Hazard Identification 1. Check Lists 2. Dow Relative .
Major tasks in safety engineeringHazard identification1. Check lists2. Dow relative ranking3. HAZOP - hazard and operability Level of protection analysis Hazard assessment- Fault tree- Event tree- Consequence analysis- Human error analysis Actions to eliminate or mitigate- Apply all engineering sciencesThis section covers hazardidentification methods, and wewill include corrective actions.We will use our group skillsand knowledge of safety layersin applications.1
Hazard and Operability: HAZOPAll of these terms! This stupid table!I hate HAZOPS. Why don’t we justlearn the engineering?NodesParametersConsequenceGuide wordsDeviation2
I suppose that Ishould have done thatHAZOP study!Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE3
What can go wrong? Where do we start?4
Safety engineering - some terms to know Hazard: A hazard introduces the potential for anunsafe condition, possibly leading to an accident. Risk is the probability or likelihood of a hazardresulting in an accident Incident is an undesired circumstance that producesthe potential for an ACCIDENT Accident is an undesired circumstance that results inill health, damage to the environment, or damage topropertyHazard incident accident(includes near misses)5
Hazard identification1. Check lists List of hazards identified from previousstudies and historical data on operatingplants Can be tailored to specific materials,equipment, operating procedures, etc.Always takeadvantage ofexperience! Very simple and low cost Especially helpful to novice But,- Does not address new processes, equipment, etc.- Past data might not contain infrequent, highconsequence accident6
Hazard identification2. Relative ranking Based on general information about materials andprocesses Very well defined procedure involving tables andstandard data sources. Some judgment, but peopleshould arrive at nearly the same results Does not consider important details of specific plant Therefore, key applications are- Early evaluations of completing projects- Insurance evaluations7
Hazard identification2. Relative ranking: Dow Index We will use Dow’s Fire and Explosion Index available to all engineers through the AIChE and inThode Library. The resulting Index value can be used to estimate thedegree of hazard (below from Crowl and Louvar,1990)Dow Index1 - 6061-9697-127128-158159 upDegree of Hazardlightmoderateintermediateheavysevere8
Hazard identification2. Relative ranking: Dow Index Further calculations can be performed to estimatepotential property loss (max cost per accident) andbusiness interruption (days downtime per accident) Uses- Evaluation by insurance companies- Quick estimate of the hazard, especially when companydoes not have prior experience- Note that process and equipment technology is not includedin evaluation9
Hazard identification2. Relative ranking: Dow IndexClass Example: Bartek Feed VapourizerPlant:Bartek Maleic AnhydrideUnit:Butane vapourizer and air blower(not including butane storage or reactor)Materials:Butane and airOperating mode:Normal continuous operation10
Hazard identification2. Relative ranking: Dow otorL1F3T1steamv2v4TcondensateParallel tubularreactors withcoolingairP3P2v511
Hazard identification2. Relative ranking: Dow IndexDOW INDEX for Bartek Vaporizer processMaterial Factor for Butane: MF 21 (Dow Index Table)For this example, theindex a value at theupper bound of “lightrisk”.BASE FACTORA. Exothermic reactionB. Endothermic reactionC. Material handlingD. Enclosed unitE. AccessF. DrainageF1 BASE FACTORA. toxic materialsB. sub-atmospheric pressureC. operation in near flammable range1. tank farms2. upset3. always in flammable rangeD. DustE. pressureF. low temperatureG. Quantity of flammable material1. In processSee lecture notes for larger version of table.GENERAL PROCESS HAZARDS1.0 (if T 140 F, see page 14)0(not a reactor)0(not a reactor)0(not in this unit)000(not known)1.0 (sum of above)SPECIAL PROCESS HAZARDS1.00.0 0.20 * Nh 0.20*0.0(Nh 0.0, short exposure under fire conditions has notoxic hazard)0000.80 (after mix point)00.25(safety relief at 70 psig, see Figure 2, page 22)02. In storage3. solidsH. corrosion and erosionI. LeakageJ. Fired HeatersK. Hot Oil SystemL. Rotating Equipment0.10(30 gal of butane is below lowest value of x coordinate,BTU .0029 x 109)000 (don’t have all data, no sight glass on vaporizer)0.10 (pump)00.00.50 (compressor)F22.75F3 (F1) (F2)F3 (1.0) (2.75) 2.75Fire and Explosion Index(F3 ) (MF) (2.75) (21) 57.812
Hazard identification3. Hazard and Operability: HAZOP HAZOP is a formal and systematic procedure forevaluating a process- It is time consuming and expensive HAZOP is basically for safety- Hazards are the main concern- Operability problems degrade plant performance(product quality, production rate, profit), so they areconsidered as well Considerable engineering insight is required engineers working independently could (would)develop different results13
Hazard identification3. Hazard and Operability: HAZOPHAZOP keeps all teammembers focused onthe same topic andenables them to workas a team:1 1 1 5Node: Concentrate on one location in the processParameter: Consider each process variable individually(F, T, L, P, composition, operator action, corrosion, etc.)Guide word: Pose a series of standard questions about deviationsfrom normal conditions. We assume that we are able to find/operate ata safe “normal” operating point.14
Hazard identification3. Hazard and Operability: HAZOPNode: Pipe after pump and splittere.g. 4.1 m3/s of 92% ammonia at 20 C; a pressureof 3.5 atm, from a pump to a heat exchanger.Parameter*: Flow rateGuide word: Less (i.e. less than normal value) Deviation: less flow than normal Cause: of deviation, can be more than one Consequence: of the deviation/cause Action: initial idea for correction /prevention / mitigation* For an expanded list of parameters and associated guide words, see Wells (1996)All groupmembers focuson the sameissuesimultaneously15
Hazard identification3. Hazard and Operability: HAZOPTypical guidewords used for processesGuide wordNO or NOT or NONEMORELESSAS WELL ASPART OFREVERSEOTHER THANSOONER/LATER THANExplanationNegation of the design intentQuantitative increaseQuantitative decreaseQualitative increase e.g.,extra activity occursQualitative decreaseOpposite of the intentionSubstitutionActivity occurring a time other than intendedSelected parameters with applicable guide words (see Wells, 1996, p. 95-6)Flow (no, more, less, reverse)Temperature (higher, lower)Pressure (higher, lower)Level (none, higher, lower)Composition (none, more, less, as well as, other than)Action (sooner, later, insufficient, longer, shorter)16
Hazard identification3. Hazard and Operability: HAZOPFired heaters are used in process plants and havemany potential hazards. Let’s perform a HAZOP study!feedWhen do we usea fired heater ina process plant?productairfuelConsider how we normally raise the temperature of a stream17
Hazard identification3. Hazard and Operability: HAZOPClass example: fired heater1.2.3.4.Discuss the first entry in theHAZOP formComplete an entry for anotherguide word for the parameterComplete an entry for a differentparameter for the same nodeComplete an entry for a differentnode/ parameter/guide wordfeedproductairfuel18
HAZOP FORMUnit: Fired HeaterfeedNode: Feed pipeParameter: Flow(after feed valve, before split)productLocation (line or vessel)or procedure (start up)Process variablesairfuelGuide WordDeviationSelect fromofficial list ofwords to ensuresystematicconsideration ofpossibilitiesnoapplying guideword to reliminary resultwhich should bereconsidered whentime is availableno feed flow1. feed pump stopsdamage to pipes inradiant section,possible pipefailure1. automaticstartup of backuppump on low feedpressureInclude existing “safeguards”CauseConsequenceAction19
2. feed valveclosed3. feed flow meterindicates false highflow (controllercloses valve)4. pipe blockage5. Catastrophicfailure of pipe“2. fail open valve“3. redundant flowmeters“4. a) test flowbefore startup5.a) damage topipes in radiantsectionb) pollution andhazard for oilrelease to plantenvironment4. b) place filter inpipeInstall remotelyactivated blockvalves at feedtanks to allowoperators to stopflowFor 1-5, SIS tostop fuel flow onLOW or NO feedflow, usingseparate feed flowsensor20
Hazard identification3. Hazard and Operability: HAZOPWe have seen examples of safety – where is the “Operability”? When equipment fails, the likelihood of personal injuryis high Identifying the cause of unsafe conditions, we canrespond with improved equipment reliability, includingmaintenance Some parameter-guideword combinations will lead toconditions that are safe, but result is significanteconomic loss. These will require responses.21
Hazard identification3. Hazard and Operability: HAZOPWhat is notacceptable withthis design?FFC1How is flow adjusted(manipulated tomeet changingsetpoints?Constant speedPD pump22
Hazard identification3. Hazard and Operability: HAZOPIs this an acceptabledesign? How is flowdetermined?FC1We cannot regulate a valvein the process streambecause the constantspeed, PD pumpprocesses a fixed volumeof liquidConstant speedPD pump23
Hazard identification3. Hazard and Operability: !speedOKExceeding the operatingwindow of the equipment couldlead to unsafe conditions.Flow24
Hazard identification3. Hazard and Operability: on!speedOKFrecycleFlowWhy recycle after the exit cooling?What else is missing at the compressor’s feed point?25
Hazard identification3. Hazard and Operability: HAZOPContinuing fuelcombustion w/owater circulationwill damageequipmentFuel gassteamPCLAH LALLCfcriserBoilerfeedwaterdowncomerair26
Hazard identification3. Hazard and Operability: HAZOPFuel gasfcContinuing fuelcombustion w/owater circulationwill damageequipmentairsupplysSISsteamPCLLAH LALLCfcriserBoilerfeedwaterdowncomerair27
Hazard identification3. Hazard and Operability: HAZOPHAZOP - Process applications Thorough review at or near the completion of a newprocess design- Equipment and operating details known- Can uncover major process changes Review of existing processes (periodic update)- Safe operation for years does not indicate that no Hazards exist Review of changes to an existing process that hadbeen “HAZOPed” - Important part of ChangeManagement- No consistency on what type of changes require formal HAZOP28
Hazard identification3. Hazard and Operability: HAZOPManaging the HAZOP process The HAZOP group should contain people withdifferent skills and knowledge- operations, design, equipment, maintenance, quality control, .- do not forget operators!!! The team should understand the plant well Documents should be prepared and distributed beforethe meeting The HAZOP leader should be expert in the HAZOPprocess Results must be recorded and retained29
Hazard identification3. Hazard and Operability: HAZOP At the conclusion, every item should be evaluatedfor further study- the need for and priority of future effort is decided- every item should be evaluated for severity, likelihood, and cost (H/M/L or weightings 1-10)- columns for the three factors above can be added to thestandard HAZOP form (See Wells, 1996, p. 104-5) For all significant items, a Hazard Assessment isperformed (one or more of methods below)-Fault TreeEvent TreeFMEA (failure mode and effects analysis)Consequence AnalysisHuman Error Analysis30
Hazard identification3. Hazard and Operability: HAZOPHAZOP - Some words of caution Recommendations are based on(likelihood x consequence x action cost)- Do not "gold plate" the plant for very unlikely scenarios- airplane hitting a plant is very unlikely; however, a nuclearpower plant has large consequence Very complex systems are prone to failure, thisincludes safety systems- remember about alarm proliferation (“crying wolf”) - this canhappen with other aspects of safety31
Hazard identification3. Hazard and Operability: HAZOPYou areresponsible for thesafety team.Without HAZOPHow will you documentthat you have performedand implemented aprofessional safety study?Without HAZOPHow will you focus allmembers of a team on thekey issues in a systematicmanner?32
REFERENCESAIChE, Dow Fire and Explosion Index 6th Ed., American Institute of Chemical Engineers, New York, 1987(ISBN 0-8169-0438-3) [7th Ed. 1994, ISBN 0-8169-0623-8]AIChE, Guidelines for Hazard Evaluation Procedures 2nd Ed., American Institute of Chemical Engineers,New York, 1992AIChE, Guidelines for Engineering Design for Process Safety, American Institute of Chemical Engineers,New York, 1993AIChE, Guidelines for Consequence Analysis of Chemical Processes, American Institute of ChemicalEngineers, New York, 1999AIChE, Guidelines for Chemical Process Quantitative Risk Analysis 2nd Ed., American Institute ofChemical Engineers, New York, 2000Crowl, D. and J. Louvar, Chemical Process Safety: Fundamentals with Applications, Prentice Hall,Englewood Cliffs, 1990 (ISBN 0-13-129701-5)King, R., Safety in the Process Industries, Butterworth-Heineman, London, 1990Kletz, T., HAZOP and HAZAN, Second Edition, The Institute of Chemical Engineers, Warkwickschire,1986 (ISBN 0-85295-165-5)33
REFERENCESLees, F., Loss Prevention in the Process Industries, Butterworth, London, 1980Lipton, S. and J. Lynch, Handbook of Health Hazard Control in the Chemical Industry, Wiley, New York,1994Richardson, M. (ed), Risk Management of Chemicals, Royal Society of Chemistry, Cambridge (U.K.),1992Wells, G., Safety in Process and Plant Design, Godwin, London, 1980Wells, G., Hazard Identification and Risk Assessment, Institute of Chemical Engineers, Gulf Publishing,Houston, 1996 (ISBN 0-85295-353-4)Some WEB siteshttp://slp.icheme.org/chemicals.html (safety-related data 1100/hdbk1100.pdf - USA DOE Safety Handbookwww.lihoutech.com/hzp1frm.htm - About one chapter on HAZOP from company that provides HAZOPsoftwarehttp://ed.icheme.org/chemengs.html - Good source of general information on chemical engineering,follow key words for safety and risk. By IChemE in the UK34
We will use Dow’s Fire and Explosion Index-available to all engineers through the AIChE and in Thode Library. The resulting Index value can be used to estimate the degree of hazard (below from Crowl and Louvar, 1990) Dow Index Degree of Hazard 1 - 60 light 61-96 moderate 97-127 intermediate 128-158 heavy 159 up severe 8 Hazard .
Several standard hazard identification tools that can help you document the hazard-identification and risk-management process are: Hazard identification is the foundation of a safe workplace. Job hazard analysis (JHA) Also referred to as a job safety analysis (JSA), a JHA is a systematic way of identifying hazards
a GHS hazard class and category. Signal Words: "Danger" or "Warning" are used to emphasize hazards and indicate the relative level of severity of the hazard, assigned to a GHS hazard class and category. Hazard Statements: Standard phrases assigned to a hazard class and category that describe the nature of the hazard.
Conducting a Hazard Identification and Vulnerability Assessment (HIVA) is the initial step supporting the emergency management process of hazard preparedness, response, recovery, and mitigation. Hazard identification refer
What is Hazard Classification? Hazard classification is the process of evaluating the full range of available scientific evidence to determine if a chemical is hazardous, as well as to identify the level of severity of the hazardous effect. When complete, the evaluation identifies the hazard class(es) and associated hazard category of the chemical.
Hazard Communication Program – 9/3/2020 5 Appropriate pictogram showing the chemical’s hazard class. Appendix A shows the pictograms that are associated with each hazard class. Hazard statement describing the nature of the hazard Precautionary statement recommending the steps to be taken to safely use, handle, store
Division 1.2 - Explosives that have a projection hazard but not a mass explosion hazard. Typical examples are certain power charges. c. Division 1.3- Explosives that have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard. Typical examples are
2.4 UNCERTAINTIES IN THE SEISMIC HAZARD ASSESSMENT 35 2.5 SEISMIC HAZARD RESULTS 37 2.5.1 Hazard curves for selected cities 37 2.5.2 Uniform hazard spectra for selected cities 39 2.5.3 Seismic hazard maps 40 2.5.4 Set of stochastic scenarios 43 2.5.5 Comparison of the results with the elastic design spectra defined in NSCE-02 and Eurocode-8 43
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