BS ISO 4406:2021 pdf download

BS ISO 4406:2021 pdf download.Hydraulic fluid power – Fluids – Method for coding the level of contamination by solid particles.
In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure within an enclosed circuit. Solid particle contaminant is always present in the hydraulic fluid and the amount needs to be determined because the contaminant can cause serious problems.
The ISO 4406 cleanliness code has gained world-wide acceptance as a means of communicating the cleanliness of a hydraulic fluid. Most hydraulic component manufacturers require a certain ISO cleanliness level for warranty purposes, to ensure proper function and for a long, trouble-free life.
The purpose of this code is to simplify the reporting of particle count data by converting the numbers ol particles into broad classes or codes, where an increase in one code generally represents a doubling of the contamination level.
The original code, in accordance with the first edition of BS ISO 4406, stated the reporting at two sizes:  5 urn and  15 urn. The sizes in BS ISO 4406 account for the use of a different calibration standard for optical automatic particle counters (APCs). The reported sizes are  4 pm(c),  6 um(c) and
CAUTION — Particle counts are affected by a variety of factors. These factors Include procurement of sample, particle counting accuracy and the sample container (where used), and its cleanliness. Proper care should be taken during sample procurement to ensure that the sample obtained is representative of the fluid circulation within the system.
4.3 AllocatIon of scale numbers
4.3.1 The scale numbers are allocated according to the number of particles counted per milWitre of the fluid sample (see Table 1).
4.3.2 A step ratio of generally two, as given between the upper and lower limits for the number of particles per millilitre in Tablet has been adopted to keep the number of scale numbers within a reasonable limit and to ensure that each step is meaningful.
4.4.1 Counting shall be undertaken n accordance with Iso 11500 or another recognized method, using an APC calibrated to ISO 11171 ora PCM calibrated to ISO 21018-3 or ISO 21018-4.
4.5 Determination of code using microscope sizing
4.5.1 Counting shall be undertaken in accordance with ISO 4407.
4.5.2 A scale number shall be allocated to the number of particles equal to or larger than 5 urn.
4.5.3 A second scale number shall be allocated to the number of particles equal to or larger than 15 urn.
4.5.4 In order to relate to counts obtained with an APC or PCM, the code shall be stated In three-part form with the first part gwen as.BS-ISO-4406-2021

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