A Fuzzy Markov Model for Risk and Reliability Prediction of Engineering Systems: A Case Study of a Subsea Wellhead Connector

Abstract

In production environments, failure data of a complex system are difficult to obtain due to the high cost of experiments; furthermore, using a single model to analyze risk, reliability, availability and uncertainty is a big challenge. Based on the fault tree, fuzzy comprehensive evaluation and Markov method, this paper proposed a fuzzy Markov method that takes the full advantages of the three methods and makes the analysis of risk, reliability, availability and uncertainty all in one. This method uses the fault tree and fuzzy theory to preprocess the input failure data to improve the reliability of the input failure data, and then input the preprocessed failure data into the Markov model; after that iterate and adjust the model when uncertainty events occur, until the data of all events have been processed by the model and the updated model obtained, which best reflects the system state. The wellhead connector of a subsea production system was used as a case study to demonstrate the above method. The obtained reliability index (mean time to failure) of the connector is basically consistent with the failure statistical data from the offshore and onshore reliability database, which verified the accuracy of the proposed method.

Reliability Analysis of the Deep-Sea Horizontal Clamp Connector Based on Multi-Source Information from an Engineering Background

“…The width w growth rate in the defect area is calculated based on the empirical equation for length growth rate, with a length-to-width ratio of 0.2, i.e., the width d is 0.6 mm/a. Then, the non-conservative Equation (20) proposed by Hopkins is used to correct the length and width growth rates, as they previously pointed out that the precise calculation of the cross-sectional area of the corrosion zone was overly conservative [47]:…”

“…The introduction of novel research and analysis methods has greatly facilitated the improvement of connector reliability. However, many of these studies only employ basic reliability methods to enhance the complex system of connectors, resulting in biases in the evaluation results due to a lack of consideration for the product reliability characteristic model and practical application [14,20]. The main obstacle to the reliability study of deepsea horizontal clamp connectors is the lack of high-quality reference information, and reliability information needs to be collected from multiple sources to ensure unbiased and credible evaluation results.…”

Analysis of the Reliability of Subsea Clamp Connector Based on Multiple Response Surface Methodology

“…Bhardwaj et al [16] used the first-order second-moment method and the Monte Carlo method to evaluate the structural reliability of the pipeline system in deep water under high internal pressure and high temperature. Pang et al [17] proposed a fuzzy Markov method that integrates risk, reliability, availability, and uncertainty analysis based on fault tree, fuzzy comprehensive evaluation, and Markov methods. The method pre-processes input fault data using fault tree and fuzzy theory to improve the reliability of the input fault data.…”

Research on bearing capacity and sealing contact characteristics of the subsea wellhead connector

“…Therefore, stainless steel is selected as the sealing ring material for the wellhead connector since it displays excellent resistance to corrosion. 4,5 The metal sealing ring is lowered and installed with the subsea Christmas tree. The remotely operated vehicle provides hydraulic power when the subsea wellhead reaches the preset position, activating the locking mechanism to realize pre-tightening sealing.…”