ASTM D6786 Test Method for Particle Count in Mineral Insulating Oil
ASTM D6786 Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
1. Scope
1.1 This test method covers the determination of particle concentration and particle size distribution in mineral insulating oil. It is suitable for testing oils having a viscosity of 6 to 20 cSt at 40°C. The test method is specific to liquid automatic particle analyzers that use the light extinction principle.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D923 Practices for Sampling Electrical Insulating Liquids
2.2 ISO Standards:
4406:1999 Hydraulic Fluid Power-Fluids-Method for Coding the Level of Contamination by Solid Particles
11171:1999 Hydraulic Fluid Power-Calibration of Automatic Particle Counters for Liquids
3. Terminology
3.1 Definitions:
3.1.1 coincidence - the presence of more than one particle in the sensing zone of a particle analyzer at the same time, causing mis-sizing and mis-counting of the particle present. The coincidence limit of the counter is determined by the maximum acceptable concentration of particles in the sensing zone and is supplied by the instrument manufacturer.
3.1.2 concentration limit - a direct function of coincidence and electronic saturation. The concentration limit of the system is determined by the maximum acceptable concentration of particles in the given sample and is supplied by the instrument manufacturer.
3.1.3 electronic saturation level - particle concentration at which the electronic circuitry of the analyzer ceases to function properly due to excessive counting rates.
3.1.4 light extinction - the reduction in intensity of a light beam passing through the sensing zone of a particle analyzer, caused by the absorption and/or scattering of the light by particles. Synonyms: light obscuration, light interruption, light blockage.
