7 quality maintenance
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currently necessitates ever more frequent changeovers.
To cope with this, production department must review
their quality assurance systems with the aim of
tackling quality through equipment management.
QUALITY MAINTENANCE IN PROCESSINDUSTRIES
!n process industries, the process comes +rst.
Quality is uilt into the product through processes that
provide the conditions needed for transformations suchas reaction, separation, and 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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ow rate, catalyst quantity, and so on/ for the
particular properties, compositions, and volumes of the
raw materials, reagents, and other su stances eing
handled. To achieve this, the equipment units that
make up the plant and their component modules and
parts must e installed and maintained so they functionoptimally 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
product, or downgraded. &ustomer complaints and
dissatisfaction are a perennial pro lem.
Meanwhile, in plants where chemical reactions
take place, poor control of conditions not only a"ects
quality ut is also dangerous. To create safe plants that
produce only awless products, a company must
analy0e processes and equipment rigorously to identify
and maintain conditions that do not lead to defects
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-defect1free conditions/. This is the role of quality
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
Quality maintenance consists of activities that
esta lish equipment conditions that do not produce
quality defects, with a goal of maintaining equipment
in perfect condition to producing perfect products.
Quality defects are prevented y checking and
measuring equipment conditions periodically and
verifying that the measured values
lie within the speci+ed range. Potential quality defectsare predicted y e amining trends in the measured
values, and prevented y taking measures in advance.
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$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
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material, equipment, method, or operating conditions
that must e maintained to produce awless product.
%nce set, these conditions are maintained and
controlled y 5competent operators,6 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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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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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 ;,
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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 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
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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 createsdefect1free 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 A QUALITY
MAINTENANCE PRO'RAM
Causes o( Quality De(ects
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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. Toachieve 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
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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%$onents an" Con"itions,
4igure 21; illustrates the construction of the seal
section of an oil1sealed process1gas compressor. This
compressor was causing a quality defect7 process gas
contaminated y sealant oil. A lock in the pipe
leading to the sealant1oil trap prevented the sealant oil
from draining completely, so it in+ltrated the impeller
side of the seal and contaminated the process gas. !n
this case, the quality component is the trap system.
The condition -that does not cause a quality defect/ isthat it must discharge a speci+c quantity of spent oil.
This can e checked y measuring the amount of
spent oil.
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Ta le 21= shows a control ta le for this quality
component. The asic aim is to investigate the causes
of the pro lem and through improvement ena le the
component to operate normally for long periods. -!n
this case, the pipe was locked y products of a
reaction the process gas and additives in the oil./
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P!ocess Con"ition Cont!ol
!n process industries, quality is governed y
process conditions as well as quality components.
)aicel &hemical !ndustries -%take Plant/ uses an
5MPQ Matri 6 to control process conditions -see
Ta le 21?/. 5Q6 is the quality check item, such as a
sensory check for defect modes such as a normal
odors caused y overheating. 5M6 is the machine or
equipment where the defect mode appear. 5P6 is the
control 5point,6
such as temperature range, through which the quality
condition -a speci+c setting/ can e achieved.
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Quality Maintenance Ste$-by-Ste$
I%$le%entation
4igure 21< is a ow diagram that illustrates the
steps in implementing a quality maintenance program.
Ta le 212 descri es each step in detail.
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QUALITY MAINTENANCE
IMPLEMENTATION. CASE STUDY
This section outlines the steps taken in a quality
maintenance program implemented for the production
of a certain product at Tokuyama (ekisui !ndustriesB
#anyo Plant.C
C A full description of this implementation appears in Dapanese in the proceedings of the
3E>E #ational 'quipment Management (ymposium , edited y the Dapan !nstitute of Plant
Maintenance.
4igure 21= shows the relevant part of the
production process. PF& slurry made y polymeri0ing
vinyl chloride monomer in the previous process entersthe slurry tank shown on the left side of the diagram.
The slurry is dried to form the product, which is then
used as a raw material for plastic moldings.
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Ste$ /. P!e$a!e a QA 0Quality Assu!ance1
Mat!i2 0Table 7-31
Preparing a QA -quality assurance/ matri
involved the following four su steps73. !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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;. $ank the defect modes according to their
seriousness and indicate which ones have caused
pro lems in the past as frequent or occasional. 8henassessing the seriousness of defect modes, e sure to
include a mem er of the quality assurance department
in the discussion.
/.
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Ste$ 4. Analy5e P!o"uction-In$ut Con"itions
0Table 7-61
After preparing the QA matri , analy0e theproduction1input -
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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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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
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impossi le to follow in 2 percent of cases and not
strictly adhered to in < percent. !n the remaining E
#achi14ujikoshi &orp. -ed./. Training for TPM .
Portland, %re.7 Productivity
Press, 3EEG.