Leaks In Joints Research Articles

Avoiding water hammer and other hydraulic transients

AbstractWater hammer may occur upon rapidly closing a water pipe valve. Oscillating pressure waves generated in the system may cause significant equipment damage, including joint leaks and even pipe rupture. Similar phenomena can occur when starting and stopping pumps. As various situations can cause potentially damaging pressure waves, water hammer and related phenomena are grouped as “hydraulic transients.” The phenomena are not limited to water pipes and may occur in any liquid, including condensed gases such as chlorine, ammonia, and liquefied natural gas (LNG). Hydraulic transients deserve more coverage in college courses and textbooks on process safety, while at an industrial level, the topic should be considered in design and hazard reviews. This article provides a brief introduction to the topic with a focus on mitigation methods. Available options should be evaluated during the design process rather than applied retroactively after a problem becomes evident.

Analysis of Boiler Start-Up Failure Risk with Grey FMEA and RCA Methods in Pt. PLTU Nagan Raya

PT. PLN (Persero) UPK Nagan Raya is a Steam Power Plant (PLTU) that uses coal as Boiler fuel to produce thermal energy. one of the initial stages of the Boiler is Startup as the basis for the start of Boiler operations. The purpose of this study is to analyze and avoid the risks that can make the operating system not run. Based on the research conducted, there are 8 risks that can cause failure. Based on the Grey FMEA method, the priority risk that occurs is that the FO fast shut-off cannot be O / C CCR with a value of 0.491 and also in the flexible joint line of the lower burner air there is a leak of 0.503. The result of the Root Cause Analysis method, the cause of the FO fast shut-off cannot be O / C CCR is the limited facilities and infrastructure for device maintenance which causes obstacles for workers so that the results worked on are not effective and efficient. Meanwhile, the risk that the flexible joint line air lower burner has a leak because it is not critical equipment only used at certain times so the check is neglected which makes the flexible joint leak. The solution that can be done is that as much as possible the operator must carry out routine maintenance/overhaul on the flexible joint so that there is no failure that can hinder the operation.

Precisión diagnóstica de la Ecografía frente a la Resonancia Magnética en la afectación articular hemofílica

Background and objectives: In hemophiliac patients, recurrent intra-articular bleeding leads to progressive arthropathy. Magnetic resonance imaging (MRI) is the gold-standard technique for joint assessment. The development of ultrasound protocols and standardized scales such as “Hemophilia Early Arthropathy Detection with Ultrasound” (HEAD-US) and “Point-of-care Ultrasonography” (POC-US) allow patient monitoring. Our main objective is to establish the diagnostic accuracy of ultrasound in the early detection of hemophilic arthropathy, with MRI as the gold standard. The interobserver variability in the ultrasound and MRI scales, the association between the POC-US and HEAD-US protocol, and the ability of ultrasound to detect haemosiderotic remnants will also be established. Patients and Methods: 45 hemophiliac patients were included. 180 joints (knees and ankles) were evaluated with MRI (Denver scale) and Ultrasound (HEAD-US and POC-US scale). Results: There is a high and statistically significant association between the ultrasound and MRI scales. Only for the ankle effusion variable the association was medium. The specificity of HEAD-US was ≥90% in both joints. Sensitivity in the knee did not exceed 82% in any assessed aspect, being high in the ankle for the cartilage and bone alterations (97%) but low for effusions (55%). In general, the predictive values ​​were high, with the exception of the negative predictive value of joint leak in knee and ankle (close to 70%). Ultrasound did not detect haemosiderotic remnants in any case. Statistically significant interobserver agreement was obtained for HEAD-US and Denver-MRI assessment. The level of association between the HEAD-US scale and the POC-US protocol was medium. Conclusions: Ultrasound is a technique with high diagnostic accuracy and reproducibility to detect and quantify the early signs of hemophilic arthropathy. Ultrasound is insensitive to detect haemosiderin in synovial hypertrophy.

A study on the effect of process parameters on the joint strength and leak tightness in electromagnetically assisted adhesive Cu-SS tube-to-tube joining through statistical analysis

This work studies an improved hybrid joining technique combining electromagnetic forming and adhesive joining to create a leak-tight Cu-SS tube-to-tube joint named as electromagnetically assisted adhesive joining (EAAJ). An experimental investigation is performed considering three discharge energy (3.9 kJ, 4.4 kJ and 5.0 kJ), four adhesive application lengths (20 mm, 15 mm, 10 mm and 5 mm), three adhesives (Loctite 638, Loctite 567, and Loctite SI 596) and four curing times (24 h, 48 h, 96 h and 120 h) ad process parameters. The mechanical properties of the joints are investigated using testing techniques like pull-out, compression, and micro-hardness tests. An increase in joint strength is observed with the decrease in adhesive application length and increase in curing time. Maximum joint strength, 90% of the base copper tube strength, is obtained in the case of Loctite 638, with 5 mm of adhesive application length, 5.0 kJ of discharge energy and 96 h of curing time. Furthermore, a three-way analysis (3-way ANOVA) of variance technique is implemented to calculate the contribution of the three factors (discharge energy, adhesive application length, type of adhesives) on the joint strength. A cohesive and adhesive failure mode combination leading to sliding failure mode is observed as a joint failure mechanism during pull-out and compression testing. A leak testing setup has been developed to investigate the joint's leak tightness by an air pressure decay test. An increment in leak tightness by 1000 times is observed in 638 EAAJ samples compared to samples joined without adhesives. A 3-way ANOVA analysis is also performed to calculate the contribution of different factors on leak tightness of the joint. Micro-hardness is observed to be increased near the joint interface compared to the base metal. Deformation analysis has highlighted the impact of field shaper slit causing a non-uniformity in radial deformation in the circumferential direction and leading to non-uniform circumferential accumulation of adhesive.

Experimental and simulation research on hydrogen leakage of double ferrule joints

Owing to the scope of large-scale use of hydrogen energy in future technology, addressing safety issues like leakage and diffusion in all steps of production, storage, transportation, etc., will become inevitable. This paper focuses on the volume change of the combustible area after double ferrule joint leaks. First, a calibrated computational fluid dynamics (CFD) model was built and calibrated for accuracy through a hydrogen horizontal jet process. Second, the schlieren method was used to observe the hydrogen leakage morphology when the pipe was scratched. The CFD model was used to investigate the morphology and combustible volume changes under different wind directions and speeds. Third, critical wind speed (CWS), representing the disturbance wind speed when the combustible volume generated by the hydrogen jet was reduced to 85% of the non-disturbed environment, was proposed. Fourth, the scratch leakage behavior with the double ferrule joint placed horizontally was simulated. This research found that forced convection in the hydrogen system reduced the combustible volume produced by the hydrogen jet, and the typical value of CWS here was 1.5 m/s.

Leakage detection of low-pressure gas distribution pipeline system based on linear fitting and extreme learning machine

Pipelines are the lifeblood of the natural gas market. Compared with the high-pressure long-distance pipeline system and medium-pressure municipal pipeline system, the leak detection of low-pressure gas distribution pipeline system inside buildings that only relies on the combustible gas alarm is relatively backward and passive. Based on the principle of the negative pressure wave method, we proposed a leak detection method combining linear fitting and extreme learning machine leak detection. We designed and built a low-pressure gas pipeline system, which truly reproduces the gas leakage scenes inside buildings. By establishing multi-dimensional sliding windows, combined with a linear fitting method, the original pressure signal can be initially screened. Small leakage and pipe network fluctuations can be effectively identified by the windows. For medium leakage, large leakage, and gas usage that are easy to be confused, the windows will accurately identify the inflection point of the pressure drop for subsequent processing. Aiming at the characteristics of negative pressure waves, we extracted 15-dimensional feature vectors by dividing different stages. After introducing extreme learning machine for training, the detection accuracy of the final model can reach more than 90 %. Compared with support vector machines and back propagation neural networks, the trained extreme learning machine model has higher accuracy and higher speed. The joint leak detection algorithm based on linear fitting and extreme learning machine can greatly reduce the number of gas leakage accidents of low-pressure gas pipeline system through single point pressure monitoring. We applied the artificial intelligence algorithm and negative pressure wave to the low-pressure pipeline system for the first time, and established a new pressure wave processing method, characteristic model and algorithm model, which has a good engineering application prospect and theoretical significance.

Root cause analysis of the folding deformation for the expansion joint in the nuclear power station

In the nuclear power station, the expansion joint of moisture separator re-heater (MSR for short) was founded locally folding deformation under the outage condition. Folding deformation increasing will lead expansion joint leak, it would cause emergency stop when leaking seriously. To solve these problems, this paper analysis mainly on three aspects: the material organization performance, the expansion joint installation and the stress characteristic of expansion joint. Both the verticality deviation in the process of installation and the material hardness value exceed standard are the root cause of these problems. At the end of the paper, the improvements have been put forward for this problem.

Sub‐optimum fast Bayesian techniques for joint leak detection and localisation

A fast tree-search algorithm for joint leak detection and localisation using surface-borne ultrasonic acoustic signals is developed through a wireless sensor network. Owing to environmental noise and multipath fading of ultrasonic signals, false sensor observations are frequent in the observation data. The problem is modelled as a Bayesian inference model and the maximum a posteriori solution is approximated through a tree-search structure. The algorithm initially divides the area into large cells and approximates the observation likelihood function over these large cells. In a tree structure, a large cell with high likelihood is divided into smaller cells and the tree is expanded until the required estimation precision is obtained. Simulation and experimental results reveal advantages of the proposed technique in terms of estimation error and convergence speed in comparison with other conventional Bayesian techniques such as particle filtering.

Joint integrity management of critical flanges

Plant owners are coming under ever increasing pressure to reduce fugitive emissions for a number of reasons including environmental (legislation) and safety and commercial (plant efficiency). The real cost of fugitive emissions is frequently not fully appreciated. A number of the resultant costs are often difficult to quantify such as loss of product, cost of labour/materials to repair leaks, cost of cleaning the affected area, environmental fines, and image. Joint integrity management service is the total package of services that provides the best possible chance of achieving a leak-free start-up. It includes engineering analysis, unbolting, inspection, machining as required, gasket installation assembly, controlled bolt up and full documentation/traceability. The assembly of a joint is not just about installing a gasket and tightening the bolts. Correct assembly of critical joint requires that the flange is analysed and the correct bolt load to seal the joint is established. It requires the most suitable gasket to be installed for the service, flange flatness/condition to be inspected and for the determined bolt load to be applied in a controlled manner. Incorrect bolt loads, flange distortion, inappropriate gasket selection and uncontrolled flange assembly/bolt tightening methods are the main reasons for joint leaks. By taking some simple steps these potential causes for failure can be eliminated.

Analytical Modeling of the Contact Stress With Nonlinear Gaskets

Gasket contact stress and its variation through the gasket width is caused by the rotation of the flange and has an influence on the leakage tightness behavior of bolted flange joints. The future implementation by the ASME of proposed design rules is based on new gasket constants obtained from the ROTT (room temperature tightness) tests conducted on rigid platens. The gasket contact stress distribution needs to be addressed for the purpose of better joint tightness predictions. This paper presents a comprehensive analytical method that predicts the gasket contact stress distribution taking into account the nonlinear mechanical behavior of the gasket material. Based on the flange rotational flexibility, the proposed analytical model that is implemented in the “SuperFlange” program is supported and validated by numerical FEA and experimental analyses on flange rotations, radial distribution of gasket contact stress, and joint leak tightness.

Knowledge‐based systems for maintenance

A prototype knowledge‐based system, a form of artificial intelligence, was developed to aid human workers in identifying and scheduling maintenance jobs.A knowledge‐based system (KBS) is useful as a management tool for crew scheduling and site preparation to enhance productivity of maintenance operations for a water distribution system. It aids in identifying tasks and their expected durations, precedence relationships, and requirements for materials, tools, and labor. A prototype KBS is developed that codifies knowledge from field experts for planning maintenance operations for a water distribution system. This case study from Hackensack (N.J.) Water Company examines the influence of weather, traffic, leak severity, and the presence of other utility connections on planning repair operations for joint leaks.

The performance of the vacuum system of the 800 MeV proton synchrotron, ISIS

The neutron source, ISIS, is the world's leading pulsed neutron facility, primarily used for condensed matter research using slow neutron scattering techniques. The source is based on the bombardment of a uranium or tantalum target by an 800 MeV high intensity proton beam from a rapid cycling synchrotron. A brief description is given of the vacuum system of the synchrotron and beam line to the target. Key factors in the design of the system are reliability and minimum maintenance, to reduce exposure of operators to radiation. Ceramic vacuum chambers make up two thirds of the ring to reduce eddy current losses in the pulsed magnets: all other chambers are constructed from stainless steel. Metal gaskets are used in all de-mountable joints. The system is pumped with triode sputter ion pumps and roughed by a carbon vane, dry combination claw and roots, and turbomolecular pumps. The entire system is free from hydrocarbons. The performance of the system is reported including an analysis of breakdown. Since operation began in 1984 there have been few failures apart from those caused by beam heating in the extracted beam line, which has caused leaks in joints. As diagnostics and beam control have improved, these occurrences have become increasingly rare. This has resulted in a vacuum system virtually fault and maintenance free.

Analysis of Bolted Joints with Nonlinear Gasket Behavior

Design methods for full face gaskets in bolted pressure vessel joints have received little attention in the literature. Such gasketed joints play a prominent role in attaching rectangular plan from water boxes to rectangular tubesheets in condenser water boxes. With higher cooling water pressures becoming evident due to cooling tower circuits, the water box-tubesheet structure, and its bolted joint connection requires rigorous analysis for both structural integrity and leak tightness. Although it is well known that gasket material has a highly nonlinear stress strain behavior, very few analyses are available to calculate and evaluate the effect of the nonlinear gasket behavior in a bolted joint connection. In this paper, an approximate method for simultaneously analyzing structural integrity and leak tightness of typical bolted flange connections with nonlinear gasket material is developed. The flange is modeled as an elastic element, the bolt is simulated by a linear spring with bending and extensional resistance, and the gasket is modeled by a series of nonlinear compression springs. A simple nonlinear stress-strain relation for initial loading and unloading of the gasket is developed based on experimental data. The analysis technique employs an incremental procedure which follows the configuration through preloading and pressurization and checks structural integrity and gasket leakage. To illustrate the method, a typical full face gasket and flange construction is studied, and the effect of gasket properties on the final state is investigated. A series of simulation results are obtained which illustrate clearly the effect of gasket prestrain, undersizing of bolts, and wall rotational resistance. Of particular importance is a simulation comparing results obtained using actual nonlinear gasket stress-strain data with results obtained using linear models for the gasket. It is demonstrated that for full face gasket configurations, simulation of the nonlinear behavior is required to achieve accurate results. The procedure developed in this work is ideal for optimization of flange gasket configurations because of its cost effectiveness while simultaneously evaluating the interaction between structural integrity and joint leak tightness.

Problems Related to Squeeze Cementing

Abstract Causes of problems relating to squeeze cementingoperations are presented. Much has been written on materialsand techniques that have been used in particular areas, but little mention is made of some problems that occurduring the operation. Introduction Squeeze cementing generally can be described as theprocess of forcing a cement slurry into holes in the casingand cavities behind the casing. These operations areusually performed during drilling and completion of a well, or for repairing or altering a well at some later date. Squeeze cementing is necessary for many reasons, butprobably the most important use is to segregate hydrocarbonproducing zones from those formations producing otherfluids. The key factor on a squeeze cementing job is thatof placing the cement at the desired point or pointsnecessary to accomplish the purpose. Squeeze cementing problems are closely related to man'sability to understand the earth's properties once its crusthas been penetrated. It is often difficult to determine whysome wells can be squeezed successfully with one job whileothers in the same field require four or five jobs. Thereseem to be a number of opinions as to the proper methodof squeeze cementing. We are not attempting to argue orfind fault with these opinions; rather we hope to approachand recognize problems that do occur in such a mannerthat we might learn to consider ways in which to solvethem. Applications of Squeeze Cementing Some of the most pertinent applications for squeezecementing that need consideration are:supplementing aprimary cementing job that may be deficient because ofchanneling or insufficient fillup (Fig. 1);reduction orelimination of water intrusion from above or below thehydrocarbon producing zone (Fig. 3);reduction of theGOR by isolating the oil zone from an adjacent gas zone;repair of a casing leak that might have developed due tocorrosion, pressure parting or joint leaks (Fig. 2); andabandoning of old perforations or plugging of a depleted orwatered-out producing zone. Terminology Breakdown The language used in squeeze cementing is rather looseand subsequently leaves much to the imagination of thoseexpected to execute the job. During training sessions heldby one of the major oil companies the past 2 years, drilling people were presented with the question, "What isyour definition of a breakdown?" Recognizing that amajority of those present were from California oil fields, andthat the major application for squeeze cementing is thatof supplementing a faulty primary job to obtain isolationof an oil zone from adjacent water zones as required bythe California Division of Oil and Gas, the type of squeezejob that was foremost in their minds was that of squeezingwater-shutoff holes. There were two definitions expressedmost frequently:That pressure necessary to break down or fracturethe formation so that it will accept fluid.That which must he done before one can attempta squeeze cementing job. Breakdown actually is a poor name for what really needsto be attained on most squeeze jobs since the prominentproblem is in the wellbore, and the desired performanceis for the perforations and cavities to accept fluid withoutfracturing. Fractures normally will accept the cementslurry and often great volumes of it, but not necessarily inthe area that needs repair. Obtaining a fracture on thebreakdown will more often than not cause extra rig time.require greater volumes of cement, and create lost timewaiting on cement-all of which are costly. Fracture Gradient A term closely related to breakdown and one that needsto be understood is formation fracture gradient which isthe pressure/foot of depth required to create a fracture. Also of interest is the fact that propagation and extensionof a fracture usually require a lower pressure than wasneeded for its creation. Too often it is assumed thatoverburden lifting is necessary for a fracture to occur. Also, due to average formation density, the fracturinggradient is anticipated to be at least 1 psi/ft of depth. This is a good round number and easy to use in calculations, but experience has indicated that due to structural stresses inthe earth and elasticity of the earth's formations, fracturesusually occur at less than 1 psi/ft and often as low as 0.6psi/ ft. JPT P. 801ˆ