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Viewing 19 posts - 1 through 19 (of 19 total)
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  • #53947

    MBBinWI
    Participant

    @ctickel – Here you go. Fire away.

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    #192175

    MBBinWI
    Participant

    Query – Is there really any difference in MSA’s for the chemical/process industries? If the item being produced is not a discrete item, does this make conducting an MSA any more difficult or challenging?

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    #192182

    Gary Cone
    Participant

    What I know –

    1) Sample prep is everything including time, temp, etc.
    2) Lots of secondary methods are used because primary method is tedious and time consuming. Make sure correlation is high to the primary, y-intercept is not statistically different from 0, slope not statistically different from one.
    3) Measure often done by techs who think they have the best method, they need to mbe made to standarize.

    And no, it’s just attention to detail like any other industry.

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    #192186

    MBBinWI
    Participant

    @garyacone – Thank you for your input Mr. Cone. Your insight I think will provide a valuable addition to the forum. I hear you have some background in this stuff.

    Some of my recent experiences have been with BB’s that believe that they have a destructive test (as might often seem to be the case in the process/chemical industry). What is your view on whether these can be done via nested vs. crossed study?

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    #192187

    MBBinWI
    Participant

    Some common problems in measurement systems – insufficient granularity (not enough divisions on the scale used), poor practice (scales with 3 decimals but only 2 actually recorded), poor procedure (not cleaning the measurement apparatus, not properly zeroing the scale), and poor technique (trying to read a pipette or needle/mirror not at eye level). Many of these are easily observable and correctable, but I’m finding that the people responsible don’t even know to question these items. There seems to be a lack of fundamentals in the quality profession development programs.

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    #192190

    Gary Cone
    Participant

    @MBBinWI Thank you for your question Mr. inWI.

    I think the advice in Minitab’s help menu is quite good. Look under general advice for GR&R studies.

    Too often, people have learned to use Destructive when it’s not appropriate because you will get a slightly better result.

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    #192193

    MBBinWI
    Participant

    @garyacone – No need for the formality, you may call me MBB if I may call you Gary.

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    #192198

    Chantel Kamm
    Participant

    @MBBinWI – Very few tests I’ve seen in the chemical process industry are destructive of the entire sample. Usually small aliquots are taken from the sample container, and then the test may destroy that subsample (an example might be flash point testing), but not the entire thing. So, most often Crossed studies are used.
    However, some tests require the entire sample and are destructive. If it is an in-process sample, or a sample from a continuous unit, then there may not be additional sample material available. In this rare case I could see a nested study approach.
    What about a test that is destructive, and requires all the sample volume in a single container, for a final analysis on a batch process? If a second sample of the same final product of that lot can be collected, should a crossed or nested Gauge R&R be used?

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    #192200

    Gary Cone
    Participant

    Crossed. You have the have an assumption of a homogeneous batch or your final analysis of the batch is flawed. It would be useful to verify that assumption.

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    #192212

    Chantel Kamm
    Participant

    @garyacone – Thank you for your guidance. Often challenging to verify homogeneity, when existing reaction vessels have one sampling port. Sometimes, the low viscosity of the material and the presence of mixing within the vessel increase the likelihood of homogeneity.
    Thanks again.

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    #192213

    Chantel Kamm
    Participant

    New Question regarding nonionics:
    Historically the pH of nonionics was measured using a 1% solution in DI water. However, pH depends on ions being present for measurement, and nonionics do not dissolve well in water and do not form appreciable quantities of ions in DI water. So, the tool was not appropriate for the job, and measurements were not repeatable.
    A 10% solution in IPA:DI Water produces more ions, has a more repeatable measurement, but also produces a different pH value. No easy way to determine which method is more accurate since you canΒ’t do a spike and recovery study easily for a non-linear pH measurement.
    Another approach is total acidity or total basicity (mg KOH/g), and with a large enough sample size this measurement is also more repeatable than the initial approach described above, and is also linear and more accurate.
    Does anybody else have experience with this? What approaches have you used to optimize your measurement precision (and accuracy, where possible)?

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    #192254

    Craig Tickel
    Participant

    @garyacone

    Thanks for the input. Homogenity of the batch is a problem that has not been adequately tested at all. Difficult to do at time, the viscosity of the material is so high that it is almost impossible to be homogenous, but customers still want the “data” on the COA. Because they use the product in such large quantities, the lack of homogenity is generally not a problem, but how do you determine the viability of running replications just to confirm that the homogenity is not changing over time and hence the small sample you have taken is not representative of the batch.

    To clarify, you run a product in batch sizes of 50,000 lb. When you pull a sample you get a 250ml jar of product…. you can do this as often as is prudent. We do control the process parameters – heat, time, pressure, raw materials are all measured and controlled. Mix rates are “common” from batch to batch. I think everyone can agree it is difficult to determine if the process is changing from that single sample. The question becomes should you run more samples or simply rely on controlling the process parameters. If you do, at what frequency would you verify the relationship between input/process and output variables…especially given the amount of variation in the output measurement method.

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    #192255

    Gary Cone
    Participant

    @ctickel I wonder if Y = f(x) requires that you understand the Y?

    The answer of course is yes and the idea that it is difficult to you and your colleague means you need help. There are several on here that can help – me, Mike Carnell, MBBinWI, …. but probably not Darth ;-)

    Do you want help or do you want to continue to think this is really an unsolvable problem?

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    #192265

    MBBinWI
    Participant

    @ctickel – If homogeneity is an issue, why not reduce the batch size? Or, alterantively, add the ingredients in multiple stages. There’s always more than one way to kick the can.

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    #192267

    Craig Tickel
    Participant

    Batch size is a function of the vessel. Customer demand is such that reducing the overall batch size would require a significant financial investment in additional equipment. Breaking the addition of ingredients into multiple stages has NOT been investigated, and is a great suggestion that we will look at to see if it will have an impact on final outcome.

    General SIPOC is; Add ingredients, Heat, Cook, Cool, then Transfer….. so if breaking the add can improve the homogenity, without impacting the overall total cycle time, it will be worthwhile.

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    #192268

    Robert Butler
    Participant

    At the moment it sounds like the issue of viscosity homogeneity is one of conjecture and not fact. When I’ve had this question in the past with respect to large batches(10,000 and 20,000 gallon reactors)we opted for a one time gross oversampling. We made sure things were in control, we had the sample bottles lined up and pre-marked to indicate order of sampling, and we coordinated everything with the QC lab before we did anything so that they were ready for a massive influx of samples. Because we knew the time order of the samples we could examine the variation in sample properties (we were interested in one in particular but since we were gathering the samples we made measurements on several other material properties).

    Given the data in time order it was easy to see how things changed over time and we were able to use the pattern to identify an optimum level of sampling for future runs.

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    #192270

    Craig Tickel
    Participant

    I would be interested in how you determined your optimum level of sampling. Certainly there would be one optimum to assure conformance to specifications, but a different one to determine change in the process, correct?

    My original point is if the process controls are in place and the process is highly capable, isn’t the sampling for conformance to spec, really non-value added work. I know the process of sampling for change would require more samples (sample size goes up in order to increase confidence), so did you trade uniform samples per batch, for increased samples on a few batches to minimize your appraisal costs?

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    #192280

    MBBinWI
    Participant

    @ctickel – the ultimate reduction in batch size is to convert to process flow. You can add ingredients, mix, heat, cook, and transfer as part of a process stream. Or even just the ingredient addition/mixing which can then be pumped into the cooker from multiple mixers for a single batch. As I said, there’s always more than one way to attack the issue.

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    #192291

    Craig Tickel
    Participant

    @MBBinWi Do recognize the opportunity that reducing batch sizes provides. However, multiple mixers to the “cooker” isn’t an option – capital and space constrained plus other issues(reaction requires heat to initiate, but requires mixing continue while “cooking”). So if you were “greenfield”, you would simply break the current large vessel into smaller units.. The vessel has a minimum batch size in order to cover the mixing blades, but your original idea of adding in stages, rather than all of A ingredients, then all of B ingredients, does have merit worth investigating. I do appreciate your comments.

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