In contrast to fault diagnosis relying solely on a single sensor, the method of multi-sensor information fusion for fault diagnosis (MSIFFD) broadens the spectrum of available information sources. It is renowned for its high accuracy and reliability, traits that have attracted growing attention within the research community and led to the generation of a substantial body of publications. However, there is currently a lack of a comprehensive and systematic review in this domain. Thereby, this review aims to thoroughly explore all research achievements in the field of MSIFFD. At the outset, an analysis is undertaken to delineate the fusion level of multi-sensor information, with a specific focus on its location and types of inputs and outputs within the information flow. Subsequently, an examination of the six primary fundamental operations for amalgamating multi-sensor information is undertaken to clarify the motivations and processes involved in information fusion across various operations. Following this, factors influencing fusion diagnostics and strategies aimed at improving their performance are examined to explore approaches for enhancing fusion accuracy. The subsequent sections delve into the analysis of sensor types and application scenarios, providing a reference guide for practical applications. Finally, this review outlines potential future challenges in the field of MSIFFD and provides a range of recommendations and possible solutions for consideration.

Bolted flange joints are widely used in the nuclear power plants and other industrial complexes. During their assembly, it is extremely difficult to achieve the target bolt preload and tightening uniformity due to elastic interaction and criss-cross talks. In addition to the severe service loadings, the initial bolt load scatter increases the risk of leakage failure. The objective of this paper is to present an analytical model to predict the bolt tension change due to elastic interaction during the sequence of initial tightening. The proposed analytical model is based on the theory of circular beams on linear elastic foundation. The elastic compliances of the flanges, the bolts, and the gasket due to bending, twisting, and axial compression are involved in the elastic interaction and bolt load changes during tightening. The developed model can be used to optimize the initial bolt tightening to obtain a uniform final preload under minimum tightening passes. The approach is validated using finite element analysis (FEA) and experimental tests conducted on a NPS 4 class 900 weld neck bolted flange joint.

Bolted flange joints are extensively used in pressure vessels and piping equipment and rotating machinery. Achieving a uniform bolt preload during the assembly process is particularly important to satisfy tightness in applications such as oil, gas, fossil, and nuclear industries. However, this task becomes very difficult due to the need of retightening the bolts because of elastic interaction and bolt cross talk. The risk of leakage failure under service loading is consequently increased because of the scatter of the bolt preload. This article presents an analytical model based on the theory of circular beams on the linear elastic foundation that simulates the elastic interaction present during the tightening of bolted flange joints to reduce the number of passes while achieving bolt load uniformity. As such, a novel methodology that optimizes tightening sequence strategies is suggested to obtain uniform bolt tension while avoiding yield under a minimum number of tightening passes. In this regard, based on the target preload, the load applied to each bolt in each pass is suggested. The developed approach is validated both numerically using finite element method and experimentally on a NPS 4 class 900 welding neck flange joint using the criss-cross tightening and sequential patterns.