7 Quality Maintenance

7 Quality Maintenance

As equipment takes over the work of production, quality depends increasingly on the condition of the equipment. Quality maintenance evolved as a major TPM TPM acti activi vity ty in cert certai ain n far faric icat atio ion n and and ass asseml emly y industries that are ecoming increasingly automated. !n environments where human intervention is decreasing, the goal of quality maintenance is to maintain and constantly improve quality through e"ective equipment maintenance. !n proc proces esss indu indust stri ries es,, qual qualit ity y has has alwa always ys een een uilt into the product through the process. The pace of new new prod product uct devel develop opmen ment, t, howev however er,, is accele accelera rati ting, ng, and the greater diversity of raw materials and products

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance currently necessitates ever more frequent changeovers. To cope with this, production department must review their quality assuran rance systems with the aim of tackling quality through equipment management.

QUALITY

MAINTENANCE

IN

PROCESS

INDUSTRIES !n proc proces esss indu indust stri ries es,, the the proc proces esss come comess +rst +rst.. Quality is uilt into the product through processes that provide the conditions needed for transformations such as reaction, separation, separation, and puri+cation puri+cation of materials as they ecome product. 'quipment complees known as process plants implement such processes.

To produce perfect products, it is necessary to set appropriate process conditions -temperature, pressure,

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance ow rate, catalyst quantity, and so on/ for the particular properties, compositions, and volumes of the raw raw mater materia ials ls,, reagen reagents ts,, and and othe otherr sus susta tanc nces es ein eing g hand handle led. d. To achi achiev evee this this,, the the equi equipm pmen entt unit unitss that that make up the plant and their component modules and parts must e installed and maintained so they function optimally creates no quality defects. Process industries always aim for this, ut the results often leave much to e desired. Quality defect losses and reprocessing losses -two of the eight major plant losses/ still occur and sustandard product often has to e recycled, salvaged y miing it with good prod produc uct, t, or down downgr grad aded ed.. &u &ust stom omer er comp compla lain ints ts and and dissatisfaction are a perennial prolem. Mean Meanwh whil ile, e, in plan plants ts where where chemi chemica call reac reacti tion onss take place, poor control of conditions not only a"ects quality ut is also dangerous. To create safe plants that prod produ uce only only awl awles esss prod produc uctts, a com company pany must ust analy0e processes and equipment rigorously to identify and maintain conditions that do not lead to defects

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance -defe -defect ct1fr 1free ee cond condit itio ions ns/. /. This This is the the role role of qual qualit ity y maintenance. A quality defect is a property that falls outside the speci+ed range. Tale 213 lists some of the ways in which quality defects appear in process industries.

QUALITY MAINTENANCE IN TPM Qual Qualit ity y maint mainten enan ance ce cons consis ists ts of activ activit ities ies that that esta estal lis ish h equi equipm pmen entt cond condit itio ions ns that that do not not prod produc ucee quality defects, with a goal of maintaining equipment in perfec perfectt cond condit itio ion n to prod produci ucing ng perfe perfect ct prod product ucts. s. Quality

defects

meas measur urin ing g

are

equi equipm pmen entt

prevented cond condiition tionss

y

checking

an d

peri period odiicall cally y

and and

verifying that the measured values lie within the speci+ed range. Potential quality defects are are predi predict cted ed y eam eamin inin ing g trend trendss in the the meas measur ured ed values, and prevented y taking measures in advance.

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance $ather than controlling results y inspecting product and acting against defect that have already occurred, quality maintenance in TPM aims to prevent quality defects from occurring altogether. This is accomplished y identifying checkpoints for process and equipment conditions that e"ect quality, measuring these periodically, and taking appropriate action -4igure 213/

The approach illustrated in 4igure 213 focuses on the

four production inputs -equipment,

materials,

people, and methods/ as sources of quality defects. 5'stalishing conditions6 means setting the range of -5-

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance material, equipment, method, or operating conditions that must e maintained to produce awless product. %nce

set,

controlled

these y

conditions

5competent

are

maintained

operators,6

and

etensively

trained in production technology as part of autonomous maintenance activities -see right side of the +gure/. (etting

and

controlling

conditions

in

this

way

eliminates process defects.

PRECONDITIONS

FOR

SUCCESSFUL

QUALITY MAINTENANCE A quality maintenance program uilds upon gains achieved through fundamental TPM activities such as autonomous

maintenance,

focused

improvement,

planned maintenance, and operation and maintenance

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance skill training. There are several preconditions for a successful quality

maintenance

program, however7

aolish accelerated deterioration, eliminate process prolems, and develop competent operators.

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance

Abolis Accele!ate" Dete!io!ation 8hen

equipment

is

suject

to

accelerated

deterioration, its modules and components have a short life

span.

The

equipment

is

unstale

and

fails

unepectedly. Progress toward 0ero quality defects is painfully slow when equipment is continually reaking down.

9efore

quality

maintenance

can

work,

accelerated deterioration must

e

aolished

and

unepected

failures

minimi0ed

through the activities in TPM implementation (tep 2 : focused improvement, autonomous maintenance, planned maintenance, and operation and maintenance skills training. -(ee &hapters ;, <, and =./

'liminate Process Prolems

Process industries are plagued y process failures such as locks, leaks, spills, composition changes, and -8-

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance other enemies of stale operation. 9locks, leaks, and stoppages are the ane of any process plant. !f any of these occur frequently, eliminate them through focused improvements

or

operator1initiated

autonomous

maintenance improvements. %nly then can quality maintenance e e"ective.

De#elo$ Co%$etent O$e!ato!s )eveloping

process1competent

and

equipment1

competent operators has already een discussed at length in &hapter <, and &hapter > gives further details. %perators must e trained to promptly spot and correct any defect1presaging anormalities in the causal system.

!n TPM activities, great importance is attached to the 5three actualities6 : actual location, actual oject, and actual phenomenon. This is ecause quality -9-

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance defects arise at speci+c locations where the process is taking place, and the actual ojects -defective product of part of equipment/ and phenomena : details of how the prolem manifested 1 provide the est clues for locating their sources. As we saw in &hapter ?, the ideal system creates defect1free plants at the product and equipment design stages. 9efore tackling quality maintenance.

@arify

its relationship with the seven other main TPM activities, including the early management of new products and equipment -see 4igure 21/

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&ASIC

ELEMENTS

OF

MAINTENANCE PRO'RAM Causes o( Quality De(ects

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A

QUALITY

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance The +rst step in practicing quality maintenance is to clarify relationships etween the productBs quality characteristics and the four production inputs shown in 4igure 213. Quality defects emanate from at least four sources7 equipment, materials, people, and methods. (ome companies add a +fth input : measurement of quality characteristics. -(ee Tale 21/

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Relationsi$ bet)een E*ui$%ent an" Quality !n process industries, product is produced y a comination of equipment units. 'ach unit consists of modules, which in turn are made up of components. *nits, modules, and components govern di"erent types of quality. !t is essential to clarity the relationship among them -Tale 21;/.

E*ui$%ent Cont!ol Con"itions The net step in maintaining quality is to estalish

the

equipmentBs

control

conditions.

To

achieve this, analy0e the causes of past quality prolems using why1why analysis and P1M analysis. 'quipment components that that a"ect a productBs quality characteristics are called 5quality components.6 Prevent defects from occurring - 13 -

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance y maintaining such components in their speci+ed condition. This is the asis of quality maintenance. Tale 21< shows the format of a quality maintenance checksheet.

+at A!e Quality Co%$onents an" Con"itions, 4igure 21; illustrates the construction of the seal section of an oil1sealed process1gas compressor. This compressor was causing a quality defect7 process gas contaminated y sealant oil. A lock in the pipe leading to the sealant1oil trap prevented the sealant oil from draining completely, so it in+ltrated the impeller side of the seal and contaminated the process gas. !n this case, the quality component is the trap system. The condition -that does not cause a quality defect/ is that it must discharge a speci+c quantity of spent oil. This can e checked y measuring the amount of spent oil.

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Tale 21= shows a control tale for this quality component. The asic aim is to investigate the causes of the prolem and through improvement enale the component to operate normally for long periods. -!n this case, the pipe was locked y products of a reaction the process gas and additives in the oil./

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P!ocess Con"ition Cont!ol !n process industries, quality is governed y process conditions as well as quality components. )aicel &hemical !ndustries -%take Plant/ uses an 5MPQ Matri6 to control process conditions -see Tale 21?/. 5Q6 is the quality check item, such as a

sensory check for defect modes such as anormal odors caused y overheating. 5M6 is the machine or equipment where the defect mode appear. 5P6 is the control 5point,6 such as temperature range, through which the quality condition -a speci+c setting/ can e achieved.

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Quality

Maintenance

Ste$-by-Ste$

I%$le%entation 4igure 21< is a ow diagram that illustrates the steps in implementing a quality maintenance program. Tale 212 descries each step in detail.

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QUALITY

MAINTENANCE

IMPLEMENTATION. CASE STUDY This section outlines the steps taken in a quality maintenance program implemented for the production of a certain product at Tokuyama (ekisui !ndustriesB #anyo Plant.C C A full description of this implementation appears in Dapanese in the proceedings of the 3E>E #ational 'quipment Management (ymposium , edited y the Dapan !nstitute of Plant Maintenance.

4igure 21= shows the relevant part of the production process. PF& slurry made y polymeri0ing vinyl chloride monomer in the previous process enters the slurry tank shown on the left side of the diagram. The slurry is dried to form the product, which is then used as a raw material for plastic moldings.

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Ste$ /. P!e$a!e a QA 0Quality Assu!ance1 Mat!i2 0Table 7-31 Preparing a QA -quality assurance/ involved the following four susteps7 3.

matri

!nvestigate the types of defect occurring in

each process. . &lassify the productBs quality characteristics precisely and identify the all defect modes related each characteristic.

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;.

$ank the defect modes according to their

seriousness and indicate which ones have caused prolems in the past as frequent or occasional. 8hen assessing the seriousness of defect modes, e sure to include a memer of the quality assurance department in the discussion. <.

)ivide the process into the smallest possile

units -suprocesses/ and indicate the relationships etween these and the defect modes. -(ee Tale 21>/.

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Ste$ 4.

Analy5e P!o"uction-In$ut Con"itions

0Table 7-61 After preparing the QA matri, analy0e the production1input -
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4or each defect mode in each suprocess, identify all the conditions for equipment, materials, people, and methods which when estalished do not give rise to defects. 9e sure to check conditions on the spot, not from ehind a desk. #et, determine whether standards for these quality conditions eist and whether people follow them. Again, e sure to investigate the level of

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance standardi0ation

and

adherence

through

on1the1spot

oservation. Fin"ins .!n this case, investigation revealed that

standards were unclear, and that each operator ran the process

di"erently.

%nly

<=

percent

of

the

suprocesses in the drying process were performed in accordance with standards. The standards were

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impossile to follow in 2 percent of cases and not strictly adhered to in < percent. !n the remaining < percent, standards were needed ut had not een set.

Ste$ 8. P!e$a!e a P!oble% Ca!t 0Table 7-/91 Prepare a prolem chart y listing any irregularity uncovered in the process y prolem type. #ote how - 26 -

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance it is investigated

and the

results and

use

this

information as a asis for proposing countermeasures. -(ee Tale 213G./ Also consider any suprocesses which the production1input conditions analysis revealed not properly standardi0ed -marked with an △,X,or⊕on Tale 21E/ investigate the prolems

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noted and propose countermeasures. As far as possile, epress the results quantitatively. 4or simple prolems, decide what action to take, assign responsiility, and act immediately. 4or more diHcult prolems, clearly record the investigation methods

and

results,

ut

donBt

jump

to

hasty

conclusions aout solutions. 4or these prolems, use 4M'A analysis to rank defect modes in terms of the seriousness of their e"ects and prioriti0e the prolems for action. Then take time to develop appropriate countermeasures through P1M analysis. Fin"ins . Through this process, teams pinpointed

prolems

in

each

suprocess

and

identi+ed

the

unful+lled production1input conditions for each defect mode. Quantifying

the prolem investigation results

made it possile to decide whether each prolem could e immediately tackled or not and helped focus the improvement countermeasures.

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Ste$

:

.

E#aluate

Se!iousness

;

Pe!(o!%

FMEA 0/1 0Table 7-//1 'amine the prolems on the prolem chart and rank them in terms of their e"ects on the defect modes. Then, prioriti0e the prolems y scoring their frequency of occurrence, e"ect, and diHculty of detection. )etermine the assessment criteria in advance. Multiply the scores for each prolem together and use the results to prioriti0e the improvement e"ort. -(ee Tale 2133/

Ste$

<.

Use

P-M

Analysis

to

De#ise

I%$!o#e%ent Measu!es 4or more challenging prolems, use P1M analysis to

clarify

the

oserved

phenomena

and

develop

improvement proposals. !n applying P1M analysis, carefully

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- 31 -


- 32 -


analy0e and understand the phenomena in terms of physical principles and steer the improvement plan in the

right

direction

y

checking

analy0ing

and

measuring. •

9egin y stratifying phenomena in terms of their type and mode of occurrence. Analy0e them physically, and identify the conditions that produce them.

•

9e sure to uncover and consider all the necessary conditions in producing a given prolem. !f improvement teams overlook vital conditions at this step, they may fail to eliminate defects, even after con+rming and eliminating numerous causes.

•

Iist all the condition that tend to produce the phenomenon, regardless of their magnitude.

!n this case, P1M analysis helped the team to formulate an improvement plan for preventing the generation of foreign matter y the feed pump gland

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance -Tale 213/. Tales 213 and 213; and 213; show the results of the P1M analysis in this case.

Fin"ins . Analysis of the causes of the prolem

for all the production input conditions revealed that condition of the +ltered water -48/ supplied to the feed pump gland was very important. (upplying the +ltered water to other processes and equipment y the same pump, however, caused its pressure to vary greatly, which resulted in insuHcient cooling and the risk of ack ow. This suggested the need for a feed pump that was not a"ected y uctuations in water pressure -4igure 21?/.

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Ste$

=.

Assess

I%$act

o(

P!o$ose"

Counte!%easu!es FMEA041 0Table 7-/:1 *se

4M'A

again

to

assess

the

e"ects

of

implementing the improvement proposals ased on the

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance P1M analysis and other investigation results -(ee Tale 213<./

Ste$ 7. I%$le%ent I%$!o#e%ents !n this case, a second 4M'A on the improvement proposals ased on the P1M analysis and investigation results showed that the est plan was to replace the feed1pump gland with a self1ushing mechanical seal. -(ee 4igure 21?./ 9ene+ts of the new seal included7 •

The new seal is self1ushing, so there is no need to supply during the operation.

•

The seal is not a"ected y water use in other processes.

•

%perators need to check water pressure only at startup and shutdown.

•

#o foreign matter is produced.

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance •

The seal does not leak, so the surroundings stay clean.

The team improved the equipment as descried aove. -(ee 4igure 21?./ They followed the same procedure of irregularities they could not de+nitely link to production1input conditions, and classi+ed improvements as either equipment improvements or materials and methods improvements.

Ste$ 3. Re#ie) P!o"uction-In$ut Con"itions 0Table 7-/<1 $eview

and

update

the

Production1!nput

&onditions Analysis Tale -Tale 21E/ to determine whether the production1input conditions are appropriate and correct, whether any de+ciencies remain in the standards, and whether conditions are eing satis+ed. !n this case, solving the easy prolems identi+ed on the Prolem &hart -Tale 213G/ and implementing the

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance equipment improvements indicated, satis+ed all the production1input conditions. -(ee Tale 213=./

Ste$ 6. Consoli"ate an" Con>!% Cec?$oints *se result of step > to consolidate and estalish checkpoints for production1input conditions. )raw up a quality check matri, standardi0e quality, @ple, and checking procedures, and ensure that standards can e followed aout diHculty. -(ee Tale 213?./

Ste$ /9. P!e$a!e a Quality Co%$onent Table 0Table 7-/71 To estalish visual control and ensure that checks are carried out, quantify destitute characteristics using the quality check matri, developed in (tep E and prepare a quality component tale to set practical standards -Tale 2132/.

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Quality

co%$onents .

)etermine

which

components a"ect quality and @. Them down for special treatment as quality components. Quality co%$onent table . To ensure that quality

components receive pri@. 4or maintenance, prepare a

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance quality

component

tale

and

develop

practical

standards.

Case Stu"y Results The

action

that

eliminates

quality

defects

originating in the drying : process feed pump has een descried. Teams used a similar procedure to develop countermeasures against contamination from other sources in this process. 4igure 212 shows the resulting defect rate decrease. !n this instance, defect losses and inspection hours dropped to 3J3G and 3J= of their original values.

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+@O

IS

RESPONSI&LE

FOR

QUALITY

MAINTENANCE, The

quality

control

department

responsile

for

promoting

quality

throughout

your

company

or

must

e

maintenance

plant.

Quality

maintenance projects vary consideraly in diHculty, however. Projects spanning a wide range of processes or requiring advanced technology should e tackled y

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance project teams headed y section managers. 'asier projects can e addressed y small groups in the workplace. After teams estalish the conditions for 0ero defects, operators should maintain and control most of these conditions as part of autonomous maintenance.

More

attacked

project

y

diHcult teams

prolems from

the

should

e

production

department with participation from department such as product design, production engineering, equipment engineering, maintenance, and quality assurance.

- 45 -


&UILDIN' IN QUALITY T@ROU'@ EARLY MANA'EMENT 8hen uilding a production plant, initial planning to set fundamental design conditions precedes asic equipment design. 8hen reviewing the initial @, +rst evaluate the process to highlight anything that is unclear, undecided, are causing concern. To uild quality in through the process and the equipment,

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TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance review quality at the same time. The di"erent groups responsile for production, maintenance, and design must conduct a thorough preliminary investigation and agree clearly on what is required. 4igure 21> is an eample

of

a

ow

diagram

for

conduction

a

preliminary assessment at the asic equipment design stage in manufacturing a certain product.

P!eli%ina!y In#estiation Ite%s •

&larify the targets that the equipment must achieve.

•

&larify the process sequence and interfaces etween processes

•

&larify the relationship etween each process and product quality.

•

)etect all possile cases of defects in each process. - 47 -

TPM !# P$%&'(( !#)*(T$!'( Quality Maintenance •

4or

defect

causes

that

quality

simulation

detects, clarify the equipment conditions in each process that will not cause defects. •

Iist all points still unclear after production1 input analysis, and all other points that require checking. )ecide who will e responsile for solving these prolems, when they must solve them, and how they should solve them.

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7 Quality Maintenance

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