Multi criteria risk analysis of a subsea BOP system

The Subsea blowout preventer (BOP) which is latched to a subsea wellhead is one of several barriers in the well to prevent kicks and blowouts and it is the most important and critical equipment, as it becomes the last line of protection against blowout. The BOP system used in Subsea drilling operations is considered a Safety – Critical System, with a high severity consequence following its failure. Following past offshore blowout incidents such as the most recent Macondo in the Gulf of Mexico, there have been investigations, research, and improvements sought for improved understanding of the BOP system and its operation. This informs the need for a systematic re-evaluation of the Subsea BOP system to understand its associated risk and reliability and identify critical areas/aspects/components. Different risk analysis techniques were surveyed and the Failure modes effect and criticality analysis (FMECA) selected to be used to drive the study in this thesis. This is due to it being a simple proven cost effective process that can add value to the understanding of the behaviours and properties of a system, component, software, function or other. The output of the FMECA can be used to inform or support other key engineering tasks such as redesigning, enhanced qualification and testing activity or maintenance for greater inherent reliability and reduced risk potential. This thesis underscores the application of the FMECA technique to critique associated risk of the Subsea BOP system. System Functional diagrams was developed with boundaries defined, a FMECA were carried out and an initial select list of critical component failure modes identified. The limitations surrounding the confidence of the FMECA failure modes ranking outcome based on Risk priority number (RPN) is presented and potential variations in risk interpretation are discussed. The main contribution in this thesis is an innovative framework utilising Multicriteria decision making (MCDA) analysis techniques with consideration of fuzzy interval data is applied to the Subsea BOP system critical failure modes from the FMECA analysis. It utilised nine criticality assessment criteria deduced from expert consultation to obtain a more reliable ranking of failure modes. The MCDA techniques applied includes the technique for order of Preference for similarity to the Ideal Solution (TOPSIS), Fuzzy TOPSIS, TOPSIS with interval data, and Preference Ranking Organization Method for Enrichment of Evaluations (PROMETHEE). The outcome of the Multi-criteria analysis of the BOP system clearly shows failures of the Wellhead connector, LMRP hydraulic connector and Control system related failure as the Top 3 most critical failure with respect to a well control. The critical failure mode and components outcome from the analysis in this thesis is validated using failure data from industry database and a sensitivity analysis carried out. The importance of maintenance, testing and redundancy to the BOP system criticality was established by the sensitivity analysis. The potential for MCDA to be used for more specific analysis of criteria for a technology was demonstrated. Improper maintenance, inspection, testing (functional and pressure) are critical to the BOP system performance and sustenance of a high reliability level. Material selection and performance of components (seals, flanges, packers, bolts, mechanical body housings) relative to use environment and operational conditions is fundamental to avoiding failure mechanisms occurrence. Also worthy of notice is the contribution of personnel and organisations (by way of procedures to robustness and verification structure to ensure standard expected practices/rules are followed) to failures as seen in the root cause discussion. OEMs, operators and drilling contractors to periodically review operation scenarios relative to BOP system product design through the use of a Failure reporting analysis and corrective action system. This can improve design of monitoring systems, informs requirement for re-qualification of technology and/or next generation designs. Operations personnel are to correctly log in failures in these systems, and responsible Authority to ensure root cause analysis is done to uncover underlying issue initiating and driving failures

Dynamic Analysis and Control of the Clutch Filling Process in Clutch-to-Clutch Transmissions

Clutch fill control in clutch-to-clutch transmissions influences shift quality considerably. An oncoming clutch should be applied synchronously with the release of an offgoing clutch to shift gear smoothly; therefore, the gap between the piston and clutch plates should be eliminated when the torque capacity is near zero at the end of the clutch fill phase. Open-loop control is typically implemented for the clutch fill because of the cost of pressure sensor. Low control precision causes underfill or overfill to occur, deteriorating shift quality. In this paper, a mathematical model of an electrohydraulic clutch shift control system is presented. Special dynamic characteristic parameters for optimal clutch fill control are subsequently proposed. An automatic method for predicting initial fill control parameters is proposed to eliminate distinct discrepancies among transmissions caused by manufacturing or assembling errors. To prevent underfill and overfill, a fuzzy adaptive control method is proposed, in which clutch fill control parameters are adjusted self-adaptively and continually. Road vehicle test results proved that applying the fuzzy adaptive method ensures the consistency of shift quality even after the transmission’s status is changed

Modelling and control of the braking system of the electric Polaris Ranger all-terrain-vehicle

I mezzi ATV sono impiegati in attività forestali, di sorveglianza e soccorso. Si è vista recentemente la nascita di ATV elettrici, sinonimo di pulizia e risparmio. La possibilità di rendere questi veicoli completamente autonomi ha stimolato l'interesse del settore automotive. L' ABS in particolare, che finora è diffusa solo tra i veicoli stradali è stata introdotta e studiata. Modelli matematici per la simulazione dell'impianto frenante sono stati derivati, come base per il futuroope

Impedance control of a hydraulic servomechanism

Mestrado em Engenharia MecânicaNo presente trabalho é proposto e implementado um controlador de impedância baseado na posição para o controlo de um cilindro, instalado numa prensa hidráulica, comandado por uma servoválvula actuada por solenóide. Foram inicialmente desenvolvidos controladores de posição, controlador PID e controlador baseado em lógica difusa, com os requisitos de precisão adequados à implementação do controlador de impedância baseado na posição. O filtro de impedância foi colocado na malha de realimentação de força para modificar a trajectória do actuador hidráulico de acordo com o comportamento especificado. Simultaneamente com as experiências na prensa hidráulica, o controlo de impedância foi experimentado em ambiente totalmente simulado recorrendo a um modelo não linear de todo o sistema hidráulico (cilindro + servoválvula). Foram realizadas várias experiências em espaço livre e em contacto com o ambiente. Foram conseguidos resultados satisfatórios em ambas as situações bem como na transição de não-contacto para contacto com o ambiente. ABSTRACT: A position-based impedance controller is proposed and demonstrated on an existing hydraulic press with a two-way vertically mounted hydraulic cylinder driven by a servo-solenoid valve. A proportional-integral-derivative (PID) controller and a Fuzzy Logic Controller (FLC) are primarily developed to meet the accurate positioning requirements of the impedance control formulation. The impedance filter was placed in force-feedback loop to modify a desired trajectory of the hydraulic actuator according to a specified behavior. Simultaneously with the experiment conducted on the real hydraulic press, impedance control was performed in computer simulation with the use of a nonlinear model of the whole hydraulic system (cylinder + servo solenoid valve). Experiments were carried out in free space and with environmental contact. Satisfactory results were achieved in both situations, as well as in noncontact/ contact transition

Utilizing Layer of Protection Analysis (LOPA) in Verification of Safety Integrity Level (SIL) of Instrumented System

The project is aimed to utilize layer of protection analysis (LOPA) to verify safety integrity level (SIL) of safety instrumented system. Safety instrumented system (SIS) is the last resort in case of emergency happened in plant. Determining the specific safety requirement of safety systems is a vital part to ensure accidents are prevented. Previous study is carried out till classification of Safety Integrity Levels (SIL) for hazardous installation by using the risk assessment techniques. In this study, the focus will be on SIL classification and verification in safety instrumented system (SIS). The program is developed using Microsoft Excel based on established methodology found in the literatures. Thorough literature surveys are expected in order to gather appropriate SIL verification information which will further integrate in existing spreadsheet. The program is tested using two case studies related to process plant industries. The results obtained show the sufficiency of the protection system and provide risk control strategy including number of SIL required in case of the protection is insufficient. If the protection system is sufficient, it will ensure the design is the optimum. Reliability and accurateness of the result are vital due to main function of the program is to assess and validate the SIS. The application is used either in designing the SIS or in auditing the effectiveness of the installed SIS. The verification of assigned SIL to a particular Safety Instrumented Function (SIF) is still new compared to SIL classification. Based on industrial perspective, there is no established method on verification of an installed SIS. Most scenarios can be catered by enhancing the existing design rather than adding safety protection layer. Future study shall be continued to improve the relevancy and reliability of the tool by integrating more parameters in assessing a case

Development Of An Integrated Solution For Multi Scroll Compressors With Wet Vapor Injection

Extensive use of Heat Pumps is essential to meet European 20-20-20. Reversible air-to-water heat pump systems have to operate at high efficiency levels on a wide operating range to be an economical alternative to the traditional heating and cooling systems. This paper presents the advantages, the control and the implementation of multi vapor injected scroll compressors systems in commercial heat pump water heater application. Enhanced Vapor Injection (EVI) technology allows both performance and reliability improvement across the compressors operating area, especially at low ambient temperatures. Wet Vapor Injection allows extending compressors operating range at very low ambient and high condensing temperatures. The development of a solution integrating injection capable scroll compressors, expansion valves and wet/vapor injection control system is presented in this paper

Blood Pressure Measurement Device for Low Resource Settings

ME450 Capstone Design and Manufacturing Experience: Fall 2015The design team spent eight weeks in the Obstetrics and Gynecology Department at a tertiary referral hospital, Komfo Anokye Teaching Hospital (KATH), in Kumasi, Ghana. During the team’s immersion experience at the hospital, the team observed healthcare providers experiencing difficulty following obstetrics patients’ blood pressure management plans. This occurred largely because of the high volume of patients and the busyness of the wards. The patient's blood pressure measurement strongly influences the treatment especially if she has hypertensive disorders. Hypertensive disorders, mainly preeclampsia and eclampsia, are the second leading cause of maternal mortality worldwide and the leading cause of maternal mortality at KATH. The team identified an opportunity for the development of a blood pressure measurement device to aid the healthcare providers in measuring the patients’ blood pressures every 30 minutes or four hours according to their management plans. This project is in collaboration with clinical mentors and advisors at University of Michigan Hospital and KATH. The final design is an auscultatory device with a microphone stethoscope and headphones to listen to the Korotkoff sounds, a hand pump for manual inflation, an automatic constant rate deflation facilitated by a solenoid valve, a LCD screen to display the current pressure, a slip-on cuff, an aneroid pressure gauge for calibration, a handle, a storage area, and a rechargeable battery. The current prototype follows the design fairly closely however the device is not powered by a rechargeable battery and the electrical components are all on a breadboard which prevents its portability. All validation testing completed so far on the current prototype has been promising including testing the accuracy and ease-of-use of the device when used by three nursing student. This device will be continued to be improved next semester so that it can be taken to KATH for further validation and feedback.http://deepblue.lib.umich.edu/bitstream/2027.42/117349/1/ME450-F15-Project07-FinalReport.pd

Solenoid Operated Gear Shifting Mechanism for Two Wheeler

Solenoid operated gear shifting mechanism is mainly designed for the handicapped persons who unable to shift the gears by their foot. The technique used in this gear shifting mechanism consists of solenoid. Solenoid completes one up and down motion called as one stroke. This stroke time depend on supplied voltage and current. According to stroke length and voltage calculation, solenoids are mounted on both sides of gear shifting pedal at ends. By pressing that switch, person easily shifts the gear with the help of foot which is most efficient to handicapped persons