How do you calculate contamination risk score?

Multiply each rating by its weight and sum: severity x 0.40 plus occurrence x 0.35 plus detection x 0.25. With 6, 4, and 3, that is 2.4 + 1.4 + 0.75 = 4.55.

Why use weights instead of a plain RPN multiply?

A plain multiply lets a low rating mask a high one. Weighting keeps severity dominant at 40%, so a high-severity contamination mode stays visible even when occurrence and detection are moderate.

What is a high contamination risk score?

On a 1-to-10 input scale the weighted score also runs 1 to 10. The 4.55 here is moderate; scores above about 6 to 7 signal contamination modes that warrant immediate filtration or sampling action.

What drives the score most?

Severity, weighted at 40%. In the example its 6 contributes 2.4 of the 4.55 total, more than occurrence and detection combined-tier contributions individually.

How do I lower a contamination risk score?

Cut occurrence with better filtration and reservoir breathers, or cut detection difficulty with inline particle counters and routine oil sampling. Improving detection from 3 to 1 in the example drops the score by 0.5.

Does this replace ISO 4406 cleanliness coding?

No. ISO 4406 measures actual particle counts; this score ranks the risk a contamination mode poses so you can prioritize where to apply cleanliness controls.

Hydraulic, Pneumatic & Fluid Power Systems calculator

Contamination Risk Calculator

Contamination Risk produces a weighted FMEA-style score for the threat that particulate, water, or air contamination poses to a hydraulic or pneumatic system. Contamination is the leading cause of fluid-power component failure, and this score blends how severe a contamination event would be, how likely it is to occur, and how hard it is to detect before damage spreads. Reliability and quality engineers use it to rank cleanliness risks across machines or build steps and to prioritize filtration, flushing, and sampling effort. Unlike a flat RPN multiply, the weighted form lets severity dominate, which is right when a single contamination event can scrap a servo valve.

What this calculator does

Calculate contamination risk for hydraulic, pneumatic & fluid power systems planning, quoting, troubleshooting, capacity review, or process improvement.
Use it when contamination risk in hydraulic, pneumatic and fluid power systems needs a defensible ranking against other hydraulic, pneumatic and fluid power systems risks for the next review.
It computes a weighted risk score: severity at 40%, occurrence at 35%, and detection at 25% of the total.

Formula used

Contamination Risk risk score = severity × 0.40 + occurrence × 0.35 + detection × 0.25

Inputs explained

Contamination severity rating:
Contamination occurrence likelihood rating:
Contamination detection difficulty rating:

How to use the result

Use it when ranking contamination failure modes for filtration upgrades, sampling cadence, or flushing investment.
The fixed 40/35/25 weights are a sensible default but are not universal; a system where undetected contamination is catastrophic may warrant a higher detection weight.

Current U.S. benchmarks

The U.S. has 21,668 machinery manufacturing establishments employing about 1,086,146 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate contamination risk score? Multiply each rating by its weight and sum: severity x 0.40 plus occurrence x 0.35 plus detection x 0.25. With 6, 4, and 3, that is 2.4 + 1.4 + 0.75 = 4.55.
Why use weights instead of a plain RPN multiply? A plain multiply lets a low rating mask a high one. Weighting keeps severity dominant at 40%, so a high-severity contamination mode stays visible even when occurrence and detection are moderate.
What is a high contamination risk score? On a 1-to-10 input scale the weighted score also runs 1 to 10. The 4.55 here is moderate; scores above about 6 to 7 signal contamination modes that warrant immediate filtration or sampling action.
What drives the score most? Severity, weighted at 40%. In the example its 6 contributes 2.4 of the 4.55 total, more than occurrence and detection combined-tier contributions individually.
How do I lower a contamination risk score? Cut occurrence with better filtration and reservoir breathers, or cut detection difficulty with inline particle counters and routine oil sampling. Improving detection from 3 to 1 in the example drops the score by 0.5.

Last reviewed 2026-05-12.