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.