Concern for the flow-induced vibration of the tube has become a serious consideration in the design of shell-and-tube equipment. These problems can lead to pipes and tubejoints that loss, increased pressure drop and noise shellside intolerably high. The result is that equipment must be removed from service for repair and modification.

Flow-induced vibrations can damage the tubes in evaporators. All tubes vibrate in all flow conditions! However, we are concerned with the vibrations that cause significant damage to the pipe. As larger evaporators, bring more speed and more shellside become more prevalent, the vibrations of the pipe damage are more likely to occur. N. evaporator design is complete without considering the possibility of damage due to flow induced vibrations.

The damage is most likely to occur with gases or vapors on shellside than with liquids. Flow induced vibrations also occur with liquids on shellside, but the damage is often limited to localized areas of relatively high speed. In severe cases, the pipes can leak in a few days or even hours after the device was placed in service. More often, the damage will appear a year after startup. Give the tube will develop after the initial damage was repaired, but the number and frequency of further damage will diminish with time.

In a number of cases, by a heat exchanger tube failures attributed to vibrations flowinduced consequential damages caused to other devices within a plant. Failures of this type have proven to be the most destructive, most costly, and required the closure of plants longer for the correction.

Currently available methods for the prediction of flow induced vibration damage is not sufficient to predict failures. At best, they identify the equipment that are susceptible to damage. The main reason for this lack of precision is that the flow induced vibrations are extremely complex. We learned a lot, but the probability of its occurrence is not yet known. However, the penalty cost for equipment designed to completely avoid the harmful vibrations is small and is almost always easily justified.

Some problem areas in question, with the prediction of vibration include:

1. the complex pattern of flow through a tube bundle
2. complex fluid mechanics of a bank of vibrating tubes
3. the role of damping
4. rates of wear and fatigue.

However, it is possible to develop design criteria, especially when tempered with experience, to ensure that the material will be safe from harm vibration.

Flow-induced vibration problems in equipment tubulars are commonly regarded as consisting entirely of mechanical failure of the tubes. However, the vibration may increase the pressure drop shellside, sometimes twice. Furthermore, a unit of acoustic vibration can produce an unacceptably high level of noise. With a growing emphasis on controlling noise, vibration noise must be an important consideration in plant design tubular

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