Engineering Design for Process Safety

8/11/2019 Engineering Design for Process Safety

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20 PROFESSIONAL SAFETY AMERICAN SOCIETY OF SAFETY ENGINEERS

DESIGN SAFETY

DESIGN

CONSIDERATIONS

DESIGN

CONSIDERATIONSts Monday morning. Youre sitting in your office drinking a cup of coffee. Its quietand peaceful. The company president strolls in and you exchange stories about theweekends activities. Nonchalantly, he asks, Based on what you know, what would

you do if you had the opportunity to design a brand new facility? You pause,knowing there isnt an infinite supply of money, and ask, Whats my budget?Enough to do the really important things, he responds.

The opportunity to innovatively design-in an inherently safe workplace and design-outhazards doesnt come along every day. Its a process that requires much research and fore-thought. Before embarking on such an effort, the design team must determine the level ofacceptable risk; identify the budget available so that funds will be spent wisely; identifyapplicable standards; research historical data from management of change (MOC) proce-dures, process hazard analyses (PHAs) and pre-startup safety reviews (PSSRs) to identifyitems that can be designed out; and review incident/accident investigation reports that have

identified root causes and outlined engineering changes implemented to prevent recurrence.

II

By MARK D. HANSEN

Engineering Design for Safety:

PETROCHEMICAL

PROCESS PLANT


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JANUARY 2000 21

SETTING THE STAGE

One of the most important steps in thisprocess is to determine the level ofacceptable risk. Risks can be evaluatedqualitatively and/or quantitatively.

Qualitative risk analysis is the mostwidely used method. The risk matrix is acommon approach (Figure 1). Althoughbased on intuitive reasoning and theengineers experience, this technique canhelp determine the relative risk of eachincident scenario and identify risk-reduc-tion methods. The objective is to deter-mine how the severity and/or frequencyof identified hazards can be mitigated.For example, installing water spray sys-tems, reducing hazardous material in-ventory or improving flare system designcan help reduce risk from high to moder-ate or moderate to low.

Quantitative risk analyses are per-formed using engineering techniques andcomputer models that analyze an incidentscenario in order to determine its impact.Such analyses assess what damage mayoccur from a fire, explosion and/or toxicrelease and how frequently it will occur.Potential impacts (e.g., fatalities, injuries,equipment loss, environmental damage)are systematically estimated to determinean incidents magnitude and severity.

The level of acceptable risk must beweighed against historical informationregarding similar incidents within theindustry. For example, several seriousincidentscausing considerable humancasualties and large property losseshave occurred in the last 15 years, leadingto greater attention being focused onfacilities that use, manufacture, store orhandle highly hazardous materials.

If one examines the impact of severalrecent incidents in the process and refin-ing industries (as summarized in Tables 1

through 6), the significant financial lossesand business interruption costs caused bysuch accidents become clear. As thesedata show, one can cite myriad reasons todesign-in safety and design-out hazards.

DETERMINING THE BUDGETAnother key step is to identify the

overall budget for constructing the newfacility. For example, suppose the budgetis $200 million; assume that this totalincludes the costs of material, labor, prop-erty, permitting, engineering drawingsand documentation.

With all costs included, the safety bud-get should be (as a general rule) one to

five percent of the total budget (in this

case, $1 to $5 million). This allocationwould include all safety-related sys-temsfrom fire water systems to controlroom design. Using the dollar value ofPHAs, MOCs, PSSRs and incident/acci-dent recommendations can provide costjustification for this budget. Engineeringeconomy principles can facilitate cost-jus-tification exercises, while sales and profitmargin data can illustrate cost avoidance(Table 7). This budget also includes use ofeconomies of scale, such as using similarequipment for alarm systems, firefightingequipment and gear, and operating pro-cedures and training systems.

RESEARCH APPLICABLE STANDARDSResearching applicable design stan-

dards for recommended guidelines andcriteria is a challenge. Myriad standardsmay be involvedranging from thosedeveloped by American National Stand-ards Institute (ANSI) and American Petro-leum Institute (API), to those promulgated

by National Fire Protection Assn. (NFPA)and American Society for Testing andMaterials (ASTM). To facilitate this proc-ess, sample design recommendations andcriteria follow.

Process Area LayoutThe use of inherently safe practices

should be incorporated early in the de-sign process. Standard siting practices in-clude the following.

Provide good access to all areas bywide-surface roads that form a griddednetwork; this permits firefighting fromany side.

Locate heaters and fired equipmentupwind (based on prevailing winds) ofprocess equipment.

Point horizontal tanks away from

equipment or occupied buildings.Buildings designed to house flam-

mables should be open structures.Locate process areas at least 150 feet

from tankage and utility areas.Locate flare stacks at least 175 feet

downwind of any floating roof tanks.Locate all service buildings outside

potential blast areas when feasible.

Fire Water SystemFire water should be supplied to each

process block and tank farm from a grid-ded fire main system. This system should

be installed according to applicable NFPAstandards and have many well-located

sectional valves and hydrants. In addition,

the following factors should be considered.Size underground piping and pumpsto handle two adjacent incidents.

Loop mains should not be less thaneight inches in diameter.

Use electrically driven fire pumpswith 100-percent diesel backup.

Site fire pumps at two locations.Design the overall system to work

for a minimum of eight hours at fullcapacity, with additional capacity atreduced rates.

Design CriteriaNFPA 24, Installation of Private Fire Service

Mains and Their AppurtenancesNFPA 20, Installation of Centrifugal Fire PumpsNFPA 14, Installation of Standpipe and Hose

Systems

Electrical ReliabilityElectrical power service design for a

process unit should include:dual primary service feeds with two

main breakers and a tie breaker withpower drawout main;

tie and feeder distribution panelbreakers;

automatic transfer system for mainand tie breakers, with capability for man-ual transfer;

emergency power generation or bat-tery system with uninterruptable powersupply that can provide for safe shut-down of the process.

Locations that require classified elec-trical installations should be identifiedaccording to Article 500 of the NationalElectrical Code (NEC). This code alsospecifies the class and group of equip-ment required in those areas. Conduitseals must also be installed as outlined.

Cable Trays

Where possible, cable trays should berouted away from potential fire exposures.Installations should be located so as toallow ready access for repair or removal.Other key design features:

Run power and instrument cables inseparate trays.

Locate cable trays above pipewaysand take measures to prevent them frombeing used to support other equipment.

Protect trays that traverse high-poten-tial fire areas either by fireproofing, or withflame shields or water spray systems.

At cable penetrations, select a UL-

listed fire seal whose rating is at leastequivalent to the wall rating.


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Ensure that cable jackets satisfy UL-

1277 flame test.Design CriteriaNFPA 70, NEC Articles 318 and 500API 2030, Guidelines for Application of Water

Spray SystemsAPI 2218, Fireproofing Practices in Petroleum

and Petrochemical Processing Plants

FireproofingFireproofing should be provided on all

load-bearing structural steelwork to fullheight, including fin-fan support struc-tures. This protection should cover:

exterior vessel support skirts, legs,lugs and anchor rings;

interior skirt surfaces if flanges orvalves are located inside skirt or if the po-tential for updrafts exists within the skirt;

horizontal members and cross-brac-ing (if load-bearing);

horizontal and vertical pipe rack

supports up to at least the first level.A three-hour-rated protection shouldbe provided on all steel structures andequipment supports; a one-hour-ratedprotection should be provided on cablingand piping supports.

Design CriteriaAPI 2218, Fireproofing Practices in Petroleum

and Petrochemical Processing Plants

Cooling TowersA pre-design assessment should be

performed to identify the business inter-ruption exposure presented by loss of acooling tower. Based on results, coolingtowers that are constructed of com-bustible materials or containing com-bustible fill materials should be protectedin the following ways.

Utilize low-flame spread (per ASTM

E-84) materials for stacks, louvers, fill,

drift eliminators and sheathing.Provide a minimum fire break sepa-ration of 50 feet from process areas.

Provide combustible gas detectors.Provide lightning protection (con-

nected to a grounding system) on coolingtowers located in fields not surroundedby taller buildings or structures.

Design CriteriaNFPA 214, Standard on Water-Cooling Towers

Fire Suppression SystemsAn integrated system of hydrants,

monitor nozzles and water spray systemsshould be installed within each processunit to support both automatic and man-ual firefighting efforts. The location andconcentration of monitor nozzles andwater spray systems depends on thedegree of unit congestion, nature of haz-

22 PROFESSIONAL SAFETY

A. Frequent (1)

Event likely to occuronce or more per year

B. Probable (2)

Event likely to occuronce every several years

C. Occasional (3)

Event likely to occur oncein a facilitys lifetime

D. Unlikely (4)

Event unlikelybut not impossible

Probability of Success

Category

I. Catastrophic (1)

Personnel: life-threateningEnvironment: large, uncontrolledreleaseEquipment: major damage resultingin loss of unit

II. Critical (2)

Personnel: severe injuryEnvironment: moderate, uncontrolledreleaseEquipment: moderate, resulting in unitdowntime

III. Marginal (3)

Personnel: lost-time injuryEnvironment: small, uncontrolledreleaseEquipment: minor damage resulting inunit slowdown

IV. Negligible (4)

Personnel: minor injuryEnvironment: small, controlled releaseEquipment: negligible damage

4

4 128

129

8

16

1

2

2

3

4

3

6

6

FIGURE 1 Risk Matrix

High: Requires Action Moderate: Further Study Required Low: Investigate as Time Permits

One of the most important steps in thisprocess is to determine the level

of acceptable risk.


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JANUARY 2000 23

ards involved and types of equipment tobe protected. General design guidelinesinclude the following.

Provide fixed monitor coverage so

that process areas which require protectioncan be reached by two monitor streams.

Set design radius for the monitorstreams at 81 feet.

Locate monitors at least 50 feet fromthe nearest hazard or use motor-operatedremote-controlled devices.

Install water spray systems over ves-

sels, pumps and compressors that han-dle/store:

flammable or combustible liquidsabove 500F or their auto-ignitiontemperature;

flammable or combustible liquidsat greater than 500 psi;

liquefied flammable gas.Perform modeling of fire water

system performance to ensure that ade-quate water supply, pump pressure andflow rates are available to provide cover-age needed.

Design Criteria

NFPA 15, Water Spray Fixed Systems for FireProtection

NFPA 11, Standard for Low-Expansion Foamand Combined Agent SystemsAPI 2030, Application of Water Spray Systems

for Fire Protection in the Petroleum Industry

Drainage and DikingUnit drainage system should slope

from the center of the process unit toperimeter trenches and/or impound-ment basins. Other key guidelines:

Ensure that paved surfaces haveat least 1 percent slope (2 percent for

unpaved surfaces).Grade paving away from pipe

racks.Where feasible, remote im-

pounding should be located 50feet away with good drainage;this is preferred to diking.

Slope surfaces within dikes forat least five feet or to the tank wall,whichever is less.

Design diking/containmentsystems to handle the largest spillpotentialplus the associated fire-water load. Minimum system

capacity should be 110 percent ofthe largest vessel volume.

Dike tanks individually. Where mul-

tiple tanks are contained within a singledike, an intermediate curb (minimum of18 inches) should be provided betweenindividual tanks.

Design CriteriaNFPA 30, Flammable & Combustible Liquids

Code

Process PumpsThese guidelines should be observed

when installing process pumps that han-dle flammable/combustible liquids.

Pumps should have double mechan-ical seals, with compatible barrier fluid.

Pumps should be located outsidecontainment dikes.

Water spray protection should beprovided over critical pumps; such pro-tection should activate automaticallythrough the temperature and/or flamma-ble gas detection systems.

Design CriteriaNFPA 15, Water Spray Fixed Systems for Fire

Protection

Emergency Isolation ValveAn emergency isolation valve (EIV) is

a protective device that isolates piping orequipment in the event of a dangeroussituation. It should provide automatic aswell as remote actuation by one of the fol-lowing methods:

air, nitrogen or hydraulic pressure toopen with spring to close; air or nitrogenconnection to the EIV should be madewith a melt-out tubing so that it functionsas a fusible link;

heat-actuated with spring to close;pneumatic operation;electrically operated.Other guidelines:Ensure that all components of the

EIV assembly can withstand 15 minutesof fire exposure.

Provide an alternate power supplywhere necessary.

Ensure that pneumatic EIVs havesufficient air for two valve strokes; theyshould also have a dedicated emergencyreservoir for closing.

Label EIV controls, which should beoperable from the control room and froma safe location.

Locate EIVs as close as possible tovessel/equipment flanges.

Make provisions that allow for on-line testing without process disruption.

EIVs should be located:at battery limit of production units;

INCIDENT IMPACT

Baton Rouge, LA December 1989Refinery pipeline rupture

$43 million damage; damage to off-site houses

Pasadena, TX October 1989Petrochemical Vapor cloud explosion

$500 to $725 million damage;severe business interruption

St. Croix, Virgin Islands September 1989Refinery (Hurricane Hugo)

$60 million damage; extensivedamage to storage tanks

Martinez, CA September 1989Refinery H

2and hydrocarbon release

$50 million damage, massivefirefighting effort

Morris, IL June 1989Petrochemical Vapor cloud explosion

$41 million damage; 40 acres ofplant damaged

Richmond, CA April 1989Refinery - H

2gas fire

$90 million damage; two years torepair plant

Antwerp, Belgium March 1989Petrochemical Column exploded

$77 million damage; businessinterruption of $267 million

PERIOD NUMBEROF LOSSES

LOSSES($BILLIONS)

59-63 6 0.1564-68 13 0.4869-73 24 0.51

74-78 30 1.1879-83 45 1.2984-88 32 1.54

OPERATION PERCENT LOSSES($MILLIONS)

Refineries 40 40.1Petrochemical 17 34.4

Terminals 13 25.8Plastics/Rubber 9 23.8

Chemical 8 18.5

Natural Gas 7 52.2Pipelines 2 45.6

Miscellaneous 4 24.6

CAUSE PERCENT LOSSES($MILLIONS)

Mechanical Failures 41 36.0Operational Error 19 38.6

Unknown 17 25.9Process Upset 10 40.7

Natural Hazard 5 43.2

Design Error 4 60.5Sabotage/Arson 4 19.0

TABLE 1 Review of Serious Industrial Losses

TABLE 2 Loss Trends5-Year Intervals

TABLE 3 Loss DistributionType of Complex

TABLE 4 Cause of Losses


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around all critical process equipment(e.g., reactors, furnaces);

where inventories of flammable orcombustible liquids in a single vessel orinterconnected vessels exceed 10,000 gal-lons (including storage areas);

where inventories of liquefied flam-mable gases in a single vessel or intercon-nected vessels exceed 1,300 gallons(including storage areas).

Design CriteriaAPI 2510, Design and Construction of LPG

Installations

Control Room DesignAs part of the initial design phase, the

team should consider locating the controlroom away from potential blast areas,

based on applicable modeling. If not feasi-ble, these guidelinesshould be followed.

Take steps to en-sure that all materialsof construction arenon-combustible.

Provide hydrocar-bon and toxic gas de-tection on return-airintake. It should bedesigned to alarm and

shutdown ventilationat 25 percent LEL.

Ensure that the enclosure is

positively pressurized to 0.10inches of water.Locate the air inlet for the

ventilation system above thebuilding.

Install self-closing externaldoors that have the same pres-

sure resistance as the controlroom walls.

Blastproof criteria should bedesigned for life safety to with-stand the following overpres-sure loadings: 10 psi for 20milliseconds; 3 psi for 100 mil-liseconds.

Design CriteriaAPI 2510, Design and Construction of

LPG InstallationsFM Data Sheet 7-45S, Process Control

Houses

Smoke Detection SystemsSmoke or heat detectors

should be installed in the follow-ing areas: control rooms; MCCrooms; battery rooms; belowraised floors with significant

runs of cable; online process analyzerbuildings/sheds; and gas turbine houses.All site alarms should be routed to thecontrol room.

Design CriteriaNFPA 72E, Standard on Automatic Fire Detectors

Combustible Gas DetectionCombustible gas detectors should be

located near rotating equipment and inother areas that may contain significantquantities of flammable liquid andhydrocarbon vapor. Specific locationsmay include:

control room intake, interlocked toshut down the ventilation system at 25

percent LEL;near exchangers, reactors and dryers;around storage and process drums;

around furnaces and compressors;

above hydrocarbon pumps;at main unit sewer outlet.Design Criteria

NFPA 70, National Electrical CodeANSI/ISA-RP 12.13, Part II, Installation, Opera-

tion and Maintenance of Combustible GasDetectors

Fixed Vibration MonitoringA pre-design assessment should be

conducted on each piece of rotatingequipment that will be installed to deter-mine the potential for business interrup-tion exposures created by loss of suchequipment. The assessment should alsoconsider the potential for a life-threaten-ing situation or serious environmentalimpact. Based on results, such equipmentshould be fitted with fixed vibrationmonitoring. It should be noted that whileequipment designated as critical tends tohave high horsepower (> 500 hp), the hpby itself is not a prerequisite for criticality.

Design CriteriaAPI 670, Vibration, Axial Position and Bearing

Temperature Monitoring SystemsAPI 678, Accelerometer-Based Vibration

Monitoring Systems

Storage TanksThe design of atmospheric (up to 0.5

psig) and low-pressure (up to 15 psig) stor-age tanks should conform to referencedAPI standards. High-pressure vesselsshould be designed according to the ASMEBoiler and Pressure Vessel Code. Protec-tion, level alarms and tank spacing shouldconform to the following guidelines.

Locate storage areas at least 150 feetfrom other hazardous areas. Recom-mended tank-to-tank separation criteria is:

50,000 bbls = 1.5 diameter250,000 bbls = special considerationEquip those tanks that store more

than 25,000 gallonsof Class 1 flammableliquids with indepen-dent high (HLA)and high level alarm(HHLA) systems. Thealarms should signalat 30 and 15 minutes,respectively, prior tooverfill based uponthe maximum pump-

ing rate to a constant-ly attended location.

24 PROFESSIONAL SAFETY

Profit MarginYearly IncidentCosts 1% 2% 3% 4% 5%

$1,000 100,000 50,000 33,000 25,000 20,0005,000 500,000 250,000 167,000 125,000 100,000

10,000 1,000,000 500,000 333,000 250,000 200,00025,000 2,500,000 1,250,000 833,000 625,000 500,00050,000 5,000,000 2,500,00 1,667,000 1,250,000 1,000,000

100,000 10,000,000 5,000,000 3,333,000 2,500,000 2,000,000

150,000 15,000,000 7,500,000 5,000,000 3,750,000 3,000,000200,000 20,000,000 10,000,000 6,666,000 5,000,000 4,000,000

TABLE 7 Sales Required to Cover Losses

TABLE 5 Equipment Involved in Cause

TABLE 6 Ignition Source

EQUIPMENT PERCENT LOSSES($MILLIONS)

Piping 31 41.9Tanks 17 40.5

Reactors 13 28.5Miscellaneous 9 34.7Process Drums 7 25.5Marine Vessels 6 32.0

Unknown 5 25.0Pumps 5 19.2

Heat Exchanger 3 24.0Process Towers 3 53.8Heaters/Boilers 1 28.8

SOURCE PERCENT LOSSES($MILLIONS)

Unknown 53 38.5Open Flame 12 32.0

Chemical Reaction 9 26.0Electrical Equipment 5 16.5Internal-Combustion

Engine6 49.0

Auto-Ignition 4 34.1Lightning 3 39.1

Hot Surface 3 39.4No Ignition 3 18.7

Sabotage/Arson 2 43.5Static 1 14.5

Cutting/Welding 1 16.0


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JANUARY 2000 25

Alarms should also be interlocked to per-

mit pump and isolation valve shutdown.Install foam systems in all cone andinternal floating roof storage tanks.

Pipelines should incorporate allwelded construction in immediate sphereor tank areas.

Locate the pumps outside the con-tainment areas.

Install and interlock remote-operatedisolation valves to allow actuation by thefire/gas detection systems.

Design CriteriaAPI 650, Welded Steel Tanks for Oil StorageAPI 620, Design and Construction of Large,

Welded, Low-Pressure Storage TanksAPI 2021, Fighting Fires In and Around

Flammable and Combustible LiquidAtmospheric Storage Tanks

API 2510A, Design and Construction of LPGGas Installations

NFPA 11, Standard for the Installation of Low-Expansion Foam

Pressure Relief Valves/Rupture DisksDesign criteria for these valves/disks

is detailed in the referenced API stan-dards. Although allowed by code, use ofrupture disks by themselves are discour-aged in tanks that contain highly haz-ardous materials because they do notclose after opening; this may result incontinuing release of toxic materials tothe atmosphere. Other key considera-tions in the area:

Provide redundancy for safety valvesto permit on-line removal and testing.

Provide rupture disks with a positivemeans of detecting a failure or rupture,through one of the following methods(listed in order of preference):

continuity check that constantlymonitors resistance across the disk;

excess flow valve, provided an envi-

ronmental review is performed;pressure gauge located down-

stream of the disk.Design Criteria

API RP 520, Sizing, Selection and Installation ofPressure-Relieving Devices in Refineries

API RP 521, Guide for Pressure-RelievingSystems

NFPA 30, Flammable and Combustible LiquidsCode

Process ControlHardware devices and software control

systems should be able to provide safe,

efficient control under normal process con-ditions, as well as a timely response in an

emergency. To facilitate this, the control

system should feature:numerous terminal display units;reliable valve position indicators;software fault tolerance;built-in system redundancy and

failover;programming capability for complex

control and shutdown actions;installed hardware to permit on-

stream trip testing with final element andshutdown testing.

CONCLUSIONAt first glance, this may seem like an

abundance of information and design cri-teria to monitor and incorporate. Thedesign team will likely reach a pointwhere it may not be able to verify thatevery minute detail has been designedinto the new facility. At some point, theengineering and design phase must stopand construction must begin.

During the design stage, as the teamworks through these tasks, it should viewits mission as akin to eating an elephant. Attimes, it may appear the team will neverfinish. But each day, a bit more gets done,until the project is complete. In the end,these efforts will be rewarded by the satis-faction of knowing that potentially life-threatening hazards have been designedout, and safety has been designed in.

REFERENCESAlderman, J.A. PHA-A Screening Tool.

Presentation at 1990 Health & SafetySymposium.

American Petroleum Institute. Manage-ment of Process Hazards. API RecommendedPractice 750. Washington, DC: API, 1990.

Bird, F.E. and G.E. Germain. PracticalLoss Control Leadership. Atlanta: InstitutePublishing, 1990.

DeHart, R.E. and E.J. Gremillion. Proc-ess Safety: A New Culture. Presentation atOccupational Safety & Health Summit,1992.

Dept. of Defense. System Safety ProgramRequirements. MIL-STD-882C. Washington,DC: DOD, 1993.

Dept. of Labor. Process Safety Manage-ment of Highly Hazardous Chemicals,Explosives & Blasting Agents. 29 CFR1910.119. Washington, DC: U.S. DOL, Occu-pational Safety & Health Administration,1992.

E.I. duPont deNemours & Co. ProcessRisk Reviews Reference Manual. Wilmington,

DE: E.I. duPont, 1998.The Environmental Protection Agency.

Chemical Process Safety Management.Section 304, Clean Air Act Amendments of1990.

The Environmental Protection Agency.Prevention of Accidental Releases. Section301, paragraph 1, Clean Air Act Amend-ments of 1990.

Guidelines for Hazardous Evaluation Pro-cedures. 2nd ed. New York: AmericanInstitute of Chemical Engineers, 1992.

Guidelines for Technical Management ofChemical Process Safety. New York: Center forChemical Process Safety, American Instituteof Chemical Engineers, 1989.

Hawks, J.L. and J.L. Mirian. Create aGood PSM System.Hydrocarbon Processing.

Aug. 1991.Krembs, J.A. and J.M Connolly. Analysisof Large Property Losses in the Hydrocarbonand Chemical Industries. Presentation at1990 NPRA Refinery and PetrochemicalPlant Maintenance Conference.

Lees, F.P. Loss Prevention in the ProcessIndustries. London: Butterworth, 1980.

Large Property Damage Losses inHydrocarbon-Chemical Industries: A 30-Year Review. 13th ed. New York: M&MProtection Consultants.

OLone, E.J. Datapro, Document Imag-ing Systems, Management Issues. Client/Server Computing.June 1993: 1-8.

NUS Training Corp. OSHAs ProcessSafety Management of Highly HazardousChemicals in Plain English. Gaithersburg,MD: NUS Training Corp., undated.

Renshaw, F.M. A Major Accident Pre-vention Program. Plant/Operations Prog-ress.July 1990.

Sherrod, R.M. and M.E. Sawyer. OSHA1910.110 Process Safety Management: ItsEffect on Engineering Design. Presentationat System Safety Conference, July 1991.

Mark D. Hansen, P.E., CSP, CPE, is director, envi-

ronmental safety and health, for WeatherfordInternational Inc., located in Houston. A profession-al member of ASSEs Gulf Coast Chapter, he hasmore than 16 years experience in the field of safety.

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As these data show, one can citemyriad reasons to design-in safety

and design-out hazards.

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Engineering Design for Process Safety