7 Quality Maintenance

8/11/2019 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.

7 Quality Maintenance

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