Shaft Alignment & Thermal Growth Calculator
Calculate machine thermal expansion growth, target cold alignment offsets, and required front/rear foot shimming using reverse indicator and rim-face methods.
Machine Foot Spacing & Dial Geometry
Cold Dial Readings & Thermal Growth
Alignment Corrections & Target Shims
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
Why must machines be aligned "cold" with intentional misalignment offsets?
When rotating machinery heats up to operating temperature, metals expand. A hot boiler feedwater pump at 300°F expands substantially more than its ambient electric drive motor. If aligned perfectly cold, thermal growth will force the hot pump shaft high, causing severe angular and parallel misalignment during operation.
What is the formula for linear thermal expansion growth?
The thermal expansion formula is ΔL = α · L · ΔT, where α is the material coefficient of thermal expansion (approx. 6.5 × 10⁻⁶ in/in·°F for carbon steel and cast iron), L is the shaft centerline height above the baseplate, and ΔT is the temperature difference between running operating temperature and ambient installation temperature.
What are acceptable alignment tolerances for 3600 RPM vs 1800 RPM?
For 3600 RPM machines, standard industrial tolerance is ≤ 2.0 mils (0.05 mm) parallel offset and ≤ 0.5 mils/inch angularity. For 1800 RPM machines, tolerance is slightly more forgiving at ≤ 4.0 mils parallel offset and ≤ 0.7 mils/inch angularity.