What is ISO 11171 about?
ISO 11171 specifies procedures for the following:
- 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
- Secondary particle-sizing calibration using suspensions verified with a primary calibrated APC
- Establishing acceptable operation and performance limits
- Verifying particle sensor performance using a test dust
- Determining coincidence and flow rate limits
ISO 11171 is applicable for use with hydraulic fluids, aviation and diesel fuels, engine oil and other petroleum-based fluids.
NOTE: ISO 11171 is not applicable to particle-sizing calibration using NIST SRM 2806b primary calibration suspensions.
Who is ISO 11171 for?
ISO 11171 on hydraulic fluid power is relevant to:
- Aviation industry
- Petrochemical industry
- Construction industry
- Mechanical and chemical engineers
Why should you use ISO 11171?
In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure within an enclosed circuit. The fluid is both a lubricant and a power-transmitting medium. Liquid automatic particle counters (APC) are an accepted means of determining the concentration and size distribution of the contaminant particles. Individual APC accuracy is established through calibration.
ISO 11171 is a standard calibration procedure for APC that are used for determining particle sizes and counts. The primary particle-sizing calibration is conducted using NIST SRM 2806x suspensions with particle size distribution certified by the United States National Institute of Standards and Technology (NIST) for particle sizes 30 μm(c) and smaller, and using polystyrene latex spheres at larger sizes.
A secondary calibration method uses suspensions of NIST RM 8631x, ISO MTD, which is independently analysed using an APC calibrated by the primary method. Minimum performance specifications are established for the APC coefficient of variation (CV) of sample volume, CV of flow rate, resolution and particle counting accuracy. The operating limits of an APC, including its threshold noise level, coincidence error limit and flow rate limits are determined.
Overall, ISO 11171 provides you with reliable hydraulic power system performance through the control of contaminants in the fluid.
What’s changed since the last update?
BS ISO 11171:2020 supersedes BS 1016108.4:1995, which is withdrawn. BS ISO 11171:2020 replaces the third edition (ISO 11171:2016), which has been technically revised.
The main changes compared to the previous edition are as follows:
- SRM 2806b are not used for sizing calibration purposes with BS ISO 11171:2020
- The definition of an automatic particle counter (APC) is clarified
- The particle size distribution for primary calibration suspension samples is found in Table 3 of the SRM 2806x Certificate of Analysis
- ISO medium test dust (MTD) or other test dust conforming to ISO 12103-1 for secondary calibration suspension is permitted
- APC are required to have a minimum of 8 channels that can be set instead of only 6
