Emergency shutdown valve reliability function test by automated Partial Stroke Testing System

Partial stroke testing (PST) is a technique that is regularly practiced in oil and gas industries to test the emergency shutdown (ESD) valve by closing a certain percentage of the valve position and stop any flow through the pipeline. Generally, it only functions when there is an emergency occurring in the production system. When the ESD valve remains in one position for a long period, there is a risk and potential of fail on demand which is, the ESD valve fail to operate during the emergency shutdown. This testing can reveal approximately 75 of unrevealed failures in valves. It can also provide predictive maintenance data that can contribute to the extension of the preventive maintenance for the ESD valve. The objectives of this paper are to design, simulate, build and test the performance of the automated PST system based on PLC. Four guidelines and methodology are used in this work. First, understanding the operation of the PST system. Then, the utilization of the capability of MATLAB-Simulink software as the simulation tool for the PST design system. Next, designing the PST automated system based on PLC design and lastly, testing the performance of the PST design system using lab scale PST system prototype that has been built. Results of the project shows that the PST system is successfully designed and simulated via MATLAB-Simulink and the PLC programming is working in the correct order as performed on the prototype

Politiques de Tests Partiels & Systèmes de Sécurité

International audienceA set of general formulas is proposed for the probability of failure on demand (PFD) assessment of MooN architecture (i.e. k-out-of-n) systems subject to partial and full tests. Partial tests (e.g. visual inspections, imperfect testing) may detect only some failures, whereas owing to a full test, the system is restored to an as good as new condition. Following the proposed approach and according to an example, performance estimations of the system and test policies are presented, by using the feedback from partial and full tests. An optimization of the partial test distribution is also proposed, which allows reducing the average probability of system failure on demand (PFDavg)

Probability of Failure of Safety-Critical Systems Subject to Partial Tests

A set of general formulas is proposed for the probability of failure on demand (PFD) assessment of MooN architecture (i.e. k-out-of-n) systems subject to proof tests. The proof tests can be partial or full. The partial tests (e.g. visual inspections, partial stroke testing) are able to detect only some system failures and leave the others latent, whereas the full tests refer to overhauls which restore the system to an as good as new condition. Partial tests may occur at different time instants (periodic or not), up to the full test. The system performances which are investigated are the system availability according to time, the PFD average in each partial test time interval, and the total PFD average calculated on the full test time interval. Following the given expressions, parameter estimations are proposed to assess the system failure rates and the partial test effectiveness according to feedback data from previous test policies. Subsequently, an optimization of the partial test strategy is presented. In the 2oo6 system given as example, an improvement of about 10% of the total PFD average has been obtained, just by a better (non-periodic) distribution of the same number of partial tests, in the full test time interval

A CFD-based Approach for Gas Detectors Allocation

PresentationAccidental gas releases are detected by allocating sensors in optimal places to prevent escalation of the incident. Gas release effects are typically assessed based on calculating the dispersion from releasing points. In this work, a CFD-based approach is proposed to estimate gas dispersion and then to obtain optimal gas sensors allocation. The Ansys-Fluent commercial package is used to estimate concentrations in the open air by solving the governing equations of continuity, momentum, and energy combined with the realizable κ-ε model for turbulence viscosity effects and species convection-diffusion. CFD dynamic simulations are carried out for potential gas leaks, assuming worst-case scenarios with F-stability and 2 m/s wind speed during a 4min releasing period and considering 8 wind directions. The result is a scenario-based methodology to allocate gas sensors supported on fluid dynamics models. The three x-y-z geographical coordinates for the sensor allocation are included in this analysis. To highlight the methodology, a case study considers releases from a large container surrounded by different types of geometric units including sections with high obstacles, low obstacles, and no obstacles. A non-redundant set of perfect sensors are firstly allocated to cover 100% detection for all simulations releases. The benefits of redundant detection via a MooN voting arranging scheme is also discussed. Numerical results demonstrate the capabilities of CFD simulations for this application and highlight the dispersion effects through obstacles with different sizes

Partial stroke testing for emergency shutdown valve using integrated PLC control design and human-machine interface

Partial stroke testing (PST) is a technique that is regularly practiced in oil and gas industries to test the emergency shutdown valve (ESD) by closing a certain percentage of the valve position and stop any flow through the pipeline. Generally, it only functions when there is an emergency occurs in the production system. When the ESD valve remains in one position for a long period, there is a risk and potential of fail on demand which is, the ESD valve fail to operate during the emergency shutdown. The partial stroke testing system still requires manual ignition by human. The distance between the control box with the plant area is limited which might increase the risk in safety issue to the workers. The objectives of this project are to design the PST automated system based on PLC design and to test the performance of the PST design system using lab scale PST system design. The capability of Mitsubishi GT-Designer 3 and Mitsubishi GX-Developer / GX Works 2 as the Human-Machine Interface (HMI) simulation platform for the PST design is applied. The system control and monitoring of PST will be developed by using Mitsubishi GT-Designer 3 interfacing it with Mitsubishi GX-Developer. This interfacing does not only control the mode of the system, it allows data monitor from the HMI which is the PC such as the state of the valve, alarm when PST failed, the alarm history records and pressure flow data. Then, the PST is simulated and tested in real time using PLC design system connected with a PC

VOTING FOR 2D FIRE MAPPING USING IMAGING OVERLAY

This project focuses on voting for 2D fire mapping based on image overlay method. Voting are commonly used in oil and gas industry including in fire mapping activities. In this project, voting are used to calculate the area of coverage for 2D fire mapping. The area of coverage for fire detector is required to meet the standards such as PETRONAS Technical Standard (PTS) for specific area in platform. This is because every area or equipment has different type of risk which determine the grades to the area

Multi-criteria decision tool applied to a system reliability for the priorization of spare parts

This paper proposes a method for spare part priorization based on the system reliability behavior. The method considers the values taken by the reliability distribution parameters, as the result of a multi-criteria decision process. The range of values is divided into possible alternatives, which depend on the importance of different criteria. The presented exercise provides a quick view about how different spare part policies can be selected by the effect, not only of the design, installation quality or performed maintenance, but also due to factors that sometimes come from subjective assessments. Hence, the Analytic Hierarchy Process (AHP) includes both qualitative and quantitative criteria in the priorization scheme. The presented method is intended to be a starting point for the analysis of external factors that make an important influence on the decision–making of complex industrial assets, with high amounts of data, system configurations, and maintenance inputs, which will be analyzed in future researches with the support of a tailored software application

VOTING FOR 2D FIRE MAPPING USING IMAGING OVERLAY

This project focuses on voting for 2D fire mapping based on image overlay method. Voting are commonly used in oil and gas industry including in fire mapping activities. In this project, voting are used to calculate the area of coverage for 2D fire mapping. The area of coverage for fire detector is required to meet the standards such as PETRONAS Technical Standard (PTS) for specific area in platform. This is because every area or equipment has different type of risk which determine the grades to the area

Reliability modelling of redundant safety systems without automatic diagnostics incorporating common cause failures and process demand

Sriramula’s work within the Lloyd’s Register Foundation Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of re-search.Peer reviewedPostprin