ss4 mwv final report daliaga-jul-11-07

8/8/2019 SS4 MWV Final Report DAliaga-Jul-11-07

http://slidepdf.com/reader/full/ss4-mwv-final-report-daliaga-jul-11-07 1/29

Packaging Resources Group: Evadale-Texas

Evadale PM2: Reduction of Sheet Break andOperational Downtime

7/31/07

Six Sigma Training/Certification ProjectFinal Report

Candidate Name: David AliagaChampion: Keith Medlock

Mentor: Sonia WestFinancial Analyst: <<insert name>>

Team Members:David Aliaga (Process Control Engineer.)

Keith Medlock (PM2 Superintendent)Larry Snipes (PM2 Supervisor)

Steve Hart (Process Control Manager)Mark Baran (Research)



1

Acknowledgement

We want to recognize and thank all individuals that contributed to this Green Belt Six SigmaProject through their direct involvement in the implementation of the tasks that made

Evadale Paper Machine No. 2 runnability better during the time of October 2006 to April of 2007.

Improving the runnabilty of Paper Machine No. 2 around the time mentioned above was aneffort of various departments: PM2 operations, Maintenance, E & I, Process Control,Process Engineering, and CPI.

This report does not attempt to describe in detail all the work done to improve PM2runnability at the time of the investigation, but instead focuses on aspects of defining,diagnosing, and correcting issues on the wet end using the six sigma approach. So, wewant to acknowledge that multiple efforts have contributed to improve PM2 runnability and

that this report is only a portion of that work.



2

Tab le of Contents:

Executive Summary................................................................................................................................... 00Define Phase............................................................................................................................................. 00

Project Language .......................................................................................................................... 00Business Case .............................................................................................................................. 00Primary Metric............................................................................................................................... 00Secondary Metric(s) ...................................................................................................................... 00COPQ Definition ........................................................................................................................... 00Team Established ......................................................................................................................... 00

Measure Phase ......................................................................................................................................... 00Process Map ....................... ........................... ......................... ............................. ......................... 00Pareto Charts ............................................................................................................................... 00Cause & Effect .............................................................................................................................. 00FMEA ........................................................................................................................................... 00Gage R&R .................................................................................................................................... 00Process Capability ........................................................................................................................ 00Complete List of X¶s ...................................................................................................................... 00Measure Conclusions ................................................................................................................... 00

Analyze Phase .......................................................................................................................................... 00Multi-Vari Analysis ........................................................................................................................ 00

Graphical Analysis ........................................................................................................................ 00Correlation and Regression ....................... ........................... ......................... ............................ .... 00Sample Size Selection .................................................................................................................. 00Hypothesis Testing ....................................................................................................................... 00

A list of X's analyzed ........................ ........................... ......................... ............................ ............. 00 Analyze Phase Conclusions ...................... ........................... ......................... ............................ .... 00

Improve Phase .......................................................................................................................................... 00Critical X¶s .................................................................................................................................... 00

Action Plan ................................................................................................................................... 00Lean Fundamentals ...................................................................................................................... 00Mistake Proofing ........................................................................................................................... 00Design Of Experiments ................................................................................................................. 00Improve Conclusions .................................................................................................................... 00

Control Phase ........................................................................................................................................... 00Final Project Deliverables.............................................................................................................. 00Control Plan .................................................................................................................................. 00Quality Management Systems....................................................................................................... 00Statistical Impact ......................... ........................... .......................... ............................ ................. 00Final Capability ............................................................................................................................. 00Financial Impact ...................... ........................... .......................... ............................ ..................... 00Lessons Learned .......................................................................................................................... 00New Project Recommendations .................................................................................................... 00Control Phase Conclusions ....................... ........................... ......................... ............................ .... 00

Appendix ................................................................................................................................................... 00 Appendix I - <<insert appendix name>> ...................... .......................... ............................ ............ 00 Appendix II - <<insert appendix name>> .......................... ......................... ............................ ........ 00

Bibliography .............................................................................................................................................. 00



3

Ex ecutive Summ ary : PM2 - Reduction of Sheet Break and OperationalDowntime

Define:In 2006, there had been increasing episodes of web breaks that made the amount of operational downtime rise. It was identified that production could be increased by 2,635TPY by attacking losses related to: grade changes, sheet breaks, and operationaldowntime.

Me a su r e:-Cause and Effect analysis led the team to focus efforts in correcting several aspects of runnability in the paper machine. A spreadsheet of action items on runnability was initiatedby October of 2006 and it was reviewed weekly.-One important measuring tool for the team was the PI database, which allowed thetracking of the machine parameters and correlation to episodes of web breaks.- In order to assist in the follow up of web breaks, operators started to record detailedcomments of web breaks in a log book placed at the dry end control room.-The statistical process control feature from Minitab (not available in PI) was used to helpfilter out noisy data and identify shifts in the process.- Process maps of the wet end of the paper machines were used to compare differences inoperation/design and help identify the area causing the web breaks.- One-on-one sessions with machine tenders at the wet end helped to understand theprocess maps and critical inputs related to the approach flow, headbox and fourdrinier tablestages of the operation.- By looking back at data from the years 2005 and 2006, the capability of the process withrespect to downtime and weight-MD sigma was identified. The increase by both measureswas significant.- The weight MD sigma measured by scanners on the paper machine became a criticalinput to predict web breaks. The investigations indicated that when the weight MD sigmawas on an increasing trend, the potential for web breaks increased.

An a lyz e:- Previous work related to basis weight upsets and web breaks was reviewed by the teamand analysis was focused on the wet end of the paper machine.- In December of 2006, when multiple paper machine parameter data from July toDecember of 2006 was correlated to weight-MD-sigma, it was found that the headboxseparator tank level had the highest correlation to MD sigma. Since high weight MD-sigmaand higher hrequency of web breaks correlated, the separator tank then became a focus of improvement.-It was found that the headbox separator tank level did not have automatic control, so thetank had been operating most of the time completely full of water. Data indicated that whenthe tank became flooded, the weight MD-sigma was higher. Also, when the level in thetank became very low, air from the headbox airpad escaped, causing instability of theheadbox pond and a weight upswing.

Imp r ove: - The team had discussions with the headbox manufacturer to determine needs for designmodifications to the headbox separator tank level.



4

- Machine tenders re-established the manual controlling of the headbox separator tanklevel. The manual control of the level required constant attention by the machine tender, soa plan to install an automatic control was initiated.- Trending data on the separator tank level and correlation to weight MD sigma was used toset a target of 32 inches in the separator tank.- Automatic controlling of the separator tank level was implemented in stages. Control of level was tuned to increase the tank valve response.- Maintenance to the headbox controls, valves, and instrumentations were performed as amethod of a complete maintenance of the headbox.- A separator tank valve procedure for the critical grade change of 20 to 24 pt. Printkotewas established to prevent the loss of air pad pressure in the headbox.

Cont r ol:- Identified and documented that the reduction in weight MD-sigma had contributed to thereduction of unscheduled downtime.- Created a PI chart so machine tenders could monitor the weight MD-sigma value beforethe size press (uncoated value) and correlate the value of the sigma to headboxoperational parameters like: secondary fan pump RPM, headbox level, total head, slice

opening, etc.- Documented the history and reason for the increased weight MD-sigma that started in2006.- Provided a set of final recommendations to supervisors that included close monitoring of the pond level in the headbox and keeping the current separator tank design.

App r ov a l Sign a tu r es:

Champion

Mentor

Financial Analyst

Process Owner



5

Define Ph a se:

B usiness C a se:PM2 production can be increased by 2635 TPY by attacking losses related to: gradechanges, sheet breaks, and operational downtime.

P r im ary Met r ic:Operational downtime, weight-MD-sigma

Second ary Met r ic(s):Web breaks, internal rejects

COPQ Definition:The following incremental value was estimated for the second quarterly 2007 100-dayprojects- Grade change reject reduction: 1.1% to 0.79% 700 TPY- After break reject reduction: 0.7% to 0.47% 475 TPY- %Unscheduled maint. Reduction: 0.7% to 0.5% 260 TPY- Sheet break/operational DT reduction: 35% 1200 TPY

total: 2635 TPY

Incremental value from production increase: $345/ton x 2635 TPY = $909,075.00

The green belt six sigma project detailed in this report is estimated to have contributed to50% of the value of production increase. This green belt project included the effort of several Departments (i.e., PM2 operations, Process Control, Process Engineering, E&IInstrumentation, Maintenance, and CPI).

Te a m E st ab lished:

Te a m Mem b e r : Ex pe r tise/Role:Keith Medlock Leader/PM2 Super IntendentDee Hinkie Champion/Paper Mill Super Intendent? Financial AnalystSonia West Mentor/Black BeltLarry Snipes PM2 Supervisor/operationsDavid Aliaga Process Control Engineer/Green Belt tra.Steve Hart Process Control /Manager Wiley Hargrove Process Control /Honeywell controlsMark Baran CPI-Research



6

Me a su r e Ph a se :

P r ocess M a p :During the initial phase of investigation, analysis of the process map of paper machine No.2focused on the areas of the wet end, wet stack, and the coaters as major items to improverunnability. Several action items that covered sections of the process flow diagram weregenerated: install new sheet break detectors, correct misalignment, improve speed controlsof paper rolls, change the operation logic, etc.



7

Further into the project, by January 2007, the headbox became the major focus of theinvestigation after discovering that the separator tank level had a significant effect on themachine direction weight variability of the paper and web breaks.

A process flow diagram of the headbox and separator tank helped in the comparisonbetween the separator tanks of paper machine¶s 2, 4, and 5. On February 20 th 2007, amemorandum detailing the operating conditions of the headbox separator tank level wassent to the manufacturer/rebuilder of the headbox, so as to ask for their recommendationsin regards to this matter.



8

P ar eto Ch ar ts:

The pareto chart below contains the count of web breaks from 1/8/2007 to 2/4/2007 thatwas recorded by dry end operators in a log book placed at the dry end of the paper machine. The data indicated that 44% of the web breaks occurred towards the wet end of the paper machine. This information was more evidence that the investigation for thesource of web breaks should concentrate in the area of the wet end.

C o u n

t

P e r c e n

t

Location

Count 1

Percent 22.2 22.2 18.5 11.1 7.4 7.4 3.7 3.7

6

3.7Cum % 22.2 44.4 63.0 74.1 81.5 88.9 92.6 96.3

6

100.0

5 3 2 2 1 1

O t h e r

J a g C o a t e r

1 s t D r y e r W i

r e

D r y S t a c k

D r y E n d

p u l l s t a c k

W e t S

t a c k

a f t e r 2 n d

p r e s s

30

25

20

15

10

5

0

100

80

60

40

20

0

Pareto Chart of Location



9

Ca use & E ffect:

The fishbone diagram above shows the areas where the efforts concentrated to improvethe runnability of the paper machine. Action items and work orders were completed for theabove items.



10

The cause & effect matrix indicates that the areas of the wet end and coaters weresuspected as the areas where a great majority of the web breaks originated.



11

G a ge R&R:The stability of the paper machine was analyzed using the weight, caliper, and moisturesigmas from the scanner outputs at the size press (base sheet) and the reel.

The sigmas for each reel are recorded in the mill-wide database (PI).

The caliper, moisture and weight outputs from the reel scanner are verified daily bycomparing them against samples taken from the reel and measured at the quality lab. If the discrepancy between the lab reading and the scanner is greater than a certainmaximum allowed, the process control personnel will make adjustments to the gain in thesensor of the scanner to bring the laboratory and the scanner readings in closer agreement.



12

P r ocess C a p ab ilit y:The time series plot of weekly operational downtime showed that before May 2006, theoperational downtime was below 200 minutes/week. After May 1 st 2006, the frequency of over 200 minutes/week of operational downtime increased.

The X-bar-R chart of monthly operational downtime from 2005 to 2006 helped pinpoint thetime when the operational downtime started on an increasing trend. The X-bar chartshowed that the monthly operational downtime started on an increasing trend sinceFebruary of 2006. By October of 2006, the operational downtime had passed the 3-sigmaupper control limit (UCL = 449). The R-chart or range chart also supported the case of machine performance deterioration; the range values since February of 2006 startedincreasing also.

As an aside note, the high R-value on downtime in September 2005 is explained by theoccurrence of hurricane Rita.

The data of downtime was separated into two groups: (1) downtime before February-2006,

and (2) downtime after February of 2006. The data were plotted as histograms two showthe distribution between the two samples.

Based on the histogram data, the long term capability (Pp) with respect to operationaldowntime before February 2006:

- standard deviation = 182.5 minutes/week- allowed variation = UCL - 115.9 minutes/week

P p = 1.33 = (UCL-115.9)/(3 x 182.5) ------- (choose 1.33 for Pp)

Therefore, the UCL is 613 and the downtime histogram for data after February 2006indicated that the machine was only partially capable of meeting the requirements.

The weight machine direction 3-sigma from 2005 to 2006 was also used to calculate thecapability of the process. The data showed in this case that the weight variability of themachine had been on a increasing since the beginning of 2006. The R-chart weightmachine direction 3-sigma more clearly showed that the variability of the weight sigmaincreased significantly since January of 2006. Before January 2006 the range of values of weight MD-3sigma were 2.72% or lower. After January 2006, the range of the weightsigma had more frequent values that exceed the UCL.

Since the X-bar R chart indicated that a shift in the paper machine process had occurredaround January 2006, we therefore, separated the data of weight MD 3 sigma% into twogroups: (1) MD sigma before January-2006, and (2) MD sigma after January-2006.

The data of the two samples was plotted as histograms. The weight MD 3 sigma% beforeJanuary 2006 had a lower average and standard deviation of 1.65 and 0.57, respectively.The weight MD 3sigma% of the data after January 2006, had a higher average andstandard deviation of 2.63 and 1.31, respectively. The comparison of the two histograms of weight MD 3sigma, clearly showed that the capability of the paper machine had changed.



13

To calculate the long term capability (Pp) with respect to the weight MD-3sigma from databefore January 2006, we proceeded as follows:

- standard deviation = 0.57 minutes/week- allowed variation = UCL ± 1.65 minutes/week

P p = 1.33 = (UCL-1.65)/(3 x 0.57) ------- (choose 1.33 for Pp)

The UCL from the above formula came out to be 3.92%. Based on this UCL, we calculatedthe capability for the data after January 2006 as being:

Pp = 0.56 = (3.92-2.63)/(3 x 1.31)

The value of 0.56 indicated that the variability of the process is greater than the size of thespecification range and therefore, corrections to the paper machine process would need tobe implemented.

O p e r a

t i o n a

l d o w n

t i m

e ( m i n u

t e s

/ w e e

k )

1 1 / 1 / 2 0

0 6

9 / 1 / 2 0

0 6

7 / 1 / 2 0

0 6

5 / 1 / 2 0

0 6

3 / 1 / 2 0

0 6

1 2 / 2 9 /

2 0 0 5

1 0 / 2 9 /

2 0 0 5

8 / 2 9 / 2 0

0 5

6 / 2 9 / 2 0

0 5

5 / 1 / 2 0

0 5

1200

1000

800

600

400

200

0

Time Ser ies Plot of Op erational Downtime (minutes/week)



14

S a

m p

l e M e a n

N ov-06Sep-06Jul-06May-06Mar-06Jan-06N ov-05Sep-05Jul-05May-05

600

400

200

0

-200

_ _X=155.4

UC L=505.5

LCL=-194.7

S a m p

l e R a n g e

N ov-06Sep-06Jul-06May-06Mar-06Jan-06N ov-05Sep-05Jul-05May-05

1000

750

500

250

0

_R=342

UC L=881

LCL=0

1

1

1

Xbar-R Chart of Op erational Downtime (average-minutes/week)

Operational Downtime (ave rage- minutes/ week)

P e r c e n t

120010008006004002000-200

25

20

15

10

5

0

Mean StDev

195.7 234.4 48

115.9 182.5 49

TIME

AFTER-FEB06

BEFORE-FEB06

H istogram of Operational¡

orma l



15

S a

m p

l e M e a n

12/17/0610/21/0608/27/0607/03/0605/09/0603/15/0601/13/0611/17/0509/10/0507/17/0505/20/05

5

4

3

2

1

_ _

X=2.270

UC L=2.512

LCL=2.028

S a m p

l e R a n g e

12/17/0610/21/0608/27/0607/03/0605/09/0603/15/0601/13/0611/17/0509/10/0507/17/0505/20/05

8

6

4

2

0

_R=3.73

UC L=5.13

LCL=2.33

1111

11

1

1

11

1

1

11

1

1111

11

1

1

1

11

1

1

11

1

1

1

1

111

11

1

1

11

1

111

11

111

1

11

111

1

1

1

11

1

1

11

1

1

11

11

11

11

1

1

11

11

11

1

11111

1111

1

11

1

1

11

1

1

1

11

11

11

11

111

1

1

1

1

1

111

11

1

1

11

11

1

11

1

1

1

1

1

11

1

1

1

111

1

1

1

1

1

1

11

11

1

1

111

1

1

1

1

1

1

1

1

1111

1

11

1

11

1

1111

11

1

11111

111

111

1

1111111

111

1

1111

11

1

1

1

1

1

1

1

1

1

11111111

11

1

1111111111

1

1

1

1

1

1

11111

1

111

1

11111111

1111111

1111111

1

1

11

11

111

1111

111

111

1

1

11111

11

11111

11111

1111111

1111111

1111111111

111111

1111

111111

11111

1

1

11111

1

1111111

11111

1

111

11111

11

11

111111

1

11111

11111111

11

11

1111111

111

1

1

111

1

1111

11111111111

1111111

1

1111

11

1

1

1

1

1

1

1

1

11

1

1

111

1

11

1

11

1

1

11

1

11

1

1

1

111

1

11111

11

1111

11

1

1

1

1

1

1

11

1

11

1

11

111

11

111

1111

11

1

1

11

1

11

1

1

1

1

1

1

1

1

1

1

1

1

1

1

11

1

1

1

1

1

11

1

11

1

1

1

1

1

11

1

1

1

1

1

1

1

1

1

1

1

1

1

1

11

1

11

1

1

1

1

1

111

1

11

11

1

11

1

11

1

1

1

1

1

1

11

11

11

1

1

11

1

1

1

1

1

111

1

1

1

11

11

1

1

1

11

1

1

1

1

11

1

1

1

1

111

111

1

111

1111

1111

111

111

111111

1

1

1

11

111

1

111

1

111

1111

1111

1

1

1111

111

1

11

111

1

11

11

11

11

1

1

Xbar-R Chart of BW_MD3S%

BW_MD3S%

P e r c e n

t

9.88.47.05.64.22.81.40.0

7

6

5

4

3

2

1

0

Mean StDev N

2.632 1.308 246751.648 0.5714 14374

CON DITIO N¢

£ TER-JAN 06BEFORE-JAN 06

Normal

H istogram of Basis Weight MD 3 Sigma%



16

Complete List of X¶s:Below is a partial list of the input X¶s. The total inputs that at one time were included in acorrelation were over 100. The reason that so many inputs were used in a multi-correlationanalysis, was that we were not absolutely certain that it was only one section of the paper machine that was the reason for the series of web breaks that were occurring on the paper machine. So, data from the reel to pulp mill was entered in multi-correlation analysis to helpprioritize the more probable causes of web breaks.

Additional input X¶s were obtained with the assistance of the CPI group from NorthCarolina. They installed on the paper machine an optical sensor located before the sizepress that was used to measure the transmissivity of the paper web and relate that to theMD weight variability. In addition, there were pressure sensors installed at the basis weightcontrol valve and at the air pad of the headbox. The GMS data collection system from CPIwas continuously recording machine data at a higher rate than the in-mill PI data basesystem.



17

REEL PM2-GRADE GRADEPM2-REEL REELPM2-SET SET

PM2-2PMTPH.PV RATEPM2-222_ST391.PV REEL_SPEEDPM2-221_LT229.PV HDBX_LEVEL

H EAD OX AND FOURDRINIER TA LE PM2-221_PC228.PV TOTAL_HEADPM2-221_ZC234.PV VERT_SLICE

PM2-221_ZT235.PV HORIZ_SLICEPM2-221_ST047.PV SEC_FAN_PMP_RPMPM2-221_NT054.PV HDBX_CONSIST%PM2-221_FC004.PV THICK_FLOW_GPMPM2-221_ST650.PV WIRE_SPEEDPM2-221_XC236.PV RUSH/DRAGPM2-221_NI065.PV WIRE_CONSIST%PM2-221_LC230.PV SEPARATOR_LVLPM2-221_TC056.PV STOCK_TEMPER

PM2-221_PT079.PV COUCH_VACUUMPM2-221_SC651.PV COUCH_DRAW

PULP MILL FL-407_KAPPA_A.PV HW_KAPPA

FL-B4_LAB.BCREP HW_CONDUCTIVFL-B4_LAB.VISREP HW_VISCOSFL-B4_LAB.FINALREP HW_BRIGHTNESSFL-507_KAPPA_F.PV SW_KAPPAFL-B5_LAB.BCREP SW_CONDUCTIVFL-B5_LAB.VISREP SW_VISCOS

FL-B5_LAB.FINALREP SW_BRIGHTNESSPM2-220_ZI617.PV HW_REFIN_POSITI_INCHESPM2-220_PI029.PV HW_REFIN_IN-PRESS_PSIPM2-220_PI030.PV HW_REFIN_OUT-PRESS_PSI

REFINERS PM2-220_JT617.PV HW_REFIN_KWPM2-220_XC617.PV HW_REFIN_HPDTPM2-220_ZI613.PV SW_REFIN_POSITI_INCHESPM2-220_PT027.PV SW_REFIN_IN-PRESS_PSIPM2-220_PT028.PV SW_REFIN_OUT-PRESS_PSIPM2-220_JT613.PV SW_REFIN_KWPM2-220_XC613.PV SW_REFIN_HPDTPM2-220_PI047.PV TICKLR_REFIN_IN-PRESS_PSIPM2-220_PI048.PV TICKLR_REFIN_OUT-PRESS_PSIPM2-220_JT615.PV TICKLER_REFIN_KWPM2-220_XC615.PV TICKLER_REFIN_HPDTPM2-220_JT611.PV COMBO_REFIN_KWPM2-220_XC611.PV COMBO_REFIN_HPDT



18

Me a su r e Conclusions:-The PI database was an important resource to track the variation of machine parametersand relate them to the episodes of web breaks. Detailed information of web break eventswere recorded in a log book at the dry end for further review.-The statistical process control feature from Minitab (not available in PI) did effectively filter out process noise of the PI data and helped identify shifts in the process.- Process maps of the wet end of the paper machines were used to compare differences inoperation/design and help identify the area causing the web breaks.- The capability of the process was identified. The weight machine direction sigmacapability after January 2006 was lower, compared to data before January 2006.- The unscheduled downtime had also increased after February 2006 because web breakshad become more frequent.



19

An a lyz e Ph a se :

Co rr el a tion a nd Reg r ession:While investigating the possible reasons for the web breaks, the team took notice on thefact that from time to time there will be unexplained occurrences of basis weight swings thatwould consequently cause web breaks. Since the noted weight swings were recorded bythe scanner before the size press, the team narrowed its investigation to the wet end of thepaper machine. Some other previous work had suggested possible causes for theseweight swings as: stock consistency variations, stuffbox level changes, or a poor approachflow piping design.

Previous efforts to improve weight CD variability in August of 2003 had shown that theheadbox separator tank level had some influence in the weight CD variability. The teamtook a closer look at the headbox separator tank level as a possible source of also affectingthe weight MD variability.

By mid-December of 2006, the analysis of trends in CD and MD weight variability wereindicating that by maintaining the headbox separator tank level at a target of 20 inches, theweight variability decreased. Efforts by the machine tenders were increased to try tomaintain the headbox separator tank level constant. Since there was no automatic controlfor the headbox separator level, the variation from shift to shift was high. This variationcreated the opportunity to evaluate the influence of the separator tank level on the weightMD sigma.

By January of 2007, the analysis was expanded to include higher number of machineparameters and historical data that included more months. So, more than 100 variables of data from July 2006 to January of 2007 were correlated against the weight MD-3sigma.The result of the correlation brought out that the weight-MD-3sigma and the headboxseparator tank level were highly correlated. The results of the correlation are shown in thetable below. Based on this correlation, efforts were increased to understand the operationof the headbox separator tank and compare it to the other paper machines.



20

G ra phic a l An a lysis:

On January 19 th- 2007, a report was issued to operations that included the plot below of weight MD sigma and heabox separator level. This plot contained data from July of 2006to January of 2007. The SPC tool from Minitab was used to obtain daily averages of both,weight MD and separator level, to more clearly show that there was indeed a correlationbetween the headbox separator tank level and the weight MD-sigma.

The plot shows that a significant downward shift had occurred on the weight MD sigma onDecember 10 th. At about the same time, the headbox separator tank level also dropped.This correlation between the two variables helped support the efforts of stabilizing the levelof the separator tank.

B a s

i s w

e i g h t_ M D

_ 3 S i g m a ( l b s

/ r e

a m )

¤

e a d b o x s

t o r a

g e l e v

e l ( i n c h e s

)

0 9 - J a n

- 0 7

3 0 - D e

c - 0 6

2 0 - D e

c - 0 6

1 0 - D e

c - 0 6

2 9 - N o

v - 0 6

1 9 - N o

v - 0 6

0 9 - N o

v - 0 6

2 9 - O c

t - 0 6

1 9 - O c

t - 0 6

0 9 - O c

t - 0 6

2 9 - S e p

- 0 6

1 9 - S e p

- 0 6

0 9 - S e p

- 0 6

3 0 - A u

g - 0 6

2 0 - A u

g - 0 6

1 0 - A u

g - 0 6

3 1 - J u

l - 0 6

2 1 - J u

l - 0 6

1 1 - J u

l - 0 6

0 1 - J u

l - 0 6

28

24

20

16

12

8

4

0

45

40

35

30

25

20

VariableBW_MD_3SigmaHDBX_STOR-LVL



21

A scatterplot of the weight MD sigma versus the headbox separator level provided theinformation about where to set a target for the separator tank level. The data showed thatwhen the separator tank level was above 32 inches, the weight MD sigma reached highvalues of 6 or above. Therefore, based on the data, we recommended that the targetshould be below 32 inches. On February 12 th, 2007 a memorandum was distributed to themachine operators (Appendix I) that the separator tank level should be maintained at 30inches and that the level should not be allowed to reach below 20 inches because of thepossibility that outside air could entrain the separator tank if the level were to become low.This air entrainment would cause the air pad in the headbox to become unstable andcreate a weight swing.

H DBX_S¥

¦

R § LVL

B W

_ M D

_ 3 S

¨

©

454035302520

12

10

8

6

4

2

S tt r

t

BW_MD_3S

!

" # H DBX_S$

%

R & LVL



22

As the implementation of automatically stabilizing the separator tank level progressed sinceDecember 2006, the operational downtime started to drop as can be seen by the plotbelow. This plot shows that since January of 2006 the operational downtime had increasedfrom 5 to almost 40 hour/week by November of 2006. By April of 2007, the operationaldowntime had come down back to 5 hours ± similar to pre-January 2006 levels. Theweight MD-3-sigma% showed a similar trend as the downtime, starting at around 2%before January 2006, reaching a peak of 5% by the end of 2006 and returning to low levelsof 2% by April of 2007.

R E E L W

'

M D 3 -

(

I G M A %

O P E R A T I O N A L D O W N T I M E , H O U R S

0 4 / 0 1

/ 0 7

0 2 / 1 0 /

0 7

1 2 / 2 2

/ 0 6

1 1 / 0 2

/ 0 6

0 9 / 1 3

/ 0 6

0 7 / 2 5

/ 0 6

0 6 / 0 5

/ 0 6

0 4 / 1 6

/ 0 6

0 2 / 2 5

/ 0 6

0 1 / 0 6

/ 0 6

1 1 / 1 7

/ 0 5

0 9 / 2 8

/ 0 5

0 8 / 0 9

/ 0 5

0 6 / 2 0

/ 0 5

0 5 / 0 1

/ 0 5

10

8

6

4

2

0

50

40

30

20

10

0

-10

REEL WT MD3 -S IG MA% vs OPERAT I ONAL DO WNT I ME

An a lyz e Ph a se Conclusions:<< Summarize key analyze findings >>



23



24

Imp r ove Ph a se:

Cr itic a l X¶s:<< List & discuss critical X¶s >>

Action Pl a n:Fe br u ary 12 th , 2007: written recommendations were distributed to the machine tenders onthe manual control of the headbox separator tank level (see Appendix I).Fe br u ary 20 th , 2007: sent a written document to the headbox manufacturer/rebuilder emphasizing the high variability in the headbox separator tank level and the need toconsider design modifications to this element.Fe br u ary 28 th , 2007: started the testing/implementation of automatically controlling thelevel of the separator tank by installing a gap controller routine in the Honeywell DCS.Mar ch 8 th , 2007: the gap controller for the headbox separator tank was modified. The gapwas increased to +2 inches and the gains were double to increase the stability of thecontroller program.Ap r il 17 th , 2007: the gains in the headbox separator tank control were increased to makethe valve in the tank close quicker when the overflow from the headbox drops.

Mist a ke P r oofing:<< Include a description of some mistake proof used in the project ± consider anythingimplemented that would reduce or eliminate mistakes >>

Imp r ove Conclusions:<< Summarize learning¶s for the Improve phase >>



25

Cont r ol Ph a se:

Fin a l P r oject Delive rab les:<< Discuss deliverable from the project ± include how ownership of solutions will pass fromanalyst to process owner >>

Cont r ol Pl a n:The final recommendations on the automatic control of the separator tank of PM2'sheadbox are:

1. The gap control strategy and gains are adequate to maintain a constant level on theseparator tank for all grades and grade changes except for the grade change from 20 to 24pt. Again, machine tenders should keep the separator level control in automatic, except for the grade change from 20 to 24 pt (further explained below).2. For the grade change from 20 to 24 pt., we have written a procedure (see attached file)that will adequately maintain seal of the air pad, specially on this grade change, where theheadbox air pad goes from positive to vacuum.3. The separator tank does not need to be replaced since we found out that the flooding of the separator tank was caused by the headbox level being too high with respect to theskimmer inside the headbox. As long as the headbox level is just enough to sustain theoverflow over the skimmer, the separator tank will not flood. It also helps that the automaticcontrol gains on the separator tank have been increased in order to make the separator valve react quicker to level changes inside the separator tank.4. The set point on the separator tank should be kept at 32 inches. The height of theoverflow stock in the separator tank is such, that it gives enough time for the separator valve to close and still maintain seal to the air pad.5. The level inside the separator tank should not stay at 40 inches or more for extendedperiods of time because this will cause backup of the overflow into the headbox which ithas been proven to cause an increase in the machine direction weight variability.

Qu a lity Ma n a gement S ystems:<< Discuss any required change to SOP¶s ± these could be ISO 9000, ISO 14000, SFI, or any other QMS used by your facility ± if no changes required state this ± address anyissues involving lack of a QMS ± get buy-in from process owner >>

St a tistic a l Imp a ct:<< Use hypo testing to prove the goal has been exceeded >>

Fin a l C a p ab ilit y:<< Insert final capability ± compare this to initial project capability >>

Fin a nci a l Imp a ct:<< Include hard dollar calculations based on project results ± include discussion of softdollar benefits and estimate those if possible >>

Lessons Le ar ned:<< Summarize key learning¶s from the project ± focus on important X¶s >>

New P r oject Recommend a tions:



26

<< Include any recommendations for future projects ± include any preliminary analysis thathas been completed >

Cont r ol Ph a se Conclusions:<< Summarize the conclusions for control >>



27

Appendi x I: PM2- Operation Guidelines of the Headbox Separator Tank to Keep the Headbox Sealed (Memorandum Feb. 12 th, 2007)

INTRODUCTION Maintaining headbox seal is critical to the runnability of the headbox and the paper machine. The headbox

separator tank serves the purpose of routing the overflow of the headbox while maintaining the headbox seal.When a loss of headbox seal occurs, the headbox pond becomes unstable and will cause swings in basis weight.

With the increase of machine speeds, the limitations of the current design of the separator tank have becomemore evident:

± Low volume of the headbox overflow in the separator tank. ± Incorrect design of the separator overflow pipes.

This report gives recommendations to the machine tender at the wet end on how to set the separator tank level to helpmaintain seal on the headbox and good stability on the paper machine. The recommendations written below are based onfeedback from the PM2 machine tenders and observations on the stability of the paper machine signals.

DISCUSSIONOperational Guidelines to Maintain a Target Level on the Headbox Separator Tank

The headbox separator tank level target is 30 inches. While the Honeywell set point (SP) can be entered as 30,the tank level control is done in manual (MAN). Therefore, the machine tender will need to monitor and adjustthe level as needed, mainly by using the headbox level to restore the separator level close to target-if it happens

to drop/rise unexplainably. ± Historical data indicates that 30 inches is the optimum setting to maintain low machine direction

variability. ± Also, 30 inches is a sufficient height in the level of the tank that if the separator tank level happens to

drop unexplainably, the machine tender will have enough time to react and bring the level back upwithout loosing seal to the headbox.

± It is very important to watch if the separator tank level drops during a planned machine speed or weight change. The back tender at the dry end should alert the machine tender at the wet end when aweight change is going to be done, so the machine tender can verify that the separator tank level isclose to 30 inches before the weight change is done. DO NOT let the separator tank level drop below20 inches, or you will loose seal to the headbox and it will cause a weight swing.

VE RY IMPORTANT: If the separator tank level drops suddenly, the machine tender should first increase theheadbox level. It is the headbox level and not the separator tank valve which has the highest influence in

increasing the separator tank level. The valve located at the bottom of the headbox separator tank is set manually between 80 to 90%. This is doneto reduce the rate of the stock evacuation of the tending side headbox overflow leg pipe, which does not connectto the separator headbox (improper design).

R egularly monitor the headbox separator tank level because it tends to vary. Again, this is because of limitations on the design of the separator tank under the higher machine speed conditions that are occurringnow.



B ib liog ra ph y: << Insert references to any material researched or used in this project, delete this page if none. Also, delete it from the table of contents. >>

Journal Reference Format (delete from the final report): Author Last Name, Author First Name. ³Article Title´. Publication Title. Issue: Pages.

Book Reference Format (delete from the final report): Author last name, Author First Name. Book Title. Publisher. Year.

ss4 mwv final report daliaga-jul-11-07

Documents