There are three principal methods to measure the contamination level in a component, circuit, or system.
The methods are: Gravimetric Measurement (ISO 4405); Particle Size Distribution Analysis (ISO 4406 or NAS 1638); Maximum Particle Size Analysis (ISO 4407).
This discussion will cover Gravimetric Measurement.
Gravimetric Measurement (ISO 4405) is a reporting method that references the total mass of
contaminant found in a hydraulic component. This total mass of contaminant measurement is then normalized by the total internal component surface area of a hydraulic component. A fluid is used todislodge contamination in a hose assembly and is then poured through a membrane catch filter.
An analytical balance is used to measure the total mass of contaminate which has been flushed out of a component. The total mass of contaminate and is referenced to the surface area or volume of the assembly.
Gates currently offers a system of four Gravimetric measurement (ISO 4405) levels of cleanliness for hydraulic assembly that can be used to meet or exceed cleanliness requirements.