The QRAQ Project Volume 26 Systematic AL PDF [PDF]

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Taylor Safety Engineering

The QRAQ Project Volume 26 Systematic ALARP Analysis Version 1 Issue 2 January 2017

J.R.Taylor

QRAQ 24 Systematic ALARP Analysis

© J.R.Taylor 2014

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QRAQ 24 Systematic ALARP Analysis

The QRAQ project Quality of Risk Assessment for Process Plant Lessons Learned Analysis ITSA Prunusvej 39, 3450 Allerød, Denmark Issue Date V1I1 Feb 2014 V1I2 Jan 2017

© J.R.Taylor 2014

Author JRT JRT

Approval

Release

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QRAQ 24 Systematic ALARP Analysis

QRAQ publications 1. The QRAQ Project – Introduction 2. Quality and completeness of hazard identification 3. Consequence calculation models 4. Risk assessment frequency data 5. Risk analysis methodologies 6. Risk acceptance criteria 7. Ignition frequency 8. Jet fire models 9. Fire water monitors as a risk reduction measure 10. Boilover and fire induced tank explosion 11. Self evacuation as a risk reduction measure 12. Major hazards scenarios - Model validation against actual accidents 13. In preparation 14. Gas impoundment 15. Domino effects and escalation 16. Momentum jets 17. Fire and Gas Detection Mapping 18. Marine risk 19. Hydrogen Sulphide Release Modelling and Incidents 20. Human error in process plant operations and maintenance 21. SIL assessment using LOPA 22. Assessment of simultaneous operations 23. In preparation 24. Systematic ALARP Analysis 25. Safety Barrier and Bow Tie Diagrams 26. Lessons Learned Analysis 27. Closing the Gaps in Risk Analysis 28. Plant layout risk analysis 29. QRA for instrumented safety systems 30. Emergency Planning for Oil and Gas Installations 31. Cost benefit assessment of Risk Analysis 32. A catalogue of failure modes

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QRAQ 24 Systematic ALARP Analysis

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QRAQ 24 Systematic ALARP Analysis Preface This report is the 24th in the series of reports covering various aspects of the quality of process risk assessment studies. ALARP assessment and ALARP demonstration have become an important part of process plant risk assessment, but the analyses performed vary greatly in quality. This report is based on results for about 30 such analyses for major process plant, and is intended to provide a reproducible approach to such assessments J.R.Taylor Abu Dhabi 2014

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QRAQ 24 Systematic ALARP Analysis

Updating history

Issue

Date

Initial version

Dec 2012

Issue 2

Jan 2017

© J.R.Taylor 2014

Affected

Change Initial release

Table 3.1

Improved data for costing

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QRAQ 24 Systematic ALARP Analysis

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QRAQ 24 Systematic ALARP Analysis Contents 1. 2.

Introduction ........................................................................................................................1 Examples ............................................................................................................................3 2.1 An oil/gas separation unit jet fire induced vessel explosion – back-fitting mitigation measures .................................................................................................................................3 2.2 Example - Gasoline pipeline jet fire accident prevention ...........................................6 2.3 Lessons from the examples .........................................................................................8 3. Systematic ALARP Analysis..............................................................................................9

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QRAQ 24 Systematic ALARP Analysis

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QRAQ 24 Systematic ALARP Analysis

1. Introduction ALARP assessment and ALARP demonstration have become an important part of process plant risk assessment, but the analyses performed vary greatly in quality. This report is based on results for about 30 such analyses for major process plant, and is intended to provide a reproducible approach to such assessments. Risk levels are now routinely assessed according to risk criteria such as those given in R2P2 or ADNOC COP V5-06. Quantitative ALARP analysis is carried out as follows: 1. Hazard scenarios giving risk in the Medium zone, between acceptable and unacceptable are identified, on an area by area basis. 2. All credible risk reduction measures are identified for each of the hazards identified in step 1. The criterion for selection of measures at this stage is that they are recommended in industry guidelines. 3. Where a measure is already incorporated into the design, this is noted and no further analysis is performed for this measure, except that it is taken into account in the risk assessment. 4. New measures are selected from a systematic check list, which is intended to cover all loss prevention measures currently available and with demonstrated efficacy 5. The practicality of each new measure is measured. Measures may be impractical for example due to: a. Having no risk reduction effect in the actual case b. Be unreliable in the actual environment c. There being insufficient spaces, or difficulties of placement in the actual plant (applies for plant already constructed, although cost benefit analysis may be required taking into account backfitting engineering costs and loss of production while modifications are made) d. Interference with operations or operational safety e. Possible hazards arising from the risk reduction measures itself (e.g. steam curtains) f. Other reasons 6. For the measures considered practical in an engineering sense, the following are calculated: a. The probabilities of loss of life (PLL) for the hazards of concern (i.e. the ones for which risk is reduced by the measure) prior to risk reduction. b. The asset risk prior to risk reduction c. The environmental risk prior to risk reduction d. The consequence reduction factor for each measure for human life, asset and environmental ( a factor of 1.0 indicates no risk reduction)

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QRAQ 24 Systematic ALARP Analysis e. The frequency reduction factor for each measure for human life, asset and environmental f. The residual risk for human life, asset and environment once the measures are implemented. g. The maximum justifiable investment (MJS) for the risk reduction measure, calculated as the reduction in annual loss multiplied by number of years over which the investment in risk reduction is capitalized. For statistical loss of life, the valuations specified in standards and guidelines are used h. The cost of each risk reduction measure is estimated. (This can be done using generic costing data () or using data developed for design costing. i. The implied cost of averting a fatality (ICAF) is calculated. j. Values of ICAF which are above the guideline levels are considered disproportionate.

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QRAQ 24 Systematic ALARP Analysis

2. Examples The following examples are based on actual cases from oil and gas industry applications.

2.1 An oil/gas separation unit jet fire induced vessel explosion – back-fitting mitigation measures The first example considered is for a separator unit in which gas is taken from a crude oil and gas mixture. The risk reduction potential for this project is restricted by the fact that the units are mainly gas separation and compression facilities handing hydrocarbon gas. If a release of gas occurs through a large hole, a fairly large inventory will be released, irrespective of any shutdown etc. Also in case of large or full bore releases, the release will be very rapid, forming fully developed gas jets in a few seconds. Shutdown by ESD will have little effect on human risk in the immediate area, since ESD takes about 2 minutes for detection, reaction and closure. Most lethal effects occur in a shorter period than this. However if ESD valve close, the pressure in the separator vessels will begin to drop as soon as closure is achieved. For this example, pressure has been calculated to drop by half in under 4 minutes due to discharge through the release hole. This is sufficiently fast to prevent excessive jet fire heating of neighbouring vessels, Long period releases from small and medium size holes can be subject to risk reduction by: 1. Detecting the gas release or fire 2. Shutting down and depressurising 3. Setting up a cordon excluding all persons, vehicles etc. which could serve as an ignition source 4. Possibly, using water spray from fire water monitors to help suppress release and to lower the potential for ignition (Fire water monitors have little effectiveness in suppressing H2S). 5. Self evacuation and the use of personal escape masks can significantly reduce risk for those employees not immediately affected by very high concentrations. The estimated success rate in the case where all carry full face masks, or escape masks and goggles, is conservatively set to 95% (Ref 13: Self Evacuation as a risk reduction measure, QRAQ report): The processing facility is designed in order to minimize the likelihood of buildings being subjected to flammable gas cloud in case of a gas release in the processing area. Operator amenity rooms and substation are pressurized and gas tight buildings to minimize ingress of gas in the building. As per dispersion modelling results, these buildings are not expected to be subjected to flammable gas concentrations even in case of large releases in the plant.

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QRAQ 24 Systematic ALARP Analysis As the plant is relative open and uncongested, high explosion overpressures are not expected to be generated. The amenity room and substation building are designed as blast resilient buildings. 2.1.1 Risk reduction measures for jet fire induced vessel explosion A range of risk reduction measures were considered for this scenario. Some of these may be implemented in the design. Maximum Justifiable Investment (MJI) for assets and personnel is calculated. The expected value of risk reduction in value of risk per year for personnel is calculated: MJIhuman

1 × 10-3 × 0.5 × $ 107 ×8 ×3 $120,000

=

=

Per year, frequency of release 50% risk reduction Maximum ICAF value Amortisation period selected by policy Persons

Here, the maximum reasonable ICAF value of $10 million is used. 50% risk reduction is calculated, and accounts for the fact that some fatalities occur immediately in the case of accidents, and are not therefore subject to risk reduction Jet fire damage is the largest contribution for asset risk. MJI for business interruption risk is significant and is calculated as: MJIBI

=

2×10-3 × 0.2 ×1 ×8 × 500,000,000

=

Frequency per year from LSAR map Approximate probability of damage (impingement probability) Year, expected downtime Amortisation period selected by policy $ Value of Production Per Year

Approx. US $ 1,600,000

Based on the MJS the following risk reduction measures are discussed. 2.1.2 Prevention of Jet fire induced explosion Jet fire is one of the most probable causes of serious accident consequences in a oil/gas separation plant. The possibilities exist for jet fires to impinge on other vessels and cause these to rupture. The active fire protection systems which may be installed:

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QRAQ 24 Systematic ALARP Analysis • • • •

Firewater system with deluge spray system Fire hydrants and monitors Inert gas extinguishing system for protection of operator rooms, local substations Portable firefighting equipment and emergency response personel.

The time taken for a jet fire to cause vessel rupture is calculated as 4 to 10 minutes. If operators in the area are not killed or seriously injured there is ample time for the operator to evacuate to a safe distance provided that he is trained to do so. The fact that the operator can evacuate when there is a possibility of fire induced explosion means that there is no human risk benefit from the protection measure. The cost of providing fire water monitors for the installation is estimated to be $10,000 per separator vessel, that is $40,000 It is concluded that fire water monitor provision for the separators is cost beneficial. This should be sufficient to conclude that no further protection is necessary, provided that the fixed fire water monitors can be put into operation and aimed within about 4 minutes (Ref 14: Birk). 2.1.3 Pre-aiming of fire water monitors Pre-aiming of fire water monitor is a zero cost measure. It is therefore recommended that fire water monitors should be pre aimed. The angle of attack for the fire monitor streams should be checked to ensure that the line of attack is not obstructed. Emergency plans emphasizing the need for rapid response are also recommended. 2.1.4 Provision of deluge system A deluge system is often fitted to separators. However a deluge system is unable to provide complete protection against jet fire (the jet fire blows the water away). However it has been shown in experiments that a deluge system can increase the time for fire induced rupture to occur. This would allow more time for fire response and for depressurisation. The value of the deluge system is therefore only realised if there is also a good firefighting service, an ability to fight jet fires despite high heat radiation, which requires powerful portable fire water monitors, or if there is a good depressurisation system with pressure reduction to a low level within 10 minutes. 2.1.5 Rapid depressurisation For the actual case, rapid depressurisation was found to be not ALARP, since it would require a very large increase in flare and flare piping size, costing several million dollars. Worse, back fitting would require shutdown for the unit for some tens of days, resulting in a very large business interruption cost. 2.1.6 Firefighting Provision of rapid response firefighting was found to be practical, but would require a fire tender with a large water capacity and a large mounted fire water monitor. The cost of this was found to be $2.2 million, and therefore not justifiable on an ALARP basis. However the

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QRAQ 24 Systematic ALARP Analysis investment could be determined to be beneficial if it could reduce risk in a wider range of scenarios. This requires a plant wide analysis.

2.2 Example - Gasoline pipeline jet fire accident prevention A gasoline pipeline is to run close to a construction large worker construction camp, with about 5000 workers living in container type caravans. The accident frequency level for the worker group is calculated by standard QRA techniques to be about 5*10-5 per year, for a number of fatalities calculated to be about 800 using standard QRA techniques, based on simple affected area and assuming a uniform distribution of persons at the construction camp. A more realistic estimate is about 200 persons, taking self-evacuation into account, based on incident records. In either case, the risk levels are considered to be unacceptable, based on national risk criteria. The risk is to be reduced. The baseline ICAF value is calculated to be ICAFbaseline

= 800 ×5×10-5 × $10,000,000 × 8 = $ 3,200,000

Where 8 is the amortisation factor to convert loss per year into a capitalised value. It corresponds to a yearly return on investment of about 10%. Note that the construction camp is semi-permanent. The possible risk reduction methods studied are: • • • •

Provision of a leak detection and automatic shutdown system for the gasoline pumps Provision of a larger corrosion allowance for the pipeline Fencing of the pipeline right of way to reduce the probability of third party interference Provision of a fire wall or a berm between the pipeline and the construction camp

2.2.1 Automatic shutdown system The automatic shutdown system can be implemented very simply in an ordinary DCS or a safety computer. A simple temperature compensated mass balance detection system is sufficient for the purpose, since small leaks are not a large threat to the construction camp. The cost involved may be for an additional safety computer, two mass flow meters, and temperature sensors, with a total cost of about $40,000. (This assumes that the DCS communications system will be used to transmit the signals). This cost would certainly be justified, provided that the safety measure is effective. The response time of the safety system depends on the time for the pressure wave due to the pipe leak to reach the end of the pipeline (For the present case about 50 seconds) and the time for the pump to run down in speed and stop, about 90 seconds in this case. The response time could be shortened by fitting an ESD valve at the pump discharge, together with a minimum flow bypass valve back to the gasoline storage tank. The response time for ESD is estimated to be about 30 seconds in all.

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QRAQ 24 Systematic ALARP Analysis With an overall response time of about 2 minutes there is a possibility of significant fuel loss, and of a fire affecting part of the construction camp, but the possibility of a large flow through the camp is eliminated. The extent of the fire could be calculated by calculating the spread of a running pool. This requires more advanced modelling than is typical for QRA, but is quite feasible. The implementation described above could be made to satisfy a SIL 1 requirement, i.e. capable of reducing risk by a factor of 10. The risk reduction is far larger than the cost, and the residual average loss is reduced to $320,000. It would be possible to improve the reliability of the shutdown system to SIL2 level, by duplicating the instruments, or using SIL2 rated types, and providing a SIL2 rated communication. The cost of this is estimated to be much less than the residual average loss. Improvement of the reliability to a 2oo3 system might be preferred anyway, in order to reduce the probability of unwanted pipeline shyutdowns. 2.2.2 Provision of piping with a higher corrosion allowance One approach to prevention of release is to increase pipe thickness, by selecting a higher pipe schedule. Increasing the schedule from 40 to 80 for example, reduces the failure rate due to corrosion by a factor of about 12 (see QRAQ report 27), at a cost of about $30000 for one kilometre of pipe. This measure reduces risk only for corrosion related failures however, typically about 30 to 40% of the total failures. The cost is nevertheless significantly less than the benefit in risk reduction. AN INCREASED CORROSION ALLOWANCE WILL ONLY REDUCE RISK IF THE INSPECTION INTERVAL IS KEPT LOW. IF THE IMPROVED CORROSION RESISTANCE IS USED AS A REASON FOR REDUCING INSPECTION INTERVAL, THEN THERE WILL BE LESS OR NO RISK REDUCTION. 2.2.3 Provision of right of way fencing Provision of fencing for the right of way is feasible in the desert environment considered, and may be feasible for new pipelines in most places, with sufficient planning. For the half kilometer of pipeline concerned here, fencing is straightforward. The cost is about $50,000. This measure reduces the likelihood of third party interference with pipelines to nearly nothing, but interference by the company’s own contractors when installing other pipes is still possible. This measure reduces risk only for Third party interference related failures however, typically about 45% of the total failures. The cost is nevertheless significantly less than the benefit in risk reduction.

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QRAQ 24 Systematic ALARP Analysis 2.2.4 Provision of a berm protecting the camp from the pipeline A 3 m. high berm can be constructed at the actual cost at the location of about $100,000 (The price varies widely from location to location, depending on availability of materials and transport cost). Ideally, the risk reduction is 100%. The jet fire risk is reduced effectively to zero. This though requires CFD modelling to confirm. There is a possibility of mist and vapour from the release drifting over the berm, and then igniting, causing an explosion. This illustrates that a full range of scenarios needs to be considered when evaluating risk reduction measures. 2.2.5 Overall assessment for the scenario Overall, the provision of the berm provides inherent safety for the scenario. Automated shutdown though is preferred, because it reduces the explosion risk, as well as the jet fire risk. The increased pipeline schedule and fencing options may be preferred by the company because they also reduce business interruption risk as well as human risk. However, a much larger project is involved in this case, because it would probably make sense for the entire pipeline, not just for the section threatening the construction camp.

2.3 Lessons from the examples One of the lessons from the example is that ALARP analysis requires expertise in detailed scenario consequence analysis and loss prevention engineering, and in cost estimating. Standard cost estimating tables may be used for some solutions, but for others, local costs need to be taken into account. A second lesson is that scenario by scenario analysis alone may not produce a result which is ALARP. Some measures will be able to reduce risk for several scenarios. If such measures are considered, a plant wide analysis may be required. A third lesson is that ALARP assessment may require considerable effort, with careful assessment of all safety measures. A QRA is needed as a basis, but most regulatory QRA’s (COMAH type) will not be adequate for the detailed assessments. For example, impingement probabilities for jet fires, engulfment probabilities for pool fires, and smoke obscuration calculation for evacuation etc. are needed (see QRAQ 27 Living Risk Analysis). In example 2, a CFD calculation was needed to validate effectiveness for the berm. Overall, there is a considerable amount of work required in true cost benefit analysis. It will be noted that for each measure, there were several aspects to be taken into account in assessing the practicality, not just the hypothetical cost and benefit. Practicality and overall pros and cons need to be considered.

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QRAQ 24 Systematic ALARP Analysis

3. Systematic ALARP Analysis One of the main problems with carrying out ALARP assessment has been that the persons able to make the risk assessment are only rarely experienced loss prevention engineers, and even loss prevention engineers are rarely experienced in accident prevention and equipment integrity assessment. Risk reduction requires a multi-disciplinary effort. ALARP workshops have only recently been introduced, and are difficult because the calculations needed take too long to be usable in a workshop, using conventional risk assessment approaches. The workshops can provide risk reduction proposals, which can later be evaluated. One of the biggest problems with ALARP assessment at present is that it is not repeatable. If two teams or two consultants are assigned to make the assessment they will generally arrive at very different suggestions. A further problem is the underlying model in process plant QRA, which assumes that any accident results from a release, and that the release occurs at a random point in time, independent of the presence of persons. This ignores the fact that about 30% of accidents are caused by latent failures and latent design errors, and that these are often triggered by persons. It also ignores the fact that about 20% of accidents are caused by human error in the field. This problem will be addressed in a separate report. The approach taken here to ensure reproducibility of ALARP assessments is to provide an exhaustive list of risk reduction measures, along with: • • • • • •

Description of the applicability of the measures, according to scenario, equipment type and process fluid. Description of the features which can make the measures impractical. Description of limitations of the measures. Description of the way in which risk is reduced Approach to calculation of the risk reduction. Guidance on calculation of the cost

In use, the scenarios are identified and the measures which can be used to reduce risk are selected from the check list. The check list can be applied by an individual analyst, or can be used as an aid in an ALARP workshop. The check list is based on the risk reduction and ALARP assessment sections of 85 QRAs and safety cases, covering a wide range of plant types.

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QRAQ 24 Systematic ALARP Analysis

S.No.

1

Risk Reduction Measures

Layout spacing between equipments

2

Layout spacing between units

3

Layout spacing to CR, workshops, offices, dwellings

Equipment Applicability

All types with flammable content

All types with flammable content

All types

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Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

JI Calculation

Cost calculation

Reference

All flammables

Has little impact on human risk, except perhaps by reducing the possibility of domino effects.

Will have some impact in reducing domino effects. Generally considered to have little impact because practical distances correspond to small releases only. See reference

Depends on availability of land/space. Otherwise easily applied.

Effectiveness depends on the range of jet fire, pool fire and explosions versus spacing distances

Full QRA with different layouts or sensitivity study for a range of items.

Site land value and additional piping

QRAQ 28

All flammables

Reduces risk to personnel in neighbouring units or trains to a limited extent. Practical distances have limited effe

Will have some impact in reducing domino effects. For effectiveness reference

Depends on availability of land/space. Otherwise easily applied.

Effectiveness depends on the range of jet fire, pool fire and explosions versus spacing distances

Full QRA with different layouts or sensitivity study for a range of items.

Site land value

QRAQ 28

All hazardous materials

This can in some cases completely eliminate risk, in otheres eliminates risk due to mall and medium releases

Depends on availability of land/space. Otherwise easily applied.

Effectiveness depends on the range of toxic plumes, jet fire, pool fire and explosions versus spacing distances

Full QRA with different locations of human groups is simplest.

Site land value may be an issue, often a no cost issue for green field sites.

QRAQ 28

Hazard applicability

Applicability Human Risk

1

QRAQ 24 Systematic ALARP Analysis S.No.

4

Risk Reduction Measures

Battery Limit ESD valves

Equipment Applicability

All equipment

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Hazard applicability

Applicability Human Risk

All hazardous fluids

Can limit the duration of a release. The inventory may be small enough to reduce gas plume volumes and release time and therefore toxic gas exposure time. Calculation is needed for exposure time versus escape time. In most cases the inventory will be too large to have much impact on human risk, because self evavuation typically take less than 2 minutes whereas even after ESD closure, releases will generally last longer than this.

Applicability for Assets and Business Interruption

Limits the duration of releases, and the pressure once the ESD valves are closed. This may be shorter than the jet fire damage time, in which case, jet fire risk will be reduced. Limits the amount of liquid release and therefore pool size.

Practicality Assessment

Battery limit ESD's will usually be practical

2

Effectiveness

Effectiveness of ESD depends on purpose. Seldom effective in reducing human risk from fire, unless trapped inventory is very small. Effective for human risk from toxics if inventory is limited, check the pressure fall over the person escape time. Effective in supporting fire fighters to prevent escalation

JI Calculation

Cost calculation

Reference

Full QRA with different layouts or sensitivity study for a range of items. QRA Pro calculates for bote ESD and no ESC

Cost of valve, installation and cabling. Small (2inch) valves about $400, 16 inc $8000, 46 inch $2.5 m!

QRAQ 29

QRAQ 24 Systematic ALARP Analysis S.No.

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Risk Reduction Measures

Inventory isolation ESD valves

Pipeline sectioning ESD

Equipment Applicability

Storage vessels, tanks, columns

Pipelines

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Hazard applicability

All hazardous fluids

All hazardous fluids

Applicability Human Risk

Can limit the duration of a release. The inventory may be small enough to reduce gas plume volumes and release time and therefore toxic gas exposure time. Calculation is needed for exposure time versus escape time. Since most releases are from piping reduces the frequency of large releases, since most releases will be limited to piping inventory.

Rarely has an impact on human risk, because ESD times and inter valve inventory self relief or drain down times are much longer than self evacuation times.

Applicability for Assets and Business Interruption Limits the duration of releases, and the pressure once the ESD valves are closed. This may be shorter than the jet fire damage time, in which case, jet fire risk will be reduced. Limits the amount of liquid release and therefore pool size. Generally more effective than just battery limit ESD. When fitted at vessel outlets, reduces the initial amount prior to valve closure plus piping inventory, and large inventory release frequency to vesse failure frequency.

Reduces the inventory released from pipeline failures to that from the ESD shutdown time and section inventory. In this way, reduces the extent of consequences for liquid releases, and the duration for all releases.

Practicality Assessment

Practical if there is sufficient space to insert the valve. Sometimes you can achieve a good solution by replacing a block valve with an ESD valve, or even by placing an actuator on an existing block valve.

Pipeline sectioning ESD's are almost always practical for single phase pipelines. The can cause hammer problems for multiphase pipelines.

3

Effectiveness

Effectiveness of inventory isolation ESD is twofold - Limits amount of release to piping inventory plus release while ESD valves closing. - Limits large inventory relese frequency to the failure rate for the vessel. Effectiveness calculation requires both ESD and No ESD calculatio n to be calculated

It is necessary to calculate the trade off between reduced release inventory, versus the increase frequency of release from flanges

JI Calculation

Cost calculation

Reference

Compare limited release QRA with full inventory release QRA (In QRA Pro select ESD an No ESD calculations can compare results

Cost of valve, installation and cabling. Small (2inch) valves about $400, 16 inc $8000, 46 inch $2.5 m!

QRAQ 29

Compare limited release QRA with full inventory release QRA (In QRA Pro select ESD an No ESD calculations can compare results

Cost of valve, installation and cabling. Small (2inch) valves about $400, 16 inc $8000, 46 inch $2.5 m!

QRAQ 29

QRAQ 24 Systematic ALARP Analysis S.No.

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Risk Reduction Measures

Blow Down

Flare system

Equipment Applicability

All pressurised process

All process and pipelines with flammable gas

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Hazard applicability

All gases

Flammable gas, in some cases ground flare for flammable liquids

Applicability Human Risk

No impact on human risk from initial accident, may reduce the likelihood or extent of escalation risk (see asset column)

No real impact on human safety, (except in cases where vents are used as an alternative, and the vents are a threat to human life or welfare).

Applicability for Assets and Business Interruption

Practicality Assessment

Reduces pressures over a 15 to 30 minute period, and can reduce the probability of escalation damage. For unignited releases, reduces the period for which potential for ignition exists.

Nearly always practical in main process plant. Can be problematic on small platforms because of the limitations on knock out capacity Due to long blowdown times the main value is in shortening fire fighting duration.

Allows blowdown and pressure relief of flammable material to proceed safely i.e is a necessary part of blowdown and relief.

Usually a necessary requirement. Costly in land. Reliability and liquid entry calculations needed.

4

Effectiveness

JI Calculation

Cost calculation

Calculate the difference in release rates for the blowdown versus no blowdown cases.

Calculate dynamic QRA, with blowdown option selected

Cost of blw down valves and flare. Blowdown is usually needed for maintenance though so usually no cost. Added capacity for rapid blow down is very expensive typically >$10 m.

Completely effective for overpressure protection within its capacity. Capacity may be for full fire engulfment, staggered relief, or may be very high for hex tube rupture

Not needed for full capacity. Determine probability of extended vessel engulfment for staggered relief

Cost of land plus flare system

Reference

QRAQ 24 Systematic ALARP Analysis S.No.

9

10

11

Risk Reduction Measures

Equipment Applicability

Flammable material drainage

All process and storage with flammable liquid

Drain fire seals

All process and storage with flammable liquid

Fire Detection

All process and storage

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Hazard applicability

Flammable liquids

Flammable liquids

Flammable fluids

Applicability for Assets and Business Interruption

Practicality Assessment

No effect on human risk except via limitation of domino effects

Reduces the possibility of flame spread and the probability of BLEVE or FIVE due to fire engulfment (pool fires)

Rarely any effect on human risk, except possibly from unexpected escalation.

Reduces the possibility of flame spread between fire zones, and therefore escalation potential.

Applicability Human Risk

Can provide good alarm for persons who cannot see the fire, improves self evacuation probability.

Provides ability to activate ESD and deluge if these are not automatic, call out emergency personnel.

Effectiveness

JI Calculation

Cost calculation

Reference

Generally a requirement.for new plants. High capacity non blocking types needed if there is a flammable oil or solvent scenario. Extremely difficult to back fit.

Capacity needs to be matched to fire water demand for largest fires.

Cost of escalation, domino effect calculation for pool fire only. (In Riskmap, input pool fires onle then do pool fire calculationn.

Civil engineering calculations

Process Safety Engineering Handbook.

Generally practical

Eliminates an escalation hazard which has caused may sever accidents. Need to be kept clear. Not practical in sanding conditions.

As above

Civil engineering calculations

Process Safety Engineering Handbook.

Effectiveness depends on coverage calculation

Comparative QRA with and without evacuation, fire fighting response. Fire and gas mapping for probability determination

Flame Detector: 3812 USD

QRAQ 17 Fire and Gas mapping

Always practical

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QRAQ 24 Systematic ALARP Analysis S.No.

12

13

14

Risk Reduction Measures

Melting plugs

Melting links

Linear fire detectors (twin wire with melting insulaion)

Equipment Applicability

Especially at pumps, sometimes at skids

Especially at pumps, sometimes at skids

Tank rim seals, above small tanks, kettle reactors, contactors etc

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Hazard applicability

Flammable fluids, most effective for liquids

Applicability Human Risk

Very little impact, because if the fire is big enough to melt the plug it is big enough to see.

Flammable fluids, most effective for liquids

Very little impact, because if the fire is big enough to melt the plug it is big enough to see.

Flammable fluids, most effective for liquids

Very little impact, because if the fire is big enough to melt the detectors it is big enough to see. Effective in unmanned areas esp. at pumps.. Effective in floating roof tanks but has reliability systems

Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

Good supplement to UV/IR or IR3 alarms where visibility is obscured

Quite practical, although tubing is a nuisance during maintenance

Quite effective when located at the most likely release points, not subject to obstruction, not subject to obstruction shadowing like optical detectors. Plugs need replacing at about 10 year intervals

Good supplement to UV/IR or IR3 alarms where visibility is obscured

Low reliability due to damage and bypassing when maintenance is carried out

Quite effective when located over the most likely release points, not subject to obstruction , not subject to obstruction shadowing like optical detectors..

Low reliability due to damage and to bypassing when maintenance is carried out

Quite effective when located over the most likely release points, not subject to obstruction shadowing like optical detectors. Plugs need replacing at about 10 year intervals

Good supplement to UV/IR or IR3 alarms where visibility is obscured

6

JI Calculation

Cost calculation

Reference

QRAQ 24 Systematic ALARP Analysis S.No.

15

16

17

Risk Reduction Measures

Gas Detection

Deluge

Sprinklers

Equipment Applicability

All process and storage

Pressure vessels, tanks, columns. Can be used on critical piping. Transformers

Buildinngs

© J.R.Taylor 2014

Hazard applicability

Flammable and toxic gas, volatile liquids

Applicability Human Risk

Can provide good alarm for persons who cannot see hear or smell the release, improves self evacuation probability.

Applicability for Assets and Business Interruption

Provides ability to activate ESD and deluge if these are not automatic, call out emergency personnel.

Flammable fluids, solids

Can provide protection for escape routes, see below

Provides protection for vessels subject to pool fire engulfment. Provides limited

Flammable fluids, structural fire hazards.

Little direct effect on human risk, but reduces risk by limiting fire spread.

Provide protection for buildings

Practicality Assessment

Effectiveness

JI Calculation

Cost calculation

Reference

Always practical

Effectiveness depends on coverage calculation. Limited number of suppliers for open path toxic gas. H2S can be detected by flammable gas detectors if the concentration is not too high

Compartive QRA with and without evacuation and emergency shutdown

Point Type Gas Detector: 2610 USD Open Path Detector: 9477 USD

QRAQ 17 Fire and Gas mapping

Fully effective against pool fire if well maintaine and there are no dry spots. Some value in delaying BLEVE for the case of jet fires

Comparative QRA with and without pool fires. Also dynamic QRA for jet fires

Generally practical if there is a clean water supple e.g. from a tank. Vulnerable to blockage by contamination when used with sea water, and with rust. Need frequent testing Cannot be used where there is electrinic or electrical equipment, such as control rooms, communications rooms and cable spreading rooms

7

Generally effective if designed correctly,

Process Safety Engineering Handbook.

Process Safety Engineering Handbook.

QRAQ 24 Systematic ALARP Analysis S.No.

18

19

20

Risk Reduction Measures

Equipment Applicability

Applicability Human Risk

A major part of plant asset protection

Usually very practical. Some measurements may be difficult such as level in a stirred reactor.

One of the major protection devices for batch processes, with direct impact on many scenario types

Generally very practical, especially if fail safe. Need to be designed to prevent unautorised bypass.

Prevents injury and fatality due to overpressure explosion

Generally required by regulations for pressure vessels etc. but dimensioning may be flexible. API 521 allows engineer to specify the overpressor cases

Process Trips (Level, temperature and pressure)

All process equipment

Flammable

One of the major aids to avoilding major hazards accidents due to process disturbances. Note that these scenarios are generally not included in regulatory QRA, but are an essential part of a SIL review

Interlocks

All process equipment sequential operation such as start up. Batch production.

All hazardous materials, reactive materials

One of the major protection devices for batch processes, with direct impact on many scenario types

PSV's

All pressurised process equipment, boilers, hudraulics, pneumatics

© J.R.Taylor 2014

Applicability for Assets and Business Interruption

Hazard applicability

All hazardous materials, water in boilers

Prevents injury and fatality due to overpressure explosion

Practicality Assessment

8

Effectiveness

JI Calculation

API 14c level is usually required as a minimum. Extension to additional parametes, SIL 2 or 3 on the basis of SIL review. Calculate by LOPA based SIL review.

Cost calculation

Reference

Process Safety Engineering Handbook.

Process Safety Engineering Handbook. Risk analysis for machinery.

Comparative QRA with and without overpressure explosion

Process Safety Engineering Handbook.

QRAQ 24 Systematic ALARP Analysis S.No.

21

22

23

24

Applicability for Assets and Business Interruption

Risk Reduction Measures

Equipment Applicability

Burst Disk

Batch reactors, reciprocating compressors, heat exchangures with high pressure tubing, cryo tanks, pentane tanks

All hazardous materials

Prevents injury and fatality due to overpressure explosion

Prevents injury and fatality due to overpressure explosion

Generally not used on oil and gas systems because the disk remains open after relieving. Is used though on some heat exchangers because PSV's do not react fast enough for tube rupture cases

Thermal Relief Valves

piping subject to solar heating, heat traced piping, cryogenic piping.

All hazardous liquids (usually not relevant for gases or gas padded liquid).

Eliminates one cause of pipeline rupture, reduces risk probability slightly. This is not usually taken into account in QRA, because causal analysis is not usually made.

Eliminates one cause of pipeline rupture, reduces risk probability slightly. This is not usually taken into account in QRA, because causal analysis is not usually made.

Generally a requirement for vulnerable piping. May introduce new risks of vapour or gas release

Design for maximum pressure

Batch reactors, heat exchangers, continuous reactors, pump discharge piping

All hazardous materials

Eliminates one cause of pipeline rupture, reduces risk probability slightly. This is not usually taken into account in QRA, because causal analysis is not usually made.

Eliminates one cause of pipeline rupture, reduces risk probability slightly. This is not usually taken into account in QRA, because causal analysis is not usually made.

Is practical where accidental pressures are not too high.

Explosion panels

Buildings or vessels handling flammable dust, compressor crank cases.

Flammable dusts, lube oil mist

Eliminates a limited risk for reciprocating compressors and for dust handling plant or plant with a dust generation problem (sugar, flour, coal, peat)

Eliminates a major asset and BI risk for reciprocating compressors and for dust handling plant or plant with a dust generation problem (sugar, flour, coal, peat)

Generally practical but there must be a free area for blast relief fire jet.

© J.R.Taylor 2014

Hazard applicability

Applicability Human Risk

Practicality Assessment

9

Effectiveness

JI Calculation

Cost calculation

Reference

Process Safety Engineering Handbook.

Proper causal analysis based QRA

Process Safety Engineering Handbook.

Inherently safe, 100% effective where feasible

Proper causal analysis based QRA

Process Safety Engineering Handbook. DOD costing manual.

100% effective where feasible and provided they are dimensioned and installed correctly

QRA for runaway reaction Fr, of explosion * 5 * damage cost > cost of quench system

Usually completely effective, reliability high, see ref.

Fr, of explosion * damage cost * 5 > additional cost of quench system

Cost of reactor, possibly building and cost of quench vessel and piping.

Process Safety Engineering Handbook. DOD costing manual.

QRAQ 24 Systematic ALARP Analysis S.No.

25

Risk Reduction Measures

Quench Tanks

26

Quench Injection

27

Snuffing for activated charcoal absorbers with nitrogen

28

Snuffing for sulphur tanks and pits with steam

29

Temporary safe refuge (TSR)

Equipment Applicability

Hazard applicability

Applicability Human Risk

Applicability for Assets and Business Interruption

Practicality Assessment The speed rundown of reactants needs to be faster than the rate of temperature rise (determined from thermal rate rise experiments) The speed rundown of reactants needs to be faster than the rate of temperature rise (determined from thermal rate rise experiments)

Effectiveness

JI Calculation

The solution is fully effective provided that the run down is fast enough and the quench fluid can

QRA for runaway reaction Fr, of explosion * 5 * damage cost > cost of quench system

The solution is fully effective provided that the injection is fast enough and the quench fluid can

QRA for runaway reaction Fr, of explosion * 5 * damage cost > cost of injection system

Applicable to batch reactors with exothermic reactions

Applicable when the reactor overheats or temperature rise too fast

Applicable to batch reactors with exothermic reactions

Applicable when the reactor overheats or temperature rise too fast

Eliminates a risk of reactor explosion and resulting operator injury or fatality

Eliminates a risk of reactor explosion and resulting reactor and installation damage

Applicable when there is a possibility of autoignition in absorber

Eliminates a risk of fire and of possible duct explosion, which may cause injury or fatality

Eliminates a risk of fire and of possible duct explosion. Eliminates a risk of possible building explosion

Readily practical

100% effective if properly designed and there is sufficient nitrogen

Reduces the risk from sulphur fire and resulting sulphur dioxide release

Reduces the risk of damage to the tank or pit.

Readily practical.

Necessary for sulphur pits – frequency of fires is otherwise high

Reduces the human consequences of major hazards accidents.

No impact from TSR as such but good protection for controls if integrated with an instrument and electrical room (IER).

Readily practical. Complete TSR’s are available as commercial modules

Applicable for vent ducting with flammable VOC absorbers Always applicable for liquid sulphur tanks. Not needed for closed sulphur vessels. Applicable where there is a risk of flammable or toxic gas release

© J.R.Taylor 2014

Applicable for vapour cloud explosions, flammable and toxic gas releases

Eliminates a risk of reactor explosion and resulting operator injury or fatality

Eliminates a risk of reactor explosion and resulting reactor and installation damage

10

Cost calculation

Cost of reactor, possibly building and cost of quench vessel and piping.

Cost of reactor, possibly building and cost of quench vessel and piping.

Cost is minimal sensors, a few runs of tubing and connection to nitrogen supply

Reference

Process Safety Engineering Handbook. DOD costing manual.

Process Safety Engineering Handbook. DOD costing manual. Process Safety Engineering Handbook.

Process Safety Engineering Handbook.

QRA and ICAF calculation versus cost

Commercial module prices available

API 752 Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

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31

32

33

34

Risk Reduction Measures

TSR and CR HVAC gas detection and ESD

Equipment Applicability

Eliminates flammable and toxic gas ingress

Hazard applicability

Applicability Human Risk

Applicability for Assets and Business Interruption

Applicable for VCE, and toxic gas

Reduces the number of people at risk from VCE etc, and toxic risk a) because operators can spend standby time in the shelter (permanent safe refuge) and b) provide a safe location for emergency muster

No impact for asset or BI risk from TSR, but good protection of local control if I&E rooms are in the TSR. Prevents damage to control ssystem

TSR Blast Valves

Fitted to TSR if there is an explosion risk

Applicable for VCE

Vent Purging

High velocity air supply or CO2 or nitrogen injection

Applicable to chemical process venting where vapour is flammable

Ducting Fire Shutters

Shutters close rapidly on fire detection in ducts

Applicable for vent ducts with flammable vapour

Vent Ducting blast panels

Explosion rupture discs at intervals to limit pressure rise

© J.R.Taylor 2014

Applicable for vent ducts with flammable vapour

May save lives if explosion indoors is possible, but usually minimal effect

Little impact on human safety

May save lives if explosion indoors is possible, but usually minimal effect

Practicality Assessment

Always practical

Effectiveness

JI Calculation

Cost calculation

Reference

Fully effective except for very highly toxic gases such as MIC

Justification not really needed if TSR and bunkerised control rooms are implemented

About $4000 for dual flammable and dual toxic gas detectors, $500 for HVAC circuit breakers and $800 for good HVAC duct valve

API 752 and Process Safety Engineering Handbook

About $2000 per duct depending on size

API 752 and Process Safety Engineering Handbook

Cost of blanket gas per kg * 5*vapour generation rate (kg/yr)

Process Safety Engineering Handbook

About $1500 per shutter depending on duct size, but many may be needed depending on duct length. See ref. for spacing

Process Safety Engineering Handbook

About $1000 per shutter depending on duct size, but many may be needed depending on duct length. See ref. for spacing

Justification not really needed if TSR and bunkerised control rooms are implemented for explosion risk Fr. of explosion * damage + Fr. of fire * damage > gas supply cost py.

Always practical

Highly effective if dimensioned correctly. Need to have a very rapid response in some cases

Very effective in preventing explosion and resulting damage and fire spread in ducts

Can be difficult to obtain adequate blanket gas supply at some locations

Highly effective if dimensioned correctly

Very effective in preventing fire spread and run up to explosion in ducts

Spacing of shutters for effective suppression can be difficult

Require explosion detectors and very rapid actuation

( Fr. of explosion * damage) * amortisation factor > shutter cost.

Very effective in preventing explosion and resulting damage and fire spread in ducts

In some cases the appropriate panel size is larger than the duct. In these cases a weak section of duct can be installed

Requires panels speed at less than the explosion pressure run up distance

( Fr. of explosion * damage) * amortisation factor > shutter cost.

11

Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

Risk Reduction Measures

Equipment Applicability

Hazard applicability

Applicability Human Risk

Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

JI Calculation

Cost calculation

Reference

Effective if the wall is strong and high enough, and buildings and protected tanks can tolerate the behind wall blast. Effective also in stopping projectiles

Fr. of design basis explosions * damage cost* amortisation factor > cost of wall

Wall should be 20% wider and higher than the protected item. Wall cost including reinforcement and labour $100 per cubic m.

Process Safety Engineering Handbook

Wall cost including reinforcement and labour $100 per cubic m. Indoor wall 50% more than non protective wall

Process Safety Engineering Handbook

outdoor in a safe location

35

36

37

38

Blast Wall

Fire Wall

Protection of critical installations e,g, CR or toxic fluid tanks

Protection of critical installations e,g, CR or tanks Separation of units to prevent fire propagation

Protection berm

Protection of critical installations e,g, CR or tanks Separation of units to prevent fire propagation

Fixed Fire Water Monitors

Protection of installations by cooling (with water) and by liquid fire suppression

© J.R.Taylor 2014

VCR, BLEVE or reactor explosion

Pressurised flammable fluids

Effective in limiting human consequences

Can have relevance for persons in otherwise CR and OR close to fire sources e.g. in jet fire or flash fire range. Useful also for

Pressurised flammable fluids

Can have relevance for persons in otherwise CR and OR close to fire sources e.g. in jet fire or flash fire range. Useful also for

Flammable liquids and gases

Little impact on human risk for humans except for firemen. Can have relevance for human if used to create a water curtain for toxic gas e.g, ammonia or HF,

Effective in limiting asset damage and BI consequences

Effective in limiting asset damage and BI consequences

Evaluate the pressure and impulse for typical large explosions vs. needed wall thickness and behind wall pressure

Generally applicable. Fire walls require fire doors and fireproof penetration seals

Effective for design basis fires for 30, 60 or 120 minutes depending on spec.

Fr. fire * Pr. Escalation * cost of escalation damage * amortisation factor > cost of wall

Effective in limiting asset damage and BI consequences

Generally practical. Needs frequent inspection to ensure that fire doors are kept closed, or use automatic door closers.

Completely effective for preventing liquid spread and heat radiation protection.

Fr. fire * Pr. Escalation * cost of escalation damage * amortisation factor > berm land valuation

Effective in limiting asset damage and BI consequences

Generally applicable provided that activation can be rapid.

Effective in cooling and suppression provided that they are adequately dimensioned

Fr. of impinging fire * Pr. Escalation * cost of escalation damage *

12

Indoor $15 to $30 pr m2 plus installation Mineral wool $25 per m2 plus $50 for cladding installed Limited cost for berm if excavated soil can be used. Largest part of the cost is the land use. Needed height calculated from heat radiation mapping

Process Safety Engineering Handbook

Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

Risk Reduction Measures

Equipment Applicability

Hazard applicability

(with foam)

39

40

Pre-aimed remotely activated monitors

Oscillating Monitors

Protection of vessels and tanks against escalation due to flame impingement and heat radiation

Protection of Tanks against escalation due to flame impingement

© J.R.Taylor 2014

Applicability Human Risk

Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

Great care is needed when applying water curtains to prevent the water causing more evaporation of liquefied gases e.g. cryogenic ammonia, LPG or LNG

Flammable liquids and gases Jet fires Pool fires

Flammable liquids and cryogenic gases Pool fires

Limited affect – self evacuation is faster than deployment. Can protect CRs

JI Calculation

Cost calculation

Reference

amortisation factor > Fire system cost.

Effective in limiting asset damage and BI consequences

Practical

Limited affect – self evacuation is faster than deployment. Can protect CRs Effective in limiting asset damage and BI consequences

Practical

13

Generally applicable and more effective than manually aimed monitors due to faster activation. . Effective in cooling and suppression provided that they are adequately dimensioned

Effective against radiation and to some extent against flame impingement. Care needed to ensure reliability

Generally there is no doubt that a system will be installed, the only question is its design basis and capacity, where risk optimisation is possible Fr. of impinging fire * Pr. Escalation * cost of escalation damage * amortisation factor > Fire system cost.

Fr. of impinging fire * Pr. Escalation * cost of escalation damage * amortisation factor > Fire system cost.

Process Safety Engineering Handbook

Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

41

42

43

44

Risk Reduction Measures

Equipment Applicability

Remotely aimed monitors

Protection of vessels and tanks against escalation due to flame impingement and heat radiation

Deluge

Protection of vessels and tanks by cooling against escalation due to flame impingement and heat radiation

Hazard applicability

Flammable liquids and gases Jet fires Pool fires

Applicability Human Risk

Limited affect – self evacuation is faster than deployment. Can protect CRs Little impact on human risk for humans except for firemen. Can be used as a water curtain as described above

Applicability for Assets and Business Interruption

Effective in limiting asset damage and BI consequences

Flammable liquids and gases Jet fires Pool fires

Limited affect – self evacuation is faster than deployment. Can protect CRs Little impact on human risk for humans except for firemen.

Foam deluge

Protection of vessels and tanks by cooling against escalation due to flame impingement and heat radiation

Flammable liquids and gases Jet fires Pool fires

Limited affect – self evacuation is faster than deployment. Can protect CRs Little impact on human risk for humans except for firemen.

Effective in limiting asset damage and BI consequences

Foam pourers

Floating roof tank fires, esp rim seal fires.

Crude oil and refined products

Virtually no effect on human risk except indirectly by reducing the probability of boilover

Effective in limiting asset damage and BI consequences

© J.R.Taylor 2014

Effective in limiting asset damage and BI consequences

Practicality Assessment

Practical

Practical

Effectiveness

Generally applicable and more effective than manually aimed monitors due to ability to activate and aim when heat radiation field is intense. . Effective in cooling and suppression provided that they are adequately dimensioned and maintained

Not fully effective against jet fires but do delay escalation

Practical

Very effective but requires care in refreshing foam solution. Dry types have a slow activation time, prefilled types are fast.

Practical

Effective against rim fires. Ineffective against full surface fires in large tanks

14

JI Calculation

Fr. of impinging fire * Pr. Escalation * cost of escalation damage * amortisation factor > Fire system cost.

Fr. of impinging fire * Pr. Escalation * cost of escalation damage * amortisation factor > Fire system cost.

Cost calculation

Reference Process Safety Engineering Handbook

Process Safety Engineering Handbook

Process Safety Engineering Handbook

Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis Applicability for Assets and Business Interruption

S.No.

Risk Reduction Measures

Equipment Applicability

46

Water curtains for heat radiation

All process equipment and process plant buildings

47

Water curtains for gas diversion

Specific hazards such as HF, flammable vapour dispersing towards fired heaters etc.

Flammable and some toxic gas releases

Effective against flammable and toxic gas ingress to an area

Effective against heat radiation and flammable gas ingress to an area

Requires very fast activation of large quantities of water

48

Water curtains for gas absorption

Specific hazards such as HF, ammonia

HF, ammonia

Effective against heat radiation and flammable and toxic gas ingress to an area

Effective against toxic gas ingress to an area

Requires very fast activation of large quantities of water

49

Water spray for explosion suppression

Hazard applicability

Pool fires Jet fires

Applicability Human Risk

Effective against heat radiation if activated rapidly

Effective for heat radiation from pool and jet fires

Practicality Assessment Requires large quantities of water, needs careful drainage design

Effectiveness

Effective

Difficult design

Difficult design

Still experimental

50

Explosion suppression

Injection of flame supressing vapour inside vessels and dry powder pneumatic transfer pipes

51

Clean gas, Energen or CO2 fire suppression

Switch rooms control rooms Server rooms

51

In cabinet smoke detection ASD

Switch cabinets Cable terminal cabinets Server cabinets

© J.R.Taylor 2014

Flammable gas and vapour

Effective in preventing confined explosion consequences

Electrical fires

Little impact on human risk, can increase human risk

Electrical fires

Little impact on human risk, can increase human risk

Effective in preventing confined explosion consequences

Effective in preventing electrical fires

Effective in preventing electrical fires

Practical

Practical

Practical

15

JI Calculation

Cost calculation

Reference Process Safety Engineering Handbook Process Safety Engineering Handbook

Process Safety Engineering Handbook Process Safety Engineering Handbook Process Safety Engineering Handbook

Process Safety Engineering Handbook Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

52

53

Risk Reduction Measures

Manual firefighting

Area Classification

54

Tank blanketing

55

Sub-surface foam injection

56

57

58

Emergency Scrubber

Passive fire protection

Fire proofing

Equipment Applicability

Alll

Areas with flammable gas and liquids, flammable dust Fixed roof tanks with volatile flammables. Slop tanks Degassing tanks

Hazard applicability

Liquid fire suppression Equipment cooling

Flammable gas and liquids, flammable dust

Flammable vapour

Applicability Human Risk

Little impact on initial human risk, self evacuation is more effective. Rescue is important

Reduces likelihood of ignition

Protects against tank explosion

Applicability for Assets and Business Interruption

Effective if correctly dimensioned and response is fast enough

Effective

Effective

Practicality Assessment

Effectiveness

JI Calculation

Cost calculation

Reference Process Safety Engineering Handbook

Practical

Effectiveness varies. There will always be fire sizes which cannot be handled. Needs a fairly complex effectiveness calculation

Practical

Effectiveness varies. Needs a calculation of ignition probabilities see QRAQ vol 7

Process Safety Engineering Handbook QRAQ vol 7

Effective if designed correctly

Process Safety Engineering Handbook

Practical

Process Safety Engineering Handbook Toxic gas vents and leak containment enclosures

Vessels, piping

Steel structures

© J.R.Taylor 2014

Toxic gas

Flammable gas or liquid

Flammable gas or liquid

Effective if properly dimensioned

Protects against FITE and BLEVE

Protects against structural collapse

Process Safety Engineering Handbook

Practical

Effective

Effective

Practical

Practical

16

Depends on type and fire type and duration

Process Safety Engineering Handbook Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis S.No.

59

60

Risk Reduction Measures

Flame shielding

Blast Resilience

62

Human occupancy separation

63

Limited human occupancy

65

Flares

Hazard applicability

Applicability Human Risk

Flares

Reduces heat radiation intensity at work areas at the flare site

Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

Self evacuation

Rescue

JI Calculation

Cost calculation

Reference Process Safety Engineering Handbook Process Safety Engineering Handbook

Blast proofing

61

64

Equipment Applicability

Process Safety Engineering Handbook Control room, workshop, offices and operator room locations

Process area

All

All

© J.R.Taylor 2014

All

All

All

All

Effective up to scenario sizes at the design basis

Effectiveness determined by detailed QRA

Zero manning design for operations phase

Requires extensive design consideration, expensive

Possible

Effectiveness determined by detailed QRA including evacuation

Possible

Effectiveness determined by detailed QRA including evacuation

17

QRA Pro Handbook

QRA Pro Handbook

Risk analysis for Process Plant pipelines and Transport Risk analysis for Process Plant pipelines and Transport

QRAQ 24 Systematic ALARP Analysis S.No.

Risk Reduction Measures

66

Temporary gas refuge

67

Blast and fire proof operator rooms

68

69

70

Equipment Applicability

Hazard applicability

Applicability Human Risk

Applicability for Assets and Business Interruption

Practicality Assessment

Effectiveness

Cost calculation

Reference Process Safety Engineering Handbook Process Safety Engineering Handbook Process Safety Engineering Handbook

Personal gas alarm

Escape mask

JI Calculation

Process equipment with toxic gas

Practical

About 95% for positive pressure types

Process Safety Engineering Handbook Process Safety Engineering Handbook

Low ignition probability

71

Bunds

Storage areas

Prevention of liquid spread

72

Impoundment basins

Storage areas

Prevention of gas dispersion

73

Hazardous fluid collecting basins

Storage areas for LPG, LNG

© J.R.Taylor 2014

Pool fire

Effective, but limited applicability

Process Safety Engineering Handbook

Effective

Requires CFD calculations

Limits potential heat radiation area

Limits potential heat radiation area

Practical if there is space

18

Process Safety Engineering Handbook Process Safety Engineering Handbook

QRAQ 24 Systematic ALARP Analysis

© J.R.Taylor 2014

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