PIPELINE QRA SEMINAR
PIPELINE RISK ASSESSMENT
SOFTWARE/TOOLS FOR RISK
ASSESSMENT
SOFTWARE/TOOLS FOR RISK ASSESSMENT
•
Different software/tools for QRA
•
Tools (hand calculations) versus software
•
Tools (hand calculations) – actually manual
development of simplified software (typically Excel)
•
There are software/tools also for qualitative risk
assessment (e.g. linked to different methods –
HAZID/HAZOP)
•
Focus on software/tools for QRA
SOFTWARE/TOOLS FOR QRA
Advantages of tools (hand calculations)
•
Simple (understanding and execution)
•
Flexibility
Disadvantages of tools (hand calculations)
•
Standardization (i.e. do we always calculate in the same way?)
•
Size and presentation (i.e. number of documents/sheets)
SOFTWARE/TOOLS FOR QRA
Advantages of software
•
More advanced (often)
•
Accepted (e.g. could be recommended from authorities)
Disadvantages of software
•
Black-box (often)
•
Non-flexible (e.g. change of parameters)
SOFTWARE FOR QRA
•
Software/tools established by consultant companies,
authorities, companies (e.g. oil and gas industry and
process industry) and software companies
Software:
SAFETI from DNVGL
QRA Open from Taylor Associates ApS
•
Method depending on the situation (e.g. complexity,
stage of project and time)
Shepherd from Shell
Riskcurves from TNO
•
Economical and technological aspects (e.g. costs for
license and knowledge of the software)
•
No single best software/tool to solve all problems
SOFTWARE FOR QRA
•
“Same, same. But different!”
•
Similarities in presentation
•
Differences in way of calculations/models (exact
differences hard to establish, since often “black-box”)
SOFTWARE: SAFETI
•
Software from DNVGL
•
Specialized for onshore process facilities and
petrochemical facilities
•
Used frequently in the oil- and gas industry (e.g. BP,
Total, Maersk and Shell)
•
Connected to the PHAST software
SOFTWARE: SAFETI
•
How does it work?
- Accident scenarios (e.g. PHAST and frequencies)
- Population
- Weather conditions
- Ignition sources
- Quantification of the risk (i.e. individual risk and group
risk)
•
Compare with presented methodology for quantitative
risk assessment
SOFTWARE: SAFETI
Advantages of PHAST
•
Easy to get some quick results from (compared to
others)
•
Interface (i.e. easy to understand and present)
Disadvantages of PHAST
•
Black-box (i.e. what happens in the model and change
of parameters)
TOOLS FOR QRA
•
Tools (and guidelines/standards) established by
consultant companies, organizations, authorities and
companies (e.g. oil and gas industry and process
industry)
•
General difference - two categories of tools:
- Scoring systems (i.e. simple ranking of pipeline segments)
- Traditional QRA (i.e. general methodology)
•
Standalone versus included in larger risk management
framework
Guidelines/standards:
Pipeline systems - Steel pipelines on land Guide to the application of pipeline risk
assessment to proposed developments in the
vicinity of major accident hazard pipelines
containing flammables (BS PD 8010-3:2009)
(part of framework BS PD 8010-1:2004) from
British Standards
Assessing the risks from high pressure natural
gas pipelines (IGEM/TD/2)
from Institution of Gas Engineers and
managers
TOOLS FOR QRA
•
Detailed difference - three categories of tools:
- Generic values for leakages
- Possibility to modify values for leakage to account for
special properties and situation (e.g. corrosion)
- Possibility to modify values for leakage to account for
special properties and situation (e.g. corrosion) as well as
including of external hazards (e.g. 3rd party interference
and similar)
•
What is best? Depending on the situation (e.g.
complexity). Most important to be aware of what is
included and what is not included.
TOOLS FOR QRA
How is a QRA carried out?
EXAMPLE OF QRA
EXAMPLE OF QRA
Ringsted, Denmark
- 30’’ gas pipeline
- 80 bar
- 12 mm
- exposed
- no construction work or agricultural work allowed within 50
meters from the pipeline
- shopping centre (opening hours 08.00-20.00) at 100 meters
- parking lot between shopping centre and pipeline
EXAMPLE OF QRA
•
What could go wrong?
- Internal corrosion (expected problems with impurities)
- External corrosion (noted damages to protection from
installation)
•
As detailed as want (e.g. is the restriction on
construction work followed and possible natural
hazards)
EXAMPLE OF QRA
•
What is the frequency for the different scenarios?
•
Where could we find information?
-
Riser & pipeline release frequencies from International
Association of Oil- and Gas Producers (OGP)
EXAMPLE OF QRA
•
Riser & pipeline release frequencies from International
Association of Oil- and Gas Producers (OGP)
- 8.1 x 10-5 per km-year (12 mm wall thickness)
- 18% are medium holes (75 mm hole)
•
Frequency for specified scenario:
- 1.5 x 10-5 per km-year
•
Just one of several scenarios!
EXAMPLE OF QRA
•
What is the consequence from the different scenarios?
•
Choice: human safety – fatalities
•
What do we need to consider?
- Gas cloud - flash fire (extent and radiation from)
- Jet fire (radiation from)
- Pin hole
- Rupture
- Large hole
EXAMPLE OF QRA
•
As detailed as want (e.g. are there some of the
combinations we can exclude?)
•
What do we need to consider?
- Gas cloud - flash fire (extent and radiation from)
- Jet fire (radiation from) (excluded)
- Pin hole (excluded)
- Rupture
- Large hole
•
Remember – all scenarios quantified (increasing effort)!
EXAMPLE OF QRA
•
What scenario?
- Gas cloud - flash fire (extent)
- Large hole (75 mm)
- LFL and ½ LFL
- All inside a cloud would be fatalities (>37.5 kW/m2)
•
Just one of several scenarios!
EXAMPLE OF QRA
•
Combine the frequency for the scenario and the
consequence for the scenario to get the actual risk
•
What do we know?
- With the frequency 1.5 x 10-5 per year there will be a
release of gas from the pipeline and the cloud will enclose
the parking lot
EXAMPLE OF QRA
•
What do we not know?
- Exposure (e.g. how often are there people in the parking
lot and how many people are there in the paring lot)
- Ignition (i.e. what is the probability of ignition of the gas)
- Weather conditions (e.g. how often wind towards the
parking lot)
EXAMPLE OF QRA
•
What do we not know?
- Exposure – in average 50 persons in the parking lot from
08.00 to 20.00 every day and a parking guard there 5 days
a week between 07.30 and 20.30
- Ignition – 50% probability of ignite the gas due to the
cars at the parking lot and the electrical signs on the
shopping centre
- Weather conditions – 10% probability of wind towards the
parking lot (defined as south) due to prevailing wind east
EXAMPLE OF QRA
•
Combine the frequency for the scenario and the
consequence for the scenario to get the actual risk
(considerations for the parking guard)
- Frequency x ignition x wind x exposure (individual)
- 1.5 x 10-5 x 0.5 x 0.1 x 0.39 per year
-
2.9 x 10-7 per year
EXAMPLE OF QRA
•
What does this mean?
- With the frequency 2.9 x 10-7 per year there will be a
release of gas from the pipeline, the cloud will enclose the
parking lot, the cloud will ignite and the parking guard will
be present (fatality)
- The individual risk (for the parking guard) from this
scenarios is 2.9 x 10-7 per year
•
Just one of several scenarios!
EXAMPLE OF QRA
•
What about the group risk?
- With the frequency 2.9 x 10-7 per year there will be a
release of gas from the pipeline, the cloud will enclose the
parking lot, the cloud will ignite and in average 50 persons
will be present (fatalities)
EXAMPLE OF QRA
•
Is the risk (from this scenario) acceptable?
•
Risk acceptance criteria for individual risk
-
1.0 x 10-6 (Danish legislation) – YES!
•
Risk acceptance criteria for group risk
- (see figure) (Danish legislation) – MAYBE!
- Separate presentation on ALARP
- Most likely not given contribution from other scenarios
EXAMPLE OF QRA
•
QRA is a tool to evaluate and support what in the end
are political decisions whether to proceed with
construction/design (or similar) within questionable,
high-risk and/or consequence areas
•
Could have a high consequence and a high frequency,
but anyway an acceptable risk
EXAMPLE OF QRA
•
Even the smallest QRA has large complexity
•
What has been simplified in this QRA?
- Wind directions (e.g. 4 or 16?)
- Wind speed (i.e. consequences different)
- Ignition probabilities (e.g. models or ignition sources)
- Frequency (i.e. just considered one scenario)
- Consequence (i.e. just considered one scenario)
- Simplified population (e.g. cars on the road and residents)
- Release frequency given per kilometre (e.g. not all releases within
kilometres would give consequences within 1 kilometre)
EXAMPLE OF QRA
How is a QRA carried out?
EXAMPLE OF QRA
•
What is the challenges of quantitative risk assessment?
- Uncertainty (i.e. the risk could be something that has
never happened before)
- Statistic (i.e. availability)
- Assumptions – big effect (e.g. sensitivity analysis)
- Complexity (i.e. how much could/should be included?)
- Ideal model (e.g. would people move from a release?)
32
QUESTIONS?
33