Statistical Quality And Process Control
The answer to your question can be found in the differences between test results determined in paired samples taken with pneumatic cross belt samples. The task can be brought down to the application of Student’s test to paired data. It’s a matter of SQC (statistical quality control). Derive mean differences and Bias Detection Limits for Type I risk only and for Type I & II, and plot the stats in a control chart. Calibrating your ash analyzer is SPC (statistical process control). Select a suitable time base, derive stats for this time base, and plot the stats for cross belt samples and online ash data on a control chart. You’ll be happy you did. JanWMerks ■
Re: Difference Between Samplers
Dear Mr Merks
Thank you for your reply and apology for my late response. Your input was valuable. But I also want to know that if any standard exists which can tell what difference is allowable between the analysis results of the two samplers i.e. when should we accept the results and when should we reject it? Or in other words when should we start suspecting the results? ■
Iso/Tc27 Standards For Coal Sampling
Your ash analyzer gives ordered sets of test results as function of time. Test for spatial dependence by applying Fisher’s F-test to the variance of a set (for a typical sampling unit or sample space) and the first variance term of the ordered set. If the set displays a significant degree of spatial dependence, then derive the central value of the set and its 95% confidence limits. You would expect this central value to be compatible with test results for your pneumatic cross belt samples. Set up a control chart to check and compare paired data. Google my name to get more info on applied statistics in mineral exploration and mining. Or join ISO/TC27 on coal to find out what standard methods are available. ■
Re: Difference Between Samplers
Thanks Merks
I have read one of your books..... Though I am a bit weak in statistics. ■
Coal
Hello,
I would suggest conducting experiment of Stopbelt v/s Autosampler.
Need to do the study with several cuts and compare size distribution of coal samples for both the methods of sampling. Also run required tests (ash, Moisture...) on the collected samples.
Once we get set of data, we can calculate repeatability and reproducibility. Also, ASTM Ash and Moisture methods have repeatability and reproducibility data which we can use as reference.
Let me know if you have further questions.
Jignesh Panchal, jpanchal@ajedmondco.com ■
Re: Difference Between Samplers
Of course, nowadays you can get an integrated unit that does both too. Sampler/Sequencer! ■
Difference Between Samplers
Originally Posted by silliker
Hi silliker
Could you please elaborate such equipment which can do sampling & sequencing both? availability etc ■
Difference Between Samplers
We have two cross belt pneumatic swing arm samplers installed on the belt carrying final product (clean coal) at our coal beneficiation plant at a distance of about 10 ft. Both the samplers move and cut samples simultaneously. The samples obtained are used for proximate analysis (ash and moisture), the data obtained from which is used to cross check / calibrate the PGNAA online ash analyzer .
My question is that what is the maximum permissible difference between the ash and moisture of the samples obtained from the two samplers if they are analysed separately? ■