Dry rising main

Dry rising main is a rising water main that is normally kept empty but with facilities at groxmd level to enable the fire brigade to connect their pumps. 

Dry rising mains - as the name suggests all dry water mains are fitted vertically within a building. They are operated exclusively by the fire service who when necessary will charge the dry mains with water via inlet... 

Wet rising mains - where a rising main is required to be used for fire service at a height above 50 metres, it is necessary to provide wet risers. Wet risers are similar to dry risers apart from that they are constantly charged with a water suppiy from a source that is able to provide water at a sufficient pressure to reach the required height. 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

The most important data during main drying is the temperature at the moving sublimation front which cannot be measured by Ths or RTDs. In 1958, Neumann and Oetjen 11.651 showed that the barometric temperature measurement (BTM) measures exactly this data. In Fig. 1.77 this is schematically shown if the drying chamber is separated from the condenser by a valve for a short time the pressure in the chamber rises to the saturation vapor pressure (ps) corresponding to the temperature of the sublimation front. ps can be converted into the ice temperature by the water vapor- temperature diagram (e. g. 0.3 mbar = -30 °C). Data for accurate conversion are given in Table 1.11 the temperatures between -100 and -1 °C. 

Dry coating is probably the main method used in preparing products for thermoplastic applications. Due to the cost of additional drying operations, it is the method of choice when the filler itself is produced by a dry process. It is also useful where wet coating procedures would give rise to effluent problems. 

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