ABSTRACT
Trying to pinpoint the root cause of pipe vibration, let alone eliminate it, can be a vexing problem. A structured, systematic approach to the problem is required. We start by noting, as illustrated in Figure 8-1, that there are two possible causes for pipe vibration in service: mechanical or hydraulic. A mechanical induced vibration, Figure 8-1 block (2), is due to the mechanical vibration of a piece of equipment such as a pump or compressor which, in turn, causes the pipe to vibrate. The equipment vibration may be transmitted directly to the pipe through its nozzle attachment, Figure 8-1 block (3), or the equipment vibration may cause a structure or floor to vibrate, and the vibrating structure would then transmit the vibration to the pipe through the pipe supports, Figure 8-1 block (4). The pipe may just follow the equipment vibration, Figure 8-1 block (6) or, if the vibration frequency of the mechanical source fMs is close to a mechanical natural frequency of the pipe fMP, the pipe may amplify the vibration, Figure 8-1 blocks (5) and (7). A hydraulic induced vibration, Figure 8-1 block (8), is due to continuous pressure pulses that cause the pipe to vibrate. The pressure pulses could be clearly periodical, Figure 8-1 block (9), or more random and turbulent, Figure 8-1 block (10). If the frequency of the pressure pulses, the hydraulic source frequency fHs, is close to the acoustic frequency of the pipe cavity fAP, Figure 8-1 block (11), the pipe will resonate and amplify the vibration, Figure 8-1 block (13). In this chapter, we will examine the logic behind Figure 8-1 in more detail to understand what causes pipe vibration in service, and how best to solve it.
