GB/T 20082-2006 Hydralic fluid power-Fluid contamination - Determination of particulate contamination by the counting method using an optical microscope
1 Scope
This standard specifies methods for determining the level of particulate contamination in liquids used in hydraulic systems by counting the number of particles deposited on the surface of a membrane filter using an optical microscope. It includes particle counting by two manual methods and image analysis, using either transmitted or incident lighting systems.
Particle sizes ≥2μm can be sized and counted by this method, but the resolution and accuracy of the results will depend upon the optical system used and the capabilities of the operator.
All hydraulic fluids with a wide range of contamination levels can be analysed according to this standard. However, the counting uncertainty at the larger particle sizes increases if the volume filtered is reduced to allow smaller sized particles to be counted, where a fine precipitate or a high particle concentration is present.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections) to, or revisions, of any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 12804 Laboratory glassware - Graduated measuring cylinders (GB/T 12804-1991, eqv ISO 4788:1980)
GB/T 14039-2002 Hydraulic fluid power - Fluids - Method for coding the level of contamination by solid particles (ISO 4406:1999, MOD)
GB/T 17446 Fluid power systems and components - Terminology (GB/T 17446-1998, idt ISO 5598:1985)
GB/T 17484 Hydraulic fluid power - Fluid sample containers - Qualifying and controlling cleaning methods (GB/T 17484-1998, idt ISO 3722:1976)
GB 50073-2001 Code for design of clean room
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 17446 and the following apply.
3.1
blank count
count resulting from contaminants introduced from other sources, such as reagents, cleaning of glassware and preparation of the membrane filter (see 9.2)
3.2
calculation factor
ratio of the effective filtration area to the total area counted
3.3
effective filtration area (EFA)
circular area of the membrane filter open to flow during filtration of liquid
Note: Both the effective filtration area (EFA) and the effective filtration diameter (EFD) are determined in 8.2.
3.4
fibre
particle longer than 100 μm with a length-to-width ratio greater than or equal to 10:1
3.5
fixative liquid
liquid that, as a result of a heat curing process, causes a membrane filter to adhere to a glass base slide, resulting in an opaque residue
3.6
grid square
square with sides of nominally 3.1mm printed on membrane filters
Note: Gridded membrane filters may not be suitable for counting using image analysis techniques.
3.7
image analyser
instrumentation to automatically size and count particles deposited on a membrane filter
Note: A video image of the particle is digitally recreated based upon the difference in the grey scale contrast of the particle and background, and the size is automatically computed. Sizing of the particle can also be undertaken on the video screen.
3.8
mountant liquid
liquid that, when heated, causes a membrane filter, previously treated with fixative liquid, to become transparent and to adhere to the cover slip (see 5.7)
3.9
