H2S Manual - Shell

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and ProductionB.V. Exploration ShellInternational

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\ H2Sin Operations

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EP 95-0317

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HSE MANUAL

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I R e v i s i o n0 : 6 O c t o b e r 1 9 9 5

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EP HsE ManuarAmendment Recordsheet Section Number:Ep 95_0317 Section Tifle: H2S in Operations

Description of amendment

Originalhard copy and CD_ROilf-G

Contents

CONTENTS

ldentificationof Sources of HZS

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Fluids 2.1 Process (SRB) Reducing Bacteria 2.2 Sulphate Assessment of Risks from HZS

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5.1

Planning Emergency

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5 . 1 . 1 E m e r g e n ce yquipment

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5.1.2 Procedurefor majorH2S release

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concernsfor H2S emission 3.2.1 Environmental and air qualitystandards

5.2.1 Hazards

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3.2.2 Dispersionin the surroundingatmosphere

5.2.2 Precautions

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3.2.3 Productionof sulphurdioxide

5.2.3 Generalprocedures/guidelines

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5.2

fety Effects of H2S

Guidelinesfor the Preparationof HZS Procedures

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6.'l

Formulation of Work Procedures

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6.2

Drillingand Well Operations

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6.3

Production Operations

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Control and Safe Working Practices

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The Framework of Controlsfor Workingin H2S Designated Areas

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6.3.1 Sampling 6.3.2 lsolation

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6.3.3 Depressurising

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4.2.1 The basisof classification

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6.3.4 Flushingand draining

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4.2.2 The effectsof dispersion

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6.3.5 Purging

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4.2.3 The classificationprocess

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H2S Detection

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4.3.1 Fixedsystems

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4.3.2 Portablesensors

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3 Personalmonitoringsystems 4.3.4 Testingand calibration

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WamingSigns

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AccessControls

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Permitto Work (PTW)

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Respiratory Protective Equipment

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4.7.1 The typesof RPE

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4.7.2 Protectionfor normalooerations

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4.7.3 Protectionin event of accidentalrelease scenanos

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4.7 4 Protectionin areas subjectto sulphatereducingbacteria(SRB)

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Procedural Controls and Standing Instructions

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H2SCompetence

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P 95-0317Revision0 5 October1995

6.3.6 Vessel entry

6.4 Maintenance Operations

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Appendices I

Formation of H2S by SulphateReducing Bacteria(SRB)

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PhysicalProperties and Physiological Effectsof H2S

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H2SCorrosion

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Pyrophoric lronSulphide

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H2SDispersion

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H2S Detection

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RespiratoryProtectiveEquipment

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1.2 H2SAreaClassification

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4.9.5 Competencereview

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ironsulphide 3.3.2 Pyrophoric

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Recovery

3.3.1 Effectson metals

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4.9.4 Competencecertification

Firefighting

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5.1.3 Rescueprocedures

Effectsof H2S 3.2 Erivironmental

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4.9.2 Trarnrngprogramme

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3.1 HealthEffectsof H2S

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4.9.3 Specificelementsof the trainingprogramme 22

Introduction

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4.9.1 Competencerequirements

HSE Manual Ep gs-O317Hydrogensurphide(Hzs) Vlll Typicalprocedures lX

Examplesof H2S AreaClassification Systemsin Use

in operations

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Gfossary

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References

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ii EP 95-0317Revision0 5 October1995

1 Introduction

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ffydrogenSulphideGIgS)is an extremely ciangeroussubstance,causingfataiiti ,".r. H.S occursfrequently in EP operations,it is consiclerednecessaryto cleclit

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The apploach is in line with the hazirds and effects supersedesEP S-SOOO-32. managementprocessdescribedin the HSE ManagementSystemEP 95-0300.

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fhe report describesfour steps:

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INTRODUCTION

of HoS exposure(Chapter'2) of all sor-rrces

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identification

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assessment of the risk to personnel(Chapter 3)

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controls and safe working practices (Chapter 4)

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recovery method.sin the event of loss of control (Chapter 5)

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Recoveryshould include contingencyplanning for all H"S-related situations (eg H:S leakage,evacuationprocedures,etc) \-

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It is of vital importance that these four steps are completedbeforeany work is r undertaken. The report is intended for use by field personnel in drilling, production and maintenance operations and does not cover design requirements for new plant.

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It does not add.ressdetails on the protection of the general public or the seiectio mabrials for HoS service.

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The Guideline provides the basis for the development of Opco specific procedure Chapter 6 gives some specific guidance on the preparation of H"S procedures fo: production, drilling and maintenance activities.

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Reference is made to Shel1 Safety Committee guide Hydrogen Sulphide, Hazard Precautions G,ef. 1). The reader's attention is drawn to the following:

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the rnajor hazard of HoS is its ability to cause rapid darnage to heal sudden death due to accidental exposure

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odour cannot be relied upon to detect the presence of dangerous .oncentrations of HoS

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50 per cent of the people killed in H,S incidents were trying to resc others.

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If the reader doesnot understand an)' part of this documentheishe must discussit wiih .omeone who d.oes.

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0 5 October1995 EP 95-0317Revtsron

of Sourcesof H2S 2 ldentification

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OF HzS OF SOURCES IDENTIFIGATION

sufficient concentrations to Liquid and gaseous hyd,rocarbons may contain HrS in present a hazard to personnel, equipment and the environment' pipelines, desulphurisation piant's' HrS can be present in oil refineries, process plants, swamps, or any area oil/gas/water wells, during drilling or well workover, sewers, (eg utility shafts in offshore where there is decayrng organic matter or stagnant water platforms). when acid is used to ciean HrS can also result from acidicaustic reactions, for example which has been used caustic equipment containing iron sulphide or to neutralise spent flowed back after well t* HrS scrubbing. HzS may also be present in spent acid stimulation. to resist the harmful effects of All facilities potentially exposed.to HoS must be designecl pressures' HzS at the anticipated operating temperatures and HrS in the upstream oil and gas industry comes from: .

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2.1

material and the the original reservoir, as a result of the hydrocarbon source gas. If this is the case then H'S cond.itions under which it was converted to oil ancl will be produced with the fluids bacteria (SRB) stagnant seawater systems, by the action of sulphate reducing (seawater, brackish, the reservoir after proionged. injection of water with oxygen 'souring' it due to the within fluids the of formation water) which *ut result in will be HrS process. Any action of SRB introduced during the injection subsequentiy produced with fluids'

Process Fluids

in the process fluids arises : The risk to personnel on a facility where HrS is present o

during an accidental release

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entry, instrumentation during normal maintenance operations, eg./sphering, vessel or valve maintenance

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during venting from tanks'

upon the concentration of HzS The level to which personnel could be subjected d.epend.s local conditions. refer to 3'2'2, in the process fluidand the d.ispersion and d.ilution under d.ispersion in sur-roundin g atmosphere'

2.2 SulphateReducingBacteria(SRB) necessaryfor SRB SRBs are the sourceof a range of hazard.sinclud.ingHgS. Cond:tions of means (including H"S), to exist an6 d.evelop,hazarclsassociatedwith SRBs prevention, detectitn and control are ali describedin Appendix I'

EP 95-0317Revision0 5 October1995

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3 Assessmentof Risksfrom H2S

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basedon broad basedconsequence This documentprovidesa set of recommendations analysisand operationalexperience. A full risk analysis may proviclea better insight into the potential frequency and of specificHoS related events and point to possiblerisk reduction consequences measures.Howe!'er, perioJs of highest risk may not always be predictable and 'HrS Risk recognisedand.it is advrseclto acloptthe recommendationsfor classificationof use the Areas,containedin this document.By doing so, procedures,including those for of protective equipment, will ensure the appropriate state of workforce awarenessand preparedness. 'HrS Risk Risks associatedwith incidents that may effect areas beyondthe classified Area, should always be assessedand this may even be a legislative requirement. Such parties risks may be to persons,for instance,in Opcofacilities or accommodation,third or the public (refer to 3.2.2). The threats presentedby HrS in a processand non-process,eg seweragethroughout the Iifetime of that facility or pi-pelinewill be recorded in the HSE Case together with the control measures.

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A S S E S S M E N TO F R I S K SF R O MH Z S

Health Effects of HrS

(ACGIH) The current American Conferenceof Governmental Industrial Hygienists (TWA) and 15 ppm 8h Threshold Limit Value (TL\ry is 10 ppm Time Weighted Average Short-Term Exposure Limit (STEL). or The major hazard of HrS is its ability to cause rapid damage to health sudden death due to accidental exposure' Brief exposureto concentrationsabove500 ppm may result in rapid unconsciousness without any warning symptoms.Exposule to HrS above500 ppm for any lenglh of time is considered.as potentially lethal. Death due to stoppageof breathing may follow within a few minutes unless the victim is removed to a safe atmosphere in time and possible in artificial respiration is applied..If the victim survives, complete recovery is most cases.Exposuresover 30 minutes to HzS concentrationsof 200 ppm and above may causer...,*r.lation of fluid in the iungs Oung oedema).At concentrationsabove of the l0 ppm, HrS can have an irritating effect on the eyes and the mucous membranes In low nose,throat an6 1ungs.The pr-imarysourceof exposureto HrS is by inhalation. concentrationsHrS has the odour of rotten eggs' at It must be emphasised.that the unpleasant od.ourof HoS, which can even be detected due ppm 100 above concentrationsof 0.02 ppm, may not be detectableat concentrations to rapid loss of the senseof smell. Odour cannot be relied upon to detect the presence of dangerous concentrations of HrS. The effect of H=S on the hoclyat clifferentconcentrationlevels and the occupational exposurelimits are shown in Appendix II' personnel at risk from exposureto H"S must be trained to know what to do if H"S is person has to be rescued.Such training is vrtal since to detected.or if an unconscior.rs 'conditioning'that might resuit in an someextent it is necessaryto controi the individual hur.r.vingimmecliatelyto the aiclof someoneovelcomeby H'S-

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EP 95-0317Revrsion0 5 October1995

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F H S E M a n u a l E P 9 5 - 0 3 1 7 H y d r o g e nS u l p h i d e ( H z S ) i n O p e r a t i o n s V

REMEMBER:50 PER CENTOF THB PEOPLEKILLED IN H.,S INCIDENTS\AIERETRITNGTO RESCUEOTHERS.

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3.2 G

EnvironmentalEffects of HzS

Emission controis should be set to protect people from toxic risks and avoid public nuisance. There are no known health effects associated with long-term exposure to HrS at concentrations at or below the point where short-term symptoms (for example eye or respiratory irritation) are observed.

3.2.1 Environmentalconcernsfor HzSemissionand air qualitystandards The air quality in respect of allowable concentrations of HoS varies considerably from country to countrS'. Alowable emission concentrations can be as low as 1 (one) ppm HrS with a corresponding air quality of 0.02 ppm HrS over a 30- (thirty-) minute period. These levels do not present a toxic risk although they can result in a pungent odour. The odour threshoid for HrS depends upon the individual and can be as iow as 0.02 ppm. Higher concentrations will most certainly cause odour ploblems.

3.2.2 Dispersionin the surroundingatmosphere Dispersion of gas containing H2S in the surrounding atmosphere depends on a number of factors: .

nature of the source of the HrS HzS in EP process operations will rareiy be present in pure form which is heavier than air, it will usually be a constituent of a process fluid such as produced gas, condensate or crude oil. (Simiiariy HrS encountered in non-process situations, such as sewerage systems will also be a constituent of a composite gas). Dispersion depends on both the nature of the process fluid (for instance a light gas will behave differently fi'om a dense gas) and the initial concentration of HoS in the plocess fluid.

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emission conditions If under plessure then process fluids containing HoS could be released to the atmosphele, for example, via a leak, weII services lubricator, maintenance or maloperation of a sampie vaive. The release pressule, duration, rate (with time), hole size, elevation and direction influence dispersion. Releases can also occur fi'om vaporising liquid pools.

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atmospheric conditions, wind speed and dilection A high pressule gas release rviil initially be diluted by air due to the turbulence of the jet, thereafter the ambient temperature and atmospheric stability become influencing factors. !\;ind speecl and dilection affect both the jet behaviout' and subsequent diiution.

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topography Dispersion is accelerateclovel mole buiIt, np or rvoodeclland. Given stabie weather' conditions a heaq;. gas rvill also tencl to accumulate in low lying areas thus the contours of the land. and plesence of. for,'instance, buncied aleas can influence dispersion.

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3 Assessment of Risks from H2S

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samPlingttme

time plym: fluctuate with time. A short sanrpling ciisper..sing a in concentrations sampie high exposureconcentrations,a longer in the dispersionmocrei*uy o"" exposure' time givesa more lealistic avelage Raciiation' using moclelswithin sIPNI's FRED 6ire' estimated be can rates Dispersion primariiy as a moclels.FRED has been rleveloped Exprosion.Dispersion)suite of thus is weli Assessmentstud.ies(seeEP 95-0352) screeningtool for euantitative Risk opco or is not available for use within an FRED where mod.elhng of type suited to this from nu."r.ury, aclviceshould be sought where specificcasestucliesu.J.or,riclered SIEP'

t . , 2t l ^ r . - clictated r r ^ + ^ + ^ . t 'by the maxrmum co n c e n t r a t i o n o f 'HnS Riskt At'ea' is an of The classification the Hzs to do harm is used othe, *or,r. the potu.rtiul for HrS in the process str.eam . In of the dispersion is that an accurate estimation acknowledgecl is it as criteria as the

difficult to Pledict' 10 ppm could occur that Hrs in concentrations above However. it may be possibre perhaps public or ,Hrs Risk Ar;" for example on a neighbouring, outsicle the classified necessitate the Determination of this risk may accommodation. or. faciiity party, thir.d aggl'egate risk to i.r.rrrairr* the calculation of the use of more rigorous eRA t".irniq..u. leak scenarios' RiskA'La'clue to the cred'ible the.I"rrifi"diHrs outside ind.ividuals neghgible region' a may be very low, perhaps in the Arthough this aggregate risk d'irection resulting in death cond.itions with irr" *i"d in a r.eleaseunder stable weather yardstick would the'efore be be feasible. A more suitable nevertheless could. effects or ill the d-istance to neighbouring d.istance oi irs r"^rT. to fix the use of the maximum effect in terms of effect gives an i.nd.icati6n of the consequences ar.easof concern. Table v. r 'worst case' dispersion scenarios' of distances of an arbitrary sel"ection in a comm'unity residents (eg infants, elderly) It shourd be noted that sorrre the working than Yrrore severely ;t lower levels around a plant rnay react population.

3.2.3 Productionof sulphur dioxide

and is also HZS is burnel i" the atmosPhere when formed products the of SOois one often Present in combination formed.whenpv'"pr'"ricironsulphicieoxidises.Itisalso with HtS.

_-.rr^^^+. gas (or liquid) with a strong suffocatrng non-flammabre Surphur d.ioxideis a colourless. in sputum and. causes coughing. an increase odour. It is a respiratory irritant at low concentrations. production and b,o,,choconstr.iction been set in order rimits for sulphur dioxicle have Recommend.edoccupational expos*re of Governmental The rggunggb American conference to prevent these acute symptoms. on an S-hour time (ACGI}I) Thr.eshord.Limit Value based. Ind.ustr.ial Hyelenists Limit is 5 ppm' 15-minute short Term Exposr'r.e weighted.average is 2 ppm.The

3.3 SafetYEffects of HzS 3.3.1 Effectson metals

conversei5'rvhetr be consicleleclto be nou-cor''.-osive' can watel' fi'ee of absence H,,S in the such zr'sstalt-upishr'rtclurLngabnorrnal situzttions' flJe rvater is plesent, especialiv u'iIl most probabl]' take lliacel' ottt a iircii' general con'osion circr'riating or d.rilling clown. present' either' ions ?l"nr"tttal sulphrtl' al'e If calbon d'ioxide. o]:ygen' chior"ide

7 1995 E P 9 5 - 0 3 1 7R e v r s t o0n 5 O c t o b e r

H S u l p h i d e( H z S )i n O p e r a t i o n s H S EM a n u a lE P 9 5 - 0 3 1 7H y d r o g e n inc iiy ic iua l l l ' o r to g e th e l th e n s e v e re col rosi on may take l tl ace w i thi n per . iod. F u rth e r. d e ta i l s a re g i v e n i n A ppendi x III.

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iron sulPhide 3.3.2 PYroPhoric pyrophoric iron sulphicle can be formeci on the internal surfaces of carbon steel equipment containing HrS. h'on oxiclepresent on the internal sttrfaces will react u the HoS ancl form p-r'rophoriciron sulphide which, on exposure to oxygen can autorgnitel This pr.ocessand the means to manage the hazard are detailed in Appendix Although pyrophoric iron sulphicle can folm and collect on ali internal surfaces of

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carbon steel equipment, likely places of accumulacions ale: Iubricatols (retrieval of wireline fishes, mill-scale from tubing) :

ff:"" vessels

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storage tanks.

\\[ei]st steps can be taken to reduce the formation of pyrophoric ilon sulphide it m never be assumed that there can be an absolute prevention of the reactionTherefore any equiprnent constructed of carbon steel which is in contact iron sour hydrocarbons should be treated as if it contained pyrophoric sulphide. Great care must be taken on opening equipment likeiy to contain pyrophoric iron sulphide, for its removal, d.isposal,etc. For further detaiis see Appendix IV.

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EP 95-0317Revtsion0 5 October1995

4 Controland Safe Working Practices

CONTROLAND SAFEWORKINGPRACTICES

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working in H2s Designated 4.1 The Frameworkof controrsfor Areas

points in turn: by examining each of the following derived is contrors of The framework in what concentrations (Hzs Area . where is H2S likely to occur and Classification)

(Hzs the concentrations measured/monitored how wilt H2s be detectecl ancl Detection) presence of H2S (warning signs) what is needed to warn of potential (Access controls) to H2s d.esignated areas what is need.edto control access areas work is carried out in H2S designated what is needed.to control how (Permit to Work) must be carried/used- in H2s designated what protective breathing equipment Protective Bquiprnent) areas (Respiratory areas for access/work in H2s designated what procedural controls are required

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(Proceduralcoot"olsandStandinglnstructions) in H2S for personnel accessing/working o what competence levels are needed. in HZS procedures) designated areas (Competence used: on the type and extent of controls The following factors have a bearing entering (eg sampling from H2s-containing equipment, . the tylpe of work activrty vessels, etc) (ie degree of exertion) o the level of human activity reiative to potential H2S sources ' the location of work personnel rthenumbersofworkpersonnelinvolved(particularlylargenumbers) release . the potential for an uncontrolled or upsel out (eg shutdown/start up, concurrent . the type of operations being carried. oPerations)

effects of vibration' of equi.pment (eg leaks, cracks, the state of integrity of items etc) still cond.itions (eg inversion, wind the occurl.ence of abnormal atmospheric etc) conditions [often at night]' storm'

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the timing of wor-k (eg at night)

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(eg where personnel have to work in the workplace and access cond.itions o' with poor access)' crampedicongested cond'itions the necessaly controls are that: The key requirements in devising taken into account . all the factors are recognised and

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the appropriatecontlols are specified

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I EP 95-0317Revision0 5 October1995

H HSE ManualEP 95-0317HydrogenSulphide(HzS)in operations V

4.2

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HZSArea Classification

4.2.1 The basis of classification The classification of HrS areas should be based on rhe likelihood of HrS presencein the area and the rnaxirnum concentration of HrS that can be present.

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Likelihood of H"S presence is defined according to a range of possibilities between impossible (ie always below the Occupational Exposure Limit (OEL), of l0 ppm) ancl expected uncler expected operating conditions. The two leveis of significa"." i" determining how concentration contributes to alea classrfication are 10 ppm (the 1evel below which there ale no health symptoms - the OEL) ancl 200 ppm (the approximate dividing iine below which the effects of HrS cause minor/reversible symptoms and above which major/permanent physiological damage is causecl).

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4.2.2 The effects of dispersion In all work situations (except those involving confinecl spaces and entry into equipment) some dispersion will occur when HoS-containing fluids are released..Gas leaks-from equipment under pressure can be considerably cliluted in a short d.istance by jet entrainment of the surrounding air (even when pressures are very low, say 0.1 kpa). The probability of inhaling undiluted process B&s, if an accidental leak occurs, is extremely low and in principle a d'ilution of e0 to 30 times can be assumed within 100 diameters of the outflow. However the consequences of an accid.entcausing exposure to high levels of HrS are extremeiy serious and it is not acceptable to ignore this small but significant risk. For example, an exposure, to 1000 ppm HrS in air, ho*"17"r brief, is Iikely to be fatal unless rescue and resuscitation are immed.iate. For this reason the maximum level in a gaseous process stream, for which the health risk can be truly considered minor in the event of an accidental leak, is 500 ppm. Even this level needs to be qualified because there are types of gaseous release in which no dilution occurs: ' .

the release of heavier than air vapours (> 1.05 x d.ensity of air) from a liquid spill an atmospheric vent at very low velocities.

Light sour condensate is probably the worst in this respect. 00 nqm HrS in the process (or 200 ppm if significant hearry vapour release is possibie) f is the limit above which the HoS concentrations in air are likely to ,"rult in *"io, symptoms, causing permanent physiologicat damage. At the iower end of the scale 50 ppm in a plocess stleam is recommended as the levei below which an accid.enrai leak is unlikely to cause any noticeable toxic effects of health hazard significance. Accurate estimation of the dispersion to detelmine HnS concentration at particular a location remains difficult. For this reason it i.s lecomrrjrendedto base the use of protective equipment on the maximum concentlation of H"-s in the process stream rather than in air'. Table 4.l summarises HrS concentrations i.rproless gas streams, derived maxima in air. the effect on expo.ud vicrims ancl the required. action in the event of exposure.

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4 Controland Safe Working Practices Table 4.1

H2S concentrations and the effectson exposedvictims

H25 concentration limit in gaseous

Derived maximum H2S concentration in air (ppm)

Effect on victim

Required action for victim

>500

R api dunconsci ousness. Deathoccurswithin minutes

200 to 500

Maj orsymptomscausi ng permanentphysiological damageor death.R api dl ossof senseof smel l .Lungoedema afterabout 30 minutes' exposureand may stilloccur some time after rescue Minor,reversiblesymptoms such as irritationof eyes,nose, throatand lungsfrom exposure for maxi mumof 10 mi nutes. A t 100 ppm senseof smel ll ost w i thi n3 to 15 mi n. A t 200 ppm senseof smell lost raoidlv. Occupationalexposurelimit(for 8 hr exposure,ACGIH documentationof TLVs). Settinqon HzS alarm svstems No svmptoms

Removalto safe atmosphere. Artificialrespiration Removalto safe atmosphere. Artificialrespiration

Process streams (ppm)

>500