Level Measurement · Glossary

What is Overfill Protection?

high high level safeguardLevel Measurement

Overfill protection is the set of alarms, independent level switches and automatic actions that stop a tank from overflowing.

Overfill Protection Explained

A tank overfill can release flammable or toxic liquid. Protection typically uses an independent high high level sensor, separate from the control level transmitter, to alarm and close inlet valves.

For petroleum storage tanks, API 2350 sets out overfill protection practice. Where the function is a safety instrumented function, IEC 61511 applies.

Calculators for Overfill Protection

CalculatorVessel Holdup Time CalculatorFree online calculator with formula and worked example.CalculatorTank Ullage CalculatorFree online calculator with formula and worked example.CalculatorProof Test Interval CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadLevel Switch Testing ProcedureFree step by step procedure, Word and PDF.

Frequently Asked Questions

What is Overfill Protection?

Overfill protection is the set of alarms, independent level switches and automatic actions that stop a tank from overflowing.

Why use an independent sensor?

If the control transmitter fails, it can show normal level while the tank overfills. An independent sensor avoids that common cause.

How often is overfill protection tested?

At the interval set by the site procedure or SIL calculation, with a full functional test where possible.

Learn more on the blog

What is SIL (safety integrity level)

A practical guide on instrumentationblog.in with more detail on overfill protection and how it is applied on real plants.

Read Full Article

More Level Measurement Terms

Level termRadiometric Level MeasurementRadiometric level measurement uses a gamma source and a detector outside the vessel; the liquid absorbs…Level termStilling WellA stilling well is a vertical perforated pipe inside a tank that calms the liquid surface for level…Level termLevel BridleA level bridle is an external vertical pipe connected to a vessel at two points, holding level…Level termSight GlassA sight glass is a glass gauge on a vessel that lets operators see the liquid level directly.Level termPoint Level MeasurementPoint level measurement detects whether liquid or solid is present at one fixed height, giving an on or…Level termHydrostatic Level MeasurementHydrostatic level measurement finds liquid level from the pressure at the bottom of a tank and the liquid…

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