Corrosive operating conditions

Complicated processes, severe corrosion operating conditions, or extensive instrumentation 3-5 4-6 7-11... 

Compressor Configuration To propeny design a centrifugal compressor, one must know the operating conditions—the type of gas, its pressure, temperature, and molecular weight. One must also know the corrosive properties of the gas so that proper metallurgical selection can be made. Gas fluctuations due to process instabilities must be pinpointed so that the compressor can operate without surging. 

Under normal operating conditions, the concentration of the trioxide is unlikely to exceed 10 ppmv, but this is sufficient to elevate the acid dew point to around 422 K (300°F). This places a limit on the lowest acceptable back-end temperature if acid condensation and resulting corrosion problems are to be avoided. 

The current yield of aluminum depends on the composition of the water and the operating conditions it usually lies between a = 0.8 and 0.9 (see Section 6.2.3). Self-corrosion occurs, as with Mg, with hydrogen evolution. 

Potential control with zinc reference electrodes presented a problem because deposits of corrosion products are formed on zinc in hot water. This caused changes in the potential of the electrode which could not be tolerated. Other reference electrodes (e.g., calomel and Ag-AgCl reference electrodes) were not yet available for this application. Since then, Ag-AgCl electrodes have been developed which successfully operate at temperatures up to 100°C. The solution in the previous case was the imposition of a fixed current level after reaching stationary operating conditions [27]. 

The determination and evaluation of potentiodynamic curves can only be used as a preliminary assessment of corrosion behavior. The protection current requirement and the limiting value for the potential control can only be determined from so-called chronopotentiostatic experiments as in DIN 50918. in systems that react with spontaneous activation after the protection current is switched off or there is a change in the operating conditions, quick-acting protection current devices must be used. Figure 8-6 shows the circuit diagram for such a potentiostat. 

Corrosion protection not only maintains the value of industrial plants and structures but also ensures safe operational conditions and the reliability of these structures it prevents damage that can endanger people and the environment. For this reason corrosion protection of such installations forms the most important means of protecting the environment. 

Operating conditions that also must be considered in selecting the enclosure type are exposure to airborne dust, dirt and moisture, the possibility of corrosive dust or vapors in the area, and the expected maximum ambient temperature. 

Causes of corrosion are the subject of extensive investigation by industry. Almost any type of corrosion can manifest itself under widely differing operating conditions. Also, different types of corrosion can occur simultaneously. It is not uncommon to see crack growth from stress corrosion to... 

The excellent corrosion resistance over a wide range of operating conditions and readily available methods of fabrication by welding and other means of shaping metals make these steels the most extensively used throughout the chemical and allied industries. 

If you conduct trials on parts and materials to prove reliability or durability, these can be considered to be verification tests. For example, you may test metals for corrosion resistance or hinges for reliability in the laboratory and then conduct validation tests under actual operating conditions when these items are installed in the final product. 

In safety applications, the corrosion resistance of the duct materials deserv es special consideration. Since material costs generally increase along with corrosion resistance, the selection of material must be determined by the desired life span in the anticipated environment this environment is a function of the characteristics of the chemical being processed and the operating conditions of the reactor. For maximum resistance to moisture or corrosive gases, stainless steel and copper are used where their cost can be justified. Aluminum sheet is used where lighter veight and superior resistance to moisture are needed. 

OPERATING CONDITIONS,EACH COMPRESSOR (Stondord Conditions 14.7psio and60 F.) Type of Gas Corrosive ... 

An ideal hydraulic liquid should be free from acids that cause corrosion of the metals in the system. Most liquids cannot be expected to remain completely non-corrosive under severe operating conditions. When new, the degree of acidity of a liquid may be satisfactory but after use, the liquid may tend to become corrosive as it begins to deteriorate. 

The construction materials should be selected to withstand the operating conditions and the condition of the pollutants. Galvanized sheet steel and black mild steel are the most common for general work. Corrosion or heat applications will have ducting constructed in stainless steel or plastic. 

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