Quality Control and traceability; the guarantee for reliable product in Cement Manufacturing

Transcription

1 Quality Control and traceability; the guarantee for reliable product in Cement Manufacturing Maggi Loubser Test and Measurement 2013 Conference Misty Hills Conference Hotel, Muldersdrift 6-9 October

2 A bit of history 3000 BC Egyptians used mud mixed with straw to bind bricks. Also furthered the discovery of lime and gypsum mortar as a binding agent for the Pyramids 2

3 A bit of history 300 BC Romans used slaked lime and volcanic ash called pozzuolana, found near Pozzouli at the bay of Naples. They used lime as a cementitious material. Pliny reported a mortar mixture of 1 part lime to 4 parts sand. Vitruvius reported a 2 parts pozzolana to 1 part lime. Animal fat, milk, and blood were used as admixtures 3

4 Not just grey powder anymore 4

5 Sophistication in design and engineering by construction industry Today complex mix designs are used to prepare a concrete for a specific application and the client demands consistency and strength performance from the cement. In the production of cement it is the manufacturer's task to ensure that the properties of cement are kept at a certain level, with variations as small as possible to meet the standard specifications and to comply with the demands and needs of the market. This implies that variability in material composition and processing throughout the manufacturing process must be minimised. 5

6 Quality Control At the beginning of the 20th century, quality control in cement production essentially consisted of CaCO 3 titration, litre weight determination on clinker and Blaine fineness determination of cement to control the product quality. 6

7 Demands for consistent product quality for both the finished product and the in-process materials The control parameters include chemical composition, chemical ratios, particle size distribution, colour, mineralogical composition and free lime content. Quality assurance systems must be developed to control the composition of all inputs to the manufacturing process and all process conditions in the manufacturing process. 7

8 Backup by GLS Classical Wet methods Instrumental Methods Colorimetric Atomic Absorption/Emission X-Ray Fluorescence X-Ray Diffraction Microscopy Inductively Coupled Plasma Ion Chromatography UV-VIS Spectrophotometry 8

9 PPC is striving not just for conformity but operational excellence Cement is manufactured to the specifications of the European standard, EN for Common cements (SANS , SANS ). The standard covers cement types based on composition and strength classes, with specifications for performance and conformity criteria (South African Bureau of Standards, 2000; 2004; 2011). Regarding management systems, all PPC factories are also ISO9001:2008 and OSHAS and ISO 14001:2004 certified. Group Laboratory Services are also ISO17025:2005 accredited 9

10 Quality Control continually improving performance This is where real value add comes in: Confidence in analytical results Control systems in place Use control systems to trouble shoot problems in laboratory and plant Data mining to optimise processes and reduce standard deviations on controls 10

11 Quality control in the XRF labs Best practises used throughout the group Daily (once a shift) check samples and drift monitor samples Sample 99 prepared on each shift to check sample preparation SiO2 Quality control chart /02/ /02/ /03/ /03/ /03/ /03/ /04/ /04/ /04/ /04/ /04/ /05/ /05/2009 SiO2 Average sd 2sd 3sd -2sd -sd -3sd 11

12 Setting up of a control system A stable material with relative high concentration of all relevant analyte elements is needed The material does not have to be in the same matrix as analyte elements a solid glass or metal works well This check sample is subsequently analysed twenty times over at least ten days and the averages and standard deviations calculated from where control (3sd) and warning limits (2sd) are set This data is then plotted on a control chart Subsequent daily data is plotted on the same chart and when control limits are exceeded corrective action needs to be taken. 12

13 Control Chart 13

14 Sample 99 prepared on every shift and analysed in combination with check sample CaO by Analyst Week 1 Week 3 Week 5 Week 7 Week 9 Week 11 Week 13 Week 15 Week 17 Week 19 Week 21 Week 23 Week 25 Week 27 Week 29 Week 31 Week 33 Week 35 Week 37 CaO by Analyst +2SD -2SD CaO by Testers Week 6 Week 6 Week 7 Week 7 Week 8 Week 8 Week 9 Week 9 Week 10 Week 11 Week 11 Week 12 Week 12 Week 13 Week 14 Week 14 Week 15 Intervention: re-training CaO +2SD -2SD

15 Round Robins FINAL DATE FOR SUBMITTING RESULT SiO 2 Al 2 O 3 Fe 2 O 3 Mn 2 O 3 TiO 2 CaO MgO P 2 O 5 SO 3 K 2 O Na 2 O LOI Total 22-Feb-10 DEH DWB GLS HERC PE RBK JUP JUPfb SLR Mar-10 DEH DWB GLS HERC PE RBK JUP JUPfb SLR Mar-10 DEH DWB GLS HERC PE RBK JUP SLR

16 Weekly reports 16

17 Weekly reports 17

18 Case study Check samples outside control limits light elements correct after manual intervention (as drift exceeded 10%) 1. too high for some time 5. within spec 2. disaster 4. drift correct 3. repair spectrometer 18

19 Case study Check samples outside control limits heavier elements (SC detector)cannot be drift corrected 19

20 On closer inspection 20

21 Case study II: two factories use the same clinker analysis differ from weekly reports First action is to check control charts and sample 99 Additional a reference material is analysed by both laboratories Sample Reference SiO2 Al2O3 Fe2O3 Mn2O3 TiO2 CaO MgO P2O5 SO3 K2O Na2O LOI Total % % % % % % % % % % % % % Clinker 17/11/2011 CERT Factory 1 results Factory 2 results On face value differences do not look significant LSF = CaO - 0.7*SO 3 2.8*SiO *Al 2 O *Fe 2 O 3 LSF

22 Control charts Ca Something happened and since drift correction trying to correct Ca high 22

23 Control charts Si No automatedcorrection done as drift was larger than 10% 23

24 After correction Difference is not is statistically significant on reference material Problems not totally eliminated on real material Sample Reference SiO2 Al2O3 Fe2O3 Mn2O3 TiO2 CaO MgO P2O5 SO3 K2O Na2O LOI Total LSF % % % % % % % % % % % % % Clinker CERT Before drift corr After drift corr Representative sampling and material change with transport is significant problems that cannot be solved by fine tuning a analytical spectrometer 24

25 Automation Hercules factory Storage Mill and press Sample receiving Particle size analyser Conveyor belt 25

26 Automation Hercules factory Mill and press XRD XRF 26

27 But not a guarantee of a quality sure life! More and more industries move towards automation to improve quality, but more expensive sample preparation equipment does not necessarily guarantee smaller analytical uncertainties either. Pressed powder briquettes prepared on an automated mill and press system. Alarm bells went off when results for a batch of samples were consistently low, but the instrument check samples showed no deviations. 27

28 Other side of the coin Expansion into Africa 28

29 Other side of the coin Expansion into Africa 29

30 How do you create a culture of quality How do you export best practises and corporate culture? You don t. You adapt your quality practises fit for purpose You convince over time and with lots of patience by exactly the kinds of exercises I showed you When profit increases, and the job becomes easier, you will get they buy in you need to implement a worldclass quality system. 30

31 Results This is when Quality Control is not just conformity This is when it becomes part of who we are and what we do Buy in only comes through positive reinforcement 31

32 By making sure of the product leaving the gates 32