PSM and Methods

 

Hazards, Accidents, Process Safety Management & Process Hazard Analysis ³As if there were safety in  stupi  st upidit dityy alone. alone.´ ´ ± Tho Thore reau au Harry J. Toups Toups LSU Department of Chemical Chem ical Engineering with significant material from SACHE 2003 Workshop

 

Lecture Topics 

Hazards and Accidents



Process Safety Management Management (PSM)



Process Hazard Analysis (PHA)

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Learning Objectives 



 

Describe

the hazard and accident-driven stimulus for, and main components of  rocess Safety Management  OSHA¶s  P rocess standard Define  P rocess rocess Hazard Analysis and related terminology Describe major hazard analysis methods Assess applicability (via pros and cons) of  major hazard analysis methods 3/49

 

Hazards 

An inherent physical or chemical c hemical characteristic characteristic that has the potential for causing harm to people, peo ple, 1





the environment, or property Hazards are intrinsic to a material, or its conditions of use Examples  ± Hydr Hydroge ogen n sulf sulfid idee ± to toxi xicc by inha inhala lati tion on  ± Ga Gaso soli line ne ± fl flam amm mab able le  ± Mov Moving ing mac machin hinery ery ± kine kinetic tic ener energy gy,, pinch pinch poi points nts

1 AICHE

Center for Chemical Process Safety 

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Hazard Management: The World as It Was Before 

Good people



« doing good things

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The Rising Case for Change 

1984 ± Bho 1984 Bhopal pal,, India India ± Toxi oxicc Mate Materia riall Released  ± 2,500 immediate fatalities; 20,000+ total  ± Ma Many ny ot othe her  r  offsite injuries

HAZARD: Highly Toxic Methyl Isocyanate

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The Rising Case for Change 

1984 ± Mexic Mexico o City, City, Mexic Mexico o ±Explosio ±Explosion n  ± 300 fa fata tali liti ties es (mostly offsite)  ± $2 $20M 0M da dama mage gess

HAZARD: Flammable LPG in tank

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The Rising Case for Change 

1988 19 88 ± No Norc rco, o, LA ± Ex Expl plos osio ion n  ± 7 onsite onsite fatal fataliti ities, es, 42 42 injured injured  ± $4 $400 00M+ M+ dam damag ages es

HAZARD: Flammable hydrocarbon vapors

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The Rising Case for Change 

1989 19 89 ± Pa Pasa sade dena na,, TX ± Ex Expl plos osio ion n and and Fire Fire  ± 23 fatali fatalitie ties, s, 130 injured; injured; damag damagee $800M+ $800M+

HAZARD: Flammable ethylene/isobutane vapors in a 10´ line 9/49

 

Enter « Process Safety Management 





Integral part of OSHA Occupational Occu pational Safety and Health Standards since 1992 Known formally as:  P rocess rocess Safety Management  of Highly Hazardous Chemicals (29 CFR  1910.119) PSM  applies

to most industrial processes containing 10,000+ pounds of hazardous h azardous material 10/49

 

In a Few Words, What is PSM? 

The proactive and systematic identification, evaluation, and mitigation or prevention of chemical releases that could occur as result of failures in a  process, procedures, or  equipment. 11/49

 

What¶s Covered by PSM? 

     

Process Safety Information Employee Involvement Process Hazard Analysis Operating Procedures Training Contractors Pre-Startup Safety Review

    

 

Mechanical Integrity Hot Work  Management of Change Incident Investigation Emergency Planning and Response Compliance Audits Trade Secrets 12/49

 

Process Hazard Analysis Simply, PHA allows the employer to: 

Determine



Identify corrective measures to improve safety



locations of potential safety problems

Preplan emergency actions to be taken if safety controls fail 13/49

 

PHA Requireme Requirements nts 





Use

one or more established methodologies appropriate to the complexity of the process Performed by a team with expertise in engineering and process operations Includes personnel with experience and knowledge knowl edge spec specific ific to the proces processs being evaluated and the hazard analysis metho me thodol dology ogy bei being ng use used d 14/49

 

PHA Must Address « 





The hazards of the process Identification of previous incidents with likely potential for catastrophic consequences Engineering and administrative controls applicable to the hazards and their  interrelationships 15/49

 

PHA Must Address « (cont¶d) 





Consequences of failure of engineering and administrative controls, especially those affecting employees Facility siting; human factors The need to promptly resolve PHA findings and recomm recommendations endations 16/49

 

Hazard Analysis Methodologie Methodologies s    

What-If  Checklist What-If/Checklist Hazard and Operability Study (HAZOP)

  

Failure Mode and Effects Analysis (FMEA) Fault Tree Analysis An appropriate equivalent methodology 17/49

 

What--If  What -If  



Experienced personnel brainstorming a series of questions that begin, "What if«?´ Each question represents a potential failure in the facility or misoperation of the facility

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What--If  What -If  



The response of the process and/or  operators is evaluated to determine if a  potential hazard can occur  If so, the adequacy of existing safeguards is weighed against the probability and severity of the scenario to determine whether  modifications to the system should be recommended 19/49

 

What--If  What -If If  ± Steps Steps 1. 2. 3. 4. 5.

Divide

the system up into smaller, logical subsystems Identify a list of questions for a subsystem Select a question Identify hazards, consequences, consequences, severity, likelihood, and recomm recommendations endations Repeat Step 2 through 4 until complete 20/49

 

What--If What -If Question Areas 



Equipment failures  ± Wha Whatt if if « a valve valve le leaks aks??

Human error 

 ± What if « operator operator fail failss to restart restart pump? 

External events  ± What if « a very hard hard free freeze ze persist persists? s?

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What--If  What -If If  ± Summary Summary  

Perhaps the most commonly used method One of the least structured methods

 ± Can be be used in in a wide range range of circum circumsta stanc nces es  ± Success highly dependen dependentt on experience experience of the analysts

 

Useful

at any stage in the facility life cycle Useful when focusing on change review 22/49

 

Checklist 





Consists of using a detailed list of prepared questions about the design and operation of the facility Questions are usually answered ³Yes´ or  ³No´ Used

to identify common hazards through compliance with established practices and standards 23/49

 

Checklist Question Categories 

Causes of accidents  ± Pr Proce ocess ss equi equipm pmen entt  ± Hu Hum man er erro ror  r   ± Ext Exter ernal nal eve event ntss



Facility Functions  ± Alarms, Alarms, constructi construction on mater materials, ials, control systems, documentation and training, instrumentation, piping, pumps, vessels, etc. 24/49

 

Checklist Questions 

Causes of accidents

 ± Is process process equip equipmen mentt properl properly y support supported? ed?  ± equ equipm ipment entedures identifi ident ed proper pr operly  ± Is Are the procedur proc esified comple com plete? te? ly??  ± Is the syst system em designed designed to to withstand withstand hurric hurricane ane winds? winds? 

Facility Functions  ±  ±  ±  ±

Is is possible possible to distingui distinguish sh between between differ different ent alarms? alarms? Is pres pressur suree reli relief ef prov provided ided?? Is the vesse vessell free free from from external external corr corrosio osion? n? Are sour sources ces of ignit ignition ion cont control rolled? led? 25/49

 

Checklist ± S Summary ummary   







The simplest of hazard analyses Easy-to-use; level of detail is adjustable Provides quick results; comm communicates unicates information well Effective way to account for µlessons µl essons learned¶ NOT helpful in identifying new or  unrecognized hazards Limited to the expertise of its author(s) 26/49

 

Checklist ± ± Su Summ Summary mmar ary y (cont¶d) (con (c ont¶ t¶d) d) 





Should be prepared by experienced engineers Its application requires knowledge of the system/facility and its standard operating  procedures Should be audited and updated regularly 27/49

 

What--If/Checklist What -If/Checklist 



A hybrid of the What-If and Checklist methodologies Combines the brainstorming of What-If  method with the structured features of  Checklist method

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What--If/Checklist What -If/Checklist ± Steps Steps 



Begin by answering a series of previously prepared µWhat-if¶ questions During

the exercise, brainstorming  produces additional questions to complete the analysis of the process under study

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What--If/Checklist What -If/Checklist ± Summary Summary 





Encourages creative thinking (What-If) while  providing structure (Checklist) In theory, weaknesses weakn esses of stand-alone methods are eliminate elim inated d and strengths strengths preserved ± not easy to do in practice E.g.: when presented with a checklist, it is typical human behavior to suspend suspen d creative thinking 30/49

 

HAZOP  H az  ard and O perability Analysis az ard 



Identify Identi fy hazards hazards (sa (safet fety, y, hea health lth,, environmental), and Problems which prevent efficient operation

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HAZOP 1. 2. 3.

Choose a vessel and describe intention Choose and describe a flow path Apply  guideword to deviation 



Guidewords include NONE, MORE OF, LESS  OF, PART OF, MORE THAN,  OTHER THAN, REVERSE Deviations are expansions, such as NO FLOW,  MORE PRESSURE, LESS  TEMPERATURE, MORE PHASES THAN (there should be), 32/49

 

HAZOP 1. Vessel 

2. FLOW PATH

(Illustrative example of HAZOP)

Feed Tank

Pump

Check Valve

To Distillation Column

3. REVERSAL OF FLOW

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HAZOP

8.

Can deviation initiate a hazard of consequence? con sequence? Can failures causing deviation be identified? Investigate detection and mitigation systems Identify recommendations Document

9.

Repeat 3-to-8, 2-to-8, and 1-to-8 until complete

4. 5. 6. 7.

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HAZOP 1. Vessel 

2. FLOW PATH

(Illustrative example of HAZOP)

Feed Tank

Pump

Check Valve

o Distillation Column 3. REVERSAL OF FLTOW 4. Distillation materials returning via pumparound 5. Pump failure could lead to REVERSAL OF FLOW 6. Check valve located properly prevents deviation

7. Move check valve downstream of pumparound35/49

 

Loss of Containment Deviations Deviations  

Pressure too high



Pressure too low (vacuum) Temperature too high Temperature too low

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D



eterioration of equipment

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HAZOP¶s Inherent Assumptions 

Hazards are detectable by careful review

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Plants designed, built and run to appropriate appro priate standards will not suffer catastrophic loss of  containment if ops stay within design parameters

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Hazards are controllable by a combination co mbination of  equipment, procedures which are Safety Critical 

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HAZOP conducted with openness and good faith  by competent parties

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HAZOP ± P Pros ros an a and nd Co C Cons ons    

  

Creative, open-ended Completene Comple teness ss ± identi identifies fies all all process hazards Rigorous, structured, yet versatile Identifies safety and operability issues Can be time-consuming (e.g., includes operability) Relies on having right people in the room Does not distinguish between low probability, high consequence events (and vice versa) 38/49

 

FMEA ± ± Failure Modes, Effects Analysis 





Manual analysis to determine the consequences conseq uences of component, module or subsystem failures

Bottom-up analysis Consists of a spreadsheet spread sheet where each failure failure mode, possible causes, probability of  occurrence, consequences, and proposed safeguards are noted. 39/49

 

FMEA ± ± Failure Mode Keywords ‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡

Rupture Crack

‡

Leak Plugged Failure to open Failure to close

‡

Failure to stop Failure to start Failure to continue Spurious stop

‡

‡

‡ ‡ ‡

‡ ‡

Spurious start Loss of function High pressure Low pressure High temperature Low temperature Overfilling Hose bypass Instrument bypassed

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FMEA on a Heat Exchanger  Failure Causes of  Symptoms Predicted Impact Mode

Failure

Tube rupture

Corrosion from fluids (shell side)

Frequency H/C at higher  pressure than cooling

Frequent has ± Critical could ± happened cause a 2x in 10 yrs major  fire

water   

Rank items by risk (frequency (frequenc y x impact) Identify safeguards for high risk items 41/49

 

FMEA ± ± Failure Modes, Effects Analysis FMEA is a very structured stru ctured and reliable method for evaluating hardware and systems.  Easy to learn and apply and approach app roach makes evaluating even complex systems easy to do.  Can be very time-consuming (and expensive) and does not readily identify areas of multiple fault that could occur.   Not easily lent to procedural review as it may not no t identify areas of human error in the process. 

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Fault Tree Analysis 

method that starts with a hazardous event and works backwards to Graphical

identify the causes of the top event  



Top-down analysis Intermediate events related to the top event are combined by using logical operations such as AND and OR. 43/49

 

FTA

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Fault Tree Analysis 



Provides a traceable, logical, quantitative representation of causes, consequences and event combinations Amenable Ame nable to to ± but for com comprehe prehensive nsive systems syste ms,, requiring requiring ± use of of softwa software re

 Not intuitive, requires training   Not particularly useful when temporal aspects are important 

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 Accident Scenarios May Be Missed by PHA 

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 No PHA method can identify all accidents that could occur in a process A scenario may be excluded from the scope of the analysis The team may be unaware of a scenario The team consider the scenario but judge it not credible or significant The team may overlook the scenario 46/49

 

Summary Despite





the aforementioned issues with PHA:

Companies that rigorously exercise PHA are seeing a continuing reduction is frequency and severity of industrial accidents will continue to play an integral role in the design and continued con tinued examination of industrial processes P rocess H  rocess  H azard azard Analysis

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Using What You Learn 

The ideas and techniques of Process Hazard will be imm i mmediately ediately useful inAnalysis upcoming recitation exercise on Hazard Evaluation



Expect to be Expect be part part of a Process Process Hazar Hazard d Analysis Team early on in your   professional career  48/49

 

Where to Get More Information Information 

Chemical Safety and Hazard Investigation b

 

www.cs .gov Board¶s web site: MPRI web site: www. Mpri.lsu.edu/main/   ± Chemical  P rocess Crowl and Louvar  ±  rocess Safety:  Fundamentals with Applications



 HAZO P  & HAZAN: Notes on the Identification Kletz ±  HAZO and Assessment of Hazards

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