As part of a commitment to understanding and minimising the risks of its operations, National Grid has carried out a programme of theoretical and experimental work, supplemented by site surveys, to develop a methodology to assess the risks from compressor sites and other Above Ground Installations (AGIs) associated with the natural gas transmission pipelines. A computer package has been produced to encode this methodology to make it easer to use. The package contains a number of models that assess the consequences of releases at fixed installations. These are linked with frequency data to enable a risk assessment to be performed.
This paper gives an overview of the package. By means of worked examples, typical input information required by the model is explained and the output information available is presented. The paper includes a discussion on how the output from the model can be used in various practical applications; from ranking the risks at a number of sites, assessing the fire fighting provision at a site or examining the impact of changes on the layout at a site. A worked example is provided to show how the results can be used to extend the guidance for the separation distances required from processing plant to the site boundary at a wider range of sites.