In-service Deterioration Research Articles

تحديد العمر المتبقي لأوعية الضغط الأسطوانية باستخدام تقنية الفحص بالموجات فوق الصوتية: دراسة حالة

Pressurized pressure vessels utilized in the upstream sector of the oil and gas industry commonly experience in-service deterioration caused by factors such as corrosion and process-related issues. Most current research has emphasized the significance of calculating remaining lifetime (RLT) but with a little concentration on the Ultrasonic test (UT) for remaining life assessment. In this work, a case study of the pressure vessel unit (20-v-200) belonging to Basra Oil Company (BOC) at Hammar Mishrif Degassing Station (HM-DGS) is conducted. A nondestructive test (NDT) by UT technique was employed over the suspected area of the pressure vessel. Where it was identified the condition monitoring locations (CMLs) around the shell and heads of the pressure vessel, were marked twenty-one locations to obtain their wall thickness measurement. The results of the remaining lifetime showed that for shell and head were computed as 52.9 years and 56.8 years, respectively. Therefore, based on the present result, it can be deduced that the pressure vessel can remain in operation or continue to be in service for the next 52.9 years under the same process conditions. This assessment considers the existing condition of the vessel and indicates that it can meet the required safety and operational standards for an extended duration. However, as an experienced entrepreneur, I would advise that thickness measurement inspections should be conducted within a timeframe that does not exceed either half of the remaining life of the vessel or a maximum of 10 years, according to API 510. This recommendation ensures that regular assessments are performed to monitor the thickness and condition of the vessel. By adhering to this practice, timely maintenance and necessary repairs can be identified and carried out, contributing to the continued integrity and safety of the vessel throughout its operational lifespan.

Heat Transfer Analysis of Damaged Shrouded High-Pressure Turbine Rotor Blades

Due to the increasingly high turbine inlet temperatures, heat transfer analysis is now, more than ever, a vital part of the design and optimization of high-pressure turbine rotor blades of a modern jet engine. The present study aimed to find out how shape deviation and in-service deterioration affect heat exchange patterns on the rotor blade. The rotor geometries used for this analysis are represented by a set of high-resolution 3D structured light scans of blades with the same number of in-service hours. An automatic meshing technique was employed to generate high-resolution meshes directly on the scanned rotor geometries, which captured all the surface features with high fidelity. Steady-state 3D RANS flow simulations with a k-ω SST turbulence model were conducted on a one-and-a-half stage computational domain of the scanned geometries. First, the distribution of the heat transfer coefficient was calculated for each blade; then, a correlation was sought between the heat transfer coefficient and parametrized shape deviation, to assess the impact of each parameter on HTC levels.

Experimental Study of Impact of In-Service Deterioration on Aerodynamic Performance of High-Pressure Nozzle Guide Vanes

AbstractIn this paper we experimentally evaluate the impact of in-service deterioration on the aerodynamic performance of heavily film-cooled high-pressure nozzle guide vanes from large civil jet engines. We study 15 mid-life to end-of-life parts removed from operational engines, and compare their performance to those of new parts. Deterioration features included: increased surface roughness; thermal barrier coating spallation; damaged film cooling holes; and trailing edge burn-back. We characterize and present statistics for the surface roughness. Aerodynamic measurements were performed in the high technology readiness level Engine Component AeroThermal (ECAT) facility at the University of Oxford, at engine-representative conditions of exit Mach number, exit Reynolds number, coolant-to-mainstream pressure ratio, and turbulence intensity. We present detailed experimental measurements of the coolant capacity characteristics, downstream loss, and downstream flow structures. The results show that service time has the following effects on high-pressure nozzle guide vanes: increased equivalent sandgrain roughness of (up by 1056% change); reduced coolant flow capacity (maximum change of −6.27% for film cooling holes and −24.7% for the trailing edge slot); increased overall mixed-out kinetic energy loss coefficient by (up to 33% change); leads to greater downstream flow angle variation (change of −6 deg). This is one of the first significant studies of its type in the open literature, and is an important step towards whole-life engine performance assessment.

Experimental Study of Impact of In-Service Deterioration on Thermal Performance of High-Pressure Nozzle Guide Vanes

Abstract In this paper, we analyze the impact of in-service deterioration on the overall thermal performance (metal effectiveness) of heavily cooled high-pressure nozzle guide vanes of a design typical of large civil jet engines. We study 15 deteriorated parts (increased surface roughness, thermal barrier coating spallation and sintering, damaged film cooling holes, and trailing edge burn-back) from operational engines and compare their thermal performance to that of equivalent new parts. A companion paper focuses on the aerodynamic impact of in-service deterioration. Overall cooling effectiveness measurements were performed in the Engine Component AeroThermal (ECAT) Facility at the University of Oxford, at engine-representative conditions of Mach number, Reynolds number, coolant-to-mainstream pressure ratio, and turbulence intensity. We characterize the degradation of overall cooling effectiveness with service time. This is an important result for whole-life modeling. Changes in overall cooling effectiveness were greatest on the pressure surface and early suction surface of the parts. Area-averaged differences in overall cooling effectiveness of −1.83% and −10.41% were measured on the pressure surfaces of mid-life and end-of-life vanes, respectively. In the analysis, we attempt to decouple the contributions from independent deterioration effects and compare the philosophy of this top-down approach to the bottom-up approach in which effects are studied in isolation and then superposed in modeling.

Research into in-service deterioration of ball-rolling rolls

This work features research findings on causes of deterioration occurring in ball-rolling rolls. The causes of such deterioration may originate not only in the excessive loads application and the use of bottleneck operating parameters but also in the specific process being implemented and the equipment used to heat-treat the rolling rolls. The deterioration occurring in roll flanges having a relatively small thickness was used to demonstrate that, to prevent the deterioration of ball-rolling roll flanges, the mill design must accommodate the minimum allowable flange widths obtained as a function of maximum allowable loads and the roll pass calculations. The next example of roll deterioration involved the use of a gas furnace to implement the heating stage of the quench hardening process for rolls made of 35KhGSA steel, which, as a result, developed roll deterioration. The use of rolls of the same steel grade, which were heat-treated in an arc furnace prior to being quenched, has been shown to deliver long-lasting positive results evidenced by many years of their operation. Rolls made of 5KhNM steel have also been shown to respond well to the heat treatment preceding the quenching process, but this time, the treatment was implemented in a gas furnace.

Variability of in-situ testing in wall coating systems - Karsten tube and moisture meter techniques

To meet customers' demand and adequate levels of satisfaction, there are various reasons for the need of proactive maintenance and knowledge about in-service performance of building façades. From this perspective, performing inspections depends on the in-service appraisal's reliability and the presence of monitored and measured parameters along the life cycle under real exposure conditions. Water, the major in-service deterioration agent, has different origins and transport mechanisms through façades, including wind-driven rain, ground moisture, and wetting/drying of surfaces, resulting in various chemical and/or physical-pathological phenomena. Thus, water resistance is considered highly relevant due to its significant influence on the durability of coating systems. This study presents results of an investigation concerning the water resistance of in-service wall coating systems, focusing on conventional and industrial renders and adapting appropriate techniques for field analyses, namely Karsten tube and moisture meter. In-service parameters (water absorption under low pressure and surface moisture) are assessed, and the techniques' sensitivity is analysed considering exposure and inspection conditions, roughness, coating and finishing types, and existing anomalies. The capacity of these techniques to monitor in-service performance is also discussed, and in-service performance criteria are proposed.

QUANTITATIVE ANALYSIS OF ASBESTOS FIBRES IN OPHIOLITIC ROCKS USED AS AGGREGATES AND HAZARD RISK ASSESSMENT FOR HUMAN HEALTH

This study focuses on the quantification of asbestiform minerals in basic and ultrabasic rocks from ophiolite suites of central and northern Greece. A combination of different methods were used for the detailed investigation of the samples, conducted in the following stages: (i) petrographic examination of thin sections with a polarizing microscope, (ii) mineral phase analysis using X-ray diffraction, (iii) determination of the fibrous mineral composition on polished thin sections using scanning electron microscopy, (iv) image analysis of back scattered electron images and secondary electron images, to quantify the dangerous asbestiform crystals. SEM is proved to be the most powerful tool for the detailed investigation of fibrous minerals, although polarized microscopy and XRD are necessary tools for a preliminary identification of these minerals. Basic rocks contain various amounts of actinolite, however not all crystals comprise asbestiform fibres. A conspicuous feature observed during careful petrographic analysis is that many of the non as best form actinolite crystals are broken up along their cleavage planes. Rocks with such features need specific consideration since these crystals may subsequently release numerous fibrous cleavage fragments during the production processes and in-service deterioration of aggregates. Among the serpentinized ultrabasic samples, only one contains chrysotile, while the other samples contain antigorite and lizardite.

Areal parametric characterisation of ex-service compressor blade leading edges

In-service the degradation of compressor blade leading edges can have a disproportional effect on compressor efficiency. The high surface curvature in this region makes quantifying the surface finish of this sensitive and prominent region difficult. An automated technique that characterises the roughness of the leading edge in terms of areal parameters is presented. A set of ex-service blades of differing sizes are used to demonstrate the procedure. Improved characterisation of this blade region will allow engine companies to better understand where in-service deterioration has the greatest effect and inform them as to how they might minimise the effect. The present work shows that the leading edges of compressor blades exhibit a significantly higher characteristic surface roughness than other blade regions, and the spatial distribution of peaks in this characteristic roughness is detailed. In addition it is shown that peak wear and roughness are not uniformly correlated.

Discussion of “Effect of Deterioration on the Performance of Corrugated Steel Culverts” by Van Thien Mai, Neil A. Hoult, and Ian D. Moore

The authors have undertaken an interesting laboratory experimental research program to validate the results of numerical analyses studies done previously (El-Taher and Moore 2008; Mai et al. 2012) to evaluate by rational means the stability of buried culverts with varying degrees of deterioration. The overall intent of the rational approach is to identify quantitatively when a culvert structure has deteriorated to such an extent that rehabilitation of the structure is warranted. This approach could result in considerable savings in costly infrastructure repair or replacement if the remaining life of a structure could be evaluated without subjectivity. The vast majority of corrugated steel pipes (CSPs) along a highway system are often composed of circular pipes or culverts of 600–900 mm diameter used in small watercourses that cross the highway alignment and at entrances to residences adjacent to the highway whereas large-diameter structural plate CSPs (SPCSPs) or multiplates, as they are frequently called, are used typically as bridgesized culverts and underpass structures. According to the Ontario Highway Bridge Design Code (Ministry of Transportation Ontario 1992), such structures classified as bridge structures are 3 m or more in diameter, whereas in Alberta, culverts of 1.5 m in diameter or greater are classified as bridge structures. The authors’ experimental results have brought out some interesting findings regarding corrosion and stiffness of the structure and backfill or the lack thereof on the structural performance of the structures. However, one aspect that was not addressed that may be important is the documented history of pipe installation in relation to any defects of the structure noted prior to and during installation. This could be important to the continued use of the structure because it would tend to provide baseline information that can be used to determine reasons why the lack of structural stability had originated or what effect the initial defects have on the structure stability other than or in addition to loss of structure thickness caused by corrosion. It is realized that this would be a significant effort by highway departments. However, with the large sums of money required for large SPSCP structure rehabilitation, the effort would be well worth the time and cost because these records should be available as a matter of quality control and quality assurance for the installation of every structure, rather than relying on the assumption that the installation was undertaken as per specifications regarding backfill density, material characteristics, and so forth. Very often, CSPs and SPSCPs are damaged during the installation process, for example, by backfill material placed over the crown containing rockfill and lack of care for the structure by equipment during the installation process. In such cases, the culvert is often deemed acceptable from visual observation because the damage may be considered not to affect the hydraulic capacity much, and, being a new structure, the structural integrity aspect is not considered inadequate. For significant multiplate structures, instrumenting these structures to evaluate the in-service structural behavior with time would also be of valued importance and could be somewhat similar to the approach being used to evaluate existing piled foundations for reuse. This aspect would also be important to understanding which type of installation damage would warrant that an installation be rejected and the installation redone with new materials. This aspect is often a contentious issue between the client and contractor, with the contractor often arguing that the integrity of the culvert is not compromised whether constructed with multiplates or SPCSP. For SPCSP structures, other modes of distress such as bolt shearing, for example, resulting from ground settlement that results in distortion of the crown and invert can eventually lead to collapse of the structure. The need for a rational approach to assessment is, therefore, very relevant. The findings of this research program would tend to indicate that installation damage may have a penalty on the performance of such a structure with time because the distortion of the crown could cause deflection around the circumference of the culvert, as shown in Figs. 4 and 5 of the authors’ paper. With in-service deterioration of the plate thickness attributable to corrosion and abrasion, this would further decrease the integrity of the structure. Overall, the authors’ paper has provided very pertinent information in assessing the stability of culvert structures to determine when repair and/or replacement is required, but it also has merits in quality control and quality-assessment evaluations during installation of these structures. Procedures for use of the rational approach separately or together with the visual-inspection approach would be of benefit to practitioners. It also would have been of interest if the authors had presented in the figures the results of the numerical analyses for comparison with those obtained from the experimental program.

The Impact of Geometric Variation on Compressor Two-Dimensional Incidence Range

An important question for a designer is how, in the design process, to deal with the small geometric variations which result from either the manufacture process or in-service deterioration. For some blade designs geometric variations will have little or no effect on the performance of a row of blades, while in others their effects can be significant. This paper shows that blade designs which are most sensitive are those which are susceptible to a distinct switch in the fluid mechanisms responsible for limiting blade performance. To demonstrate this principle, the sensitivity of compressor 2D incidence range to manufacture variations is considered. Only one switch in mechanisms was observed, the onset of flow separation at the leading edge. This switch is only sensitive to geometric variations around the leading edge, 0–3% of the suction surface. The consequence for these manufacture variations was a 10% reduction in the blade's positive incidence range. For this switch, the boundary in the design space is best defined in terms of the blade pressure distribution. Blade designs where the acceleration exceeds a critical value just downstream of the leading edge are shown to be robust to geometric variation. Two historic designs, supercritical blades and blades with sharp leading edges, though superior in design intent, are shown to sit outside this robust region and thus, in practice, perform worse. The improved understanding of the robust, region of the design space is then used to design a blade capable of a robust, 5% increase in operating incidence range.

Implications of High-Pressure Turbine’s Erosion for a Military Turbofan’s Fuel Consumption

Some in-service deterioration in any mechanical device, such as an aeroengine, is inevitable. As a result of experiencing deterioration (of the engine as a whole or any of its components individually), an engine will seek a different steady operating point, thereby resulting in a variation of the specific fuel consumption and/or fuel flow to provide the same thrust to keep the aircraft’s performance invariant. Any rise in specific fuel consumption and/or fuel flow and thereby the increased quantity of fuel required is of prime importance in military aviation. For a military aircraft’s mission profile, using computer simulations, the implications of high-pressure turbine’s erosion of a turbofan aeroengine upon the weight of the fuel that has to be carried and consumed are predicted. This will help in making wiser management decisions, such as whether to remove an aeroengine from the aircraft for maintenance or to continue using it with some changes in the aircraft’s mission profile). Hence, improved engine utilization can be achieved, resulting in lesser overall life-cycle costs.

A polymer solution to in-service deterioration of heat exchangers

A polymer solution to in-service deterioration of heat exchangers

Implications of Turbine Erosion for an Aero-Engine’s High-Pressure-Turbine Blade’s Low-Cycle-Fatigue Life-Consumption

Abstract Some in-service deterioration in any mechanical device, such as a military aero-engine, is inevitable. As a result of experiencing any deterioration, an aero-engine will seek a different steady operating point thereby resulting in a variation in the high-pressure spool speeds in order to provide the same thrust to keep aircraft’s performance invariant. Any increase in the high-pressure spool speed results in greater low-cycle fatigue damage for the hot-end components and thereby higher engine’s life-cycle costs. Possessing better knowledge (of the impacts of high-pressure turbine’s erosion upon the low-cycle fatigue life-consumption of aero-engine’s hot-end components) helps the users to take wiser management decisions. For a military aircraft’s mission profile, using bespoke computer simulations, the impacts of turbine erosion for high-pressure turbine-blade’s low-cycle fatigue life-consumption have been predicted.

Implications of day temperature variation for an aero-engine's HP turbine-blade's creep life-consumption

Abstract Some in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. Also in a country like Pakistan, there is a significant variation of day temperature over the year. As a result of experiencing deterioration (of the engine as a whole or any of its components individually) and/or any alteration in the conditions (such as day temperature) of incoming air stream, an engine will seek a different steady operating point thereby resulting in a variation of the spool speeds and/or turbine-entry temperatures in order to provide the same thrust. Rises in the turbine entry-temperatures and spool speeds result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine's life cycle costs. Possessing a better knowledge of the impacts of day temperature variation upon the creep life-consumption of aero-engine's hot-end components, helps the users to take wiser management-decisions. For a military aircraft's mission-profile, using a bespoke computer simulation, the implications of day temperature variation for a turbofan aero-engine's high pressure turbine-blade's creep life-consumption have been predicted.

Impacts of low-pressure (LP) compressor’s deterioration of a turbofan engine upon fuel-usage of a military aircraft

AbstractSome in-service deterioration in any mechanical device, such as an aircraft’s gas-turbine engine, is inevitable. However, its extent and rate depend upon the qualities of design and manufacture, as well as on the maintenance/repair practices followed by the users. Deterioration of an engine normally results in the engine seeking a different steady operating-point relative to that for an engine without any deterioration. The variation in engine’s steady operating point leads to changes in the specific fuel consumption (SFC) and/or fuel flow (FF). Any rise in SFC and/or FF and thereby the increased quantity of fuel required is of prime importance in military aviation.For a military aircraft’s mission-profiles (consisting of several flight-segments), using a bespoke computer simulations, the consequences of low-pressure compressor’s deterioration of an aeroengine upon the weight of the fuel that has to be carried and consumed are predicted. This will help in making wiser management decisions (such as whether to remove an aero-engine from the aircraft for maintenance or to continue using it with some changes in aircraft’s mission profile). Hence improved engine utilization can be achieved, so resulting in lower overall life-cycle costs.

Impacts of low-pressure (LP) compressors’ fouling of a turbofan upon operational-effectiveness of a military aircraft

Some in-service deterioration in any mechanical device, such as an aircraft’s gas-turbine engine, is inevitable. However, its extent and rate depend upon the qualities of design and manufacture, as well as on the maintenance/repair practices followed by the users. As a result of experiencing deterioration (of the engine as a whole or any of its components individually), an engine will seek a different steady operating point relative to that for an engine with no deterioration. This results in changes in the available thrust from the engine(s) at the same TETs and/or rotational-speeds. Any reduction in the available thrust at specified engine settings, especially maximum available thrust from the engines, will have a significant adverse effect upon the aircraft’s operational-performance. These adverse effects can be reduced by having a better knowledge of the effects of each such deterioration on the aircraft’s operational-performance. Subsequently improvements can be made in the design and manufacture of adversely-affected components as well as in maintenance and repair practices. For a military aircraft’s mission-profile (consisting of several flight-segments), using a bespoke computer simulation, the consequences of low-pressure compressors’ fouling of a turbofan upon the aircraft’s mission operational-effectiveness have been predicted. This will help in making wiser management decisions, such as whether to remove the aero-engines from the aircraft for maintenance or to continue using them with some changes in the aircraft’s mission-profile, or planning different take-off times and/or carrying different fuel/weapon loads for aircraft with the various extents of low-pressure compressors’ fouling. Hence improved engine utilization and the optimal mission operational-effectiveness for a squadron of aircraft can be achieved.

Durability testing of basic crystalline rocks and specification for use as road base aggregate

One of the most important materials for the construction of high quality pavement layers in roads in South Africa is the Basic Crystalline group of rocks. The major deposits of these materials are associated with the dolerites and basaltic lavas of the Karoo Supergroup. Problems related to the in-service deterioration of road aggregates produced from the crushing of these materials, despite their conforming to the necessary specifications, have been experienced in southern Africa for many years. This has usually resulted in the use of more expensive materials being transported further to the road project. Twelve such materials were collected from various parts of southern Africa and tested for their durability using the standard specified tests as well as a range of non-standard and new tests. Based on the results, new test methods and tentative specification limits have been proposed for assessing and predicting the durability of basic crystalline materials obtained by crushing unweathered material sources.

Impacts of low-pressure (LP) compressor’s deterioration upon an aero-engine’s high-pressure (HP) turbine blade’s life consumption

AbstractSome in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. As a result of experiencing a deterioration of efficiency and/or mass flow, an aero-engine will automatically adjust to a different set of operating characteristics; thereby frequently resulting in changes of rpm and/or turbine entry temperature in order to provide the same thrust. Rises in the turbine entry-temperatures and the high-pressure turbine’s rotational speed result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine’s life cycle costs. Possessing a better knowledge of the effects of engine deterioration upon the aircraft’s performance, as well as fuel and life usages, helps the users to take wiser management decisions and hence achieve improved engine utilisation. For a military aircraft, using a computer performance simulation, the consequences of low-pressure (LP) compressor’s deterioration upon an aero-engine high-pressure (HP) turbine blade’s life-consumption have been predicted.

06/00805 Lignite-water interactions studied by phase transition-differential scanning calorimetry: Fei, Y. et al. Fuel, 2005, 84, (12–13), 1557-1562.

Some in-service deterioration in any mechanical device, such as an aircraft’s gas-turbine engine, is inevitable. However, its extent and rate depend upon the qualities of design and manufacture, as well as on the maintenance/repair practices followed by the users. As a result of experiencing deterioration (of the engine as a whole or any of its components individually), an engine will seek a different steady operating point relative to that for an engine with no deterioration. This results in changes in the available thrust from the engine(s) at the same TETs and/or rotational-speeds. Any reduction in the available thrust at specified engine settings, especially maximum available thrust from the engines, will have a significant adverse effect upon the aircraft’s operational-performance. These adverse effects can be reduced by having a better knowledge of the effects of each such deterioration on the aircraft’s operational-performance. Subsequently improvements can be made in the design and manufacture of adversely-affected components as well as in maintenance and repair practices.For a military aircraft’s mission-profile (consisting of several flight-segments), using a bespoke computer simulation, the consequences of low-pressure compressors’ fouling of a turbofan upon the aircraft’s mission operational-effectiveness have been predicted. This will help in making wiser management decisions, such as whether to remove the aero-engines from the aircraft for maintenance or to continue using them with some changes in the aircraft’s mission-profile, or planning different take-off times and/or carrying different fuel/weapon loads for aircraft with the various extents of low-pressure compressors’ fouling. Hence improved engine utilization and the optimal mission operational-effectiveness for a squadron of aircraft can be achieved.

In-service deterioration of compressed earth blocks

With the increasing backlog of shelter in most of the third world, attempts are being made to evolve low-cost but durable walling units. The introduction of compressed earth blocks (CEBs) some 50 years ago was seen as a major milestone. These blocks are made by compressing a damp mix of soil (90–95%), and cement (5–10%) to form strong and dense blocks used for walling. While considerable knowledge is available regarding their initial performance characteristics, little research has so far been conducted on their long-term durability and deterioration due to prolonged exposure to environmental factors. It is now widely recognised that rapid and premature deterioration does take place when the material is used in unrendered walling in most humid tropical environments. Premature defects such as roughening, pitting, erosion, volume reduction, cracking as well as crazing, etc., have all been witnessed within periods ranging from 1 month to 5 years after completion of construction. This paper reports on recent research conducted in Uganda where in-service defects such as pitting and cracking where measured directly from existing exposed walling to quantify their nature and extent. It can be concluded that the greatest deterioration was found to occur on east–west facing facades, and on the lower wall sections. The deterioration was also found to correspond to the age of the structure.