Computer-aided Hazard Identification Paul Chung Department of Computer Science

Hazards and Operability (HAZOP) Studies Established and widely used technique in the process industry for hazard identification Time consuming, labour intensive process: –Tedious –Expensive

Computer-aided HAZOP Different levels of support: –Electronic report form –Electronic data (on plant, on fluids, etc.) –Automated Hazard Identification Continuous operation Batch operation

Automated Hazard Identification Continuous operation –From basic research to commercial product – HAZID –Basic technology Signed directed graph (SDG) representation Fault propagation –Go through a list of deviations systematically and identify the faults that cause the deviations and the consequences that result from the faults and deviations

HAZID Overview Automated extraction of plant design from a CAD system, e.g. Intergraph SmartPlant P&ID Convenient forms for adding any missing process specific information Tick boxes for selecting analysis options: –Deviations, e.g. more flow, less flow, etc. –Items to HAZOP, etc.

HAZID Overview HAZOP style output in different output formats –XML, with HTML web page view. –Excel spreadsheet. Query facility for viewing analysis results –e.g. viewing faults and consequences relating to a particular plant item –e.g. viewing the propagation path between a particular fault and consequence Compare facility for viewing the difference between two HAZID runs –Useful for after making a change to the design

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

Mapping SmartPlant to Hazid models SmartPlant Database References Hazid Model Types Mapping created by user for all company, then mapping is >95% automatic Automatic mapping by Hazid: = = Centrifugal Pump Valve = ????? Mixer Stripper Absorber Reactor User makes choice 8 **This User mapping is required only once for the whole Project**

Checking Automatic Nozzle Mapping Hazid model is process function: But P+ID is piping: User confirms nozzle functions: N1 is vapour/liquid in port, N2 and N3 are liquid out ports, N4 is a vapour out port N5 is Cleanout liquid in port. Liquid Vapour Vapour/Liquid In Port Liquid Out Port Vapour Out Port 9 N1 N2 N3 N4 N5

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

Interaction between Faults, Deviations and Consequences Consequence Deviation Fault Fault - can cause Consequence Fault - can cause Deviation to process variable Deviation – can cause another Deviation Deviation – can cause Consequence Equipment Knowledge Base Knowledge about behaviour of equipment These links are called “arcs” in Hazid

Equipment Knowledge Base Knowledge about Faults and Consequences This is mainly engineering knowledge and experience In Out Fault – Bearing failureConsequences Casing damage Seal damage and leakage Loss of discharge pressure Flow disturbance Pump stops

Select SP P+ID From SmartPlant Run Hazid data wizard, Extract plant data from SP database: *Plant Items *Piping, valves, fittings *Controls *Fluids information: Temperature Pressure Fluid name Hazid maps SP icons to Hazop “Process” models Converts P+I diagram to Analysis model Hazid analyses plant and generates Hazop Report Hazid Operation 7

HAZOP Style Output from HAZID

HAZID Viewer Queries Standard format questions: –What causes could there be for a selected hazard? –What consequences are there for a given failure mode? –How is a given hazard realised? Show a path of deviations for propagation –Display all hazards with a given severity rank or higher

Filtered Output showing Fault Paths for a given Hazard

Automated Batch Plant Hazard Identification Batch operation –Early research prototype (CHECKOP) –Basic technology Action representation State-based simulation –Go through a set of operation instructions systematically and identify potential ambiguities, operating problems and hazards –Applying guidewords such as before, after, no action, etc.

CHECKOP System Overview

Simple Batch Reactor Example

CHECKOP Plant Description instance(tank101 isa tank, [content info [reactantA], outports info [out is [pump101,in]]]). instance(pump101 isa pump, [status is offline, outports info [out is [valve101,in]]]). instance(valve101 isa valve, [status is closed, outports info [out is [reactor101, in2]]]). instance(reactor101 isa stirred_tank_reactor, [ outports info [out1 is [valve103,in], out2 is [valve106,in]], heatSink info [hout is [jacket101,hin]], reaction info [reaction_ab_p] ]).

Operating instruction format Natural language –Easy for user –Requires natural language processing –Could be ambiguous Structured template –Easy for computer to process –Limited expressive power

Operating instruction format Object Action –valve101 open Object Action until Condition –mixer on until elapsed-time 20 minute Object1 Action Object2 Filler-word Fluid until Condition –reactor101 fill-from tank101 with reactantA until volume 30 percent

CHECKOP Operating Procedure Input charge reactor101 with reactantA: { (1) valve101 open (2) pump101 start (3) reactor101 fill_from tank101 with reactantA until volume 30 percent (4) pump101 stop (5) valve101 close } etc…

Deviation Generation Combine each single action in the procedure with guide words, from: –No action – Simple omission. –Early/Late action – Sequence of procedure changed (how many steps feasible?). –Early/Late action termination – “until” condition of action varied. Then, simulate the effect of executing the new procedure on the plant, detect hazards.

Batch HAZOP Output OperationKeywordConsequences (3) reactor101 fill from tank101 with reactantA until volume 30 percent No action(6) agitator running while vessel empty (17) cannot empty [reactantA, productP] from reactor101 to tank103 because content of reactor is [reactantB]. Early action (-2) reactor101 cannot be filled from tank101 because there is no flow path. Late action (+3) reactor101 cannot be filled from tank101 because there is no flow path.

Batch HAZOP Output OperationKeywordConsequences (3) reactor101 fill from tank101 with reactantA until volume 30 percent Early termination (to only 10 percent) no consequence. Late termination (to 50 percent) (17) cannot empty [reactantA, productP] from reactor101 to tank103 because content of reactor is [reactantA, productP]. (17) contamination in tank103.

Future Work on CHECKOP A formal structured language for operating instructions More guide words –“Other” Action – change other variables of the Action model Rules for reasonable deviations –What are the most likely mistakes in operation? Integrate with HAZID –HAZID is strong on process hazards, CHECKOP better for operating errors, etc. –HAZOP of start-up, shutdown, maintenance, etc.

Conclusions Automated hazard identification –continuous operation commercial tool that can reduce the time of HAZOP –batch operation promising area of research and development for identifying problems associated with human errors and operating procedures Benefits: –Doing HAZOP earlier, and on modifications. –Consistent, repeatable, complete hazard identification method.

Acknowledgements The work described in this presentation is being funded by –HAZID Technologies Ltd –Engineering and Physical Sciences Research Council, UK Thanks are also due to my colleagues –Dr Steve McCoy –Mr Dingfeng Zhou