Ricardo Rodrigues. Chemist, Executive Director do ITSEMAP Brazil
Major advances in Brazil’s energy
sector, particularly oil and gas,
have required a series of
investments not only in production
and exploration, but also in the
infrastructure for transporting the
products extracted from the
exploitation fields to the
refineries.
In this context, one would emphasise the
investments made in recovering the country’s
rail network as well as in building pipelines
to transport oil, derivatives, gas and alcohol
– an infrastructure that has been extended
in recent years.
PETROBRAS TRANSPORTE (TRANSPETRO)
alone currently has a network of 7,000 km of
oil pipeline and 4,000 km of gas pipeline, in
addition to 26 river terminals and 20 land
terminals.
In the area of natural gas distribution, Brazil
currently has 26 distribution companies present
in almost all of the country’s states. One
would highlight the presence of multinationals
such as Gas Natural and the Eni Group,
among others.
In addition to the oil and gas area, significant
investments have been made in biodiesel and
ethanol, the latter given that Brazil is a major
alcohol producer and exporter.
There are many pipeline projects and works
underway, generating intense demand for
technical improvement in all stages of development
of these installations, as well as in
aspects related to environmental risk analysis.
Hence, a large number of studies and technical
progress have been made not only by
project developers but also by those responsible
for the risk engineering chain. As a
result advanced technical tools have been
designed for identifying, evaluating and controlling
the risks associated with pipelines
used to transport hazardous products.
The analysis of risks
associated to
projects operating
with hazardous
substances has been
regulated in Brazil
since 1981
In Brazil, the analysis of risks associated with
projects operating with hazardous substances
has been regulated since 1981, both in terms
of occupational health and environmental safety.
In that year, Federal Law no. 6938 came into
force, establishing the National Environment
Policy. Subsequently, in 1986, with the publication
of the Resolution 01/86 of the National
Council for the Environment (CONAMA), risk
analysis reports were included in the process
for obtaining environmental licences.
Therefore, for more than 20 years, all new
projects that affect the environment or that
represent a threat to neighbouring communities,
must submit a Quantitative Risk Analysis
(QRA) to the competent environmental
bodies in order to verify that the levels of
transferred risk are tolerable in comparison
to internationally accepted standards.
QRAs (Quantitative Risk Analyses)
In general, QRAs cover the following aspects:
Figure 1. Example of a Pipeline Route Map
(ITSEMAP Brazil)
- Regional and project description: the purpose of this first stage is to present the
project/process under analysis in outline,
as well as the main environmental characteristics
of its location, populated areas,
environmentally sensitive areas and climate
and meteorological conditions. In the case
of pipelines, since they are linear projects,
it is important for the entire route to be
mapped and for all vulnerable elements to
be identified that could be affected by an
accident, whether by a spill into bodies of
water, fires or explosions or toxic gas emissions
into the atmosphere. Figure 1 is an
example of a pipeline map for the purposes
of a QRA, prepared by ITSEMAP Brazil.
- Characteristics and properties of the substances: all of the hazardous substances
involved in the process under evaluation
must be described. From a general point
of view, the main information to submit is:
- Physical and chemical composition and properties;
- Hazardous nature;
- Fire hazards, fire protection and fire fighting methods;
- Toxicological parameters;
- First aid;
- Actions to be taken in an emergency.
- Accident History Analysis (AHA): the main
purpose of this is to report the frequencies
of defined accidents, the types of scenarios
and likely damage, as well as its causes.
To do this, accident data banks and international
references are consulted such as:
- UKOPA (United Kingdom Onshore Pipeline Operator’s Association, UK);
- DOT/OPS (Department of Transportation, Office of Pipeline Safety, USA),
- CONCAWE (Conservation Of Clean Air, Water and the Environment, BE);
- PARLOC (Pipelines and Risers, Loss of Containment, UK);
- MHIDAS (Major Hazardous Incident Data Service, UKAEA);
- EGIG (European Gas Incident Data Group).
- Identification of scenarios: the purpose of
this stage is to identify the various typical
hypotheses for accidents in the operating
phase of the project under study. In the case
of pipelines, they are normally associated to
lost contention capacity due to major cracks
or the appearance of holes in the pipes. In
order to typify the causes various methodologies
are usually applied, such as: HazOp, FME
or, Checklist’s, among others. At the same time,
for pipeline studies the use of a Preliminary
Hazard Analysis is fairly common (PHA).
- Estimation of frequencies: the annual frequencies
with which each of the accident
scenarios identified in the previous stage
occur must be estimated, taking as reference
the historical records analysed in the
AHA carried out previously. The preparation
of Event Trees, as shown in Figure 2, illustrates
the different accident scenarios (evolutions)
that can arise from the accident
hypotheses, and calculates the frequency
with which they are likely to occur.
- Calculation of consequences and vulnerability
analysis: the different consequences (physical effects) associated to the accident
scenarios under study are calculated using
suitable simulation models that represent
studied phenomena, such as fires, explosions
and the emission of toxic substances.
These effects are appraised in terms of the
vulnerability of the affected areas by means
of PROBIT - type equations (Probabilistic Unit
Method). In general, the considered ranges
of physical effects, for both risk evaluation
and support in developing future emergency
response plans, are:
- Heat radiation: Probits corresponding to
1%, 50% and 99% probability of occurring
and corresponding effects at 3.0 kW/m2.
- Vapour Cloud Fire (Flashfire): Lower Flammability
Limit (LFL).
- Overpressure: Probits corresponding to
1%, 50% and 99% probability of occurring
and corresponding effects at 0.05 bar.
In the case of pipelines used to transport
liquids it is necessary to calculate spilled
volumes prior to carrying out the physical
effect simulations. Depending on the course
and extension of the pipeline under study, this
calculation can be very complex, also taking
into account operational aspects (pump stop
times and intermediate and final valve closing).
Figure 2. Example of a Gas Pipeline Event Tree
All new projects
that affect the
environment or that
represent a threat to
neighbouring
communities, must
submit a
Quantitative Risk
Analysis (QRA)
LeakMAP
In order to cover this need, ITSEMAP has
developed a specific computer application
to carry out these calculations, known as LeakMAP.
In general terms, the LeakMAP Programme
determines the total spilled volume from a
pipeline taking into consideration the sum of
the volume spilled until detection of the leak
and that occurring during the emptying of the
hydraulic column. Thus, these calculations
take the following parameters, among others,
into account:
- Fuel discharge coefficient.
- Pipe burial depth.
- Nominal diameter and thickness of the pipe wall.
- Pressure gauge heights at product inlet and outlet.
- Density and pressure of the vapour of the transported product.
- Hydraulic profile of the pipe.
- Diameter of the leak hole.
- Maximum time estimated for containing the spill.
- Estimated time for detecting the spill.
- Time to cease pumping.
- Time needed to block the valves in order
to isolate the leak point.
As a result, the programme supplies the
initial discharge rate, initial discharge speed,
spill duration and total spill volume.
The LeakMAP
Programme
determines the total
volume leaked from
a pipeline taking
into consideration
the sum of the
volume spilled in
the time until the
leak was detected
and that occurring
during emptying of
the hydraulic
column
- Risk estimation and evaluation: the combination
of frequencies of occurrence with
the studied physical effects provides a
quantification of the risks, which must be
expressed as Individual Risk (IR) and Social
Risk (SR), the latter represented in the form
of a curve F-N (accumulated frequency x
number of potential fatalities).
In order to carry out these complex calculations,
ITSEMAP has developed the QuantoX
tools with a specific complement to analyse
linear risks, such as pipeline routes.
The estimated risk levels must be compared
with the tolerance criteria established by
the Environmental Bodies that authorise
and tax the projects, whose IR criteria (individual
risk of fatality per year) are presented
in Figure 3.
Another important aspect is that for the installation
of additional pipelines on existing routes
where other pipes used to transport hazardous
substances already operate, the total risk of
the affected stretch of land must be estimated.
If the level of accumulated risk is higher than
admissible, an additional stretch of land will
be determined for production where construction
of any type will be prohibited, so as to
guarantee the safety of the people in the vicinity
of the pipeline as shown in Figure 4.
- Mitigating measures and risk management: need to be defined and established in the event
of the risks of the pipeline under study exceeding
the tolerance level according to the criteria
established in the corresponding legal
norms. Their objective is to reduce the risks
and guarantee the necessary level of safety.
Finally, it is worth noting that before a new
pipeline starts functioning, the operator must
have established a Risk Management Programme
(RMP) as a means to guarantee the
safe start-up of the project with all risks
fully under control. In general, the scope of
a RMP extends to:
- Safety information.
- Risk analysis and review policy.
- Management of modifications.
- Maintenance and guarantee of critical systems’ integrity.
- Operating norms and procedures.
- HR training policy for personnel involved in the pipeline’s operation.
- Procedures for investigating incidents.
- Audit programme.
- Emergency plan.
Figure 3. Tolerance Criteria of Individual Risk for Pipelines
(CETESB, 2003)
Figure 4. Individual Risk Criteria for the Non-Buildable Plot
(IBAMA, 2005)
Before a new
pipeline starts
functioning, the
operator must have
established a Risk
Management
Programme (RMP)
Conclusion
Pipeline transport of hazardous substances,
though noticeably reducing the risk in relation
to other ways of transport presents residual
risks with a high potential impact on human
activity and the environment.
With a view to controlling that risk, the competent
authorities for approving and supervising
the operation as well as the operators
themselves have policies and criteria for
determining acceptable risk levels as well
as the necessary technical and management
procedures.
The complexity of risk evaluation methodologies
make the use of specific tools necessary,
many of which ITSEMAP has developed in
order to satisfy its customers’ needs.
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