Application of Vibration Stress Relief Technology in Eliminating Residual Stress in Steel Manifolds

Abstract Vibratory stress relief is now one of the most widely used power saving techniques in many industries of China. The application of vibratory stress relief to a large steel manifold at the Baishuikeng Hydroelectric Power Plant has made great progresses in eliminating residual stresses of manifolds.

Keywords Vibration stress relief, penstock, large steel manifold, Baishuikeng Hydroelectric Power Plant, Zhejiang Province, stress elimination, residual stress

1. Introduction

In the fields of hydraulic metal structures and hydraulic machinery, there are widely used special hydraulic components, such as extra-large components, multi-material assemblies, and on-site welded components. Due to the lack of extra-large annealing furnaces, long processing time and difficult transportation, heat stress relief cannot be used to eliminate residual stress. For example, the steel manifold at the outlet of the pressure penstock designed by Zhejiang Province Investigating and Designing Institute for Water Conservancy and Hydropower Projects (hereinafter referred to as our institute) for the Baishuikeng Hydroelectric Power Plant in Zhejiang Province is a T-shaped manifold with a main pipe diameter of 3.85m and two branch pipe diameters of 2.27m each. The manifold is 10.78m long, 7.35m wide, made of 16Mn material, weighing 36000kg. The pressurized static head is 115m long. This component has a complex structure, consisting of multiple irregular steel plates and thick crescent ribs welded together, resulting in significant welding residual stress, especially near the welds between the crescent ribs and the main and branch pipes. Since this manifold is a large welded component, it is imperative to find a reliable and efficient method for eliminating residual stress.

2. Vibration Stress Relief TechnologyVibration stress relief technology (VSR), introduced from abroad in the late 1970s, has undergone systematic research and absorption in China. In recent years, it has been widely promoted in industries such as aerospace, petrochemicals, machine tools, locomotives, metallurgy, shipbuilding, mining machinery, and hydraulic machinery. Corresponding industry guidance technical documents and recommended standards have also been formulated—HB/Z229-93 Main Parameters and Technical Requirements for Vibration Stress Relief and JB/T5926-91 Selection of Vibration Stress Relief Process Parameters and Technical Requirements. The above demonstrates the maturity of vibration stress relief technology and its established basis.Vibration stress relief is based on the principle of harmonic resonance. The resonance factor amplifies the periodic vibration force generated by the exciter, enabling the processed component to acquire the corresponding energy.

This energy is equivalent to the thermal energy in heat stress relief, which can drive the atoms within the workpiece to produce greater vibrations, causing local .............

Lear more.......