Stability Characteristics and Mechanism of U-Shaped Metal Bellows under Symmetrical Cyclic Tension and Compression Process

The U-shaped metal bellows expansion joint compensates for the pipeline displacement by its own deformation. The compensation performance of the metal bellows in the initial stage of tension and compression deformation is unstable. In this paper, the symmetrical cyclic tension and compression (SCTC) process of metal bellows was simulated by ABAQUS software. Then, the SCTC process experiment of metal bellows was completed on the universal material testing machine. The distribution law of axial load with displacement and that of axial stiffness and yield load with cycles of metal bellows were obtained. Finally, the X-ray diffraction peak confirmed the deformation-induced martensite in the wave trough and proved that the plastic strain and hardness values of metal bellows increased with the displacement amplitude. The microstructure in the wave trough area was observed by a Zeiss microscope, and the stability characteristics mechanism of the metal bellows was revealed. The martensite in the wave trough increases the grain boundary area under SCTC loading. The forward movement of the slip band in the grain caused by large deformation reached an equilibrium state with the resistance at the grain boundary, which promotes the macroscopic mechanical properties of the metal bellows to be stable characteristics under SCTC loading.

OPTIMIZATION OF BELLOWS AND TUBES CUTTING BY DISC KNIFE TO ACHIEVE THE MINIMUM BURR SIZE

The paper solves the determination of the optimal size of the shear gap when dividing components with a circular cross section (hydroformed metal bellows and tubes) with a disc knife to achieve the smallest burr size on the divided surfaces. The analyzes were performed on bellows with an outer diameter of 15 mm and a wall thickness of 0.4 mm. During the experiments, the size of the shear gap between the inner disc knife and the outer knife was changed, and the pressing force of the inner disc knife was changed. The experiments were carried out using a cutting tool after 20,000 cuts and after 120,000 cuts. The optimal size of the cutting gap was determined, allowing the minimum size of the burr to be achieved, thus reducing the time to remove it by brushing or tumbling in the subsequent operation. The mentioned procedure can be applied to analogous cases of division.

Steam Inlet Expansion Joint Design & Case Study: Surface Condenser Application

This paper is comprised of three sections and outlines the outcome achieved from instituting an effective preventative maintenance program; specifically, highlighting a steam surface condenser application that was originally equipped with a stainless-steel metal bellows type expansion joint system. In the first section of the paper, a general overview of steam inlet type expansion joint systems will be presented to provide an understanding of the specific application, typical design parameters and conditions, system components, varying expansion joint designs, configurations, and installation methodologies. The second section will outline types of inspections that typically support preventative maintenance programs within the power generation industry. Lastly, the case study will examine the account of an actual project and the practice of implementing a preventative maintenance program; outlining inspection types, how those measures supported a root cause analysis, and ultimately developing a unique solution to address the issues identified during subsequent inspections and analyses. The case study focuses on developing a retrofitted rubber ‘dog bone’ expansion joint system to replace the failed metal bellows expansion joint. Various points within the overall project life cycle will be reviewed; from the point of initial inspection that identified the root cause and defined loss in performance, evaluation and engineering to support the replacement design, onsite execution and installation methodology, and post-maintenance testing and operation.