Bolted flanged joints

Flanged joints are used for connecting pipes and instruments to vessels, for manhole covers, and for removable vessel heads when ease of access is required. Flanges may also be used on the vessel body, when it is necessary to divide the vessel into sections for transport or maintenance. Flanged joints are also used to connect pipes to other equipment, such as pumps and valves. Screwed joints are often used for small-diameter pipe connections, below 40 mm. Flanged joints are also used for connecting pipe sections where ease of assembly and dismantling is required for maintenance, but pipework will normally be welded to reduce costs. 

Flanges range in size from a few millimetres diameter for small pipes, to several metres diameter for those used as body or head flanges on vessels. 

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Lake, G. F. and Boyd, G. (1957) Proc. Inst. Mech. Eng. 171, No. 31, 843. Design of bolted flanged joints of pressure vessels. 

EN 1450 Glass-reinforced thermosetting plastics (GRP) components - test methods to prove the design of bolted flange joints. 

For joining the strings together a number of possibilities existed. These were butt welds, extrusion welds and bolted flange joints. Hoechst and Messer Griesheim who are material suppliers and welding machinery manufacturers respectively, were visited for discussion and demonstration of welding techniques. In the event, it did not prove practical to use... 

In the event, bolted flange joints were used. The HOPE flanges were made separately from cast sheet and were welded to the stub pipe at the sub-contractoPs works. 

Razi P, Esmaeel R A, Taheri F (2012) Improvement of a vibration-based damage detection approach for health monitoring of bolted flange joints in pipelines . Journal of Structural Health Monitoring, under review. May 2012. 

Machining (lathe/mill/drill) Bolting (flanged joints)... 

Fig. 7.32. Bolted-flange joint for cryogenic transfer line.

Vacuum-Insulated Line Joints. A variety of connectors or joints are commonly used to link the sections of vacuum-insulated pipe. One low-performance type of joint is the bolted-flange joint shown in Fig. 7.32. The flange must be sealed with stainless steel or Teflon O-rings and the bolts must be checked periodically to ensure that they have not loosened by thermal cycling. The flange is usually insulated with fiberglass, foam, or powder insulation. 

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. 

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