Why do bearings fail at high temperature?

High temperatures cause bearing failure through multiple mechanisms: the steel loses hardness above 120–150 °C (through-hardened bearings), lubricant breaks down and oxidizes faster, thermal expansion reduces internal clearance leading to increased friction and heat generation, and grease thickens or liquefies losing its ability to form a proper lubricating film. As a rule of thumb, every 15 °C rise above the rated temperature roughly halves bearing life.

What is motor insulation class and why does it matter?

Insulation class (per IEC 60034-1) defines the maximum allowable temperature for the winding insulation in an electric motor. Classes A (105 °C), B (130 °C), F (155 °C), and H (180 °C) indicate the hotspot temperature the insulation can withstand continuously without degrading. Exceeding the rated class temperature accelerates insulation breakdown — every 10 °C above the limit roughly halves insulation life (Arrhenius rule).

How does temperature affect seal life?

Elevated temperatures cause seals to harden, lose elasticity, and develop cracks (compression set). Each elastomer has a characteristic maximum temperature above which degradation accelerates exponentially. For example, NBR (nitrile) seals begin hardening rapidly above 100 °C, while FKM (Viton) remains flexible up to 200 °C. Running a seal at just 10–15 °C above its rated limit can reduce its service life by 50% or more.

How do you measure component temperature accurately?

Common methods include: contact thermocouples or RTDs placed directly on the component surface, infrared (IR) thermometers for non-contact spot readings, thermal imaging cameras for full surface temperature mapping, and embedded temperature sensors (e.g., PT100 in motor windings). For bearings, measure on the outer ring housing — actual bearing raceway temperature is typically 10–20 °C higher than the outer surface reading.

What is the rule of thumb for temperature and bearing life?

A widely used rule of thumb states that for every 15 °C increase in bearing operating temperature above the recommended limit, bearing life is approximately halved. This is because higher temperatures degrade lubricant faster, reduce steel hardness, and increase thermal expansion. Conversely, reducing operating temperature by 15 °C can roughly double bearing life. This makes temperature monitoring one of the most effective predictive maintenance tools.

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元件溫度極限

軸承、密封件、潤滑劑、電動馬達與彈性體之最高操作溫度互動參考。輸入您的測量溫度以檢查安全極限。

IEC 60034-1 軸承 · 密封件 · 馬達 °C / °F

結果

最高連續溫度

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最高短期溫度

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軸承

元件	最高連續溫度	最高短期溫度
標準鋼製軸承（通體硬化）	120 °C	150 °C
高溫軸承（特殊鋼材）	200 °C	250 °C
陶瓷混合軸承	300 °C	350 °C
軸承潤滑脂（標準鋰基）	120 °C	130 °C
軸承潤滑脂（合成聚脲基）	160 °C	180 °C

密封件

材料	最低溫度	最高連續溫度	最高短期溫度
NBR（丁腈橡膠）	−30 °C	100 °C	120 °C
FKM (Viton)	−20 °C	200 °C	230 °C
PTFE	−200 °C	260 °C	300 °C
EPDM	−50 °C	150 °C	170 °C
矽膠	−60 °C	200 °C	230 °C

潤滑劑

類型	最高連續溫度
礦物油	90 °C
合成 PAO	150 °C
合成酯類	180 °C
PFPE（全氟化）	260 °C
鋰基潤滑脂	120 °C
聚脲基潤滑脂	160 °C

電動馬達 — 絕緣等級 (IEC 60034-1)

級別	線圈最高熱點溫度
A 級	105 °C
B 級	130 °C
F 級	155 °C
H 級	180 °C

橡膠 / 彈性體

材料	最低溫度	最高連續溫度
天然橡膠	−50 °C	80 °C
氯丁橡膠	−40 °C	100 °C
矽橡膠	−60 °C	200 °C
聚氨酯	−30 °C	80 °C

溫度換算

所有內部資料均以 °C 儲存。攝氏與華氏的換算公式：

狀態閾值

正常（綠色）： 測量溫度低於最高連續溫度的 80%
警告（黃色）： 測量溫度介於最高連續溫度的 80% 至 100% 之間
危險（紅色）： 測量溫度超過最高連續溫度

實務範例

範例 — 泵驅動中的標準軸承

已知： 標準鋼製球軸承在外殼測得 105 °C。

最高連續溫度 = 120 °C，最高短期溫度 = 150 °C

測量值 105 °C = 最高連續溫度的 87.5% → 警告區間 （80–100%）

實際內圈滾道溫度可能為 115–125 °C（比外殼高 10–20 °C）

建議： 接近熱極限。請調查根本原因 — 可能是潤滑劣化、不對心或過載。

💡 提示： 每高於額定溫度 15 °C，軸承壽命約減半。溫度監測是最有效的預測性維護工具之一。