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After only one year of operation, thermowells in feed gas supply pipeline at a
natural gas production plant was failed due to fatigue damage accelerated by
improper thermowell design for the current operation. It is believed that
thermowell configuration having a neck acted as local stress raiser played a
remarkable role in initiation of fatigue damage. Besides, the medium flow past a
thermowell causes vortices to be shed at a frequency, termed the wake frequency,
proportional to the flow velocity. If the wake frequency is at or near the natural
frequency of thermowell, a resonance condition may occur where massive
amounts of energy are absorbed by the thermowell, resulting in very high
stresses and possible failure.