# Leak rate — Air or vacuum leakage rate

> Source: https://rodlesspneumatic.com/resource-center/pneumatic-glossary/leak-rate/
> Language: en-US
> Category: Vacuum

## Definition

Air or vacuum leakage rate: Rate at which gas enters or escapes a system under stated conditions. It sets pump/ejector demand and pressure retention time. Read the applicable product data and technical standard before treating a catalog value as interchangeable.

## Key facts

- **Term:** Leak rate
- **Full form:** Air or vacuum leakage rate
- **Selection effect:** It sets pump/ejector demand and pressure retention time.

## Leak rate: definition and engineering context

Air or vacuum leakage rate. Rate at which gas enters or escapes a system under stated conditions.

The term belongs to the vacuum context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.

## Why Leak rate affects pneumatic selection

It sets pump/ejector demand and pressure retention time.

- Vacuum level: Record the reference and unit; percentages of vacuum can hide assumptions.
- kPa abs: Lower absolute pressure means a stronger vacuum.
- Holding force: Derate for acceleration, orientation, leakage, surface texture, and cup geometry.
- Safety factor: Choose it from motion, surface, failure consequence, and application guidance.

## How to evaluate Leak rate in a catalog or replacement project

Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.

For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.

- Pressure below atmosphere: Magnitude of sub-atmospheric pressure stated as gauge vacuum or absolute pressure.
- Kilopascals absolute: Absolute-pressure unit commonly used for vacuum work.
- Vacuum-cup holding force: Ideal pressure-difference force over effective cup area before losses and safety factors.
- Design factor: Multiplier between calculated minimum and selected capacity.

## What to verify before selection

- It sets pump/ejector demand and pressure retention time.
- Record the reference and unit; percentages of vacuum can hide assumptions.
- Lower absolute pressure means a stronger vacuum.
- Derate for acceleration, orientation, leakage, surface texture, and cup geometry.

## Common mistakes

- Treating Leak rate as a universal definition without checking the manufacturer or standard context
- Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
- Selecting a component from the term or nominal value alone without checking the complete operating point and drawing

## Frequently asked questions

### What does Leak rate mean in pneumatics?

Air or vacuum leakage rate. Rate at which gas enters or escapes a system under stated conditions.

### Why does Leak rate matter when selecting a component?

It sets pump/ejector demand and pressure retention time.

### Can Leak rate values be compared directly between catalogs?

Only after the unit, reference condition, test method, operating point, and manufacturer definition have been reconciled.

## Technical references

- [ISO 5598:2020](https://www.iso.org/standard/67985.html): Provides the international fluid-power vocabulary used to interpret pneumatic terminology.
- [ISO 3529-1:2019](https://www.iso.org/standard/75929.html): Provides general vacuum-technology vocabulary and definitions.