What is shaft alignment?

Shaft alignment is the process of positioning two or more shafts so that their rotational centerlines are collinear during normal operating conditions. Proper alignment minimizes vibration, bearing loads, seal wear, and energy consumption.

What is the difference between offset and angular misalignment?

Offset (parallel) misalignment occurs when two shaft centerlines are parallel but displaced from each other. Angular misalignment occurs when shaft centerlines intersect at an angle. Most real-world misalignment is a combination of both.

How precise must shaft alignment be?

Alignment precision depends on operating speed and coupling type. At 1500 RPM with flexible couplings, tolerances are typically 0.08 mm offset and 0.10 mm/100mm angular. Higher speeds require tighter tolerances because misalignment forces increase with the square of speed.

Laser alignment vs dial indicators — which is better?

Laser alignment systems are faster, more accurate, and easier to use, especially for long spans. Dial indicators are lower cost and work well for simple setups. Laser systems typically achieve ±0.01 mm accuracy vs ±0.02–0.05 mm for dial indicators.

Why are tolerances tighter at higher speeds?

Misalignment generates dynamic forces that increase with the square of rotational speed. A small misalignment at 6000 RPM produces 16 times the force of the same misalignment at 1500 RPM, leading to accelerated bearing and seal wear, higher vibration, and potential coupling failure.

免費工程工具

軸對中公差計算器

根據聯軸器類型與運轉速度，計算旋轉機械允許的偏移與角度不對心公差。

產業經驗法則偏移與角度所有聯軸器類型

結果

偏移（平行）公差

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角度公差 (mm/100mm)

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角度公差 (mrad)

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間距處的角度間隙差

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速度等級

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聯軸器類型修正

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軸對中基礎知識

軸對中確保耦合機組在運轉條件下，其旋轉中心線保持共線。不對心是旋轉機械軸承與密封件早期失效最常見的原因。

不對心類型

偏移（平行） — 軸中心線平行但存在位移。以聯軸器處的 mm 為單位測量。
角度 — 軸中心線以一定角度相交。以 mm/100mm 或毫弧度 (mrad) 為單位測量。

依速度劃分的公差指南

下方的 RPM 分級數值為廣泛使用的產業經驗法則，源自雷射軸對中實務（由對中系統製造商如 Prüftechnik 與 Fixturlaser 發布的公差表）；並非由 ISO 標準定義。聯軸器標準如 ISO 14691（石油、石化與天然氣產業用一般用途彈性聯軸器）規範了聯軸器要求，包含不對心容許度 — 請務必以聯軸器製造商的資料為準。

轉速範圍	偏移 (mm)	角度 (mm/100mm)
≤ 750 RPM	0.10	0.15
750 – 1500 RPM	0.08	0.10
1500 – 3000 RPM	0.05	0.07
3000 – 6000 RPM	0.03	0.04
> 6000 RPM	0.02	0.03

聯軸器類型修正

彈性一般 — 基準公差 (×1.0)
彈性高性能 — 更嚴格 (×0.5)
剛性聯軸器 — 最嚴格 (÷2，等同於 ×0.5)

角度間隙差 = 角度公差 (mm/100mm) × 間距長度 (mm) / 100

實務範例

範例 — 1500 RPM 離心泵浦

已知： 速度 = 1500 RPM，聯軸器 = 彈性一般，間距 = 100 mm

速度範圍：750–1500 RPM → 偏移 = 0.08 mm，角度 = 0.10 mm/100mm

聯軸器修正：×1.0（彈性一般）

偏移公差 = 0.08 mm

角度公差 = 0.10 mm/100mm = 1.00 mrad

間距處的間隙差 = 0.10 × 100/100 = 0.10 mm

⚠️ 注意： 這些為一般產業指引。請務必查閱聯軸器製造商的規格，其要求可能因設計不同而更嚴或較寬。對於高溫運轉的機組，需考量熱膨脹效應。

軸對中公差計算機 | 免費線上工具

結果

軸對中基礎知識

不對心類型

依速度劃分的公差指南

聯軸器類型修正

實務範例

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