ISO 4406 defines a code system for reporting particle contamination in hydraulic fluids using three numbers X/Y/Z for particles ≥4μm(c)/≥6μm(c)/≥14μm(c) per mL. Each code number represents a range of particle counts doubling with each increment.

What target cleanliness for servo valves?

Servo valves require 16/14/11 or cleaner. Proportional valves: 18/16/13. Standard directional valves: 20/18/15. Gear pumps: 20/18/15. Vane pumps: 18/16/13. Piston pumps: 17/15/12.

What is a β-ratio (beta ratio)?

The β-ratio (filtration ratio) is the ratio of upstream to downstream particle counts at a given size. β₁₀ = 200 means the filter removes 99.5% of particles ≥10μm. Higher β = better filtration. Per ISO 16889.

How to improve oil cleanliness?

1) Install finer filters with higher β-ratio. 2) Add kidney-loop (offline) filtration. 3) Use sealed reservoirs with breather filters. 4) Filter new oil before adding. 5) Use clean fill practices. 6) Reduce ingression sources.

How often should oil samples be taken?

Critical systems (servo): monthly. Standard hydraulics: quarterly. Low-duty systems: semi-annually. Always sample after maintenance, fluid changes, or when problems occur. Use consistent sampling points and methods.

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液壓油清潔度分析儀

ISO 4406 代碼計算器，提供目標清潔度查詢、濾芯 β 值建議，以及依元件類型的採樣間隔指引。

ISO 4406濾芯 β 值目標清潔度

分析結果

目前 ISO 4406 代碼

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元件目標值

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狀態

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所需濾芯 β 值

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建議濾芯精度

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採樣間隔

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每小時液體交換次數

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預估清潔時間

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ISO 4406 代碼刻度

每個代碼數字 R 代表一個顆粒計數範圍：2^(R-1) × 0.01 至 2^R × 0.01 顆粒/每 mL（簡化）。代碼每增加一級，數值加倍。

依元件類型的目標清潔度

元件	目標 ISO 代碼	濾芯 μm	β 值
伺服閥	16/14/11	3 μm	β₃ ≥ 200
比例閥	18/16/13	6 μm	β₆ ≥ 200
活塞泵/馬達	17/15/12	6 μm	β₆ ≥ 200
葉片泵	18/16/13	10 μm	β₁₀ ≥ 200
齒輪泵、標準閥	20/18/15	10 μm	β₁₀ ≥ 75
僅油缸	21/19/16	25 μm	β₂₅ ≥ 75

清潔時間預估

降低一個 ISO 代碼等級所需的近似清洗循環次數：

實務範例

範例 — 配備伺服閥的系統，目前為 20/18/15

目標： 16/14/11 → 需降低 4 個代碼等級

每個代碼等級 ≈ 透過適當過濾進行 2 次系統循環

200 L 系統，60 L/min 流量：循環時間 = 200/60 = 3.3 分鐘

預估清洗時間：4 個等級 × 2 次循環 × 3.3 分鐘 ≈ 26 分鐘 的腎臟迴路過濾時間