-service degradation mechanisms including physical and chemical aging. GRE pipes are designed using the regression curve as per ISO14692-Part 2. The design life of the GRE pipes is based on the log (stress) / log (time) curve established by the manufacturer. This curve is established on the basis of regression testing of 1000 hours test in accordance with ASTM D2992. Based on the established regression curve, the design life of the GRE pipes are up to 20 years. The same regression curve was used in establishing the required test pressure for the life extension study of this pipeline. Approaching end of design life it was a challenge for a company using a huge number of GRE pipelines since 2000. The study is to summarize the life extension journey of several GRE pipelines with different design data/manufacturers/joint type,…..etc. The study also summarize the challenges of getting GRE samples/de-oiling and operation side challenges.

Root Cause Investigation of Leakage in Condenser Tubes of Admiralty Brass

Several radiators used for locomotive engines, manufactured from a 65/35 copper/zinc yellow brass tube, were found to have leaking problems shortly after manufacture. The radiators were found to experience widespread leaks at varying locations during pressure testing conducted before use in service. A large population of radiators produced during the same production cycle (approximately 80%) experienced leaks. The radiators were returned to the manufacturer as defective. In the months following the discovery of the leaks, a dispute regarding the cause of the leaks arose between the supplier of the yellow brass tube and the manufacturer of the radiator.