Thermal shock equipment

EXPERIMENTAL PROCEDURE Ablation/Thermal Shock Equipment... 

The resistance of graphite to thermal shock, its stabiUty at high temperatures, and its resistance to corrosion permit its use as self-supporting vessels to contain reactions at elevated temperatures (800—1700°C), eg, self-supporting reaction vessels for the direct chlorination of metal and alkaline-earth oxides. The vulnerabiUty of cemented joints in these appHcations requires close tolerance ( 0.10 mm) machining, a feat easily accompHshed on graphite with conventional metal machining equipment. 

Thus, unacceptable stresses can arise in rigid construction materials in apparatus, equipment, piping, etc. if subjected to large temperature fluctuations. For example, conventional glass is prone to failure due to thermal shock. 

Ring-seals of all kinds tend to be mechanically weak and sensitive to thermal shock. Tungsten-through-glass seals and pockets for thermocouples or conductivity probes are the most frequent instances of ring-seals on vacuum equipment, and these should never be subjected to extreme cold. 

It is costly to make and fabricate because temperature in excess of 1800°C is required lo manufacture it. However, its refractory character coupled with its very high resistance to thermal shock makes it ideal for special laboratory equipment, windows in high-temperature environments, and instruments. 

Another cause of water hammer is lack of proper drainage ahead of a steam control valve. When the valve opens, a slug of condensate will enter the equipment at a high velocity, producing water hammer when it impinges on the walls. In addition to this, the mixing of the steam that follows with the relatively cool condensate will produce water hammer from thermal shock. This condition can be corrected by dripping the supply riser as shown in Fig. 1. 

A technique which has proven useful for our studies is that of cylindrical internal reflectance (CIR), coupled with a Fourier transform infrared spectrometer. In this study, an IBM-85 FTIR equipped with either a DTGS (deuterated triglycine sulfate) or MCT (mercury-cadmium-tellurium) detector was used. The infrared radiation is focused by concave mirrors onto the 45° conical ends of a transmitting crystal (Figure 1). The crystal may be made of any material which is optically transparent, has a high mechanical strength and high index of refraction, and is resistant to thermal shock and chemical attack. Suitable materials include ZnS, ZnSe,... 

Erosion/Attrition/Thermal Shock. The high velocities of balls in lift pipes and the turbulent nature of the fluidized beds lead to the possibility of erosion of the equipment and attrition or fracturing of the balls. Erosion can be reduced by using abrasion resistant refractory linings in pipes. Attrition and fracturing of balls can be reduced by proper design to reduce the effect of impaction at elbows and on deflection plates. 

Channeling] nonuniform catalyst bed density/low superficial flowrate <1.4 kg/s m /off set, tilted or faulty feed distributor/thermal shock to upstream pipes or equipment causes scale to dislodge and buildup on bed/intemal vessel obstructions such as thermowells or supports. 

The chief problem with outdoor installation is the exposure to weather, especially in a cold climate. A building not only protects woikers fix>m exposure to the weather, it also shields equipment from sun, rain and snow (with their thermal shock), sand and dust storms, and corrosion. The protection offered by a building slows the natural process of deterioration of system components and helps to avoid foreign deposits that can allow short-circuiting of cell connections. 

The cheapest form is soda-glass, which is brittle and sensitive to thermal shock, but borosilicate glass, for example Pyrex or Hysil, is stronger and has a greater resistance to thermal shock. It has a wide range of application as pipes, valves, heat exchangers, and small vessels. It enables several acids to be handled in the same pipeline and has the added advantage that, since it is transparent, the interior of such equipment is clearly visible. 

Stainless steel fibres are added to concrete refractory elements to provide better resistance against cracking and spalling due to thermal cycles and thermal shocks. A considerable increase in service life abundantly covers the additional costs paid for fibres. Strongly reinforced cement-based elements are also applied as part of machinery equipment. 

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