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How HSE informed on-shore pipeline risk assessment guidelines in Brazil

Onshore Pipelines

The Challenge

Petrobras, Brazil commissioned HSE to help inform the development of on-shore pipeline risk assessment guidance for the Sao Paulo region of Brazil. HSE carried out a survey of international regulators and identified the details of guidance in those countries which use QRA for pipelines. Interviews were also held with experts from HSE, the Netherlands and UK industry standards' working groups. In addition, HSE commented on draft guidance from the Sao Paulo regulator, in light of worldwide practices.

In Brazil, the application of pipeline risk tolerability criteria had been carried out using different approaches by the different local environmental agencies. There was therefore the need for evaluating existing Brazilian risk criteria, as well as understanding existing risk criteria from overseas.

Petrobras contracted HSE Science Division (then the UK Health and Safety Laboratory) to carry out an independent review of worldwide pipeline risk tolerability criteria and the associated risk assessment methodologies for pipelines containing dangerous fluids.

The Solution

Existing international methodologies were researched first. This focused on existing methodologies and criteria for pipeline risk assessment defined by: a) environmental licensing agencies and b) pipeline codes. Information was obtained by a number of methods:

  • A literature search;
  • Visits to the relevant government regulators in the UK and the Netherlands to discuss and obtain information. These were chosen because they have each been using risk assessment to make planning decisions for a considerable time and have well-developed methodologies;
  • A questionnaire which was developed and sent to a number of international government regulators; and
  • Discussion with an expert on the UK pipeline codes PD 8010 Part 3 (2009) and IGEM/TD2 (2009).

Approaches using individual risk (IR) and/or societal risk (SR) were of interest. The questionnaire was also used to inform the discussions with the UK and Netherlands Government regulators. The questionnaire was developed to start with more general questions including the role of the regulator, whether applicable pipeline design codes cover safety, and whether risk is used as a criterion for granting permits for pipelines and/or for land-use planning adjacent to a pipeline. More detailed questions were then asked. These included asking about the risk criteria used, but also included detailed questions about the assumptions in the accompanying risk assessment methodology. It is HSE's experience that consistent assumptions need to be made in the risk assessment, so that the risk criteria lead to consistent decisions about different pipelines. Issues about the risk assessment methodology (to which it was known that the results of a pipeline risk assessment can be very sensitive) included:

  • Pipeline rupture scenarios modelled as pools and jets;
  • Jet direction (for natural gas and LPG pipelines);
  • Methodologies used for explosion consequence modelling;
  • Hole sizes modelled for releases;
  • Crater size and shape (for natural gas pipelines);
  • Harm criteria including Probits;
  • Failure rates;
  • Ignition probabilities;
  • Interaction length assumed for societal risk calculations; and
  • Intermediary stations along pipelines.

The Outcome

The HSE work informed the revision of the Sao Paulo guidelines and was expected to be adopted federally throughout Brazil. A paper was published jointly with Petrobras on the results of the international survey: Mendes RF, Chaplin Z, Macbeth R, Wilday AJ, Wardman MJ (2011). Pipeline risk criteria and methodology. Rio Pipeline Conference, September 20-22, 2011.

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