1、BRITISH STANDARD BS 5540-6: 1990 Evaluating particulate contamination of hydraulic fluids Part 6: Method of calibrating liquid automatic particle-count instruments (using mono-sized latex spheres)BS5540-6:1990 This British Standard, having been prepared under the directionof the Machinery andCompone
2、nts Standards PolicyCommittee, was publishedunder the authorityofthe Board of BSIandcomes intoeffect on 31 December 1990 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference MCE/18 Draft for comment 88/72515 DC ISBN 0 580 19178 8 Committees responsible fo
3、r this British Standard The preparation of this British Standard was entrusted by the Machinery and Components Standards Policy Committee (MCE/-) to Technical Committee MCE/18, upon which the following bodies were represented: Advanced Manufacturing Technology Research Institute Association of Briti
4、sh Mining Equipment Companies Bath University Library British Compressed Air Society British Fluid Power Association British Steel Industry Department of Trade and Industry (National Engineering Laboratory) Institution of Mechanical Engineers Ministry of Defence The following bodies were also repres
5、ented in the drafting of the standard, through subcommittees and panels: British Hydromechanics Research Association British Railways Board Society of Motor Manufacturers and Traders Ltd. Amendments issued since publication Amd. No. Date CommentsBS5540-6:1990 BSI 07-1999 i Contents Page Committees r
6、esponsible Inside front cover Foreword ii 0 Introduction 1 1 Scope 1 2 Definitions 1 3 Apparatus 2 4 Materials 2 5 Preliminary procedures 3 6 Calibration procedures 4 Figure 1 Typical example of percentage distribution curve for38.8m spheres 7 Publication(s) referred to Inside back coverBS5540-6:199
7、0 ii BSI 07-1999 Foreword This Part of BS5540 has been prepared under the direction of the Machinery and Components Standards Policy Committee and is one of a series relating to the evaluation of particulate contamination in hydraulic fluids. This Part of BS5540 describes a method of calibrating liq
8、uid automatic particle counters working on the light obscuration principle, using mono-sized latex spheres. Other Parts in the series are as follows. Part 1: Qualifying and controlling of cleaning methods for sample containers; Part 2: Method of calibrating liquid automatic particle-count instrument
9、s (using AC Fine Test Dust contaminant); Part 3: Methods of bottling fluid samples; Part 4: Method of defining levels of contamination (solid contamination code); Part 5: Method of reporting contamination analysis data. A British Standard does not purport to include all the necessary provisions of a
10、 contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to8, an inside back
11、 cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5540-6:1990 BSI 07-1999 1 0 Introduction In hydraulic fluid power applications power is transmitted and con
12、trolled through a liquid under pressure within an enclosed circuit. The liquid is both a lubricant and power-transmitting medium. The presence of solid contamination particles in the liquid interferes with the ability of the fluid to lubricate and causes wear to the hydraulic components. The extent
13、of contamination in the liquid has a direct bearing on the performance and reliability of the system and has to be controlled to levels that are considered appropriate for the system. Quantitative determination of particulate contamination requires precision in obtaining the sample and determining t
14、he extent of contamination. The liquid automatic particle counter working on the light obscuration principle has become an accepted means of determining the extent of contamination. The accuracy of repeatability and reproducibility of particle count data is affected by both the procedures used and t
15、he method of calibration. 1 Scope This Part of BS5540 describes a method for the calibration of liquid automatic particle counters (APCs) working on the light obscuration principle. It establishes a uniform and precise method of calibrating these instruments which will enhance the degree of reproduc
16、ibility of particle count data between laboratories. The calibration material used is mono-sized latex spheres whose size can be verified by a number of different methods. The particle size parameter reported is the equivalent optical diameter based upon the projected area of a spherical particle. T
17、he method described first confirms the maximum concentration limits of the instrument being calibrated, verifies the particle size distribution of the latex spheres and, finally, enables the instrument to be calibrated in an accurate and precise manner. The calibration curve of an APC is the referen
18、ce that relates the particle size to the electrical threshold settings of the instrument. The development of the calibration curve is of primary importance in establishing the accurate sizing of particles being counted. A procedure is described that enables the voltage threshold value for any partic
19、le size within the sizing range of the sensor to be obtained. This method is intended for application to any APC working on the light obscuration principle in which particles interrupt the passage of light from a source to a detector. It assumes that the counter is equipped with at least two channel
20、s with adjustable voltage thresholds. Although this Part of BS5540 is intended for fluid power applications, it may also be applicable to other fields where this method of calibration is considered appropriate. NOTEThe titles of the publications referred to in this standard are listed on the inside
21、back cover. 2 Definitions For the purposes of this Part of BS5540 the following definitions apply. 2.1 agglomerate two or more particles that are in intimate contact and can not be separated by the small shear forces generated by gentle stirring 2.2 channel a particle size range as set into the liqu
22、id automatic particle counter 2.3 coincidence the presence of more than one particle within the sensing volume at the same time 2.4 dynamic sizing range the diameter of the smallest particle detected compared to the diameter of the largest particle passing through the sensor NOTEThis is usually quot
23、ed by the instrument manufacturer. 2.5 equivalent optical diameter the diameter reported by the counting/sizing device in use. It is the diameter of a sphere giving the same optical response as the particle 2.6 light obscuration the reduction of intensity of a light beam through the sensing volume c
24、aused by adsorption and/or scattering of the light by a single particle 2.7 minimum particle size the diameter of the smallest latex sphere used in the calibration procedure that is also within the size range that can be resolved by the counterBS5540-6:1990 2 BSI 07-1999 2.8 mono-sized latex spheres
25、 spherical polymeric calibration material having a narrow size range which is essentially Gaussian in distribution and having a coefficient of variation of typically less than12% 2.9 “noise” level the minimum voltage setting of the instruments detection circuit below which spurious signals of electr
26、ical noise become significant and are recorded as particles 2.10 saturation level the maximum counting rate above which the instrument will miscount NOTE 1The saturation level is usually specified by the manufacturer of the instrument. NOTE 2A procedure for checking the saturation level is described
27、 in6.3. 2.11 sensing volume the illuminated volume through which particles pass and can be detected 2.12 sensor a device through which the sample to be measured is passed and which contains the sensing volume 2.13 voltage threshold levels voltage levels representing the passage of reference particle
28、s of specific sizes against which the particle pulse is compared NOTEAdjustment is usually made using potentiometers. 3 Apparatus 3.1 Liquid automatic particle counter (APC), working on the light obscuration principle, fitted with a sensor suitable for counting within the specified range. NOTEThe pa
29、rticle counter should include an automatic bottle sampling apparatus or a similar means of allowing for the passage of liquid directly to the sensor and then to a measuring vessel. The air or gas used to pressurize the sample chamber causing sample flow through the sensor should be filtered through
30、a0.45 m membrane filter and should be free from oil and water. 3.2 Vacuum apparatus, for filtering the various liquids used in the procedure via a0.45m membrane filter, which is compatible with the liquids to be used. 3.3 Solvent dispensers, each fitted with a0.45 m membrane filter directly at the o
31、utlet. 3.4 Sample agitating device, that will not alter the basic size distribution of the latex spheres during agitation NOTEAn ultrasonic bath has been shown to be an acceptable means of both dispersing agglomerates within the liquid and removing air introduced by manual agitation. The ultrasonic
32、bath would normally be of0.5L capacity and typically between50W and100W at40kHz to80kHz. 3.5 Sample containers, which are a number of cylindrical glass bottles possessing the following features: a) dimensions that are compatible with the sample bottle facility in use with the counter (usually250 mL)
33、; b) a flat bottom; c) either of the following: 1) a polypropylene threaded cap forming a seal with the bottle without the use of an insert; 2) a cap with a suitable internal seal. 3.6 Dosing pipettes, comprising a range of one mark graduated pipettes complying with BS1583. 3.7 Optical microscope, f
34、or use if it is found necessary to verify the absolute diameter of the latex spheres. NOTEA binocular microscope with a magnification range of 40 to 400 and a mechanical X-Y stage is considered appropriate. The eyepiece graticule should be calibrated using a reference stage micrometer and microscope
35、 illumination should be either oblique or incident, as required. 4 Materials 4.1 Cleaning liquids for glassware, comprising the following: a) distilled/deionized water; b) liquid detergent that is water soluble; c) isopropyl alcohol (IPA), reagent grade, that has been filtered through a0.45 m membra
36、ne filter. 4.2 Latex spheres calibration material, comprising a range of six mono-sized latex sphere dispersions suspended in a suitable carrier liquid which is totally miscible with the suspension liquid. NOTEThis range should be selected so that it covers the sizing range of the sensor being calib
37、rated. The minimum size of sphere should be carefully selected so that the complete distribution is above the “noise” level of the instrument. The manufacturer of the instrument should be consulted to verify the choice made. 4.3 Suspension liquid, consisting of distilled or deionized water that has
38、been filtered through a0.45 m membrane filter.BS5540-6:1990 BSI 07-1999 3 5 Preliminary procedures NOTEThe calibration procedures described in clause6 generally involve the use of only two channels of a counter. Where the principle of detection is by using more than one voltage threshold detector, t
39、he instrument should be serviced by the manufacturer, or competent agent, and the voltage threshold levels adjusted to “trigger” at the correct value before proceeding with calibration. 5.1 Preparation and cleaning of apparatus NOTEThe procedure described in 5.1.1 is based upon BS5540-3. 5.1.1 Proce
40、dure 5.1.1.1 Wash the apparatus with warm tap water containing liquid detergent 4.1 b) to an approximate concentration of one part of detergent to20parts of water and rinse thoroughly with warm tap water. 5.1.1.2 Rinse with distilled/deionized water and allow to drain in an inverted position. 5.1.1.
41、3 Rinse thoroughly with filtered isopropyl alcohol 4.1 c) and allow to drain in the inverted position. 5.1.1.4 Using suspension liquid (4.3) supplied from a solvent dispenser (3.3), flush-out the glassware and allow to drain in the inverted position. 5.1.1.5 Clean the sample container caps in a simi
42、lar manner and fit them to their respective containers. 5.1.1.6 Store the cleaned apparatus under clean air conditions. 5.1.2 Verification of cleanliness levels Using the suspension liquid (4.3) adopt the procedure specified in BS5540-1. NOTEAs it is usual to analyse up to100 mL of liquid this requi
43、res a larger liquid volume than that specified in BS5540-1. The required cleanliness level (RCL) shall be less than five particles greater than5 m/mL per container. 5.2 Sensor system cleanliness 5.2.1 Clean the sensor and associated pipework prior to use, by flushing with a filtered solvent before a
44、nalysis of the samples. The liquid shall be either the suspension liquid (4.3), or a liquid that is totally miscible with it, and that is dispensed from a dispenser (3.3). 5.2.2 If the sensor has previously been used to analyse a liquid that is not miscible with the liquid to be analysed, carefully
45、clean the sensor (see6.6) before proceeding. 5.2.3 Inspect the sensing volume on a regular basis for the presence of particles in either the sensing volume itself or the entry to it. 5.2.4 Reverify the RCL. 5.3 Determination of “noise” level of the instrument 5.3.1 Since all particle counters are af
46、fected by “noise”, to a greater or lesser extent, determine the level in the manner prescribed by the instrument manufacturer. 5.3.2 If a procedure is not prescribed by the manufacturer, use the following procedure (which is recommended by some manufacturers of automatic particle counters) to indica
47、te the level at which “noise” becomes significant. a) Disconnect the sensor from the sampling system, inspect for blockage and flush with filtered suspension liquid or a solvent that is compatible with it, and allow to dry. b) Place the sensor on a surface that is free from vibration so that the axi
48、s of the sensor connections is horizontal. c) Adjust the level of the first and lowest threshold voltage setting until the instrument counts at a rate of approximately60 counts per minute. This is deemed the “noise” level. NOTEIf this procedure can not be completed dry the manufacturer, or competent
49、 agent, should be consulted. 5.3.3 Use the “noise” level so determined to indicate the minimum sizing diameter and make all subsequent measurements at voltage settings above this value. 5.4 Precautions 5.4.1 Instrument location Locate the instrument in a class K clean environment or better in accordance with BS5295-1. 5.4.2 Electrical interference As the APC is typically a high sensitivity device and may be affected by radio frequency or electromagnetic interference, take precautions to ensure that the test area environment does not interfere with the op
