ISO/TC 131/SC 6/WG 1 - Sampling, contamination analysis and reporting

This document establishes methods for: —  validating equipment used to prepare secondary calibration suspensions for automatic particle counters; —   performing online secondary calibration of automatic particle counters; —   matching two or more online particle counters, i.e. to count the same number of particles at a given size by two APCs associated online; —   validating online particle counting systems with and without online dilution as used, for example, to measure the filtration efficiency of a hydraulic filter as described in the multi-pass filter test in ISO 16889.

This document describes a recommended method for the interpolation of particle concentration and filter Beta Ratio data when results are not otherwise available at the desired particle sizes. It is applicable for assessing conformance with existing fluid cleanliness and filter Beta Ratio specifications whereby the specification and actual test results are provided in different units of particle size, for example, the specification is in µm(c), but the particle counts or Beta Ratio data are in units of µm(b). This document is also applicable when particle sizes in specifications and available data use the same units of particle size, but do not correspond to exactly the same sizes, for example, when particle counts at 20 µm(c) are specified, but data was collected at 21 µm(c). This method allows interpolation to intermediate particle sizes within the range of existing data and does not permit extrapolation to particle sizes outside the range of available data.

This document provides the background for ISO 11171:2020 and the use of µm(c) as the sole means of reporting particle size for APC particle count data. It also summarizes results of the international inter-laboratory study (ILS) of its reproducibility using SRM 2806d candidate material and suspensions of Reference Material (RM) 8632a. The ILS results provided the basis for certification of SRM 2806d used for primary calibration of APC. Their implications with respect to particle counting and filter testing are discussed in this document.

This document specifies the code to be used in defining the quantity of solid particles in the fluid used in a given hydraulic fluid power system.

This document specifies procedures for the following: a) primary particle-sizing calibration for particle sizes 1 µm(c) and larger, sensor resolution and counting performance of liquid automatic particle counters that are capable of analysing bottle samples; b) secondary particle-sizing calibration using suspensions verified with a primary calibrated APC; c) establishing acceptable operation and performance limits; d) verifying particle sensor performance using a test dust; e) determining coincidence and flow rate limits. This document is applicable for use with hydraulic fluids, aviation and diesel fuels, engine oil and other petroleum-based fluids. This document is not applicable to particle-sizing calibration using NIST SRM 2806b primary calibration suspensions.

This document explains the use of the two acceptable methods of reporting particle size, µm(c) and µm(b), that are defined in ISO 11171:2016. It also explains the reasons for the existence of two alternative size reporting methods and its implications with respect to particle count and filter Beta Ratio data.

This document specifies a method for the determination of the particulate contamination level using the light extinction technique (also known as light blockage or light obscuration) either online or offline in containers. It also defines procedures for calibrating the instruments and verifying their correct operation both in the laboratory and in service. In general, the techniques described in this document are suitable for monitoring: — the general cleanliness level in hydraulic systems, — the progress in flushing operations, and — support equipment and test rigs. The use of this method is applicable to single-phase liquid systems only.

This document establishes methods to: — validate equipment used to prepare secondary calibration suspensions for automatic particle counters; — perform online secondary calibration of automatic particle counters; — match two or more online particle counters, i.e. to count the same number of particles at a given size by two APCs associated on line; — validate online particle counting systems with and without online dilution as used, for example, to measure the filtration efficiency of a hydraulic filter as described in the multipass filter test in ISO 16889.

ISO 4406:2017 specifies the code to be used in defining the quantity of solid particles in the fluid used in a given hydraulic fluid power system.

ISO 11171:2016 specifies procedures for the following: a) primary particle-sizing calibration, sensor resolution and counting performance of automatic particle counters (APCs) for liquids capable of analysing bottle samples; b) secondary particle-sizing calibration using suspensions verified with a primary calibrated APC; c) establishing acceptable operation and performance limits; d) verifying particle sensor performance using a truncated test dust; e) determining coincidence and flow rate limits.

ISO/TR 16386:2014 discusses the impact of changes in International Standards for particle counting, contamination control, and filter testing. Liquid automatic particle counters (APCs) are used in monitoring contamination levels in hydraulic fluids, to establish component and assembly cleanliness level specifications, and in determining filter efficiencies and particle size ratings. As a result of the replacement of ISO 4402 with ISO 11171 (APC calibration), the replacement of ISO 4572 with ISO 16889 (multi-pass filter test), and the publication of ISO 11943 (online particle counter calibration), the quality and reliability of particle count and filter test data have improved, increasing their usefulness to industry. However, the resultant redefinition of particle sizes and the use of a new test dust affect how contamination levels and filter performance are reported and interpreted. NOTE The first editions of ISO 11171, ISO 16889 and ISO 11943 were published in 1999; all three of these International Standards either have been, or are in the process of being, revised.

ISO 11500:2008 specifies an automatic particle-counting procedure for determining the number and sizes of particles present in hydraulic-fluid bottle samples of clear, homogeneous, single-phase liquids using an automatic particle counter (APC) that works on the light-extinction principle. ISO 11500:2008 is applicable to the monitoring of the cleanliness level of fluids circulating in hydraulic systems, the progress of a flushing operation, the cleanliness level of support equipment and test rigs and the cleanliness level of packaged stock.

ISO 21018-3:2008 specifies a method for the semi-quantitative determination of the particulate contamination level using the filter blockage technique (also known as the mesh-obscuration method or the pore-blockage technique) either on-line or off-line in containers. ISO 21018-3:2008 also defines procedures for calibrating the instruments and verifying their correct operation both in the laboratory and in service. In general, the techniques are suitable for monitoring the general cleanliness level in hydraulic systems, the progress in flushing operations and support equipment and test rigs. The use of ISO 21018-3:2008 is applicable to all single- or multi-phase liquid systems.

ISO 21018-1:2008 specifies methods and techniques that are applicable to the monitoring of particulate contamination levels in hydraulic systems. It also describes the relative merits of various techniques so that the correct monitor for a given application can be selected. The techniques described in ISO 21018-1:2008 are suitable for monitoring the general cleanliness level in hydraulic systems, the progress in flushing operations and support equipment and test rigs. ISO 21018-1:2008 can also be applicable for other liquids (e.g. lubricants, fuels and process liquids).

This International 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 greater than or equal to 2 micrometres 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 International 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.

The preferred method is to extract fluid samples from a main flowline in such a manner that the particulate contaminant in the sample is representative of the fluid flowing at the point of sampling. An alternative method is to extract a sample from the reservoir, but this method should only be used if a suitable sampler is not fitted.

Specifies a method, and establishes a means for ensuring that the accuracy of particulate contamination analyses in hydraulic systems is not degraded by a lack of sample container cleanliness. Gives definitions and tabulates the inspection ratios together with the AQQL values of concern.

ISO 21018-4:2016 specifies a method for the determination of the particulate contamination level using the light extinction technique (also known as light blockage or light obscuration) either online or off-line in containers. It also defines procedures for calibrating the instruments and verifying their correct operation both in the laboratory and in service. In general, the techniques described in ISO 21018-4:2016 are suitable for monitoring - the general cleanliness level in hydraulic systems, - the progress in flushing operations, and - support equipment and test rigs. The use of this method is applicable to single-phase liquid systems only.

ISO 11171:2010 specifies procedures for: a) primary particle-sizing calibration, sensor resolution and counting performance of automatic particle counters (APCs) for liquids capable of analysing bottle samples; b) secondary particle-sizing calibration using suspensions verified with a primary calibrated APC; c) establishing acceptable operation and performance limits; d) verifying particle sensor performance using a truncated test dust; e) determining coincidence and flow rate limits.

ISO/TR 16144:2002 describes the procedures used by the United States National Institute of Standards and Technology (NIST) for the certification of the calibration material SRM 2806, which is used in the primary calibration of liquid automatic particle counters. SRM 2806 is a suspension of ISO MTD in hydraulic fluid with a number size distribution certified using a scanning electron microscope (SEM) and image analysis techniques.

Specifies methods for reporting data relating to contamination levels of fluids used in industrial, mobile and marine applications for the following types of contamination analysis techniques: microscopic particle counting, automatic particle counter, gravimetric. Is intended to establish the minimum information required to allow valid comparison and interpretation of contamination level data. The figures show the data sheet of concern.