Gettign the Most Out of the Clean Room Design

8/13/2019 Gettign the Most Out of the Clean Room Design

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652 2005 ASHRAE.

ABSTRACT

This paper discusses the design of cleanrooms anddescribes a five-step process that developes the informationneeded to identify, clarify, and prioritize cleanroom require-

ments.

INTRODUCTION

When building a cleanroom facility, special attentionshould be given first to the essential tasks for defining clean-room requirements, specifically determining cleanroom areas,building areas, filtration coverage, airflow quantities, powerconsumption, and budget items.

Think of design activities asproblem solvingand program-ming activities asproblem seeking. Programming develops thebody of information needed to identify, clarify, and prioritize thecleanroom requirements. The key to developing a goodprogramming process is being able to manage tremendous

amounts of data. This can be accomplished by creating a matrixof different types of preliminary information. One excellentapproach is an organized, methodical, five-step process called,

problem seeking.Five quantitative project elements are produced during

the programming process.

1. Process Tool List.This initial information platform drivesutilities, areas, and cleanliness levels.

2. Space List. An analysis of functional areas.

3. Utility Matrix.An analysis of services to each of the processtools for including process cooling, exhausts, pure water,gases, and bulk chemicals.

4. Project Budget. The description of anticipated project-

related costs prior to design.5. Project Schedule. The description of project milestone

dates outlining major activities and approval-submittaltargets.

Tools, people, activities, equipment, storage, and efficien-cies generate the area requirements. The numbers of peoplethat will work in the project require workspace, circulationspace, gowning space, offices or desk space, and parking

space.Perhaps the forgotten type of space in any building is stor-

age space. Particularly in a cleanroom, clean storage isrequired for material, chemicals, equipment, WIP storage, andmaintenance.

Beyond this, the efficient use of space in terms of walls,structure, chases, etc., will greatly affect the total area AND,hence, the total cost, of a cleanroom. Another often over-looked space requirement is additional space for new tools orequipment in the near future, say two to five years.

The process of programming is the management of allpreliminary project data. To make this as easy and as organizedas possible, the five-step process called problem seeking hasproven very successful. In each of the following five steps,

different types of information are developed and analyzed.The order is a natural progression of developing data withouthaving to retrace your steps. Validation of the data is always anintegral part of the process and allows for feedback and eval-uation loops.

THE FIVE-STEP PROCESS

Establish Goals

First, establish the objectives for constructing the clean-room. Clearly delineating the project goals is one of the mostoften neglected contributions upper management can make toa project. Originating from upper management, 10 to 20 well-stated objectives will have an extremely positive effect on the

outcome of your cleanroom project. Goals provide a set ofclear expectations for the project team that parallel thecompany's business plan. The goals should deal with each ofthe four considerations of cleanroom design:

Getting the Most Out of a Cleanroom Design

Thomas E. Hansz, AIA

Thomas E. Hanszis president of Facility Planning and Resources, Inc., Pittsburgh, Pa.

DE-05-9-3

2005, American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Inc. (www.ashrae.org). Reprinted by permission from ASHRAE

Transactions, Volume 111, Part 2. The material may not be copied nor distrib-

uted in either paper or digital form without ASHRAEs permission.


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ASHRAE Transactions: Symposia 653

FunctionAspects of activities, relationships, people,and operations.

FormPhysical considerations of form, space, and sys-tems.

EconomyAspects of construction costs, life-cyclecosts, and energy.

TimeConcerns the project schedule, expansion, andchange.

Analyze Facts

The second step in the programming process requires

establishing a database of cleanroom information. Accurate

staffing projections for cleanroom personnel should be devel-

oped. Information regarding all manufacturing equipment

should be assembled. Utility bills for the preceding 12 months

will be very useful and should be assembled. In short, all the

information that will give the architects and engineers a thor-

ough knowledge of existing conditions should be assembled

now. At the end of this paper is a suggested list of typical infor-mation that should be given to the programming consultants to

initiate gathering of facts.

For processes using hazardous production materials, an

accurate inventory of chemicals will be required to satisfy the

fire code and building code regulations. Another critical area

of analysis, which should be done during the fact-gathering

step, is the building code analysis. Whatever building code is

in force, your cleanroom will be regulated as to how large an

area it can be, how high the roof can be above it, how many exit

doors will be required, and to some extent what the layout will

be to ensure occupant safety in case an emergency should

arise. Cleanrooms using hazardous production materials

(HPMs) will be required to have separate routes for peoplecirculation and for the movement of HPMs. Exit distances

from any point within the cleanroom may be as short as 75 ft.

Walls surrounding the cleanroom will be required to meet

specified fire resistance.

Cleanroom Concepts

Before the start of design, the project team should exam-

ine concepts applicable to work flow, flexibility, utility distri-

bution, and other such issues. The team should address what

types of changes can be anticipated. Will additional equipment

or improving the classification of contamination control be a

real possibility in the future? The predictability of the cleanenvironment should be examined as well. All this should be at

least addressed if not resolved before the design effort gets

underway.

Production or research engineers should determine prod-

uct contamination sensitivity by this time. If not, it needs to be

a first priority, along with establishing a flow chart identifying

cleanroom functions and their required level of control.

Beyond controlling the particulate counts, the production

process may also require specific temperature, humidity, and

pressure levels with fixed limits of variance. How to provide

the level of control is answered during the design phase. Now

is the time to establish the control criteria.

DETERMINE PROCESS REQUIREMENTS

The Relation of Process to Facility

Cleanrooms in themselves are not aesthetic features but

are adjuncts to specialized activities that must be conducted in

clean environments. Cleanroom concepts are therefore depen-

dent upon the level of cleanliness required and upon the type

and scale of the activity. Each successively cleaner environ-

ment requires stricter operating procedures, or protocols, to

maintain that cleanliness level. The strictest protocols may

require clean buffer zones to isolate the cleanest areas from

less clean environments or from office environments. These

Table 1. Potential Cleanroom Issues

Process Facility People

Equipment Organization Safety

Work flow Flexibility Gowning

Material flow Site services Aesthetics

Automation Functional relations Work socialization

Technology Contamination control Productivity

Process utilities Aseptic conditions Communications

ESD Reliability Interaction

EFI/RFI Redundancy Home base

JIT inventories Vibration Orientation

Energy Waste treatment Facility image

Tool installation Storage Security

Figure 1 The five-step process.


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654 ASHRAE Transactions: Symposia

protocols and the nested space configurations have defining

effects on personnel circulation, process flows, material

movement, maintenance activities, new equipment installa-

tion, and old equipment decommissioning.

Materials and equipment must be meticulously wiped

down during their staged entry. Other supplies, which were

produced and packaged in a cleanroom, will be delivered indouble-sealed bag enclosures for protection from the outside

world during shipment and handling. These double-bag enclo-

sures must be wiped and sequentially be removed as they

progress through the staged entry.

Avoiding unnecessary cleanroom traffic, greater quality

control, safety, and lower unit costs for bulk raw materials are

factors that compel facilities to pipe or convey materials to

their cleanroom processes. As usage quantities increase,

frequent handling of chemicals, gases, and process wastes

increase exposure hazards for the workers and contamination

hazards for the cleanroom.

The risks imposed by chemicals and gases vary with

material properties and concentration. The most universallyaccepted procedure for assessing and identifying relative

chemical hazards was developed by the National Fire Protec-

tion Association (NFPA) for safeguarding emergency

response personnel. Published as NFPA Standard 704, this

system of identifying hazards rates each chemical on a scale of

0 to 4 in three hazard categorieshealth, flammability, and

instability. Nearly all chemical containers and tanks are

required to display the NFPA 704 diamond, which identifies

the hazard ratings.

Process Equipment and Process Support Services

A key to developing a meaningful and useful program is

to gather as many facts as possible, especially about the activ-

ities and processes. For example:

What are the processing goals?

What are the hours of operation?

What are the process steps and how does the work flow?

How should work-in-progress be managed?

What are the most critical steps in the process?

What is the philosophy for maintenance and outages?

How should expansion and future changes be accommo-

dated?

THE UTILITY MATRIXFor market-driven products, such as pharmaceuticals and

semiconductors, the clients process assumptions are typically

being refined concurrently with the programming and early

design stages. Frequently complete equipment lists are not

available. In the interim period, data for similar equipment

may be used or assumptions may be made. The important issue

is to develop a comprehensive database to record information

and assumptions and to track the changes as design and

construction proceed. To compound the complexity, major

pieces of equipment frequently have auxiliary or support

equipment. In the concept development phase, optional equip-

ment configurations must be explored for fit, operational func-

tions, and accessibility.

Cleanroom facilities are typically intensive users of

equipment and therefore are large consumers of utilities and

raw materials. Frequently auxiliary or support equipment has

separate utility services. The equipment database should bestructured in a manner that allows utility and raw material

consumption data to be associated with each process tool and

each piece of auxiliary equipment.

This technique has several advantages:

Data may be sorted by equipment to show or to change

basis.

A sort by utility or raw material will give demand at

100% utilization.

As equipment is grouped into areas, a utility sort on the

equipment groupings will indicate use patterns that may

aid distribution decisions.

If process equipment is to be added in phases, the data-base will allow the engineers to study expansion options

for central utility systems.

During the course of the project, as equipment lists are

refined, having a database will allow project managers

to identify scope changes.

Depending on the projects size assembling, these data

can be a huge effort. So, can a project be programmed and

designed without a utility matrix? Perhaps one can, but these

facilities are both complex and expensive. Without sufficient

data, even experienced professionals will have difficulty

guessing and will have no way of knowing whether the esti-

mates are high or low. Too low an estimate will lead to insuf-ficient capacities, and too high an estimate will result in

expensive overbuilding.

There may be as many individual ways to organize the

data as there are people collecting it. Some of the most

successful techniques are:

Supplying special data collection forms for each piece

of equipment to the owners process engineers or equip-

ment users for recording equipment data.

Using the owners anticipated equipment list and exist-

ing engineering database.

Using the owners equipment list and consultants data-

base. Assembling a notebook of data sheets from the owners

equipment operations and maintenance manuals.

Assembling a notebook of vendor-supplied data.

Hard copies are good for record keeping, but when it

comes to sorting, summing, editing, and transferring all or part

of the data, electronic copies have an overwhelming advan-

tage. Some of the methods in the preceding list may involve

handling the data twice, i.e., recording on forms, then entering

into electronic files.


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When collecting data, particularly from vendor sources,

make sure that the data represent actual consumption data and

not the nominal service capacity, which does not represent

utility usage. For example, many vendor data sheets list for the

electrical utility requirements the electrical service, 20 amps at

120 volts, rather than the connected load, which may be only

300 watts or 2.5 amps at 120 volts. Accumulated data errors

such as this could dramatically distort demand requirements to

the entire facility.

Once the utility and raw material data have been

collected, one critical task remains. If one were to sum the

flows or consumption of each utility or raw material, the total

demands would be far greater than those actually experienced.

What is missing is an accounting of

down time for scheduled maintenance and cleaning,

idle time for lags in work-in-progress flow,

wait time for process step sequencing, and

unexpected outages or breakdowns.

This accounting is usually incorporated as an efficiency

factor. Since most manufacturing facilities operate around the

clock, the most common basis for evaluation is 24 hours. If the

mean time between failure (MTBF) is over 1000 hours for

minor incidences, nonproductive time due to breakdowns

would be less than one percent, which is negligible. However,

a piece of equipment may need to be shut down once a shift,

or once a day, for shift change, cleaning, or preventive main-

tenance. If such downtime lasted two hours, available uptime

would be 92%. Equipment waiting cumulatively eight minutes

every hour for lags in work flow would be working 87% of the

available time. If the equipment sequentially processes the

work in four steps and the utility of interest is used in only

three of the four steps, the utility would be consumed only

75% of the equipments operating time. As a result the total

utility consumption by this single tool would be 60% (0.92 *

0.87 * 0.75) of the tabulated peak demand.

Considering group equipment operations, if one of six

tools is not operating in sequence with the others, then the

average utility consumption would be 83% of the single tool

usage. Applying this operational diversity factor to the single

tool consumption as illustrated above, the average utility

consumption would be 50% (0.83 * 0.60) of the published util-

ity consumption data.

Working Through Critical Design Issues

The programming process driven by the cleanroom

consultant has the potential to fully describe the project that

will be built. The readiness of the client to participate in the

process, the depth of preparation of participating client team

members, their willingness or ability to answer the hard ques-

tions, as well as their enthusiasm and time commitment to the

processall will affect the result of the programming phase.

This phase is the first iteration, of several, that will take place

as the project unfolds. Most likely changes will be occurring

through the construction process and even after turnover of the

project as a host of good ideas emerge. These are called

change orders.

The information accumulated during the programming

process will be the foundation upon which the development of

construction documents rests. It is the function of the design

team to sort out and interpret the data as it addresses architec-tural, structural, mechanical, plumbing, and electrical issues.

Architectural Issues

The clean facility is intended to house a process. The

layout of the facility is based on personnel interaction with

material flow and includes raw materials entering the clean-

room, work in progress, and finished products leaving the

cleanroom. Depending on the scope of the project, the design

team may examine raw material receiving, storage, and trans-

port to the clean facility, as well as finished product transport,

storage, and shipping.

Walls/Floor/CeilingAfter the facility layout has been determined, the materi-

als of construction must be specified. Wall options include

stick built using a drywall system on steel studs. This has been

around for years and continues to be quite popular due to its

relatively low cost. A variety of coatings and cladding is avail-

able for the gypsum panels to make them suitable for even the

more stringent cleanrooms. Modular systems permit quick

installation and have a full array of cleanroom-compatible

materials for the most stringent applications. Windows are

generally incorporated into the wall system to permit super-

vision from the outside, as a safety feature, and to support

marketing during the plant tour, which invariably includes apeek into the cleanroom. Windows should be flush to the wall

on the clean side to prevent accumulation of particles. Designs

are available for flush windows on both sides of the wall, a

particularly useful feature for windows between adjacent

clean spaces.

Floors on grade are frequently covered with a high solids

epoxy finish applied to an appropriately prepared concrete

surface. Vinyl tiles and vinyl sheeting, with standard, static

dissipative or conductive characteristics are also used,

depending on the application. Generally in Class 100 and

more stringent cleanrooms, a raised floor is considered.

A raised floor system should be a forged aluminum

construction perforated to permit airflow from the cleanroomto the return plenum space below the floor. A grating type

panel may be used in which case the finish may be anodized

or powder coated. A perforated panel will usually have a stan-

dard, static dissipative or conductive high-pressure laminate

applied to it as a wearing surface.

The most common cleanroom ceilings use an inverted

T support grid made of extruded aluminum. The nominal

2 ft 4 ft system supports filters, blank panels, and lights. In

health science-related facilities, the ceiling may be of mono-

lithic design, employing a water-resistant drywall construc-


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tion and epoxy paint to eliminate as many contamination

collecting seams as possible. Lights are typically fluorescent

fixtures specifically designed for cleanroom application. In

more stringent cleanrooms, the lighting may be integrated into

the grid system to minimize air turbulence within the clean-

room. The blank panels are frequently made of the same mate-

rial as the walls or may be specifically designed with lowshedding characteristics for use in the cleanroom.

Entry/Exit

Getting people and material into and out of the cleanroom

is an important aspect of the facility design. Doors are of a non-

shedding solid, half-glass or full-glass construction. They

typically have sealing on all four edges to minimize loss of

clean air from the facility.

Personnel generally enter through a gowning room,

which acts as an airlock. Airlocks are used between clean and

unrated areas as well as between higher- and lower-rated areas

to maintain pressure differentials of the clean spaces. The

gowning room will be large enough to accommodate all or

most of the workforce using the cleanroom, while airlocks are

commonly only large enough for one or two people to pass

through at a time.

Material may need to be removed from its packaging and

otherwise prepared before entering the cleanroom. A material

airlock will facilitate such handling. Non-clean material-

handling equipment would move the material into the airlock.

Cleanroom personnel would remove the packaging and

prepare the material for entry into the cleanroom. For material

leaving the cleanroom, a similar material airlock can be used.

Depending on the layout of the facility, one material airlock

might serve for entering and leaving material. The use of amaterial airlock and following the protocol associated with its

use can result in a major source of outside contamination being

kept out of the cleanroom.

Structural Issues

There may be significant structural challenges when the

decision is made to retrofit an existing building to house a

cleanroom facility. It is common that the space required for all

the ancillary equipment described above is lacking. It becomes

necessary to think in terms of equipment mezzanines or roof-

mounted equipment. This requires an analysis of the building

to ensure that the structure can be modified to accommodatesuch loads.

It is not uncommon to install equipment, suspended from

the roof structure, above the cleanroom. While some buildings

have a robust overdesign associated with them and can support

additional weight, others are designed to the basic building

code for a specific occupancy and cannot support additional

weight. In such cases, a ground-supported structure must be

imposed on the cleanroom design. In some cases, the walls

then become load bearing. In other designs, support columns

are integrated into the wall system to support the ceiling. In

either case, footings may have to be cut into the existing

concrete floor, adding to schedule and cost impact.

Mechanical Issues

Cleanrooms are a special case of general air-conditioning

design and require that certain practices be followed to ensure

that the operating facility is cleaner and under more stringentcontrol than the typical human comfort conditioned space.

Cleanliness

Selection of cleanliness classification is the domain of the

client and/or process consultant. The cleanliness level should

not be greater than required to meet the objectives of the

project. The concept that if class 10,000 is good, then class

1,000 is better will be very costly in terms of airflow, filtra-

tion, and air-conditioning first cost as well as ongoing operat-

ing cost. Facilities with small specific-class rooms can be less

costly than a large single-class space rated at the most stringent

level.

Airflow

Air change rates into the hundreds of changes per hour

dictate that air-moving equipment, and therefore energy to

move the air, be much higher than the standard air-condition-

ing application. The final selection of air change rate is based

on the best guess by designer and client as to the need for

high or lower airflow. An evaluation of the process and the

potential of the process to generate contaminants within the

cleanroom typically determine this. A contaminating process

will require higher airflow than a more benign process. The

mechanical system designer is challenged to find a place fornumerous large air handlers or fans and devise the routing of

an extensive duct system.

Filtration

Air entering a cleanroom is usually filtered by HEPA

(high-efficiency particulate, air) filters or ULPA (ultra-low

penetration, air) filters. The most widely used HEPA filter has

an efficiency of 99.97% on 0.3-micron particles and is speci-

fied for the pharmaceutical and health-related industries as

well as some mid-class cleanrooms in other industries. The

most common ULPA filter has an efficiency of 99.9995% on

0.12-micron particles and finds wide use in sophisticatedmicroelectronics facilities of class 10 and class 1. While some

less stringent applications allow filters to be installed in air

handlers or ductwork remote from the cleanroom, the most

common site for the filters is in the ceiling of the cleanroom

housed in a framework compatible with the ceiling system.

Air Pattern

It is not enough to introduce clean air into the cleanroom.

The air should be introduced in a manner that captures and

removes from the cleanroom particles that are considered


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contaminants to the process. The most efficient scheme has

100% of the ceiling covered with filters. Note that even when

an inverted T grid ceiling has all 100% filter coverage, only

about 85% of the ceiling has air flowing through filter media

due to the width of the grid and filter frames. The air moves

straight down through a perforated raised floor. This is called

unidirectional airflow and permits particles generated within

the cleanroom to be captured by the airflow streamlines and

removed from the room without impinging on a critical

surface within the room. Many class 100 and most, if not all,

class 10 and class 1 cleanrooms are designed in this way.

Temperature

The temperature to be maintained in the cleanroom is

driven by either comfort or process need. Comfort can gener-

ally be met by maintaining a temperature of 722F in clean-

rooms where lab coats or smocks are worn. In the more

stringent cleanrooms, where full bunny suits are worn, a

temperature specification as low as 662F would be appro-

priate.Care should be taken when specifying temperature values

and tolerances as a result of a perceived need by the process.

High or low temperature values can be costly to maintain.

Even more costly can be the need to hold a tight tolerance

when not really needed. A 1F tolerance is more costly than

a 2F tolerance. A F tolerance is more costly yet. This

becomes even more evident if the need is to maintain a tight

tolerance throughout the entire cleanroom, 24 hours per day,

year-round, with widely fluctuating outside air conditions and

process equipment heat generation. High first cost, high oper-

ating cost, and many out of spec periods can result.

Probably the most common approach to maintaining

temperature in larger cleanroom installations is by using

chilled water for cooling and hot water for heating. In smaller

cleanrooms direct expansion cooling and electric heat are

used. A characteristic of cleanroom design that separates it

from standard construction is the fact that practically all clean-

rooms require cooling year-round. This is due to the high inter-

nal heat gain created by moving large amounts of air coupled

with the heat generated by process equipment in operation. An

additional factor is the generally high rate of exhausts, and,

therefore, need for conditioned makeup air, present in many

cleanroom facilities. The cooling system should be designed

to operate round the clock 365 days a year.

Humidity

Many of the remarks relative to temperature control apply

to humidity control as well. The selected value and tolerance

should be realistic to the application. Comfort can be realized

over a range of 30% to 65% RH if the temperature is held at

a comfortable level. The only reason for a tighter tolerance is

if the process requires it. Humidity control is costly. In dry

areas, humidification drives the cost. In wet areas, dehumidi-

fication is the driver. In most areas both humidification and

dehumidification equipment must be incorporated into the

mechanical system if a tolerance such as 5%RH is required.

If a tolerance of 2%RH is required, particular care must be

taken with the controls as well as the means of adding and

removing moisture from the air.

Pressurization

Controlling pressure differential between clean andunrated spaces is one of the characteristics of cleanrooms.

Typically, the pressure of the most stringent space is the high-

est. It is maintained at a pressure of .02 inches of water column

(in.w.c.) above an adjacent less stringent clean space or .05

in.w.c. above an adjacent unrated space. Higher differentials

will work as well; however, if it gets too high, noise problems

develop and there can be difficulty in opening doors or keeping

doors closed. It also contributes to higher operating cost.

Where containment is required, and the pressure in a

cleanroom must be lower than an adjacent space, care must be

taken to ensure the space is tight and contaminants do not enter

the space. A room within a room approach may be appro-

priate. A single pass configuration may also be used. Suchrooms should be as small as possible and still support the

process.

Exhaust and Makeup Air

In order to maintain positive pressurization, the amount of

air introduced into the cleanroom must exceed the amount

leaving. The amount leaving is typically equal to exfiltration,

that is, leakage through doors, and other cracks due to the posi-

tive pressure plus the amount leaving by design through vari-

ous process exhaust systems. It is important, therefore, to

identify all process equipment along with exhaust values asso-

ciated with it before designing the cleanroom mechanical

system. Generally, a value of 2 air changes per hour for exfil-

tration when added to the total exhaust will allow the designer

to proceed with the design of the makeup air system.

Acoustics and Cleanroom Sound

This is a topic that tends to generate excitement during the

design phase but that disappears as a significant concern once

the cleanroom is in operation. The high volume of air move-

ment, coupled with the hard reflective nonshedding surfaces

that are characteristic of cleanrooms, brings with it sound

levels that are typically unacceptable in commercial work.

Designers unfamiliar with cleanrooms tend to specify sound

levels on the order of NC50 to NC55. These are very difficult,and costly to achieve, if they are in fact achievable. A more

realistic specification of NC60 to NC 65 can be achieved by

mechanical designers familiar with cleanroom applications at

a reasonable cost and is well within the OSHA-specified levels

for comfort in the workplace.

Plumbing Issues

In this tutorial,plumbingis the heading under which all

piping activity is gathered. Actual installation in the field may

be accomplished by a variety of subcontractors depending on


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their skills and practice common in the project locale. A single

designer or a number of specialty designers, depending on

how the engineering office is organized and the complexity of

the project, may address design issues.

HVAC Piping

HVAC-related piping for chilled water, hot water, steam,or potable (city) water has to be installed between the source

and air handlers, makeup air units, and humidifiers. Drain

lines for the equipment must also be installed. Generally, this

piping work is done early in the cleanroom construction

process before a cleanroom protocol has been put into effect.

Frequently there is a requirement for the lines to be oversized

to accommodate future expansion of the facility. Additional

shutoff valves may be installed to facilitate installation of

additional equipment at a future date. Where possible it is

advisable to avoid running water or other liquid lines over the

cleanroom to prevent damage to process equipment in the

event of a leak.

Process Piping

Process piping is designed to carry process-cooling water,

deionized water, hazardous gases, bulk gases, and specialty

chemicals as well as specialty drain systems. Materials of

construction include PVC, PVDF stainless steel, and copper,

typically provided highly cleaned and protected from contam-

ination and installed in accordance with strict guidelines. The

issues surrounding process piping is that the piping preserves

the high degree of cleanliness and delivers the fluids to the

point of use in a safe manner. Bulk gas facilities are laid out to

minimize piping runs and to facilitate bulk delivery by suppli-

ers on a regular basis. DI water systems must be designed with

sufficient water velocity to prevent buildup of organic contam-

inants and be smooth with no interior edges for contaminants

to accumulate. Piping conveying hazardous chemicals is

commonly double contained and provided with extensive leak

detection systems. The process piping requirements are suffi-

ciently complex as to require firms specializing in the design

and installation of such systems to be employed.

Fire Protection

Sprinkler systems and fire protection are also a specialty

unto themselves. The cleanroom sprinkler system may be as

simple as extending drops down from an existing piping

system to the cleanroom ceiling. It may be significantly more

complex depending on the flammable agents being usedwithin the facility. The presence of expensive process equip-

ment in the clean space usually suggests that sprinkler systems

above the ceiling be dry until needed. The airflow patterns

within the cleanroom makes standard means of sensing a fire

less effective. Careful development of the system, in conjunc-

tion with the fire marshal and insurance company representa-

tives, is recommended.

Electrical and Energy Issues

The electrical designer is responsible for meeting the

high-energy needs of the clean facility. In addition to standard

lighting and convenience outlets, the electrical design must

include power for the extensive air-handling and cooling/heat-

ing equipment as well as process equipment. There is a

requirement for specific UV light filtration in certain micro-

electronic processes. Outlets for process equipment must be

selected based on the specific power needs of the equipment.

Where hard wiring is required, termination means must be

identified. In most cases, process equipment will be installed

over a period of time so provision for future connections

should be addressed.

In most cases, the cleanroom is the critical part of a manu-

facturing operation. Downtime is measured in hundreds of

thousands if not millions of dollars per hour. One challenge to

be faced by the electrical designer is to minimize the likeli-

hood of such downtime. This can be done by providing redun-

dant power circuitry to the facility from the power company.

As a standby, an emergency generator with quick-acting

changeover control mechanism is part of the electrical design

scheme. Since it is not practical to provide emergency power

to the entire facility, the electrical designer must identify thoseloads that are safety-related and are key to safe shutdown of

key process equipment. The emergency circuitry can then be

designed to overlay the standard circuits within the facility.

Redundancy can also extend to specific process and

process support equipment. Here again the electrical designer

must identify equipment that will be provided with a backup.

Dual chilled water pumps, dual exhaust fan motors, backup DI

water system pumps, and hazardous waste lift station pumps

are examples of a requirement for a rapid changeover control

scheme in the event of primary motor failure.

Lighting

Much fine work is done in cleanrooms and there is a

tendency to specify high lighting levels, i.e., 100 ft-candles

(1000 lux) with resulting high-energy input and high contri-

bution to cooling load as result. Use of task lighting for fine

work and a general specification of 70-80 ft-candles lowers the

cooling load and reduces cost by reducing the number of light-

ing fixtures. An added benefit for more stringent cleanrooms

is that the systems employing integral lighting into the ceiling

grid can be used as they can more easily provide this lower

level of light.

RENOVATION CONSTRAINTS

Retrofitting an existing operational cleanroom carries an

uncommon set of issues and concerns. Addressing these issues

in advance of construction will ensure a successful retrofit

project while maintaining targeted production and existing

yield levels. It is unrealistic to expect to maintain optimum

production levels during retrofit; however, proper planning

and sequencing of work will ensure a minimum of unexpected

events that affect budget, time, and facility operation. Cost

versus benefit analysis must be evaluated for each sequential

step of work to evaluate its practicality. Budget and schedule

success cannot merely be evaluated by the lowest cost basis or


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shortest construction duration but more by the optimum

compromise of schedule, cost, and lost production time and

yield. Careful up-front planning and scheduling must be fore-

most in thought and mindset.

Specific Concerns

Demolition and disposal of hazardous materials oftenmay be of concern in older facilities. Materials such as asbes-

tos and items contaminated by process chemicals require

disposal in compliance with local regulations.

Maintenance of fire exit conditions and sprinkler systems

during renovation often requires re-routing of piping systems,

temporary disablement of sprinkler zones, and temporary

egress corridors. In these areas of concern, local codes and

code officials should be consulted in the planning stages to

understand what work can be accomplished during normal

work hours, what must be accomplished during off hours, and

what must be accomplished during shutdown periods. Both

EHS and insurance requirements tend to dictate the extent ofthese temporary measures.

Material, equipment, and worker access must be

addressed in planning to ensure production workers can access

operational areas in a timely fashion and construction workers

are not burdened with time-consuming access criteria to

construction sites. Temporary access corridors and gown

rooms often save significant time entering and exiting clean

space for production workers. Separate construction entrances

may seem to be a luxury during planning but often pay for

themselves in work production in just a short period of time.

Lay down and storage space for materials and compo-

nents must be integral to renovation plan and schedule. Properprovisions for material handling will significantly cut labor

cost and the potential for contamination generation. Constant

movement and shifting of materials puts them at risk to

damage and ultimately can compromise a projects comple-

tion. Careful planning and construction management allows

for just-in-time deliveries and ease of staging of materials for

installation, requiring the minimum amount of staging area

and maximum amount of flexibility.

We cannot ignore cost when evaluating the upgrade of a

facility, nor do we suggest it should be last on your list of

concerns. Simply, this issue becomes the most complicated to

evaluate. In the process of facility renovation, while maintain-

ing operation, cost is not necessarily equal to price, as we

previously addressed when discussing the issue of production

window of opportunity. Actual cost must include price of the

work along with lost production, potential for lost yield, and

inconvenience. In reality, often actual cost cannot fully be

detailed until well after the project is complete.

The only true preventive steps you can take are to care-

fully select your contractor and base your decision not only on

their price but also on their experience, reputation, proposed

schedule, and operational plan to complete the work.

Implementing the Renovation Plan

The first step requires that we survey the existing facility

to determine how closely documented plans reflect actual

existing conditions. Identifying the level by which we can rely

on the facility plans will significantly affect the aggressiveness

of the schedule, material stock requirements, and man loading.

At the same time we are surveying the existing conditions,

we must survey acceptable components within the market-

place to match existing facility conditions where required and

understand their availability to meet schedule and perfor-

mance requirements. Material selection may depend more on

its availability to meet the required schedule than anything

else. We must set performance criteria and prioritize price,

product, and delivery issues.

A detailed sequence of work to be performed now must be

documented and incorporated into a preliminary schedule.

The preliminary schedule must then be compared with the

production requirements of the facility and other potential

events that would require schedule flexibility. In areas ofschedule conflict, the team must determine priorities and

adapt requirements appropriately. This part of the work is the

most critical to overall project success. Consideration has to be

given to squeezing or expanding construction task durations to

match schedules and maintain a cooperative interface. Overall

project duration must be measured considering holiday sched-

ules, manpower availability, man loading within a confined

workspace, and, most importantly, continued operation of the

facility.

A potential significant cost issue, which depends greatly

on our schedule flexibility and confidence in the documenta-

tion of the existing conditions, is excess material stock. What

and how much excess stock material we require must beweighed with potential for restocking, the associated charges

and the critical nature of certain sequences along with lead

time availability of potential shortfall products. Local sourc-

ing of as many materials as possible must be achieved to prop-

erly plan for possible contingencies.

Construction area separation must be maintained at all

times. Consideration should be given above the ceiling, in duct

systems, plenums, return walls, conduit, and below the floor to

ensure contamination spread from demolition is both minimal

and contained.

The window of down time for work has now opened.

Removal or protection of existing equipment and curtainingoff of the actual construction area can now be achieved. This

action must be performed with painstaking detail to eliminate

potential for compromise of the existing operational facility

and delays in restarting production or yield percentage in the

renovated area. Whenever and wherever possible, equipment

should be removed or isolated from the construction area.

Demolition should occur in accordance with a sequential

plan with materials removed from the controlled area and

properly disposed of. A slow deliberate process should be

utilized to minimize contamination generation; hazardous


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materials should be identified in advance and removed accord-

ing to regulations.

Contamination-generating materials should be properly

bagged upon removal and immediately removed from the crit-

ical environment. A staging area for outgoing and incoming

materials should be established. Personnel should be badged

and identified as critical environment workers and noncriticalenvironment workers. The established acceptable protocol

should be identified and maintained at all times.

Products identified as salvageable and slated for re-instal-

lation or re-use should be identified immediately upon

removal to the staging area and be cleaned and wrapped for

storage. When re-installing they should be unwrapped and

cleaned with the accordance of the incoming material proto-

col.

With demolition complete, re-installation of the salvaged

materials and new material installation can now begin. All

materials should be treated as new and follow the incoming

material protocol. Construction should occur under a build

clean protocol that is equal to or exceeds that of the operatingfacility. Final (super) clean should occur prior to removal of

temporary construction barriers. Equipment should then be

moved in through the staging area under the incoming material

protocol and set in place under operating protocol conditions.

PRINCIPLES FOR CONTROLLING COSTS

Design to the appropriate level of contamination control

required.

Design for changing conditions.

Design utilities to be easily connected and disconnected.

Design utilities to flow at adequate rates, constant pres-

sure, and typical levels of purity.

Place much of the process equipment outside of the

clean environment.

Control entry and egress of people, material, and equip-

ment.

Provide for ease of maintenance, access, and periodic

inspections.

Manage each of the disciplines to the approved project

budget throughout the design and the constructionphases.


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Documents

Gettign the Most Out of the Clean Room Design