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DOMINO EFFECTS ANALYSIS FOR THE LPG STORAGEINSTALLATION OF HELLENIC PETROLEUM ASPROPYRGOSREFINERY

P. D. Petrolekasa and I. Andreoub

a SPEC Process Services S.A., 75 Patission Str., Athens 104 34, Greece

b Safety and Hygiene Department, Aspropyrgos Industrial Complex, Hellenic PetroleumS.A., 193 00 Aspropyrgos, Greece

AbstractThis study examines domino effects related to the LPG storage installation ofHellenic Petroleum refinery at Aspropyrgos, in accordance with the new SEVESO IIDirective requirements. The analysis involves a systematic procedure for theevaluation of potential domino accident scenarios, based on a set of damage-to-equipment criteria. The results show that the main concern is for a potential BLEVEaccident in the nearby LPG handling establishment, which could result to a BLEVEaccident in the refinery LPG installation.

1. INTRODUCTION

The LPG storage installation of the Hellenic Petroleum refinery at Aspropyrgos,includes four 4000 m3 LPG storage spheres, two 1600 m3 propane spheres, an 1800m3 butane sphere, an 800 m3 LPG sphere and a truck loading station. Figure 1shows the layout of the installation, which is located across the southern fence of therefinery establishment. Nearby installations include refinery process units, oil storagetanks, an oil truck loading station, and an LPG handling terminal. The latterestablishment includes eight cylindrical LPG storage tanks, 170 m3 each, incomingpipeline from the refinery, truck loading and packaging facilities.

The Safety Study of the refinery LPG installation [1], performed according to theSEVESO I Directive requirements, examined accident scenarios resulting fromfailures in the installation itself, and assessed their consequences to people and theenvironment.

This Study, performed in accordance to the SEVESO II requirements, examinesdomino accident scenarios that result from failures in nearby installations and couldhave an impact to the refinery LPG installation. This is particularly important withrespect to the identification of external hazard sources for the facility [2]. In addition,the study examines domino accident scenarios that result from failures in the refinery


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LPG installation and could have secondary effects to nearby installations. This is alsoimportant with respect to a complete off-site consequences evaluation.

2. METHODOLOGY

The domino effects analysis involves identification of domino scenarios, describing asequence of accidents, using the following procedure:

(a) Identification of the initial accident.This involves identification of potential accidents in all installations involved, bymeans of systematic process hazard analyses.

(b) Assessment of domino effects zone.This involves assessment of the initial accidents consequences and evaluation of

domino effects zones according to a set of damage-to-equipment criteria.

(c) Evaluation of the secondary accident.This involves visualisation of domino effects zones into suitable plot plans andidentification of the equipment in nearby installations that could be subjected tohigh loads and fail, thus leading to a secondary accident.

The procedure is employed for the identification of domino scenarios resulting fromaccidents in nearby installations that could have an impact to the refinery LPGinstallation, as well as, accidents in the refinery LPG installation that could causesecondary effects to nearby installations.

2.1 Damage criteria

Thermal radiation and explosion overpressure produced during an accident cancause severe damage to nearby process equipment, and thus may initiate asecondary accident. The extent of the damage depends on radiation or overpressureintensity, the duration of exposure, the type of material, the presence of protection(e.g. water deluge) systems, etc. Practical rules of thumb found in literature, providevalues of thermal radiation or overpressure corresponding to a given degree ofdamage. AIChE considers heat flux of 37.5 kW/m2 as the limit for severe damage toprocess equipment [3], while TNO identifies critical radiation intensities of 100 kW/m2

and 25 kW/m2

, for rupture and deformation of structural elements, respectively [4]. Inboth cases, the duration of exposure is considered to be of the order of 15 - 20minutes. Concerning explosion consequences, TNO suggests that overpressures of0.5 -1 bar can cause cylindrical tank displacement or failure of connecting pipes, andoverpressures above 1 bar can cause failure of spherical tank supports [4].


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3. RESULTS

3.1 Domino scenarios due to accidents in nearby installations

Accidents in nearby installations could be an important external hazard source for therefinery LPG installation. The first step in the domino effects assessment is theidentification of potential accidents in nearby installations. These include:

Catastrophic failure of an LPG tank in the LPG handling establishment leading tofireball (BLEVE) or vapour cloud explosion.

Catastrophic failure of an LPG road tanker in the LPG handling establishmentleading to fireball (BLEVE) or vapour cloud explosion.

Catastrophic failure of a liquid LPG pipeline in the LPG handling establishmentleading to flame jet.

Fire in a refinery oil storage tank. Failure of a gasoline road tanker in the refinery loading station leading to

unconfined pool fire.

The assessment of domino effects zones leads to the identification of dominoscenarios. Figure 1 presents the results for the case of a fireball due to BLEVE of anLPG tank in the nearby LPG handling establishment. It can be seen that the dominoeffects zone includes the refinery four 4000 m3 LPG spheres, and thus there isdanger for them to BLEVE.

Similar analysis shows that BLEVE of an LPG road tanker in the nearby LPG

handling establishment can also cause BLEVE of a refinery LPG 4000 m3

sphere.Conversely, accidents in the other refinery installations do not appear to involve anypotential effects to the LPG installation.

3.2 Domino scenarios due to accidents in the refinery LPG installation

The identification of domino scenarios that result from accidents in the LPGinstallation is also performed according to the procedure described above. Theresults show that, BLEVE of a refinery LPG sphere will have a substantial impact tonearby installations and could cause several, though smaller, secondary accidents(Figure 1).

In addition, there is concern for a potential BLEVE of an LPG road tanker that couldcause further BLEVEs in the nearby LPG establishment.Smaller accidents e.g. flamejets associated with catastrophic failures of LPG pipelines, do not appear to have animpact to nearby installations.


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200 m

Figure 1. Plot plan of the refinery LPG storage installation and the nearby installations.Domino effects zones of BLEVE accidents in the LPG handling terminal (solid line) and therefinery LPG installation (dotted line), are presented.

LPG terminal


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