Volume 5  Number 10                            Dennis R. Dinger                                1 August 2007

Updates

"... for Ceramists" Series Books

          Requests for Multiple Copies

I have had several recent inquiries about the purchase of multiple copies of these books.  Here are my two suggestions:  

          (1)  If you purchase downloadable versions, purchase the required number of copies (please be honest about the number) from the Books and Downloads page of this website.  Then download a single copy and distribute it (or print it and distribute it) to the people for whom you purchased the copies. ... or ... 

          (2) Purchase the required number of paperback copies from the Books and Downloads page of this websiteand distribute them to your people.  My books are priced $19.95, $24.95, and $29.95 with this in mind.  You won't find many other good ceramics books in this price range.  Most others start at $80 to $100 each and prices rise from there.  For example, our PPC book (when it was available) was $195 per copy.  (I had no input when that price was set.  During one phone conversation, after they made sure I was sitting down, they simply told me the price.)          

          Spanish Language Books

For those of you who speak Spanish as your primary language, a downloadable PDF version of Rheology for Ceramists in Spanish is currently in progress.  Reología para Ceramistas is currently being edited to be made available as soon as possible.  Best estimate at this time is that it will be available sometime this fall.  The PDF file will be set up so it can be printed on your printer if you prefer a hard copy.  Depending on the reception this version receives, I will then consider translating the Particle Calculations book as well.  I will also then consider translating it into Portuguese.  Any thoughts, comments, and/or suggestions will be appreciated.

          English Language Books

The paperback version of Characterization Techniques for Ceramists is available on the Books and Downloads page at the web site!    Retail price is $29.95 plus shipping and handling. The book has 256 pages and it covers 34 different characterization techniques that are commonly used by ceramists.  Purchase a copy NOW!

The book sets on the web site have also been revised to include this new book.  A 3-book set of paperbacks, including one each of Particle Calculations for Ceramists, Rheology for Ceramists, and Characterization Techniques for Ceramists, is now available for $64.85 plus shipping and handling.  This is a $10 saving off the total retail price of the 3 paperback books.  A 3-book set of downloads is also available for $52.85.  This, too, represents a $10 saving off the total retail price of the 3 downloadable books.  

The E-Book version of Characterization Techniques for Ceramists is available for downloading at the Books and Downloads page of the website for $24.95.  The download is a 2.889 Mb self-extracting Zip® file for the Windows® environment which unzips to the 2.998 Mb book in PDF file format.  Those of you who order the downloadable book will want to know that the PDF book is formatted to print on 5.5" X 8.5" paper (i.e., 8.5" X 11" sheets cut in half.)

The other two books, Rheology for Ceramists and Particle Calculations for Ceramists, continue to be available for purchase as downloadable E-books and as paperback books at the Books and Downloads page of the web site.

The E-zine

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This month's article is another in a series discussing PPC, its applications, and mind set.

Practical Questions Required Prior to PPC Implementation

Introduction

There are two areas in which changes must be made in preparation for a switch from traditional control methods to PPC controls:  (1)  Multiple sources, patios, storage tanks, etc., of each raw material and scrap ingredient must be produced, and (2) Lots of characterizations of all of the raw materials and scrap ingredients must be made and recorded in a data base.  We will consider these:

Initialize a Data Base

When the decision has been made to begin to implement PPC within a production plant, the first step must be to begin to collect appropriate characterization data for EACH raw material and store it in a central repository -- i.e., a data base.  This itself has three areas for consideration:  Which tests should be run?  Which locations should be tested? and How much staff will be required to perform these tasks?

          Which Tests?

Some tests are relatively obvious.  Others are not.  Some testing instruments might already be available at a particular production site.  Some may not.  Are any new instruments required, or must some new capacity be added to available instruments?  Questions like these must be addressed.

Some tests must be performed.  Some are optional.  Some properties are tough to characterize and may require some ingenuity to measure.  Particle size distributions, specific surface areas, methylene blue indices, soluble ion contents, and viscosities are necessary tests for implementation of PPC.  Optional tests include X-ray diffraction, X-ray fluorescence, zeta potential analysis, chromatography, etc.  Analyses that are not easy to measure but might be required include analysis of porosity and pore size distribution of powders, surface texture,  inherent chemistry contents, etc.

Preparations must be made to perform all such analyses.  Labs may need to be rearranged, designed, or added for these purposes.  Instruments and other test equipment may need to be puchased and installed so staff have time to learn how to perform the techniques.  When several different types of instruments are available to perform a particular analysis, decisions must be made concerning which types of instruments will provide the best, most useful information.  Economic trade-offs must also be made during such decisions.  Which instrument provides the most and best information in the shortest time for the least cost?  Lots of preparation precedes a changeover to PPC.

For example, most clay suppliers and traditional ceramic production companies use sedimentation techniques for particle size analysis.  Analysis times extend from about 20 minutes to an hour for each sample.  How many samples need to be analyzed each day and can these be performed in the available time?  Are multiple instruments required to do so?  How much preparation time is required for each sample?  Are preparation techniques similar to plant processing techniques?  Is it better to use laser analysis techniques for particle size analysis which can each be performed in as little as a few seconds?  

If new analysis techniques need to be learned and implemented (methylene blue index, MBI, for example) should the older manual technique be implemented or should the more modern technique using a spectrometer be learned and used?

Are there sister companies within the corporate organization with whom your lab needs to remain compatible?  Should you choose test instruments that allow you to remain compatible with suppliers' lab analyses?  When several different people perform the same analyses, are the techniques simple enough that all results from all the different people are consistent?  (This applies to tests such as the standard filter paper test for performing MBI analyses, which require experience and "calibrated eye balls" on the part of each technician?)   

Are all such test results easily compatible with the selected computer data base?  Can results be automatically imported into the data base, or must results be manually entered?

Lots of questions need to be considered with regard to characterization techniques to be used.

          Which Locations?

Once a particular analysis technique has been chosen, samples from which locations in the process need be routinely analyzed?  ... and how often must those samples be taken and analyzed?  If a particular powder is stored in a patio in a storage shed, how many samples must be taken (and from where) to sufficiently characterize the whole patio?  Is it necessary to routinely take that many samples?  Can those many samples be combined and reduced (with a riffler, for example) to achieve one final representative small analysis sample for the whole powder?  Can a single sample be taken for each slurry or slip from each holding tank to characterize the whole tank?

Will PSD be used to determine the completion of milling operations?  Can the analyses be performed in sufficiently short times to do this?  How else can milling operations be controlled?  Should each mill be characterized or should the final holding tank (following milling operations) be characterized when it is full?

Obviously, the tradeoff here is to pull and analyze sufficient samples to characterize the powders without taking too many samples to over-tax the characterization lab.  It is easy to say that a sample must be pulled each time "blah-blah-blah" happens, but unless each of those samples can be characterized and the results meaningfully used to control the process, "each time" might be too many times.  

This really amounts to a sampling accuracy problem.  Enough samples must be taken and analyzed to achieve representative samples and results.  Too many samples may not hurt the representative nature of samples and results, but too many samples cause extra work for technical staffs.

Are these same analysis techniques to be used to improve production techniques?  One supplier used many characterization results to improve its techniques which ultimately required many fewer samples and analyses to accurately and representatively characterize their materials.  

Many such questions need be addressed concerning locations and numbers of samples to be taken and analyzed.

          Which Staff?

Who is going to perform all of these analyses?  PPC usually requires a substantial commitment to laboratory staff and instrumentation.  Personnel are needed to take samples.  Sometimes regular production staff personnel can pull the samples.  Sometimes staff from the lab must be sent out to take the samples.

How many samples must be analyzed?  How many samples can be analyzed during a single shift?  How many people will be required to perform all of these analyses?

Can the instruments be set up during the day shift to run automatically at night, or is that not a possibility?  If it is possible, what is its cost?  Can the current staff set up all instruments and prepare all samples during the 1st shift to keep the automatic instrument busy all night?  Must a second or third shift be added to perform all of the analyses?  

Are multiple personnel capable of performing the same analyses equally well?  If every staff member analyzes the same sample, will all results be comparable and accurate?  Standard operating procedures for each instrument should be written so any operator can perform an analysis equally well.  All operators must be trained and tested so results are all similar.

Staffing presents a variety of questions that must also be addressed when PPC is to be implemented.

Having addressed all such questions, the data needs to be quickly and easily combined into a single data base for use by the responsible process engineer and by the Simplex program used to calculate the day's batch formulations.

Such a data base also allows statistical process control graphs to be utilized to track all of this data.  With the appropriate PPC body formulation, such a data base can be used as the source for the program (the Simplex routine) that will calculate how much of each ingredient is needed to achieve the desired properties in each day's batch.  Graphs (X-bar R charts) showing each property from sample to sample, and from day to day, also produce a nice plot to track property variations from day to day and from batch to batch.

On days when the Simplex routine cannot achieve a body formulation that produces all desired properties, the tracking graphs help the process engineer to see what has been happening and how best to fix the body on that particular day.

With time and with use of PPC techniques, it should be possible to narrow important variations and reduce the ranges of data spread in the important body property data.

Multiple Sources of Each Material

The second major task that must be preplanned is to have at least three storage areas available for each raw material or scrap ingredient.  We suggest this take the form of at least three slurry tanks or multiples of three maxibags or three silos or three patios or etc.  We suggest each of each three volumes include (1) a volume of characterized powder that is being used, (2) a volume of fresh powder that is being characterized, and (3) a volume container that is being refilled with fresh powder.  When, for example, maxibags of powder are used for several raw material ingredients, then if several such bags are characterized and available for use in any given batch, that is better than having only 1 of each bag available.

          Type of Storage

The first decision that needs to be made is how to do this.  Can any of the raw materials be slurried and stored as slurries (suspensions)?  Are enough tanks available?  How big must each tank be?  Ideally, each tank should contain enough of each material to make a batch of body.  If you need 3 tons of clay in a batch, each slurry tank should hold at least 3 tons of clay.  If you have smaller tanks, you need more of them.  If you need 3 tons of clay in a batch, and each slurry tank holds a ton of clay, then you need at least 3 tanks available for each batch.  If you have 6 or 9 tanks of material available, that would be better.  If each tank holds 12 tons, then a single tank can be the source material for each of several batches.  

The same reasoning can be applied to dry powder storage.  The previous paragraph could be rewritten using maxibags, silos, patios, etc., in place of storage tanks.  

The goal is to have a variety of powders of each type available for each batch.  If the batch requires a 6micron median particle size and there are two slurry tanks available for use -- one containing median 4 micron and the other containing median 8 micron powders, they can be combined to produce 6 micron median powders.  

The tradeoff here is between having more tanks, silos, maxibags, patios, etc., and more flexibility, or fewer large tanks, silos, etc., which limit flexibility, but also limit the number of storage containers.   

          Water Balance

Obviously, if several ingredients are slurried, water balance must always be considered.  It is possible that single ingredients used to form slurries will not pack well, so relatively low solids contents must be used in the slurry tanks.  If these are to be combined to form higher solids content body slips, water balance will be a problem.  When several low solids content slips must be used in body formulations, some dry powders must also be added to batches to raise solids contents in body slips.  

This is not necessarily a major problem, but it can be a problem if it is ignored or overlooked.

          Sampling

A necessary problem for implementing PPC is to achieve truly representative sampling in each case.  How does one accurately sample a maxibag of powder, or a silo, or a slurry tank, or a patio?  Sampling is a whole science in itself, and one must study and utilize this to take meaningful samples to achieve meaningful characterization results.  The easiest type of storage to sample is a slurry sample -- assuming that mixing intensity is sufficient to keep the tank well mixed as the sample is pulled.  Then, pulling a good representative sample in one sampling operation is highly probable.  Representative sampling of large quantities of dry powders is probably the most difficult form of sampling to accurately obtain.  

Even if a representative sample is acquired, the sampling processes must continue to smaller and smaller samples until the sample size required by the instrument is achieved.  Then, one must also address the question regarding whether or not ALL samples going to ALL instruments are testing the SAME representative samples.  

If a rail car holds 100 tons of material, and a few grams are required for characterizations, how does one go about achieving a small, representative sample from such a large source?  Personnel from each plant must address and answer such questions?  

If and when suppliers can achieve truly consistent body properties, this becomes less and less problematic.  For example, if a raw materials supplier has implemented PPC to produce raw materials with truly consistent body properties, characterization and control in the process body is much less problematic.  Most raw materials suppliers do utilize controls that attempt to produce consistent properties.  In their cases, however, each property range is broader than that required by individual ceramic production companies.  I am not criticizing suppliers' procedures.  But a raw material called Dinger #3 that was available for the last 20 years will not be absolutely nor totally consistent over all of those 20 years.  Variations will occur within a relatively narrow range ("narrow" being defined by the raw materials supplier), but "narrow" according to raw materials suppliers usually translates into "broad" by ceramic production companies.  

Again, this is not a critique -- it is a simple fact of life.  Production companies need to know the exact properties of each raw material available for today's production batch.  If only ballpark approximations of properties of each raw material are available, the company is essentially still using the old, traditional batch formulation methodology.  

Recommendation:  Assign an Analysis "Expert"

From my experience, someone at each production facility needs to be the expert characterization person who understands in great detail how each instrument works and what it measures.  This is not to suggest that this person must perform all analyses.  To the contrary -- the author performed this function on the coal slurry project years ago -- and he was not the primary analysis technician on the project.  Each of our instruments, however, didn't perform exactly as expected or as desired.  

For example, when particle size analysis results from sedimentation, laser scattering, and sieve analyses didn't totally agree, the author had to resolve the problem.  When two different laser scattering analyzers didn't agree, the author had to resolve the problem.  When the author held the bob so it could not move at the beginning of each viscosity analysis on the cup and bob viscometer, yet even with a stationary bob, the viscometer was reporting viscosities, the author had to address that.  Considering that coal is transparent to X-rays, we had to use optical light scattering sensors to perform particle size analysis by sedimentation.  The author, not the technicians, was responsible for resolving this problem and working out techniques which allowed us to quickly and easily perform the analyses.  

When the digital plotter required software programs that were too large for the local lab computer -- so we could not plot any results with the fancy plotter we purchased to support the other analysis instruments, the author had to address those problems.

When the laser scattering analyzers did not record any submicron particles of coal or bentonite, even though the analzers supposedly had lower size limits of analysis of 0.1 micrometers, the author had to address those problems.  

Each production site needs such an expert.  The author was certainly not an "expert" on any of this, but he was the person responsible for addressing such problems, interfacing with instrument representatives, and working with local technicians to handle such problems.

Even though today's instruments are much advanced in comparison to the instruments available 25-30 years, a local "expert" is still highly recommended.

Conclusions

There are many logistical questions that need to be answered in advance of PPC implementation.  Many such questions have been included here as examples of the types of questions that need to be asked, the answers that need to be learned, and the decisions that must be made in preparation for implementation of PPC in any production process.