Expansion joint presetting ⏬
In order to increase axial movement, the expansion joint can be presetted to its maximum extension during installation. For expansion joints with swivel flange there is a risk during the extension that the sealing bulge will spring from the groove of the backing flange. If presettings of more than 10 mm are needed, a flange connection will need to be disconnected at another location. Now the expansion joint can be installed relaxed and the flange disconnection sites that were opened before can be closed again.
In order to increase axial movement, the expansion joint can be presetted to its maximum extension during installation. For expansion joints with swivel flange there is a risk during the extension that the sealing bulge will spring from the groove of the backing flange. If presettings of more than 10 mm are needed, a flange connection will need to be disconnected at another location. Now the expansion joint can be installed relaxed and the flange disconnection sites that were opened before can be closed again.
n order to increase lateral movement, the expansion joint can be presetted to its maximum lateral displace- ment against the direction of movement during installation. During operation, it will move back to the opposite side through the zero point. In this way, the lateral movement can be increased by up to 100%. For expansion joints with swivel flange there is a risk during displacement that the sealing bulge will spring from the groove of the backing flange. If presettings of more than 5 mm are needed, a flange connection will need to be disconnected at another location. Now the expansion joint can be installed relaxed and the flange disconnection sites that were opened before can be closed again.
Small-Bore Connections⬇️
Small-bore connections, also called branch connections, to the main process piping represent the most common vibration problem on rotating and reciprocating machinery and associated process piping.
Small-bore connection design assessment and field vibration testing are strongly recommended to avoid piping integrity risks.
Small-bore connections, also called branch connections, to the main process piping represent the most common vibration problem on rotating and reciprocating machinery and associated process piping.
Small-bore connection design assessment and field vibration testing are strongly recommended to avoid piping integrity risks.
Piping vibration and fatigue can account for up to 20% of hydrocarbon releases; and a large portion of those are due to failure of small-bore connections per Energy Institute, 2008, Guidelines for the avoidance of vibration induced fatigue failure, (AVIFF). Hydrocarbon emissions can lead to fire, explosions, injuries, property and environmental damage, and penalties.
A small-bore connection (SBC) is generally defined as a branched connection on mainline piping that has a nominal diameter 2” (DN 50) and smaller, including connections that have a branch pipe to mainline pipe ratio of less than 10%, and excluding connections that have a ratio of greater than 25% (see Figure below). Note that “mainline piping” could also describe equipment like a vessel or cooler to which the SBC is attached.
Small-bore piping (SBP) is defined as the piping attached to the small-bore connection, extending until the effect of the mainline piping vibration is negligible (typically, the nearest support or brace), as shown in the illustration below.
Multiple excitation sources exist within modern process plants that can cause damage due to vibration related degradation mechanisms. Without identification and control, these can lead to component failure and the associated safety, environmental, business and reputational losses.
One such issue is acoustically induced vibration (AIV) choked gas flow through pressure reduction devices which can generate high levels of acoustic energy. This can excite the higher frequency pipe shell modes of the downstream piping and potentially lead to excessive cyclic stress at discontinuities such as small bore connections and pipe supports.