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DET NORSKE VERITASTM 

R EPORT NO./DNV R EG NO.: 2013-4091 / 17TLT29-6

R EV 1, 11.06.2013

Appendix E

PHAST RISK SOFTWARE

PACKAGE DESCRIPTION 

SKANGASS AS

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Det Norske Veritas Report for Skangass AS 

Phast Risk Software Package Description 

MANAGING RISK

DNV Reg. No.: 17TLT29-6 Revision No.: 1

Date : 11.06.2013 Page i of ii

Table of Contents Page

1  MODEL OVERVIEW ........................................................................................................................ 1 

2  INTRODUCTION ............................................................................................................................... 2  2.1  Document Layout ...................................................................................................................... 2 

3  THE PHAST RISK PROGRAM......................................................................................................... 3  D.1.1 Overview ................................................................................................................................................. 3

3.1  Layout of PHAST RISK ........................................................................................................... 6 

4  BACKGROUND DATA ..................................................................................................................... 8 

4.1  Weather Conditions ................................................................................................................... 8  4.2  Parameters ................................................................................................................................. 9 

4.3  Materials Data ......................................................................................................................... 10  4.4  Maps ........................................................................................................................................ 11 

4.5  Risk Data ................................................................................................................................. 12  4.5.1 Populations ............................................................................................................................................ 12 4.5.2 Ignition Sources .................................................................................................................................... 12 4.5.3 Risk Ranking Points .............................................................................................................................. 13

5  CONSEQUENCE ANALYSIS ......................................................................................................... 13  5.1  Discharge Modelling Theory .................................................................................................. 13 

5.1.1 Types of Release ................................................................................................................................... 13 5.1.2 Instantaneous Releases.......................................................................................................................... 14 5.1.3 Continuous Releases ............................................................................................................................. 14

5.2  Dispersion Modelling Theory ................................................................................................. 15  5.2.1 Overview ............................................................................................................................................... 15 5.2.2 Release Phenomenology ....................................................................................................................... 16 5.2.3 Dispersing Cloud Models ..................................................................................................................... 18 5.2.4 The Unified Dispersion Model ............................................................................................................. 19

5.3  Consequence Modelling Theory ............................................................................................. 21  5.3.1 Overview ............................................................................................................................................... 21

5.3.2 Toxic Consequences ............................................................................................................................. 21 5.3.3 Flammable Consequences ..................................................................................................................... 21

5.3.4 Flash Fires ............................................................................................................................................. 22 5.3.5 Pool Fires .............................................................................................................................................. 22

5.3.6 Jet Fires ................................................................................................................................................. 23 5.3.7 Fireballs / BLEVEs ............................................................................................................................... 23 5.3.8 Explosion Models ................................................................................................................................. 24

6  IMPACT ANALYSIS ....................................................................................................................... 25 

6.1  Event Trees .............................................................................................................................. 25  6.1.1 Overview ............................................................................................................................................... 25 6.1.2 Continuous Release, Without Rainout, Event Tree .............................................................................. 26

6.1.3 Continuous Release, With Rainout, Event Tree ................................................................................... 28 6.1.4 Instantaneous Release, Without Rainout, Event Tree ........................................................................... 30

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Phast Risk Software Package Description 

MANAGING RISK

DNV Reg. No.: 17TLT29-6 Revision No.: 1

Date : 11.06.2013 Page ii of ii

6.1.5 Instantaneous Release, With Rainout, Event Tree ................................................................................ 31

6.2  Vulnerability ........................................................................................................................... 33  6.2.1 Approach ............................................................................................................................................... 33 6.2.2 Vulnerability Parameters ...................................................................................................................... 34

7  RISK ANALYSIS ............................................................................................................................. 37  7.1  Risk Calculation ...................................................................................................................... 37 

7.2  Graphical Output ..................................................................................................................... 37  7.3  Tabular Output ........................................................................................................................ 40 

8  REFERENCES .................................................................................................................................. 41 

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Phast Risk Software Package Description 

MANAGING RISK

DNV Reg. No.: 17TLT29-6 Revision No.: 1

Date : 11.06.2013 Page 1 of 41

1  

MODEL OVERVIEWDNV Software’s PHAST RISK program is a user -friendly, industry standard method for carrying out Quantitative Risk Assessments (QRA) of process facilities. PHAST RISK allows you to quickly

identify major risk contributors. Time and effort can then be directed to mitigating these highest risk

activities.

PHAST RISK analyses complex consequences from accident scenarios, taking account of local

 population, land usage and weather conditions, to quantify the risk associated with the release of

hazardous materials. Phast Risk incorporates the industry standard consequence modelling of PHAST.

Key features:

  Integrated dispersion modelling

  Wide range of toxic and flammable

  effect models

  Risk contour and FN curve generation

  Risk ranking of failure scenarios

  Facility to overlay results using

  Geographical Information Systems (GIS),

  aerial maps, plans and photographs

  

Traceability and consistency in   calculations

This document provides a description of the PHAST RISK software.

For further details contact:

  DNV Software   Palace House, 3 Cathedral Street, London, SE1 9DE