Machinery Alignment Tools
Calculators and reference data for rotating machinery alignment, prepared in line with applicable API standard requirements (such as API RP 686). Turbomachinery.ai is independent and is not affiliated with, endorsed by, or authorized by API. Select a tool to get started.
Unit Conversions
mil/mm, mil/inch to mm/m, temperature conversions for alignment work
Sag Indicator
Calculate dial indicator bracket sag correction for reverse-indicator setups
Thermal Growth
Estimate vertical thermal expansion based on material, temperature rise, and centerline height
Shim Calculator
Calculate required shim changes at each foot from alignment readings and targets
Alignment Moves
Convert reverse-indicator readings to foot corrections at inboard and outboard bolt planes
Alignment Check
Compare measured alignment against Vendor or commonly used industry tolerances — PASS/FAIL assessment
API RP 686 Tolerances
Look up typical alignment tolerances by coupling type, prepared in line with applicable API standard requirements (such as API RP 686)
Unit Conversions
Common conversions for machinery alignment fieldwork.
Length / Displacement
Angularity (Slope)
Temperature
Sag Indicator Correction
Calculate the sag of a dial indicator bracket assembly. Sag must be measured and subtracted from bottom readings in reverse-indicator alignment.
Sag Measurement
Thermal Growth Estimation
Estimate vertical thermal expansion from ambient to operating temperature. Used to determine cold alignment offset targets.
Growth Parameters
Shim Calculator
Calculate required shim changes at each bolt plane to correct vertical offset and angularity.
Machine Geometry
Vertical Correction at Coupling
Alignment Move Calculator
Convert reverse-indicator dial readings to required corrections at each bolt plane.
Distances
Reverse-Indicator Readings (mils, TIR)
Enter Total Indicator Readings (TIR). Top set to zero. Positive = indicator pushed in (shaft high).
Alignment Tolerances Reference
Typical industry tolerances for rotating machinery shaft alignment. Values shown are commonly used field practices prepared in line with applicable API standard requirements (such as API RP 686); they are not reproduced from any copyrighted standard. Always verify against the current published edition of the relevant API standard (which must be obtained from API or authorized official sources) and OEM/Vendor requirements.
Select Coupling Type
Flexible Element
Disc, diaphragm, metallic membrane
Gear Coupling
Lubricated gear-tooth mesh
Elastomeric
Rubber, urethane element
Rigid / Flanged
Solid or bolted flange
Typical Alignment Tolerances
| Parameter | Tolerance | Notes |
|---|---|---|
| Offset misalignment (reverse-indicator / laser) | ≤ 0.5 mil/in (0.05 mm/100mm) | At each flex plane, after sag & thermal offsets |
| Rim & face angularity | ≤ 0.03° | At each coupling hub |
| Rim & face offset | ≤ 1 mil (0.025 mm) | At coupling center |
| Piping-induced shaft movement | ≤ 2 mils (0.05 mm) | Any direction, all flanges bolted |
| Indicator bracket sag | ≤ 0.8 mil/in of span | Measured and compensated |
| Shim packs per foot | ≤ 5 shims max | Stainless steel, clean, flat |
DBSE / Axial Spacing Check
Verify coupling axial gap against specified tolerances, prepared in line with applicable API standard requirements (such as API RP 686).
Coupling Data
Soft Foot Check & Correction
Step-by-step procedure for identifying and correcting soft foot conditions, prepared in line with applicable API standard requirements (such as API RP 686).
What is Soft Foot?
Soft foot is a condition where one or more machine feet do not make full, flat contact with the baseplate. It causes frame distortion when bolts are tightened, leading to internal misalignment, bearing distress, and unreliable alignment readings.
| Type | Description | Fix |
|---|---|---|
| Parallel (Gap) | Uniform gap under one foot | Add shim equal to gap |
| Angular (Rock) | Foot rocks on corner or edge | Machine/grind foot or step shims |
| Induced (Piping) | External forces from piping | Correct piping strain first |
| Squishy | Too many or dirty shims compress | Replace with clean SS shims (≤5) |
Check Procedure
- Torque all hold-down bolts to specified values (refer to OEM specifications; applicable API standards such as API RP 686 provide general torque guidance — obtain the current published edition from API or authorized official sources).Use calibrated torque wrench. Oil-lubricate threads unless otherwise specified.
- Mount a dial indicator on the baseplate touching the machine foot near one bolt.Use magnetic base secured to the base — not to the machine.
- Zero the indicator, then loosen the bolt at that foot.Loosen only the single bolt being tested.
- Record the indicator movement (foot lift).Positive reading = foot lifted = soft foot at that location.
- Re-tighten the bolt and confirm indicator returns to zero.If it does not return, investigate for angular soft foot.
- Repeat for all feet, one at a time.Test all four (or six) feet. Test the fixed machine if alignment proves difficult.
- Correct any foot showing > 2 mils (0.05 mm) of lift.Add pre-cut stainless steel shims matching the gap. Re-check after correction.
Alignment Condition Check
Compare measured alignment values against Vendor or commonly used industry tolerances (prepared in line with applicable API standard requirements such as API RP 686) to determine if the machine is within acceptable limits.
Coupling & Tolerances
Measured Alignment Values
Enter the measured offset and angularity from laser or reverse-indicator results. Use absolute values (unsigned).