2016-S-RPT-000-0001 Rev 1 Fire and Explosion Report 06-12-2012

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KHOR MOR LPG Loading Facilities Revamp Project

PETROFAC PROJECT NO. : JI 2016

FIRE AND EXPLOSION STUDY

Doc No. 2016-S-RPT-000-0001

1 16/12/12 Reissued for Design DB CSS CSS SK

0 27/11/12 Issued for Design DB CSS CSS SK

A 03/11/12 Issued for Review DB CSS CSS SK

Rev Date Description Prepared Checked ApprovedProject

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2016 S RPT 0001 1


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FIRE AND EXPLOSION STUDY 2016-S-RPT-000-0001 REV.1

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CONTENTS

1.0 INTRODUCTION .................................................................................... 41.1 Background ...................................................................................... 4

1.2 BLEVE ............................................................................................. 4

2.0 MODELLING ASSUMPTIONS ...................................................................... 4

2.1 LPG Truck Design ............................................................................... 4

2.2 LPG Fluid ......................................................................................... 5

2.3 Modelling Software ............................................................................. 5

2.4 Weather Data .................................................................................... 5

2.5 Impairment Criteria ............................................................................ 5

3.0 CONSEQUENCE RESULTS ......................................................................... 7

3.1 BLEVE radiation result .......................................................................... 8

3.2 BLEVE Blast Overpressure ..................................................................... 11

3.3 Flexible hose leak/rupture ................................................................... 14

4.0 CONCLUSIONS..................................................................................... 18

5.0 REFERENCES ...................................................................................... 19

APPENDIX-1: PHAST BLEVE RADIATION REPORT .................................................... 20

APPENDIX-2: PHAST BLEVE OVERPRESSURE REPORT ............................................... 21


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ABBREVIATIONS

BLEVE - Boiling Liquid Expanding Vapour ExplosionHSE - Health, Safety and Environment

LPG - Liquefied Petroleum Gas

NGL - Natural Gas Liquid

tdu - Thermal Radiation Dose Units


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1.0

INTRODUCTION

1.1

Background

On 22 of June 2012, an incident occurred at the Khor Mor LPG facility involving twoLPG road tankers. The subsequent fire and explosion caused damage to the LPGloading area. With the exception of the LPG bullets and the LPG pumps, all of theLPG loading facility will be rebuilt.

Petrofac has investigated the worst-case hazard consequence scenario, a BoilingLiquid Expanding Vapour Explosion (BLEVE) of a fully loaded 18MT LPG road tanker.

This report presents the results of the BLEVE investigation.

1.2

BLEVE

A Boiling Liquid Expanding Vapour Explosion (BLEVE) is one of the serious hazards inthe LPG industry. Following description is given for BLEVE in Reference 1.

When a vessel containing liquid under pressure is exposed to fire, the liquid heatsup and the vapour pressure rises, increasing the pressure in the vessel. When thispressure reaches the set pressure of the pressure relief valve, the valve operates.The liquid level in the vessel falls as the vapour is released to the atmosphere. Theliquid is effective in cooling that part of the vessel wall which is in contact with it,but the vapour is not. The proportion of the vessel wall which has the benefit ofliquid cooling falls as the liquid vapourises. After a time, metal which is not cooledby liquid becomes exposed to the fire; the metal becomes hot and weakens andmay then rupture. This can occur even though the pressure relief valve isoperating correctly. A pressure vessel is designed to withstand the relief valve setpressure, but only at the design temperature conditions. If the metal has itstemperature raised, it may lose strength sufficiently to rupture. A large fraction ofthe flammable liquefied gas released, vapourises and forms a burning vapour cloud,often called a fireball.

2.0 MODELLING ASSUMPTIONS

This section presents the assumptions used for the BLEVE modelling.

2.1 LPG Truck Design

The BLEVE modelling has been carried out for the failure of one fully loaded LPGroad tanker containing 18MT (38.3m3) of LPG. The road tanker details arepresented in Table 1.

TABLE 1: LPG ROAD TANKER OPERATING PARAMETERS

ScenarioNo.

Name Truck Operatingpressure (barg) OperatingTemperature(0C) Inventory (kg)

1 LPG Road Truck 8 30 18,000





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Note: Scenario 1 & 2 operating temperature is selected as 30OC so that the fluid

phase is liquid. Scenario 3 is assumed as normal operating case, however, Scenario4 has been considered conservatively as the design case to determine safe distancerequirement.

2.2 LPG Fluid

The respective LPG compositions employed for the modelling is based on Reference2 and presented in following table.

TABLE 2: LPG COMPOSITION

ComponentMol Fraction

Design Case (70:30 LPG) Alternative Case (50:50 LPG)

Ethane 0.0105 0.0076

Propane 0.6992 0.5089

i-Butane 0.0956 0.1485

n-Butane 0.1802 0.3220

i-Pentane 0.0100 0.0100

n-Pentane 0.0045 0.0028

n-Hexane 0.0000 0.0000

M-Mercaptan 0.0000 0.0000

E-Mercaptan 0.0001 0.0001

2.3 Modelling Software

The assessment has been carried out using the BLEVE model available within PHAST(Version 6.7) that predicts the explosion overpressure and fireball distances.

2.4 Weather Data

Table 3 presents the weather/atmospheric assumptions (Reference 2).

TABLE 3: ATMOSPHERIC CONDITIONS

Parameter Criteria

Temperature 52oC

Weather Conditions (Atmospheric Stability Class and WindSpeed)

2F and 5D

Relative Humidity 80 %

2.5

Impairment Criteria

The following tables (Table 4 & 5) indicate the general thermal radiation(Reference 3) and overpressure criteria (Reference 4) that have been consideredfor the consequence modelling and relate to the impairment of escape routes andstructural failure. In Table 4, impairment criteria definition for 6.3 kW/m2 is


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selected from API-521 which provides an unambiguous statement on radiationimpact.

TABLE 4: HEAT RADIATION IMPAIRMENT CRITERIA

Thermal RadiationIntensity (kW/m2)

Impact Description

4.7The onset of 1st degree burns. The pain threshold is reached in 15- 20 seconds and injury after 30 seconds exposure.

6.3

Maximum radiant heat intensity in areas where emergency actionslasting up to 30 s can be required by personnel without shieldingbut with appropriate clothing. Appropriate clothing consists ofhard hat, long-sleeved shirts with cuffs buttoned, work gloves,long-legged pants and work shoes (API-521).

12.5

Limiting radiation for escape actions lasting a few seconds. Atthis level, the pain threshold is reached in about 4 seconds, andsecond degree burns of exposed skin in about 40 seconds.

Thin steel with insulation on the side away from the fire mayreach a thermal stress level high enough to cause structuralfailure.

37.5

Criterion for immediate fatality. At this level, the pain thresholdis virtually instantaneous and second degree burns on exposedskin occurs in about 8 seconds.

Threshold for the onset of structural failure of steel. Steelsupports for large vessels fail.

Within fireball radius

A person within a fireball is assumed to be a fatality. If the personis outside the fire radius then they will likely suffer minor burns orno effects. Fatalities are caused not only by the heat of the flamebut also by the heat of the gases left after the fireball. Thebreathing of hot combustion gases has effects due to threedistinct reasons breathing air with little or no oxygen, burningof the lungs and breathing toxic by-products of combustion.

For short exposure (upto a few tens of seconds, typical of fireballs), thermalradiation dose units (tdu) should be used [5].

Thermal Dose (tdu) = (I4/3)t

Where, I = incident thermal flux (kW/m2)

t = duration of exposure (s)

Unit of tdu: (kW/m2)4/3s

For this project, tdu of 1000 (kW/m2)4/3s has been used which is equivalent to 1%fatality as per the OGP guideline (Reference 5).


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TABLE 5: EXPLOSION OVERPRESSURE EFFECTS

Explosion Overpressure(psig/barg)

Impact

1.0/0.069 Storage tank cone roof collapse

3.0/0.207 Storage tank uplift (half tilted)

3.5/0.241 Pipe support frame deforms

6.0/0.414 Pipe support frame collapse, piping breaks

3.0

CONSEQUENCE RESULTS

This section discusses the results of the modelling with respect to explosion overpressures and fireball radius.

A sensitivity analysis is done with Design case LPG and Alternative case LPG. It hasbeen observed that overpressure effect distances using Design case LPGcomposition are more than that using Alternative case LPG composition (referFigure 1). It was also found that BLEVE thermal radiation does not changeappreciably with LPG composition (refer Figure 2). Since the Design case LPGcomposition shows the conservative result, detailed result with Design case LPGcomposition has been reported.

It may also be noted that the blast overpressure effect distance does not dependon weather stability.

Figure 1: Overpressure effect distance sensitivity with LPG composition at17barg operating pressure.

0

20

40

60

80

100

120

140

0 20 40 60

Overpressuredistance,m

LPG Temperature, C

Sensitivity on LPG composition

69mbar- Design case LPG

69mbar - Alternative

case LPG

241mbar - Design case

LPG

241mbar - Alternative

case LPG


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Figure 2: Radiation effect distance sensitivity with LPG composition at17barg burst pressure.

3.1

BLEVE radiation result

The following table summarizes the BLEVE radiation results for fully loaded LPGroad truck

TABLE 6: BLEVE RADIATION RESULTS

Sl. No Name Burstpressure

(barg)

WeatherCondition

FireballRadius

(m)

FireballDuration

(sec)

Distanceto 37.5

kW/m

2

(m)

Distanceto 12.5

kW/m

2

(m)

Distanceto 6.3

kW/m

2

(m)

Distanceto 4.7

kW/m

2

(m)

1

LPG tanker

8.0

2F 79 10.9 0 193 297 347

LPG tanker 5D 79 10.9 23 205 312 366

2

LPG tanker

11.0

2F 79 10.9 33 206 312 364

LPG tanker 5D 79 10.9 52 219 328 384

3

LPG tanker

17.0

2F 79 10.9 64 225 335 389

LPG tanker 5D 79 10.9 79 237 352 410

4

LPG tanker

22.0

2F 79 10.9 80 236 349 405

LPG tanker 5D 79 10.9 91 249 367 426

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40

Radiationdistance,m

Radiation, kW/m2

Sensitivity on LPG composition

Radiation_2F_Design case

LPG

Radiation_2F_Alternative

LPG

Radiation_5D_Design case

LPG

Radiation_5D_Alternative

LPG


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FIGURE 4: SCENARIO-4: HEAT RADIATION DESIGN CASE

Thermal radiation contour (Figure 5) based on existing loading location has also

been drawn to see the impact distances.

FIGURE 5: HEAT RADIATION CONTOURS FROM FIREBALL CONSIDERINGEXISTING LOADING BAY LOCATION


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3.2

BLEVE Blast Overpressure

The BLEVE blast overpressure results are included in Table 7.

TABLE 7: EXPLOSION OVERPRESSURE RESULTS

Sl. No. NameOperatingpressure

(barg)

OperatingTemp. (C)

Distance to0.069 barg

(m)


(m)


(m)


(m)

1 LPG tanker 8 30 107 56 51 37

2 LPG tanker 11 30 107 56 51 37

3 LPG tanker 17 50 121 63 57 42

4 LPG tanker 22 50 121 63 57 42

It may be noted that LPG at temperature 50OC is in vapour phase at both 8barg &11barg operating pressure and hence 30OC has been selected for the calculation

with LPG as liquid. Although 14barg has been assumed as the plant operatingpressure, to keep conservatism in the design, 22barg LPG pressure with 50OCoperating temperature has been considered as the design conditions to evaluatesafe distances.

Overpressure contour assuming BLEVE location at the existing loading bay is shownin Figure 6. Based on the explosion contours in Figure 6, it is concluded that thepresent location is not suitable since there can be blast overpressure impact onNLG tank and the NGL/LPG pumps along with the nearby piperack supportingpiping. Hence, the location of the new loading bay is required to be shifted awayfrom NGL tank and NGL piping to protect these items in case of BLEVE in the LPGloading bay.

The explosion overpressure contours for Scenario-4 considering the BLEVEoccurrence at the new location are presented in Figure 7. Detailed overpressure

report from PHAST is included in Appendix 2. Based on the revised location theoverpressure values at the NGL piping and NGL tank are well below the explosiondamage criteria.

The report shows that blast overpressure at 70m away from BLEVE scenario isapproximately 0.18barg along with 131 N.s/m2 impulse (corresponding to 16msduration). Based on the explosion results it is suggested that the control room shallbe designed to protect an explosion overpressure of 0.2barg for 20ms durationwhen located about 70m away from the nearest LPG loading bay.


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FIGURE 6: SCENARIO-4: EXPLOSION OVERPRESSURE CONTOURS FROM BLEVECONSIDERING EXISTING LOADING BAY LOCATION


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FIGURE 7: SCENARIO-4: EXPLOSION OVERPRESSURE CONTOURS FROM BLEVECONSIDERING NEW LOADING BAY LOCATION


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3.3

Flexible hose leak/rupture

Four release scenarios have been considered for consequence analysis:

1. Flexible hose leak with maximum rated flow of 72m3/hr (9.42 kg/s with liquiddensity 471.2 kg/m3) with which the tanker will be filled.

2. Rupture of flexible hose

3.

A small leak (5mm)

4.

Release from LPG tanker- slam shut valve malfunction (open)

In all above cases, normal operating pressure of 14barg & temperature 50OC hasbeen considered for calculations.

Leak case with maximum rated flow

Consequence analysis has been done with 9.42 kg/s. The LFL distances with 2F m/s

and 5D m/s weather stability are calculated as 45m and 41m respectively. The0.5LFL (9301ppm), LFL (18600ppm) & UFL (92920ppm) contours are presented inFigure 8 & Figure 9.

Figure 8: Flammable cloud dispersion contour with 2F weather stability

Figure 9: Flammable cloud dispersion contour with 5D weather stability

Comment [Shaji1]: What is this contours?it LFL, 0.5LFL or some other value. Pleasemake a statement which corelate the ppm tLFL limit.


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Jet fire radiation (4.7 kw/m2) distances are found to be 62m & 57m with 2F and 5Dweather stability respectively. Thermal radiation contours are shown in Figure 10

below.

Figure 10: Jet fire radiation contour with 2F & 5D weather stability

Rupture of flexible hose

During a rupture case of the flexible hose, the pressure inside the hose will dropsuddenly. Excess flow check valve is connected in the upstream section of flexiblehose and slam shut valve is fitted at the liquid inlet of the tanker. In HAZID studythese valves have been considered as safe guards. In the event of hose rupture, ithas been assumed that both the valves will be closed immediately. The amount ofLPG released will be limited to approximately the inventory within the flexiblehose, which will be much less than the previously discussed leak case. A model hasbeen made considering rupture of a 3 flexible hose having 10m length resulting torelease of 0.0442m3of LPG. The result shows that initially approximately 25m long

LFL cloud can be generated. The LFL cloud will be disengaged from the source soonbut it can travel to a distance of approximately 75m.

Figure 11: Flammable cloud dispersion contour with 2D weather stability from hoserupture

Comment [Shaji2]: If such small reelasehappen then how much is the cloud extent?


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Small release case

A small leak (5mm) release has been studied to decide the height of flammable gasdetector. A downward impingement model with releasing from 1m height has beenconsidered. It was found that 0.2 (20%) LFL cloud reaches a height ofapproximately 1.1m (refer Figure 12). Since the flammable gas detector will be setat 20% LFL level, detector height of 1.0m should be suitable to detect flammablegas. Less than 1m detector height may create problem to the detectors due to dustingress.

Figure 12: Flammable cloud dispersion contour m/s from 5mm leak leak

Release from LPG tanker- slam shut valve malfunction (open)

A scenario has been considered in the event of flexible hose rupture and at thesame time the slam shut valve is malfunctioning. A 2inch leak has been considered

for modeling. In such situation entire tanker content (18000 kg of LPG at 14bargpressure) is assumed to be released through ruptured hose lying in the ground. Theresult shows that 0.5LFL distance extends to 276m and 187m during 2F & 5Dweather conditions respectively. The 0.5LFL cloud coverage is shown in Figure 13 &Figure 14. Such release can create a LPG pool of maximum radius approximately17m.

Figure 13: Flammable cloud dispersion contour with 2F m/s weather stability from tankerrelease.

Comment [Shaji3]: This is only a horizontjet and the cloud is only 0.5m above the leapoint. See if the spil falls on to ground and ivapourises how much will be the cloud heighCheck a pool vapourisation can help to bettdefine the location of detector or not.

Comment [Shaji4]: What is the 20575.3mand 28056.7m in the legend?


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Figure 14: Flammable cloud dispersion contour with 5D weather stability from tankerrelease.

The liquid LPG will be partially flashed and the remaining liquid will flow to theopen drain which is located towards east of loading area. The liquid LPG will flowthrough the drain and ultimately flow outside fence to the adjacent wadi. Vapourwill be continuously generated during such liquid LPG flow until entire liquid isconverted to vapour.

Release calculation indicates that 54% of total release quantity (18000kg) can comeout as liquid amounting to 9720kg of liquid LPG. A part of this liquid will beevaporated while flowing through loading area to open drain. The wet loading areais assumed as 13.7mx3.8m (52.1m2) and the open drain length is considered as 90mhaving 0.3m width (27m2). Thus total wet area is 79.1m2. Pool evaporation model isused to calculate how much of liquid LPG can be evaporated until it reaches openarea outside the fence using a spreading pool model. It has been found that 1068kg

of liquid LPG can be evaporated within fence and the rest amount (8652kg) ofliquid LPG will be evaporated outside fence. Pool evaporation model shows that amaximum spreading pool radius of approximately 12.5m is possible. A dischargemodel is then developed to check the dispersing cloud length in open area. It showsthat the LFL and 0.5LFL cloud can reach approximately 125m & 175m respectivelyin a flat terrain (refer Figure 15).

Figure 15: Flammable cloud dispersion contour with 2F weather stability with LPG releasefrom tanker and flowing into the open area outside fence.




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4.0

CONCLUSIONS

Consequence modelling has been carried out for LPG road tanker failure scenarioleading to a BLEVE to evaluate thermal radiation and overpressure effects.Following are the conclusions:

1.

The full volume of the LPG truck (18MT, 38.3m3) has been considered as theworst-case scenario for the purposes of this assessment. This worst case eventhas been modelled for four different operating conditions (scenario 1 toscenario 4) with two different LPG compositions (Design case LPG composition(approximately 70:30 propane:butane) & Alternative LPG composition(approximately 50:50 propane:butane)). Since Alternative LPG compositionprovides lesser effect distances than that using Design case LPG composition,only Design case LPG composition has been used for consequence assessment.

2.

Overpressure contours drawn on the existing plot plan (Figure 6) indicates apossibility of the NGL storage tank being impacted (roof collapse) if a BLEVEoccurs at the existing location of loading bay. Hence a new location of theloading bay away from the existing location towards south direction issuggested. The overpressure contours from the proposed loading location(Figure 7) shows that the NGL tank is located away from 0.069bar overpressuredistance from the LPG loading location. The existing process area, NGL pumparea & the nearby pipe supporting structures are located outside 0.24baroverpressure contour and hence do not pose any risk of damage from blastoverpressure impact.

3.

The blast overpressure at 70m away from BLEVE scenario is approximately0.18barg along with 131 N.s/m2impulse (corresponding to 16ms duration). It isrecommended to design the LPG control room to protect explosion

overpressure of 0.2barg for 20ms duration and shall be located 70m away fromthe nearest LPG loading bay.

4. The maximum fireball radius is 79m from the LPG road tanker loading bay. Thefireball can last for 10.9 seconds. The model assumes that the full mass of LPGhas been released from the truck before ignition and as such the differentoperating conditions have no effect on the fireball results.

5.

People working in compressor & other main plant areas are outside 1% fatalityzone. People working in LPG/NGL pump area are within 1% fatality zone. In theevent of any fire scenario at LPG loading area, all the personnel within theplant must move away from the incident site and proceed to the Muster areaon West side of the plant. Those who are unable to reach the muster area cantake shelter against the radiation under a covered area to avoid directexposure to radiation.

6.

Muster point located at the north-west corner & south-west corner will not beimpacted from BLEVE scenario since this is outside 6.3kW/m2 radiationcontour.

7.

For a credible leak horizontal jet fire scenario, firefighting using monitorshould be done from the reverse side direction of the jet fire. However, onsitejudgment shall be made to decide on the selection of monitor depending onsize of fire & the direction of fire.

8.

Flammable gas detector height should be selected 1.0m.


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9.

Any open guard house should be located minimum of 275m away from theloading bay.

5.0

REFERENCES

1.

Loss Prevention In The Process Industries, F P Lees, Volume 2, HazardIdentification, Assessment and Control, Third Edition, 2005.

2.

Crescent Petroleum/ Dana Gas, LPG Loading Consequence Modelling Workscope, Doc No. CPCI-20xxx September 2012 Rev.1 as referenced inConsequence report by Risktec (Document no. DNG-04-R-01).

3.

DNV Technica, A Guide to Quantitative Risk Assessment for OffshoreInstallations, Centre for Marine and Petroleum Technology (CMPT), 1999.

4.

Vulnerability of plant/structure, Oil & Gas Producer (OGP) data, Report No.434-15, March 2010.

5.

Vulnerability of humans, Oil & Gas Producer (OGP) data, Report No. 434-14.1,March 2010.


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APPENDIX-2: PHAST BLEVE OVERPRESSURE REPORT

(6 pages)

2016-S-RPT-000-0001 Rev 1 Fire and Explosion Report 06-12-2012

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