Flanged joints flange design

Differential thermal expansion between various components of calandrias, especially shell-and-tube types, has an important effect on the mechanical design of the equipment. Some types of tubular exchangers incorporate into the basic design and fabrication means to provide for thermal expansion. Other types, specifically fixed tubesheet units, must often be provided with expansion joints in the shell to meet specified differential thermal expansion between the tubes and shell. Another critical area affected by thermal expansion in fixed tubesheet units is the shell-to-tubesheet juncture. Gasketed joints may also be affected by thermal expansion therefore both the flange design and the gasket selection in... 

Sheet 2. Slip-on or lap-joint flange design with ring-type gasket... 

A variation on the bolted-flange joint is the field-welded joint. This design is most suitable for lines that are rarely dismantled. The lines are shipped unassembled to the site and the inner and outer casings are then welded together. The joint sleeve is then evacuated and sealed. The field-welded joint is relatively inexpensive but difficult to disassemble. 

Pressure-seal joints (Fig. 10-142) are used for pressures of 4.4 MPa (600 Ibf/in") and higher. They use less metal than flanged joints but require much more machining of surfaces. There are several designs, in all of which increasing fluid pressure increases the... 

Because there are neither flanges, nor packed or gasketed joints inside the shell, potential leak points are eliminated, making the design suitable for higher-pressure or potentially lethal/toxic service. However, because the tube bundle carmot be removed, the shellside of the exchanger (outside the tubes) can only be cleaned by chemical means. 

Containment sound design of equipment and piping, to avoid leaks. For example, specifying welded joints in preference to gasketed flanged joints (liable to leak). 

Processes and equipment should be designed to reduce the chances of mis-operation by providing tight control systems, alarms and interlocks. Sample points, process equipment drains, and pumps should be sited so that any leaks flow into the plant effluent collection system, not directly to sewers. Hold-up systems, tanks and ponds, should be provided to retain spills for treatment. Flanged joints should be kept to the minimum needed for the assembly and maintenance of equipment. 

In assembling flanged joints, the gasket shall be uniformly compressed to the proper design loading. 

A so-called Rosett cell can be fitted with a flanged lid (Fig. 7.12). The design of the Rosett cell allows the irradiated reaction mixture to be sonically propelled from the end of the probe around the loops of the vessel and thus provides both cooling (when the vessel is immersed in a thermostatted bath) and efficient mixing. A PTFE sleeve provides a vapour tight fit between the probe and the glass joint. 

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