What are the causes of metal expansion joint failure?
Release time:
2021-11-02
The two primary factors in designing metal expansion joints are fluid velocity and noise frequency. When the fluid velocity is below the speed of sound, the energy level of the noise increases to the eighth power of the velocity—demonstrating just how critical this factor is. At the same time noise energy level, it is advantageous to increase the average frequency, because higher frequencies experience greater attenuation as they pass through the valve body and downstream pipe walls. Cavitation refers to the phenomenon that occurs when a fluid flows through a metal expansion joint: as the fluid passes through the constricted section, the static pressure drops to or below the saturation vapor pressure of the fluid at the valve inlet temperature, causing some of the liquid to vaporize and form bubbles. Subsequently, as the static pressure recovers to the saturation vapor pressure, these bubbles collapse and revert back to the liquid phase. The entire process of bubble formation and collapse is known as cavitation.
Cavitation refers to the erosion of materials caused by cavitation. Cavitation or cavitation-induced erosion can cause significant erosive damage to metal expansion joints. Unlike flash steam flushing, cavitation flushing leaves the expansion joint and downstream piping with a rough surface resembling coal slag. To enhance material hardness and reduce erosion, it is advisable to select hard alloys for expansion joints or to weld hard materials at locations where flash steam is likely to occur. Different types of metal expansion joints and flow directions have varying pressure recovery coefficients. By choosing expansion joints and flow directions with high pressure recovery coefficients, you can prevent flow blockage. For instance, for liquids that easily vaporize, high-pressure recovery metal expansion joints should be avoided; however, low-pressure recovery metal expansion joints can be used instead.
Similar methods can be employed to prevent flash vaporization—for example, by increasing material hardness or reducing flow rate—to minimize the impact of cavitation. When the load in the production process or the operating conditions change, the controlled variables of the process are detected and transmitted via sensing elements and transmitters to the metal expansion joint. The output from the control algorithm is then sent to the metal expansion joint, adjusting the corresponding fluid flow rate in the process to ensure that the controlled variable matches the setpoint. The quality of the control system is influenced by its components, particularly by the weakest links within those components.
Related News
A specialized enterprise dedicated to the design and manufacture of desulfurization damper doors, non-metallic expansion joints, bellows, expansion compensators, stainless steel flexible metal hoses, dust collectors, conveyors, compensators, silencers, dampers, and stainless steel flexible metal hoses, as well as metallic and non-metallic corrugated expansion joints (expansion compensators).
Jiangsu Yaxing
Contact Us
Address: Qingdun Industrial Park, Hai'an City, Jiangsu Province
Phone: 86-513-88483622 ，86-513-88480666,
Fax: 86-513-88482423
Email: yx@ntyxbwg.com
Copyright © 2026 Jiangsu Yaxing Corrugated Pipe Co., Ltd.