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Management of Process Laboratory in Mill Environment By D K Singhal Chandpur Enterprises Ltd., Sargam Theatre, Chandpur

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Presentation on theme: "Management of Process Laboratory in Mill Environment By D K Singhal Chandpur Enterprises Ltd., Sargam Theatre, Chandpur"— Presentation transcript:

1 Management of Process Laboratory in Mill Environment By D K Singhal Chandpur Enterprises Ltd., Sargam Theatre, Chandpur

2 What is Data? Improvement of product quality through the use of statistical techniques. Improvement of product quality through the use of statistical techniques. Raw material for such techniques is DATA Raw material for such techniques is DATA We get data from different testing and evaluations. We get data from different testing and evaluations. For simplicity methods for standardization of techniques used are available. For simplicity methods for standardization of techniques used are available.

3 Then, what is the problem? One may ask, One can use equipments and instruments to check quality parameters and get the result. Then, why should we consider laboratory management as something different? One may ask, One can use equipments and instruments to check quality parameters and get the result. Then, why should we consider laboratory management as something different? Let us have a look at next example. Let us have a look at next example.

4 Hardness of Water In a mill, the chemists were checking total hardness regularly. Once, when it was required to check temporary hardness, the chemist obtained negative result. In a mill, the chemists were checking total hardness regularly. Once, when it was required to check temporary hardness, the chemist obtained negative result. We know any hardness cannot be negative. We know any hardness cannot be negative. They repeated the experiment, but the result was same. Why? They repeated the experiment, but the result was same. Why?

5 Hardness of Water Total Hardness (TH)= Temporary + Permanent Total Hardness (TH)= Temporary + Permanent Temporary hardness is removed by Boiling Temporary hardness is removed by Boiling Permanent hardness cannot be removed by boiling Permanent hardness cannot be removed by boiling so, so, Temp. Hardness Temp. Hardness = TH of water - TH of boiled water

6 Temporary Hardness If we boil water, some of its content would get evaporated. If we boil water, some of its content would get evaporated. If we forget to add water to make up volume, we may get wrong results. The chemists were making the same mistake. They just forgot to add make up distilled water.

7 Another Example

8 CD Profile A chemist checks CD profile. A chemist checks CD profile. CD GSM Variation is often within acceptable range. CD GSM Variation is often within acceptable range. Occasionally, whenever variation is higher than acceptable, papermaker objects that the chemist has made some mistake. Occasionally, whenever variation is higher than acceptable, papermaker objects that the chemist has made some mistake. On rechecking, many a times, variation is within acceptable limits. On rechecking, many a times, variation is within acceptable limits.

9 Why did it happen? Was the chemist careless? Was the chemist careless? Did he not checked CD variation properly? Did he not checked CD variation properly? Or did the papermaker force the chemist to alter the CD profile results reported earlier? Or did the papermaker force the chemist to alter the CD profile results reported earlier? Or there was something else that was creating unreliability? Or there was something else that was creating unreliability?

10 Sample CD Profiles in 1Minute Best Profile Variation: 2 gsm Worst Profile Variation: 4 gsm We may see that within one minute, profile varies significantly. In such a case getting any profile of the two above or in between is just a chance or luck.

11 Sample CD Profiles We may see that within one minute, average gsm varies significantly. In such a case getting any gsm in between the above two is just a chance or luck.

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13 CD Profile We may see that something else (paper machine approach flow, pulsations etc.) altered the results every fraction of second. We may see that something else (paper machine approach flow, pulsations etc.) altered the results every fraction of second. Hence, in this case reliability of laboratory data for CD profile is mainly governed by process, and not by sophisticated equipment or adoption of some specific testing technique. Hence, in this case reliability of laboratory data for CD profile is mainly governed by process, and not by sophisticated equipment or adoption of some specific testing technique.

14 Breaking Length Breaking length is tested for every roll. Breaking length is tested for every roll. There are some variations roll to roll. There are some variations roll to roll. To confirm whether variations are governed by paper properties or testing error, several rolls were checked checking breaking length at 5 positions, and average of these was compared with the reported data. To confirm whether variations are governed by paper properties or testing error, several rolls were checked checking breaking length at 5 positions, and average of these was compared with the reported data.

15 Breaking Length Average of 5 samples in a roll.

16 Breaking Length We can see that there is a very high fluctuation in reported data. We can see that there is a very high fluctuation in reported data. Similar to the case for basis weight, probably, something else is altering the results. Similar to the case for basis weight, probably, something else is altering the results. To know this, each property from each machine has to be studied carefully in detail. To know this, each property from each machine has to be studied carefully in detail.

17 Breaking Length Unfortunately, test methods published by a leading research institute in India, does not explain breaking length. Unfortunately, test methods published by a leading research institute in India, does not explain breaking length.

18 Burst Sometimes, Burst Factor as tested in a mill, may not be same as found in the same mill some times later. Sometimes, Burst Factor as tested in a mill, may not be same as found in the same mill some times later. Customer may complain having a paper of lower BF, than that was actually produced in a mill. Customer may complain having a paper of lower BF, than that was actually produced in a mill.

19 Cobb In some grades, sizing is extremely important. In some grades, sizing is extremely important. Most customers complain paper melting (wet rupture of paper when in contact with glue), without understanding what caused the problem. Most customers complain paper melting (wet rupture of paper when in contact with glue), without understanding what caused the problem. Papers affinity to water is more at higher water pH. Papers affinity to water is more at higher water pH.

20 Cobb Fortunately, mill can check Cobb; Unfortunately, many customers cannot. Fortunately, mill can check Cobb; Unfortunately, many customers cannot. If glue is made of water of higher pH, customer may face problem even though that paper was of same pH. If glue is made of water of higher pH, customer may face problem even though that paper was of same pH. The same paper (same Cobb value) cannot give same results on gluing in Rajasthan and West Bengal where there is a significant variation in atmospheric relative humidity. The same paper (same Cobb value) cannot give same results on gluing in Rajasthan and West Bengal where there is a significant variation in atmospheric relative humidity.

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22 Are There any Standards? Yes! Standards do exist for almost all properties. Yes! Standards do exist for almost all properties. These require sophisticated equipment, techniques, operating conditions and manpower. These require sophisticated equipment, techniques, operating conditions and manpower. Some equipment are frequently calibrated to give accurate results. Some equipment are frequently calibrated to give accurate results.

23 So, Whats the Problem?

24 We may get wrong results due to: Human carelessness. Human carelessness. Non-adherence to proper testing conditions. Non-adherence to proper testing conditions. Alteration in sample/equipment. Alteration in sample/equipment. Process Fluctuations. Process Fluctuations.

25 What Can We Do? Improve testing methods or develop new methods for testing in plants, so that such errors could be minimized. Improve testing methods or develop new methods for testing in plants, so that such errors could be minimized. Consider working environment equally important as standard atmospheric conditions. So far, testing methods standardization has been done only for laboratory testing, and not for plant conditions. Consider working environment equally important as standard atmospheric conditions. So far, testing methods standardization has been done only for laboratory testing, and not for plant conditions. Ensure that chemists are able to do testing without stress. Ensure that chemists are able to do testing without stress.

26 What Can We Do? In case results seem unreliable, check out possible reasons instead of just rejecting a lot. In case results seem unreliable, check out possible reasons instead of just rejecting a lot. Review test methods requiring unnecessary high parameters. Review test methods requiring unnecessary high parameters.

27 Some Details! Here, well discuss some of the testing along with the problems associated and how to get reasonably accurate and repeatable data. Here, well discuss some of the testing along with the problems associated and how to get reasonably accurate and repeatable data.

28 Consistency Consistency is calculated as- Consistency is calculated as- Weight of solids Weight of solids Cy % = X 100 % Volume of slurry Volume of slurry But, some error is possible while making measurements. Lets have an example- But, some error is possible while making measurements. Lets have an example-

29 Error in Consistency Measurement Let solids = 1.5 gm; Volume = 50 ml Let solids = 1.5 gm; Volume = 50 ml Error in weight = gm (1 mg); Error in weight = gm (1 mg); Error in volume = 1 ml Error in volume = 1 ml (Do you expect to measure volume of a 3% consistency pulp sample with a better accuracy?) Cy. obtained Cy. obtained MAX:= ( )*100/(50-1) = 3.063% MIN:= ( )*100/(50+1) = 2.939% Difference = percent points Difference = percent points

30 Consistency Measurement So, measurement in consistency may produce errors to the tune of %. So, measurement in consistency may produce errors to the tune of %. Even if we take 100ml pulp slurry, we may get error of +0.03%. Even if we take 100ml pulp slurry, we may get error of +0.03%. This is fairly good for routine measurements, but, for measurement of °SR and CSF, our standard test methods require more accuracy. This is fairly good for routine measurements, but, for measurement of °SR and CSF, our standard test methods require more accuracy.

31 Consistency Measurement For Example, for CSF, the desired value is 0.3% %. For Example, for CSF, the desired value is 0.3% %. Above technique for consistency measurement is unsuitable for conducting CSF test. Above technique for consistency measurement is unsuitable for conducting CSF test. So, So,

32 Error Analysis Furthermore, was the pulp sample well mixed? Also, entrained air and ambient temperature affect measurements. In case mixing was not perfect, we cannot assume that the sample of pulp was true representative of stock. Furthermore, was the pulp sample well mixed? Also, entrained air and ambient temperature affect measurements. In case mixing was not perfect, we cannot assume that the sample of pulp was true representative of stock. In other words, maintaining desired consistency conditions for CSF measurement is virtually IMPOSSIBLE. In other words, maintaining desired consistency conditions for CSF measurement is virtually IMPOSSIBLE.

33 What can we do? If the pulp sample taken is pre-diluted to approximate target value for the desired consistency, and consistency is checked from this sample, we may get reasonably good accuracy. If the pulp sample taken is pre-diluted to approximate target value for the desired consistency, and consistency is checked from this sample, we may get reasonably good accuracy. Let us see how…. Let us see how….

34 Slurry Preparation for CSF Take pulp slurry. Take pulp slurry. Dilute to 0.3% (+) approximately. Dilute to 0.3% (+) approximately. Measure consistency accurately. Measure consistency accurately. Take calculated volume for CSF measurement. Take calculated volume for CSF measurement. Make up with water to 1000 ml. Make up with water to 1000 ml.

35 Error Analysis Volume Taken = 1000ml, error = 1 ml Volume Taken = 1000ml, error = 1 ml Weight = 3gm (App.), error = 0.001gm Weight = 3gm (App.), error = 0.001gm Cy Obtained Cy Obtained MAX = 3.001/999 = % MAX = 3.001/999 = % MIN = 2.999/1001 = % MIN = 2.999/1001 = % So, error ( ) is less than desired limit of % So, error ( ) is less than desired limit of % Now, we may get reasonably acceptable consistency measurement. Now, we may get reasonably acceptable consistency measurement.

36 GSM & Profile Similar to above, we know that there is always some CD profile variation. Similar to above, we know that there is always some CD profile variation. This means no single sample from a roll can be considered to be a true representative of paper GSM. This means no single sample from a roll can be considered to be a true representative of paper GSM. Still, we are reporting GSM to one or even two decimal point accuracy in most of our work, including research papers. Still, we are reporting GSM to one or even two decimal point accuracy in most of our work, including research papers.

37 GSM & Profile: Mill Practice Errors due to carelessness in measurement, alteration of data are also possible in process laboratories. Errors due to carelessness in measurement, alteration of data are also possible in process laboratories. To eliminate these, two CD profiles can be extracted from the roll, the one is used for testing and other is kept for future cross check. To eliminate these, two CD profiles can be extracted from the roll, the one is used for testing and other is kept for future cross check. The cross checking is done the next day by a senior chemist. The cross checking is done the next day by a senior chemist.

38 GSM & Profile: Mill Practice A significant variation between reported figure and cross check indicates the possibility of data manipulation. A significant variation between reported figure and cross check indicates the possibility of data manipulation. In many cases, when this technique was implemented, chemists became cautious and careful so the reporting improved. In many cases, when this technique was implemented, chemists became cautious and careful so the reporting improved.

39 GSM & Profile: Mill Practice Later on, approach flow modifications were made to ensure that there are no profile fluctuations. Later on, approach flow modifications were made to ensure that there are no profile fluctuations. This also helped reducing joints significantly. This also helped reducing joints significantly.

40 Roll Joints Always, the first target is to have nil or minimal joints. Always, the first target is to have nil or minimal joints. Even if there is a joint, it must be marked properly on the reel. Even if there is a joint, it must be marked properly on the reel.

41 Roll Joints Joint can often be ignored, and sometimes not possible to detect when the roll sides are good. Joint can often be ignored, and sometimes not possible to detect when the roll sides are good. To minimize such situation, flags are put after every joint or sample drawn from the pope reel. To minimize such situation, flags are put after every joint or sample drawn from the pope reel. RED FLAG: JOINT GREEN FLAG:.. SAMPLE Unmarked joint or sample is reported by rewinder operator. Unmarked joint or sample is reported by rewinder operator.

42 Brightness For frequent calibration of the brightness tester, it is suggested to have Multi Level Standards. For frequent calibration of the brightness tester, it is suggested to have Multi Level Standards. Frequent cross check with customer/ other mills is often useful. Frequent cross check with customer/ other mills is often useful. In the next slides, mill wide multi level standards are discussed. In the next slides, mill wide multi level standards are discussed.

43 Brightness Standards Typical Mills Multi Level Standards: Typical Mills Multi Level Standards: Primary Standard: Primary Standard: Purchased from an ISO-9000 equipment supplier/calibrated by some third party. Can be used maximum twice in a month for calibration of secondary standard, and replaced every year. Secondary Standard: New blank plastic coated visiting cards calibrated by primary standard for calibration of tertiary standard/equipment. Each can be used maximum of thrice only.

44 Brightness Standards Tertiary Standard: Tertiary Standard: To be used every time before testing. Made up of glazed ceramic tile. To be replaced every month with a new one.

45 Tensile Strength To avoid fluctuation in readings as well as to save time in pre-conditioning of the sample at standard conditions, the following approach may be used. To avoid fluctuation in readings as well as to save time in pre-conditioning of the sample at standard conditions, the following approach may be used. Conditioning of Sample Conditioning of Sample Heat in oven at °C, 2-4 min. Allow to cool for 2-4 min. Continue testing Results match closely with testing under standard conditions. Results match closely with testing under standard conditions.

46 Burst Strength Preconditioning as for tensile can be done for Burst testing also. Preconditioning as for tensile can be done for Burst testing also. Burst testing on a number of different samples in a roll, and average is taken discarding abnormal reading, if any. Burst testing on a number of different samples in a roll, and average is taken discarding abnormal reading, if any. If there is a variation, by more than 8-10%, there is a need to study the machine itself for the same. If there is a variation, by more than 8-10%, there is a need to study the machine itself for the same.

47 Cobb Cobb is highly sensitive to environmental conditions (Temp., RH etc.) Cobb is highly sensitive to environmental conditions (Temp., RH etc.) Cobb is highly sensitive to water pH. Cobb is highly sensitive to water pH. Cobb is highly sensitive to paper condition, moisture, temperature, formation etc. Cobb is highly sensitive to paper condition, moisture, temperature, formation etc.

48 Cobb Oven treatment for 1 min. and cooling to 2 minutes before testing gives fairly good results comparable to standard testing. Oven treatment for 1 min. and cooling to 2 minutes before testing gives fairly good results comparable to standard testing. Modification of Cobb targets depending on probable date of dispatch, weather conditions, location of customer, water properties in customer area etc. can be considered. Modification of Cobb targets depending on probable date of dispatch, weather conditions, location of customer, water properties in customer area etc. can be considered.

49 Cobb: On the basis of above, while cobb targets were modified, it became possible to reduce Rosin consumption for some customers. On the basis of above, while cobb targets were modified, it became possible to reduce Rosin consumption for some customers. For some customers (qualities), savings in rosin consumption were to the order of 30-40%. For some customers (qualities), savings in rosin consumption were to the order of 30-40%.

50 Remember: It is easy to maintain standard conditions for testing in laboratory, but, customer may be using paper in extremely different conditions. It is easy to maintain standard conditions for testing in laboratory, but, customer may be using paper in extremely different conditions. Mill wise, testing methods should be flexible enough so that testing can be done in short time before a huge quantity is rejected. Mill wise, testing methods should be flexible enough so that testing can be done in short time before a huge quantity is rejected.

51 Can we- Develop/modify testing methods for rapid in house testing? Develop/modify testing methods for rapid in house testing? Minimize human errors to a minimum by motivating our TESTING TEAM to be more attentive? Minimize human errors to a minimum by motivating our TESTING TEAM to be more attentive? Make our quality tests more flexible? Make our quality tests more flexible?

52 For better testing and quality of laboratory data, For better testing and quality of laboratory data, we need we need

53 Initiatives in Testing Excellence in Manufacturing.

54 Thank You.


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