Study On The Calibration Of Liquid Particle Counter And The Development Of Reference Materials

In the field of modern enginerring machinery,for the purpose of preventing particle pollution in hydraulic system,it is necessary to establish the particle concentration monitoring system and control system,as well as a complete and accurate particle pollution assessment system.Now,the liquid particle counter(LPC)can monitor the particle concentration in hydraulic system in real time,and because of its economy and friendly-operation,it is widely used in solid contaminent monitoring in hydraulic system.In order to obtain accurate and reliable results,liquid particle counter should be calibrated regularly.Typically,liquid particle counters can be calibrated using polydisperse MTD reference material,which is recommended by ISO and LPC's manufactors.But because of the wide distribution of MTD sample and the exponential decline in sample distribution for large particles,there actually are few large particles in its particle size distribution.Thus,few large particles can be measured in LPC calibrtion,and may result in poor measurement repeatability or inaccurate results.In order to establish a traceability system for liquid particle counters,seven kinds of monodisperse ISO medium dust(MTD)particle size reference materials and highaccuracy liquid particle counters were developed.A new LPC calibration traceability system(Monodisperse MTD--High Accuracy Liquid Particle Counter--Polydisperse MTD Reference Material--Liquid Particle Counter)has been established,which has the advantages of good traceability and high accuracy.The main work in this investigation as follows,1.A prepariton method for monodisperse MTD samples nominal 4-60 ?m was developed from a wide distribution sample by using gravity sedimentation and ultrasonic sieving methods.Finally,seven kinds of monodisperse MTD reference materials were prepared,whose nominal values are 4 ?m,8 ?m,18 ?m,30 ?m,40 ?m,50 ?m and 60 ?m,respectively.2.The MTD reference materials uncertainty evaluation method were developed.The monidispersed MTD reference materials were determined by using Scanning Electron Micriscope(SEM)which can trace to SI unit,and finally,the MTD reference materials traceability chain were developed.With the SEM and laser diffraction method which were developed in this study,NIM participate in the Inter-laboratory study(ILC)program to co-certify the ERM reference materials,and NIM has very good results.This proves that our developedt methods are accurate.The obtained reference material can be used for the LPC's high accuracy calibration of particle size division and particle size setting.The homogeneity and stability of the reference materials were tested with a Coulter Counter for more than one year.3.Pulse height analyzer(PHA)calibration method and LPC's particle size division calibraitn method were developed,and based on the work as mentioned,high-accuracy calibration method for liquid particle counter was established and a liquid particle counter with high accuracy was developed,the accuracy of the calibrated liquid particle counter is comparable to that of the SEM and can be used for the determination of polydisperse MTD reference materials.