Prism Ball Back-Point Location
Back Point Measurement
Establishing pipe orientation and centerline vectors using direct prism observations in automet® FAB.
Overview
The back point establishes the trajectory and orientation of the attached pipe run relative to the measured flange face plane.
Unlike diameter points or stop points, **the back point is measured using the standard 44 mm prism ball directly on the pipe surface without any survey adapter device** (such as a type 7 device).
Direct prism ball placement for back point observation on pipe body
Measurement Guidelines
- Hardware setup: Place the prism ball directly against the outer pipe wall along the pipe centerline. Do not attach the type 7 device.
- Placement location: Position the observation anywhere along the pipe run heading away from the flange face.
- Data purpose: automet® FAB uses the back point vector in conjunction with the diameter points to calculate spatial alignment and determine elbow/fitting offsets during analysis.