How do I identify a vibration source from frequency?

Most vibration faults produce characteristic frequency patterns related to shaft running speed. 1x RPM typically indicates unbalance, 2x RPM indicates misalignment, sub-synchronous frequencies (0.42-0.48x) indicate oil whirl in journal bearings. By analyzing which frequencies are dominant in the vibration spectrum, you can narrow down the most likely fault sources.

What is 1x vibration?

1x vibration (also called synchronous vibration) occurs at exactly the shaft rotational frequency (1 times RPM). It is the most common vibration component and is primarily caused by mass unbalance. Other causes include bent shaft, misalignment, looseness, and resonance. Phase angle analysis helps distinguish between these causes.

What causes sub-synchronous vibration?

Sub-synchronous vibration occurs below shaft running speed. Common causes include: oil whirl (0.42-0.48x in journal bearings), oil whip (locked at rotor natural frequency), rub (various sub-harmonics), looseness (0.5x and fractional harmonics), and belt drive problems.

What causes high-frequency vibration?

High-frequency vibration (above 10x RPM) is typically caused by: rolling element bearing defects (BPFO, BPFI, BSF), gear mesh frequencies, blade/vane pass frequencies, electrical noise, resonance of structural components, or cavitation in pumps.

What role does phase angle play in vibration diagnosis?

Phase angle is critical for distinguishing faults with similar frequency signatures. For 1x vibration: stable phase = unbalance, 180-degree phase difference across coupling = misalignment, unstable/shifting phase = looseness. Phase is measured using a tachometer reference signal and indicates the angular relationship between the vibration peak and shaft position.

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振動來源識別器

互動式診斷工具 — 輸入振動頻率（以運轉轉速的轉數表示）以識別旋轉機械的可能故障源。

頻譜分析故障診斷轉數追蹤

診斷結果

最可能來源

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運轉轉速頻率

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振動轉數

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完整頻率–故障對照表

振動頻率分析

每種機械故障都會產生與軸旋轉速度相關的特徵頻率振動。透過識別振動頻譜中的主要頻率，並將其表示為軸轉速的轉數（倍數），即可確定最可能的故障源。

轉數計算

轉數 = f_vibration / f_running = f_vibration / (RPM / 60)

其中 f_vibration 為測得的主要頻率（單位 Hz），而 RPM 為軸旋轉速度。

常見故障頻率

階次	頻率	主要來源	其他指標
1x	軸轉速	不平衡	相位穩定，與轉速平方成正比
1x	軸轉速	軸彎曲	軸向振動高，相位穩定
2x	2 x 軸轉速	不對心	軸向振動高，聯軸器兩側相位差 180°
3x	3 x 軸轉速	嚴重不對心	存在多個諧波
0.42–0.48x	次同步	油膜渦動	滑動軸承，與轉速相關
0.5x	軸轉速的一半	鬆動 / 摩擦	分數次諧波
多個諧波	1x, 2x, 3x…	機械鬆動	運轉轉速的多個諧波
非同步	BPFO, BPFI, BSF	軸承缺陷	受運轉轉速調變
Z x RPM	葉片通過頻率	流體問題	脈動、空蝕
Z x RPM	齒輪嚙合	齒輪問題	邊帶指示是哪個齒輪
2x 線 (100/120 Hz)	固定頻率	電氣	斷電後消失

相位角指南

相位分析至關重要 用於區分相同頻率下的故障。在 1x：相位穩定 = 不平衡，聯軸器兩側相位差 180° = 不對心，相位不穩定 = 鬆動。務必使用轉速計參考。

實務範例

範例 — 轉速 1500 RPM 的馬達，振動頻率 75 Hz

已知： 運轉轉速 = 1500 RPM，主導頻率 = 75 Hz

運轉轉速頻率 = 1500 / 60 = 25 Hz

轉數 = 75 / 25 = 3.0x

主要疑點： 嚴重不對心或機械鬆動

建議：檢查聯軸器對中，檢查安裝螺栓，確認基礎

⚠️ 注意： 此工具提供基於常見故障頻率關係的指導。確切診斷需結合相位資料、時間波形、軌跡圖、運轉條件及設備歷史進行比對。務必透過額外測量進行驗證。