Different Erosion Categories Faced in Industry
Erosion in industrial systems refers to the gradual wear and tear of materials due to mechanical action or chemical reactions with fluid particles. It can be broadly categorized into:
- Abrasive Erosion
- Cavitation Erosion
- Chemical-Assisted Erosion (Erosive Corrosion)
- Gas-Solid Erosion
- Liquid Droplet Erosion
Liquid Droplet Erosion
Liquid droplet erosion is a type of erosion which needs to be mitigated in process heater applications. It arises when high-velocity liquid droplets hit a surface repetitively and is common in boilers and turbines and fired heaters
Flowlines, production manifolds, process headers and other lines transporting gas and liquid in two-phase flow should be sized primarily on the basis of flow velocity.
Experience has shown that loss of wall thickness occurs by a process of erosion/corrosion. This process is accelerated by high fluid velocities, presence of sand, corrosive contaminants such as C02 and H2S, and fittings which disturb the flow path such as elbows. To solve this, “erosional velocity” concept is introduced.
Erosional velocity
Erosional velocity is the threshold speed of a fluid at which significant erosion begins to occur on the internal surfaces of piping or equipment. This parameter is crucial in designing and operating pipelines, heat exchangers, and fired heater tubes.
This parameter is defined as a constant divide by square root of mixture density by API 14E. This constant is denoted as “c”. Different values of “c” may be used where specific application studies have shown them to be appropriate.
However, erosional velocities corresponding to constants “c” below 220 is not an acceptable practice in heaters coil design. Therefore, maximum allowable erosional velocity is set by minimum “c” value of 220.
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