Jackets selection

The jacket pressure and reactor pressure also influences jacket selection. If the jacket pressure is large the reactor wall thickness becomes large, reducing... 

The fact that the polymer contains no halogens along with certain unique compounding techniques for flame resistance prompts the selection of ethylene—acryflc as jacketing material on certain transportation/mifltary electrical cables and in floor tiles. 

Recommended Thickness of Insulation Indoor insulation thickness appears in Table II-2I, and outdoor thickness appears in Table 11-22. These selections were based upon calcium silicate insulation with a suitable aluminum jacket. However, the variation in thickness for fiberglass, cellular glass, and rockwool is minimal. Fiberglass is available for maximum temperatures of 260, 343, and 454°C ( 500, 650, and 850°F). Rock wool, cellular glass, and calcium sihcate are used up to 649°C (I200°F). 

The general charac teristics of the main types of reac tors—batch and continuous—are clear. Batch processes are suited to small production rates, to long reaction times, or to reactions where they may have superior selectivity, as in some polymerizations. They are conducted in tanks with stirring of the contents bv internal impellers, gas bubbles, or pumparound. Temperature controf is with internal surfaces or jackets, reflux condensers, or pumparound through an exchanger. 

The pitch of the coils and the area covered can be selected to provide the heat transfer area required. Standard pipe sizes from 60 imn to 120 mm outside diameter area are often used. Half-pipe construction can produce a jacket capable of withstanding a higher pressure than conventional jacket design. 

Figure 9-88 illustrates a falling film type absorber using water jacketed tubes in the cooler-absorber. The tails tower removes last traces of HCl in the vents. Figure 9-89 is a preliminary selection chart for this type of unit. 

When boiler aesthetics play some part in the selection process, modem vertical boilers also win, as apart from being highly efficient and compact units, some designs look particularly smart and provide a quality image because of their polished stainless-steel outer jackets. 

Jacket or Zone Select Wall temp control (1)... 

Factors to consider when selecting the type of jacket to use are listed below ... 

Heat transfer rate required select a spirally baffled or half-pipe jacket if high rates are required. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

A major goal in wall cooling is to spread out the hot zone and prevent very high peak temperatures. High peak temperatures cause poor reaction selectivity, cause carbon formation, deactivate catalysts, and cause corrosion problems in the reactor walls. CocuJTent flows spread out the hot zone and cause lower peak temperatures, but many additional design features must be considered in designing jacketed reactors. 

One problem with temperature programming in both GC and HPLC is the cooldown time after each run [70]. An interesting solution to this problem was the use of two thermostated baths that could be selectively circulated through the column jacket. This allowed the column temperature to be quickly cycled back to the initial temperature after a step-gradient elution. 

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