The raised face is not included in Flanges' strength calculations. The standard thickness of the raised face is 0.06in (1.5mm) for all flange ratings up to and including 300lb and 0.25in (6.35mm) for all other flange ratings.
Raised Faces are used for a number of reasons:ġ) Easier gasket positioning and visibilityĢ) Facilitate high pressure (RTJ) gasketsģ) It is easier to install a leak detection facility ( Fig 2) Swivel Ring flanges are used for loose or integral flanges whose bolting ring must rotate to allow for stud-bolt alignment during assembly. These flanges tend to be reserved for low pressure applications and those where external loads are negligible.
This facility is handy where the flange and pipe are manufactured from different materials. A stub-end is inserted in the flange and the stub-end is butt welded to the pipe. Lapped (loose) flanges are for applications where the flange and pipe are not to be welded together. These flanges tend to be used in low-cost, low-demand applications. Slip-On (loose) flanges are for similar applications as the Socket design, except that they are more susceptible to erosion, corrosion, shock loading and vibration. The socket design provides a smooth-bore through the joint significantly reducing erosion potential from multi-phase fluids. Socket (loose) flanges are usually found on small-bore (≤3"), high-pressure, high-flow, multi-phase piping systems where external flange loading is minimal. For example: Welding Neck (integral) flanges are mostly used in pipelines and for the most demanding applications in terms of mechanical and hydrostatic loading. Whilst these flanges are, in theory, interchangeable, each type is normally associated with a preferred application. The principle flange designs are show in Fig 1. Standard flanges are designed to remain pressure-tight even if yield stress is exceeded. it is not a focus for weakness, because it would otherwise leak before it fails structurally. It is usual to ensure that a flanged joint is stronger than the pipe or nozzle to which it is attached, i.e. that contain flowing and/or pressurised fluid(s). A flange is a means of joining two conduits such as nozzles, pipelines, piping, tubing, etc.