API 686 Shaft alignment tolerances

Hello members

I would like to have clarification with regards to shaft alignment tolerances mentioned in API 686 second edition dec 2009 clause 5.4.6.2 which states"When using reverse rim ( dial) indicator methods or laser equipment that resolves alignment into reverse rim equivalent readings, the max out of tolerance is 0.5 mm per meter ( 0.5 mils per in)at both flex plane locations.

Kindly clarify if the inch mentioned in tolerance ( 0.5 mils per inch) denotes the separation between flexing planes (spacer length) or the shaft diameter or the coupling dia?

Shall be thankful for your responses

Sree60

 

[geesamand]

I would interpret that as an angular misalignment. .0005" of run over 1.0000" of length. They give it that way instead of the equivalent angle because it's easier to convert the fraction to real-world indicator readings.