PARTICLE COUNTING

PARTICLE  COUNTING 

Particle counting is the technic used to monitor the solid contamination of new and in-service Oil.When implementing machine condition monitoring for machinery lubricating oils, typically the first strategy you implement is contamination control. 

Particle counting standards: which define permissible limit of contamination size and quantity in lubricating & hydraulic oil . 

ISO 4406 Standard

NAS 1638 standard

ISO 4406 Standard:

The ISO 4406/2000 classification of particle contents was introduced to facilitate comparisons in particle counting.

Sudden breakdown in an oil system is often caused by large particles (>14 micron) in the oil while slower, progressive faults, e.g. wear and tear, are caused by the smaller particles (4-6 micron).

This is one of the explanations why the particle reference sizes were set to 4 micron, 6 micron and 14 micron in ISO 4406/2000.

A typical sample contains in every 100 ml of oil:

450,000 particles >4 micron

120,000 particles >6 micron

14,000 particles >14 micron

Introduced in the ISO classification table (on the right), this oil sample has a contamination class of 19/17/14.

NAS 1638 standard:

NAS 1628 is a American standard that references the contamination load based on a breakdown of the different particle sizes for specific particle sizes: 
5 to 15 micron, 
15 to 25 micron, 
25 to 50 micron,
 50 to 100 micron,
 >100 micron

Contamination guide for hydraulic and lube oil systems:

ISO 14/12/10 - NAS 4: Very clean oil, best for all oil systems.

ISO 16/14/11 - NAS 5: Clean oil, an absolute necessity for servo & high pressure hydraulics.

ISO 17/15/12 - NAS 6: Light contaminated oil, standard hydraulic and lube oil systems.

ISO 19/17/14 - NAS 8: New oil, for medium to low pressure systems.

ISO 22/20/17 - NAS 12: Very contaminated oil, not suitable for oil systems