One documented plane · comparison arithmetic only

Documented Shaft-Alignment Criterion Comparison

Normalize one signed planar shaft-offset and angularity measurement, compare their magnitudes with externally approved values and derive the small-geometry quantities transparently.

no RPM lookupno coupling multiplierno automatic targetno machine-acceptance verdict

This page does not generate alignment tolerances. The applicable method, quality grade, flex-plane or offset/angularity format, vertical/horizontal criteria, cold targets, thermal movement, coupling geometry, OEM limits and uncertainty treatment must be established in the controlling procedure.

Controlled planar measurement record

Use values from one declared vertical or horizontal plane, one declared reference plane and one machine state. Signed measurements are allowed; comparison values must be positive.

Offset unitChanging the unit clears both offset entries and the result.

Signed measured offset oSign follows the recorded plane/direction convention.

Approved offset comparison value O_limPositive magnitude in the selected offset unit.

Angularity-slope unitThese are slope units; changing unit clears both angular entries.

Signed measured angularity a

Approved angularity comparison value A_limPositive magnitude in the selected angularity unit.

Reference-span unitChanging unit clears the span and result.

Documented reference span LUsed only for Δ=sL; this page does not choose the correct machine dimension.

Machine train, shafts and coupling ID

Coupling type, format, flex planes and geometry record

Measurement state and operating target record

Measurement plane, reference plane and sign convention

Measurement method, rotation practice, repeatability and calibration

Governing source, edition/revision, exact location and jurisdiction

Meaning and inclusivity of entered comparison values

Measurement error, uncertainty and acceptance-decision rule

Calculation record ID, intended use and competent reviewer

Required compatibility confirmation The two measurements and two comparison values use the same declared offset/angularity format, reference plane, coordinate plane, sign convention and machine state. The comparison values were approved outside this page for the recorded machine, coupling geometry, operating state, speed and jurisdiction; no RPM table or multiplier from this page was used. Thermal/OLTR targets, soft foot, runout, pipe strain, measurement uncertainty, coupling limits and both required planes/flex planes are handled in the controlling procedure. I will treat “within/outside entered comparison” only as arithmetic, not as proof of machine acceptance, reliability, safety or standards conformity.

Documented arithmetic comparison

Offset relation to entered comparison value

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Uses |o| and the user-controlled inclusive O_lim.

Signed offset, normalized

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Offset utilization and headroom

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Headroom = O_lim−|o|; negative means outside the entered value.

Angularity relation to entered comparison value

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Uses |a| and the user-controlled inclusive A_lim.

Signed angularity slope, normalized

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Exact angle θ=atan(s)

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mrad is calculated from atan(s), not the small-angle identity θ≈s.

Angularity utilization and headroom

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Signed linear separation change over L

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Δ=sL; not automatically a shim move, coupling-face gap or foot correction.

No overall pass/fail is produced. Both coordinate planes and, where applicable, both flex planes must be evaluated under the correct controlled method. The result does not assess foot moves, thermal targets, runout, soft foot, pipe strain, coupling loading or uncertainty.

Equations, source boundaries and removed defects

o(mm)=o(mil)×0.0254; 1 mil=0.001 in=0.0254 mm exactly

s=a(mm/100 mm)/100=a(mil/in)×0.001; θ=atan(s)

Δ=sL; utilization=|measurement|/comparison value; headroom=comparison value−|measurement|

These are unit conversions, plane-geometry relationships and arithmetic comparisons. They are not presented as an ISO, ANSI/ASA or API tolerance-selection formula. The signed value preserves the recorded direction; the comparison uses magnitude.

Why the former speed/coupling lookup was removed

The previous page selected one five-band table from RPM alone, then applied ×1.0, ×0.75 or ×0.5 according to “flexible”, “high-performance” or “rigid” coupling. No controlled source established those values or factors. It also used a spacer length as a generic gap dimension, although the correct tolerance format and geometry depend on the measurement method and coupling arrangement.

The official Prüftechnik on-board help states that, even for the same tolerance type, RPM and coupling diameter, values differ with coupling format; it also says there are no tolerance tables for consolidated spacer-shaft formats. That directly contradicts a universal RPM table plus coupling multiplier.

Official lifecycle and public scope inspected

Source	Public status and scope used
ANSI/ASA S2.75-2017/Part 1	The official ASA catalogue lists “Shaft Alignment Methodology, Part 1: General Principles, Methods, Practices, and Tolerances” as reaffirmed in 2025. The licensed grade equations/tables and application details are not reproduced here.
ISO 14691:2008	Published edition 2, confirmed in 2024. It covers specified general-purpose petroleum/petrochemical/gas flexible couplings, typically stiff-shaft applications not exceeding 4000 r/min; it excludes rigid and several special coupling types and does not define coupling-type selection criteria.
ISO 10441:2007	Published edition 2 and under systematic review in 2026. It covers specified special-purpose couplings for large/high-speed/critical services, excludes rigid and several other types, and does not define coupling-type selection criteria.
Prüftechnik Shaft Alignment on-board help, Version 2.0, p.56	Official manufacturer manual visually inspected. It documents the coupling-format dependency and spacer-format limitation described above; it is not treated as a universal machine acceptance standard.
NIST Guide to the SI, Appendix B.8	Exact length conversions: 1 in=0.0254 m and 1 mil (0.001 in)=0.0254 mm.

Accessed: 15 July 2026. Licensed-source boundary: NEEDS_LICENSED_SOURCE for ANSI/ASA alignment-grade formulas/tables, any exact API/ISO clause or value, and any OEM/site acceptance target. This page therefore requires externally approved values instead of guessing them.

Exact numerical checks

Entrées	Expected normalized result
o=−0.05 mm; O_lim=0.08 mm; a=0.10 mm/100 mm; A_lim=0.12 mm/100 mm; L=150 mm	offset utilization=0.625; headroom=0.03 mm; slope=0.001; θ=0.999999666666867 mrad; angular utilization=5/6; Δ=0.15 mm
o=−1.96850393700787 mil; O_lim=3.1496062992126 mil; a=1 mil/in; A_lim=1.2 mil/in; L=5.90551181102362 in	same physical quantities and comparison relations, within numerical tolerance
o=0 and a=0 with positive controlled limits	valid zero measurements; zero utilization and full entered headroom

Competent alignment procedure required. Do not move or release machinery from this worksheet alone. Verify the controlling licensed standard/OEM instructions, lockout and safety procedure, soft foot/base/pipe condition, measurement repeatability, thermal targets and all required planes.