SAND EROSION

We is the pure erosion rate, i.e. mass loss rate when corrosion is eliminated, and Wc is the corrosion rate in the absence of sand erosion. Wec and Wce are both synergy effects Wec is the increase in erosion rate due to corrosion and Wce is the increase in corrosion rate due to erosion. 

In several cases, materials for combined erosive and corrosive conditions have been evaluated on the basis of separate erosion and corrosion studies and data, with the consequence that the synergistic effects are left out of the evaluation. Since one or the other of these effects may be large, the conclusions may be quite wrong. For materials fliat usually are passive due to a dense oxide film, such as stainless steels, Wc is by definition very low. But since sand erosion more or less destroys the passive film, the corrosion rate increases strongly and may reach very high values, i.e. the contribution of Wce may be particularly high for these materials. The other synergy effect, Wec, is most pronounced for ceramic-metallic materials in which the metallic phase has inferior corrosion resistance, e.g. for a cemented carbide with a metallic phase of cobalt (WC-Co). 

Possible operating problems for such dryers include deposit formation and erosion of the flash tubes due to high-velocity transport of particles that may contain abrasive impurities such as sand. Erosion, particularly in bends, can be minimized or taken care of by using special materials or replaceable elbows. Deposits may form within the dryer walls if the transporting steam temperature falls to saturation level. Corrosion is also a problem to be considered. Often, stainless steel construction is required. It is important to disintegrate the solids prior to feeding in the flash dryer as the transport steam does not suspend large lumps and the like. 

Calculated sand erosion mass loss values at 80 m/s for ZnS and Ge (to allow a comparison with CVD diamond) are based upon up-scaling theories (using erosion rate velocity scaling factors) from work undertaken at the Cavendish Laboratory [45]. 

Figure 16. Reduction in transmission as a function of sand erosion time for a CVD diamond window compared to a sapphire window.

Figure 8. Aluminum phosphate-coated barium aluminosilicate (BAS) showed 30-40% improvement on erosion test. The eroded area during a sand erosion test is circled in the right side photograph.

This paper focuses on how to model the deterioration of static pressurized process equipment to enable efficient inspection and maintenance planning. Such equipment tends to gradually deteriorate over time from erosion, corrosion, fatigue and other mechanisms, and at some point of time inspection, repair or replacement is expedient with respect to safety, production and costs. The deterioration of the equipment is influenced by many factors such as type of equipment, system design, operation and process service, material and environment. For hydrocarbon systems, the most critical deterioration mechanisms are corrosion due to CO2 and H2S, microbially influenced corrosion, sand erosion and external corrosion (DNV 2002). In general, CO2 is the most common factor causing corrosion in oil and gas system of low alloy steel (Singh et al. 2007). 

Wind, dust, sand Erosion and deposition - strength change - deterioration of surface - malfunction of components... 

Rain and sand erosion Both Protect surfaces with paint or elastomer, composite response is significantly different from metals. 

The case-study is based on an actual sand erosion issue present in an offshore oil production system. Material degradation due to processes of erosion/corrosion is the main focus. The production system is located subsea and connected to a spread-moored FPSO (Floating Production Storage and Offloading) unit, which is used as a hub, processing the fluids produced from the subsea wells. 

The top event is material degradation due to sand erosion/corrosion. The identified consequences that can derive from sand erosion/corrosion are ... 

Material degradation may be caused by sand erosion or corrosion. As shown in Figure 1, two potential threats leading to sand erosion or corrosion are identified. The first threat focuses on excessive sand production rate. This does not only mean that there is an increase in sand production, but also that the velocity of the flow in which sand is carried exceeds a critical threshold. In order to prevent this threat to develop into pipeline material degradation, two safety barriers are in place ... 

A variety of problems may occur in condensers and heat exchangers using seawater as a coolant. These include impingement corrosion, sand erosion and pitting. External corrosion may also occur if gases, such as carbon dioxide, are dissolved in the condensate. The following are the causes of major tube failures ... 

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