Annulus (Ring) Area

The area of a ring between two circles - the metal cross-section of a pipe or tube, a washer/gasket/ring-flange face, or a circular border. ring = (pi/4)(D^2 - d^2) = pi(R^2 - r^2), the outer circle minus the hole. A 6.625 OD, 6.065 ID pipe (NPS 6 sch 40) has a 5.58 in^2 metal cross-section - the published value, which times the steel density (0.2836 lb/in^3) gives 19 lb/ft or times the allowable stress gives the tension capacity; the 28.89 in^2 bore is the flow area, and the wall is 0.280 in. d = 0 gives a full circle. An eccentric ring, a sector ring, and the tube volume are separate. A shop and layout aid; verify critical dimensions on the work.

ring area = (pi/4)(D^2 - d^2) = pi(R^2 - r^2); outer = (pi/4) D^2; bore = (pi/4) d^2; wall = (D - d)/2. d=0 -> full circle.

The annulus (ring) area (pi/4)(D^2 - d^2) - standard plane geometry as in Machinery's Handbook (Industrial Press), by name; public domain.

Pure plane geometry, public; the outer and inner diameters are user-supplied measurements.

Estimate. AHJ and licensed professional govern.

Field names used by the API: outer_diameter, inner_diameter, ring_area, bore_area, wall_thickness

• Ring area (pi/4)(D^2 - d^2) = outer circle minus the boreplane geometry
• Pipe metal the ring is the pipe/tube metal cross-section; bore is the flow areageometry
• Scope concentric flat ring; eccentric/sector rings and tube volume are separatescope of this tile