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Cavitation Detection and Monitoring
Jonas, Inc. evaluation of water and other fluid systems (during design and operation) for propensity to cavitation and field service is provided to detect cavitation during system operation. When needed, monitoring equipment is supplied for long-term monitoring of effects of operation.
Background
Cavitation is damage to metal and plastic components of liquid handling systems caused by the collapse of gas bubbles (steam, vapor, air, or other gases) on a metal surface. The repeated collapse of a large number of bubbles damages the protective metal oxide and removes the metal by the mechanical action of the minute shock waves generated by the collapse. The result is thinning of the attacked components which, in the case of piping, can lead to leaks and even a catastrophic failure.
Cavitation is often misdiagnosed as erosion-corrosion (flow-accelerated corrosion). It is most likely to occur when the liquid is near its saturation point, when there are dissolved gases in the liquid, or when the local flow velocity and turbulence are high. The flow velocity reduces the static pressure, bringing the liquid closer to saturation where gases come out of the solution and vapor bubbles form. Pumps, valves, orifices, and piping components which produce high local flow velocities are susceptible.
Description of the Services
1. The first step is a system evaluation based on the design and operating data. Pressures and temperatures are compared to the saturation conditions and the change of the static pressure is calculated for all major components. The results are compared to experience.
2. When the results of the Item 1 investigation or experience show that cavitation is possible, an in-plant survey and one-time monitoring of the cavitation noises are performed.
3. Long time monitoring is performed when there is a suspicion that cavitation only occurs during specific types of operation or upsets. A multi-probe instrument is provided (rented or sold) which will detect cavitation noises when they occur.
4. Troubleshooting of problems includes root cause analysis and development and application of engineering solutions.
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