Lethality Contours

Individual Risk Contours

"What-if" scenario

Risk Assessment

Risk assessment, which should be part of any integrity management program, uses a variety of inputs and provides an improved understanding of the natures and locations of risks along pipelines.

In a risk analysis the risk is typically described as the product of two primary factors: the likelihood that some adverse event will occur and the resulting consequences of that event.

Different risk assessment approaches can be used. The ASME recommends four of them, which are: (i) the Subject Matter Experts, (ii) the Relative Assessment Models, (iii) the Scenario-Based Models and (iv) the Probabilistic Models.

The Netherlands is particular familiar with the last one and the term QRA (Quantitative Risk Analysis) is often used to qualify this probabilistic risk approach in which not only the consequence of an adverse event is calculated but also the likelihood is quantified.

PSL reflects the Dutch methodology for performing QRA's and helps calculate, rapidly and easily, LSR (Location Specific Risk) and SR (Societal Risk) but also other intermediary calculations such as the lethality, being the final consequence of the adverse event, or the heat radiation.

PSL is the quantitative risk analysis module of the PiMSlider® system. This module enables both the safety manager as well as risk analyst to perform analyses at the required detailed level. Managers will be for example interested in the global performances of their operating system and will appreciate the KPI (Key Performance Indicators) function of PSL whereas the risk analysts will use PSL for understanding better the nature and locations of risks along the pipelines.

Key Functions

PSL's two main functions are the KPI calculation and the realization of pipelines' QRA:

KPI Function The KPI function allows quick and clear view of the performances of a full-length pipeline as well as the complete system (batch mode calculation). The KPI give indications on, for example, the number of inhabitants within the proximity distances or the building density.

QRA Function The realization of a QRA with PSL is automatic as the methodology being already implemented. The user needs then only few inputs and manipulations for performing its study. The QRA function can be split into the following sub-functions:

Heat radiation

The heat radiation sub-function enables the user to see the heat radiation resulting from the ignition of the gas release (adverse event) of a certain pipeline. The heat radiation is given in kw/m² in the form of contours.

Lethality

The lethality sub-function enables the user to see the lethality resulting from the heat radiation as previously described. The lethality is a percentage and is represented by iso-contours.

Location Specific Risk

The location specific risk sub-function enables the user to calculate the location specific risk due to one or more pipelines by multiplying the consequence of an adverse event (lethality) by the likelihood of this event (pipeline failure frequency, ignition). The location specific risk is expressed per year and is represented by iso-contours.

Societal Risk

The societal risk sub-function enables the user to calculate the FN-curve of a pipeline where N is the number of fatalities and F the frequency per year of having at least N fatalities

Gas dispersion

The gas dispersion sub-function enables the user to calculate the 50% and 100% LEL in case of a gas release. The dispersion is given in the form of contours.

What if?

The "What if?" sub-function enables the user to vary the pipeline parameters in order to look at the influence of these changes on the consequences and risks due to an adverse event of the pipeline.