1 Hazard Evaluation, HE, Techniques The following are types of HE, techniques: What if Check Lists Quantitative HAZOP FMEA FTA CPQRA Quantitative FMEA, Failure Mode Effects Analysis is a preliminary qualitative technique that may require preliminary quantitative analysis (Mini-QRA) This presentation only considers the HAZOP technique. Press Page Down for 9 pages of further information on HAZOPS. (Best viewed with 24 lines per screen - adjust your Zoom% to suit) continue to page 2 2 HAZOP Hazards and Operability Analysis HAZOP was developed by Lawley (1974) of ICI. Based on early account by Elliott & Owen (1968) Hazop studies are carried out by an experienced, multidisciplanary team, who review all physical aspects of a process (lines, equipment, instrumentation) to discover potential hazards and operability problems using a check list approach. The basis for a HAZOP is a critical examination of information found in a word model, a process flowsheet, a plant layout, equipment specification or a P&ID, (Piping and Instrument Drawing). The principals of examination include: 1 2 3 4 Intention Deviation Causes Consequences (a) hazards (b) operating difficulties 5 Safeguards 6 Recommendations / Actions continue to page 3 See tabs D1 to D3 for examples of computer forms. 3 Early HAZOP studies used the following set of Guide Words to systematically review the process: NO or NOT MORE LESS Negation of intention Quantitative increase Quantitative decrease No Flow of A Flow of A greater than design flow Flow of A less than design flow Transfer of some component additional to A Failure to transfer all components of A Flow of A in direction opposite to design direction Transfer of some material other than A AS WELL AS Quantitative increase PART OF REVERSE Quantitative decrease Logical opposite of intention OTHER THAN Complete substitution More recent computerization techniques use a Standard Set Of Generic Deviations For Specific Section Types. See Dev'ns tab for examples. continue to page 4 4 Some Common HAZOP Analysis Process Parameters Flow Pressure Temperature Level Time Composition pH Speed Frequency Viscosity Voltage Toxicity Mixing Addition Separation Reaction continue to page 5 5 Prepare for the review Attitude Preparation HAZOP Review By Team Knowledge Experience Meeting Leadership Documentation Follow-up Teams HAZOP Experience Info for study P&Ids, Layout Table Deviation Causes Consequences Safeguards Action continue to page 6 6 HAZOP analysis method flow diagram Select a process section or operating step Explain design intention Repeat for all process sections Select a process variable or task Repeat for all process variables Apply guide word to process variable Repeat for all guide words contiue page down 6 con't Examine Consequences associated with deviation Develop action items List possible causes of deviation Assess acceptability of risk based on consequences Identify existing safeguards to prevent deviation continue to page 7 7 Potential HAZOP Pitfalls 1 Poor understanding by management of the HAZOP procedure An Ethylene plant has 100 P&IDs, 625 equip't items. Consider 5 variables, Pressure, Temperature, Flow Composition and Function. Consider 6 Guidewords, None, More of, Less of Part of, More than and Other than. Questions to be answered = Consider 5 minutes per question = Time for ethylene plant HAZOP study = 4 hour, 240 minutes sessions per day = No. working of days = Days per week = No. of weeks to complete HAZOP for plant = 2 3 Inexperienced HAZOP team Inadequately trained or in-experienced leader 625 5 6 18750 5 93750 250 375 5 75 items variables guide words questions min./question minutes minutes/day days days/week weeks a b c d = axbxc e f = dxe g h=f/g I j=h/I continue to page 8 8 Common Mistakes 1 Failing to establish a "safe" environment for team members 2 Consequences of events not carried to conclusion. 3 Taking unwarranted credit for safeguards 4 Too little credit given for safeguards 5 Maing recommendations as specific as possible 6 Poor recording of HAZOPS 7 Failure to HAZOP start-up and shut-down procedures 8 Poorly up-dated P&IDs 9 A HAZOP is performed in lieu of properly executed design reviews 10 Wrong technique for system being reviewed (See spreadsheet titled Fig 5.3) See example on page 9 - one page down continue to page 9 9 HAZOP Example See page 8 - item No. 3 To Compressor Inlet LAH FV 1 Teams tend to quickly identify alarms, shut-downs and controls, and claim them for safeguards. An alarm not tested may not work when called upon to do so. Inlet Line LIC Nuisance alarms are frequently bypassed and are not effective as safeguards. Often operators are not monitoring control panel. Valve in manual Automatic control routines are often set in manual mode. end See tab D1 for computer documentation example Dev'ns Table 1 Source Example Standard Set Of Generic Deviations For Process Section Types Lessons Learned From HAZOPS Reviews of FCCUs by P.E. McCluer et al, Hydrocarbon Processing, Aug 1992, p-140-C ID No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Deviation High Flow High Level High Interface High Pressure High Temperature High Concentration Low / No Flow Low Level Low Interface Low Pressure Low Temperature Low Concentration Reverse / Misdirected Flow Tube Leak Tube Rupture Leak Rupture Column X X X X X X X X Tank or Vessel X X X X X X X X X X Line X Heat Exchanger Pump Compressor X X X X X X X X X X X X X X X X X X X X X X X X X X X X Some other typical HAZOP deviations More Flow Less Flow More Pressure Less Pressure More Level Less Level Part of, wrong concentration As well as, contaminants other than, wrong material More Reaction Less Reaction No Reaction More Mixing Less Mixing More Corrosion More Erosion Sampling Press Page Down Page 10 D1 Company Nova Location Corunna Leader RAH Scribe GFR Prod'n PM Node No. 1 Describe Revision Dwg No. Proc Des Instr'ts Mech JB GH FD 0 Cor -123-4567 Research Electrical HH Safety MN Date Page Op Tech Other Other 2-Jun-97 1 Transfer Ethane from Deethanizer to C2 KO Pot Intention The intent is to transfer 150,000 lb/hr of C2/C2= mix at 300 psig and at -30 °F for the startup period. Guide Wrd High Param Flow Dev'n High Flow Possible Causes 1 FV-1 Wide open 2 3 Consequences 1 High level in KO pot with liquid carry-over to compressor with serious damage to rotor. Potential hydrocarbons release. 2 3 Safeguards 1 High level alarm LAH-1 2 3 Recommendation / Actions Respib By Date 1 Consider limiting flow orifice, auto SD trip on High-High level, smart check valve. 1 JB 1-Jan-99 2 2 3 3 Page 11 D2 Company Location Leader Scribe Prod'n Node No. Nova Corunna RAH GFR PM Proc Des JB Instr'ts GH Mech FD Revision 0 Dwg No. Cor -123-4567 Research Electrical HH Safety MN 0 Date Page Op Tech Other Other 2-Jun-97 2 0 0 0 1 Describe Transfer Ethane from Deethanizer to C2 KO Pot Intention The intent is to transfer 150,000 lb/hr of C2/C2= mix at 300 psig and at -30 °F for the startup period. 0 0 Guide Wrd Low Param Flow Dev'n Low Flow Possible Causes 1 2 3 Consequences 1 2 3 Safeguards 1 2 3 Rec / Actions 1 2 3 Respib 1 2 3 By Date Page 12 D3 Company Location Leader Scribe Prod'n Node No. Intention Describe Revision Dwg No. Proc Des Instr'ts Mech Research Electrical Safety Date Page Op Tech Other Other Guide Wrd Param Dev'n Possible Causes 1 2 3 Consequences 1 2 3 Safeguards 1 2 3 Rec / Actions 1 2 3 Respib 1 2 3 By Date Page 13 Chk List Hazard & Operability Studies Check List Example 1 Changes In Quantity a High Flow 1 Pump racing, delivery vessel pressure lost, suction pressurized, scale dislodged, leak in heat exchanger 2 Pump failure, scaling of delivery, presence of foreign body, poor suction condition, cavitation, leak in heat exchanger, drain leak, valve jammed 3 Pump failure, delivery vessel overpressurized, gas blockage, presence of foreign body, scale, sediment, suction vessel empty. 4 Pump failure, pump reversed, delivery vessel over pressurized, poor isolation, gas locking, surging, back siphoning. 1 Boiling, cavitation, freezing, chemical breakdown, flashing, condensation, sedimentation, scaling, foaming, gas release, priming, exploding, imploding. Changes in viscosity, density. External Fire, Weather conditions, Hammer. 2 same as 1 3 Source of Ignition, Personnel shock. 1 Changes in proportion of mixture, in water or solvent content. 2 Ingress of air, water, steam, fuel, lubricant, corrosion products, other process materials from high pressure system, leakage through heat exchangers. gas entrainment, spray, mist. Loss of automatic control Operator error b Low Flow c No Flow Failure of joint, pipe, valve, trap, bursting disc, relief valve. d Reverse Flow 2 Changes in physical condition a High or Low pressure b High or Low Temperature c Static buildup 3 Changes in chemical a condition b High or Low Conentration Contaminants 4 Startup and Shutdown Condiotion. a Testing 1 Vacuum, pressure testing with with harmless material. 2 Concentration of reactants, intermediates 3 Purging, venting, sweetening, drying, warming. Access, spares. 1 Should this pipe be considered for registration? b c Commissioning Maintenance 5 Hazardous Pipelines a Pipeline registration Page 14