H2S Manual - Shell

Shell International

Exploration

and Production

B.V.

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H2S in Operations

EP 95-0317

MANUAL

H S E

R e v i s i o n 0 : 6 O c t o b e r 1 9 9 5

EP HsE Manuar

_Amendment

_Record

sheet

S e c t i o n Number: Ep 95_0317 Section Tifle: H2S in Operations

Description of amendment Original _{hard copy and CD_ROilf-G}

Contents

CONTENTS

1 Introduction

2 ldentification of Sources of HZS 2.1 Process Fluids

2.2 Sulphate Reducing Bacteria (SRB) 3 Assessment of Risks from HZS

3.1 Health Effects of H2S 3.2 Erivironmental Effects of H2S

3.2.1 Environmental concerns for H2S emission and air quality standards

3.2.2 Dispersion in the surrounding atmosphere 3.2.3 Production of sulphur dioxide

1.3 .. fety Effects of H2S

\,

3.3.1 Effects on metals 3.3.2 Pyrophoric iron sulphide

I Control and Safe Working

Practices

t 1 The Framework of Controls for Working in H2S Designated Areas

1.2 H2S Area Classification

4.2.1 The basis of classification 4.2.2 The effects of dispersion 4.2.3 The classification process

'.3 H2S Detection

4.3.1 Fixed systems 4.3.2 Portable sensors

. 3 Personal monitoring systems 4.3.4 Testing and calibration

.4 Waming Signs .5 Access Controls .6 Permit to Work (PTW)

7 Respiratory Protective Equipment

4.7.1 The types of RPE

4.7.2 Protection for normal ooerations 4.7.3 Protection in event of accidental release

scenanos

4.7 4 Protection in areas subject to sulphate-reducing bacteria (SRB)

Procedural Controls and Standing Instructions H2S Competence

3

5 rt ,B I I I 1 0 1 0 1 0 1 1 1 2 1 a 1 3 1 A I T 4 t t $ 1 5 4 t r 1 5 4 7 t t 1 7 1 8 1 8 1 9 1 9 2 0 P 95-0317 Revision 0 5 October 1995 4.9.1 Competence requirements 4.9.2 Trarnrng programme

4.9.3 Specific elements of the training programme 4.9.4 Competence certification

4.9.5 Competence review

5

Recovery

5.1 Emergency Planning

5 . 1 . 1 E m e r g e n c y e q u i p m e n t

5.1.2 Procedure for major H2S release 5.1 .3 Rescue procedures

5.2 Firefighting

5.2.1 Hazards 5.2.2 Precautions

5.2.3 General procedures/guidelines

6 Guidelines for the Preparation of HZS Procedures

6.'l Formulation of Work Procedures 6 . 2 D r i l l i n g a n d W e l l O p e r a t i o n s 6 . 3 P r o d u c t i o n O p e r a t i o n s

6 . 3 . 1 S a m p l i n g 6 . 3 . 2 l s o l a t i o n 6.3.3 Depressurising 6.3.4 Flushing and draining 6 . 3 . 5 P u r g i n g

6.3.6 Vessel entry

6.4 Maintenance Operations A p p e n d i c e s

I Formation of H2S by Sulphate Reducing Bacteria (SRB)

ll Physical Properties and Physiological Effects of H2S

lll H2S Corrosion

lV Pyrophoric lron Sulphide

V H2S Dispersion Vl H2S Detection Vll RespiratoryProtectiveEquipment 2 0 2 1 22 22 1'2

25

25

2 5 2 5 z o 28 2 8 2 8 28

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29 3 0 30 a 1 . 2 1 J I .r..) 5 Z 32 3 3 34 37 4 1 45 47 4 9

H S E Manual Ep gs-O317 H y d r o g e n s u r p h i d e _{( H z s ) in operations}

Vlll Typicalprocedures

lX Examples _{of H2S Area Classification} Systems in Use

Gf

ossary

References

5 9 A 2

6 5

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EP 95-0317 Revision _{0 5 October 1995}

1 Introduction

1

I N T R O D U C T I O N

I ffydrogen Sulphide GIgS) is an extremely ciangerous substance, causing fataiiti I

,".r. H.S occurs frequently in EP operations, it is consiclered necessary to cleclit

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supersedes EP S-SOOO-32. The apploach is in line with the hazirds and effects I management process described in the HSE Management System EP 95-0300.

I fhe report describes four steps:

. _{identification of all sor-rrces} of HoS exposure (Chapter' 2)

| ' ! i r ' r

| . assessment of the risk to personnel (Chapter 3) o controls and safe working practices (Chapter 4)

I _t . recovery method.s in the event of loss of control (Chapter 5)

Recovery should include contingency planning for all H"S-related situations (eg H:S I leakage, evacuation procedures, etc)

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It is of vital importance that these four steps are completed before any work is r undertaken.

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I The report is intended for use by field personnel in drilling, production and maintenance operations and does not cover design requirements for new plant. I It does not add.ress details on the protection of the general public or the seiectio

l _{mabrials for HoS service.}

I The Guideline provides the basis for the development of Opco specific procedure

I Chapter 6 gives some specific guidance on the preparation of H"S procedures fo: production, drilling and maintenance activities.

I Reference is made to Shel1 Safety Committee guide Hydrogen Sulphide, Hazard

I Precautions G,ef. 1).

The reader's attention is drawn to the following:

1

| . 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} I

.oncentrations of HoS

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

I others.

If the reader does not understand an)' part of this document heishe must discuss it wiih 'l

.omeone who d.oes.

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2 ldentification of Sources of H2S

2

I D E N T I F I G A T I O N

O F S O U R C E S

O F H z S

Liquid and gaseous hyd,rocarbons may contain HrS in sufficient concentrations to present a hazard to personnel, equipment and the environment'

HrS can be present in oil refineries, process plants, pipelines, desulphurisation piant's' oil/gas/water wells, during drilling or well workover, sewers, swamps, or any area where there is decayrng organic matter or stagnant water (eg utility shafts in offshore platforms).

HrS can also result from acidicaustic reactions, for example when acid is used to ciean equipment containing iron sulphide or to neutralise spent caustic which has been used t* HrS scrubbing. HzS may also be present in spent acid flowed back after well

stimulation.

All facilities potentially exposed. to HoS must be designecl to resist the harmful effects of HzS at the anticipated operating temperatures and pressures'

HrS in the upstream oil and gas industry comes from:

. the original reservoir, as a result of the hydrocarbon source material and the cond.itions under which it was converted to oil ancl gas. If this is the case then H'S will be produced with the fluids

o stagnant seawater systems, by the action of sulphate reducing bacteria (SRB) o the reservoir after proionged. injection of water with oxygen (seawater, brackish,

formation water) which *ut result in 'souring' of the fluids within it due to the action of SRB introduced during the injection process. Any HrS will be

subsequentiy produced with fluids'

2.1 Process Fluids

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

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

o during venting from tanks'

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

2.2 Sulphate

Reducing

Bacteria

(SRB)

SRBs are the source of a range of hazard.s includ.ing HgS. Cond:tions necessary for SRB to exist an6 d.evelop, hazarcls associated with SRBs (including H"S), means of

prevention, detectitn and control are ali described in Appendix I'

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3 Assessment of Risks from H2S

3

A S S E S S M E N T

O F R I S K S F R O M H Z S

This document provides a set of recommendations based on broad based consequence analysis and operational experience.

A full risk analysis may provicle a better insight into the potential frequency and consequences of specific HoS related events and point to possible risk reduction measures. Howe!'er, perioJs of highest risk may not always be predictable and

recognised and. it is advrsecl to aclopt the recommendations for classification of 'HrS Risk Areas, contained in this document. By doing so, procedures, including those for the use of protective equipment, will ensure the appropriate state of workforce awareness and preparedness.

Risks associated with incidents that may effect areas beyond the classified 'HrS Risk Area, should always be assessed and this may even be a legislative requirement. Such risks may be to persons, for instance, in Opco facilities or accommodation, third parties or the public (refer to 3.2.2).

The threats presented by HrS in a process and non-process, eg sewerage throughout the Iifetime of that facility or pi-peline will be recorded in the HSE Case together with the control measures.

3.1 Health Effects of HrS

The current American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TL\ry is 10 ppm Time Weighted Average (TWA) 8h and 15 ppm Short-Term Exposure Limit (STEL).

The major hazard of HrS is its ability to cause rapid damage to health or sudden death due to accidental exposure'

Brief exposure to concentrations above 500 ppm may result in rapid unconsciousness without any warning symptoms. Exposule to HrS above 500 ppm for any lenglh of time is considered. as potentially lethal. Death due to stoppage of breathing may follow within a few minutes unless the victim is removed to a safe atmosphere in time and artificial respiration is applied.. If the victim survives, complete recovery is possible in most cases. Exposures over 30 minutes to HzS concentrations of 200 ppm and above may cause r...,*r.lation of fluid in the iungs Oung oedema).At concentrations above l0 ppm, HrS can have an irritating effect on the eyes and the mucous membranes of the nose, throat an6 1ungs. The pr-imary source of exposure to HrS is by inhalation. In low concentrations HrS has the odour of rotten eggs'

It must be emphasised. that the unpleasant od.our of HoS, which can even be detected at concentrations of 0.02 ppm, may not be detectable at concentrations above 100 ppm due to rapid loss of the sense of smell.

Odour cannot be relied upon to detect the presence of dangerous c o n c e n t r a t i o n s o f H r S .

The effect of H=S on the hocly at clifferent concentration levels and the occupational exposure limits are shown in Appendix II'

personnel at risk from exposure to H"S must be trained to know what to do if H"S is detected. or if an unconscior.rs person has to be rescued. Such training is vrtal since to some extent it is necessary to controi the 'conditioning' that might resuit in an individual hur.r.ving immecliately to the aicl of someone ovelcome by

H'S-l

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I i I EP 95-0317 Revrsion 0 5 October 1995

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

V

t)

REMEMBER:

50 PER CENT OF THB PEOPLE

KILLED IN H.,S

INCIDENTS

\AIERE

TRITNG TO RESCUE

OTHERS.

3.2 Environmental Effects 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 Environmental

concerns for HzS emission and air quality standards

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 D i s p e r s i o n

i n t h e s u r r o u n d i n g

a t m o s p h e r e

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.

o _{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.

. 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.

. topography

Dispersion is acceleratecl ovel mole buiIt, np or rvoodecl land. 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

o samPling ttme

concentrations in a ciisper..sing plym: fluctuate with time. A short

sanrpling time in the dispersion mocrei *uy o"" high exposure concentrations, a longer sampie time gives a more lealistic avelage exposure'

Dispersion rates can be estimated using moclels within sIPNI's FRED 6ire' Raciiation' Exprosion. Dispersion) suite of moclels. FRED has been rleveloped primariiy as a

screening tool for euantitative Risk Assessment stud.ies (see EP 95-0 352) thus is weli suited to this type of mod.elhng where FRED is not available for

use within an opco or where specific case stuclies u.J.or,riclered nu."r.ury, aclvice should be sought from

S I E P '

t ^ r . - r r ^ + ^ + ^ . t ' t . , 2 t l o n c e n t r a t i o n o f

The classification of an 'HnS Risk At'ea' is clictated by the maxrmum c

HrS in the process str.eam . In othe, *or,r. the potu.rtiul

for the Hzs to do harm is used

as the criteria as it is acknowledgecl that an accurate estimation

of the dispersion is

difficult to Pledict'

However. it may be possibre that Hrs in concentrations

above 10 ppm could occur

outsicle the classified ,Hrs Risk Ar;" for example on a neighbouring,

perhaps public or

thir.d party, faciiity or. accommodation. Determination of this risk

may necessitate the

use of more rigorous eRA t".irniq..u. i.r.rrrairr* the calculation of

the aggl'egate risk to

ind.ividuals outside the.I"rrifi"diHrs RiskA'La'clue to the cred'ible

leak scenarios'

Arthough this aggregate risk may be very low, perhaps in

the neghgible region' a

r.elease under stable weather cond.itions with irr" *i"d in

a d'irection resulting in death

or ill effects could. nevertheless be feasible. A more suitable

yardstick would the'efore be

the use of the maximum effect d.istance oi irs r"^rT. to fix

the d-istance to neighbouring

ar.eas of concern. Table v. r gives an i.nd.icati6n of the consequences

in terms of effect

distances of an arbitrary sel"ection of 'worst case' dispersion scenarios' It shourd be noted that sorrre residents (eg infants, elderly)

in a comm'unity

around a plant rnay react Yrrore severely ;t lower levels than

the working

population.

3 . 2 . 3 P r o d u c t i o n

o f s u l p h u r d i o x i d e

SOo is one of the products formed when HZS is burnel i" f o r m e d . w h e n p v ' " p r ' " r i c i r o n s u l p h i c i e o x i d i s e s . I t i s a l s o

w i t h H t S . _{_ - . r r ^ ^ ^ + .}

Surphur d.ioxide is a colourless. non-flammabre gas (or liquid)

with a strong suffocatrng

odour. It is a respiratory irritant and. causes coughing. an increase

in sputum

production and b,o,,choconstr.iction at low concentrations.

Recommend.ed occupational expos*re rimits for sulphur dioxicle have been set in order to prevent these acute symptoms. The rggunggb American

conference of Governmental

Ind.ustr.ial Hyelenists (ACGI}I) Thr.eshord. Limit Value based. on an S-hour time weighted. average is 2 ppm.The 15-minute short Term Exposr'r.e

Limit is 5 ppm' the atmosPhere and is also often Present in combination

3.3 SafetY

Effects of HzS

3.3.1 Effects on metals

H,,S in the absence of fi'ee watel' can be flJe rvater is plesent, especialiv clurLng clown. d.rilling or circr'riating ottt a iircii' If calbon d'ioxide. o]:ygen' chior"ide ions

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

consiclelecl to be nou-cor''.-osive' conversei5' rvhetr abnorrnal situzttions' such zr's stalt-upishr'rt-general con'osion u'iIl most probabl]' take lliacel' ?l"nr"tttal sulphrtl' al'e present' either'

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

l ) i n c i i y i c i u a l l l ' o r t o g e t h e l t h e n s e v e r e c o l r o s i o n m a y t a k e l t l a c e w i t h i n a v e l ' y s h o l t p e r . i o d . F u r t h e r . d e t a i l s a r e g i v e n i n A p p e n d i x I I I .

3 . 3 . 2 P Y r o P h o r i c

i r o n s u l P h i d e

pyrophoric iron sulphicle can be formeci on the internal surfaces of carbon steel G

equipment containing HrS. h'on oxicle present on the internal sttrfaces will react u the HoS ancl form p-r'rophoric iron sulphide which, on exposure to oxygen can

auto-A L r l

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rgnitel This pr.ocess and the means to manage the hazard are detailed in Appendix Although pyrophoric iron sulphicle can folm and collect on ali internal surfaces of carbon steel equipment, likely places of accumulacions ale:

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: ff:""

Iubricatols (retrieval of wireline fishes, mill-scale from tubing)

vessels

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pig

receivers

\-

o 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

reaction-Therefore any equiprnent constructed of carbon steel which is in contact sour hydrocarbons should be treated as if it contained pyrophoric iron 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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4 Control and Safe Working Practices

CONTROL

AND SAFE WORKING

PRACTICES

4.1 The Framework

of contrors for working in H2s Designated

Areas

The framework of contrors is derived by examining each of the following

points in turn:

. where is H2S likely to occur and in what concentrations (Hzs Area Classification)

. how wilt H2s be detectecl ancl the concentrations measured/monitored (Hzs

' _Detection)

r what is needed to warn of potential presence of H2S (warning

signs)

r what is need.ed to control access to H2s d.esignated areas

(Access controls)

r what is needed. to control how work is carried out in H2S designated areas

(Permit to Work)

\- _{o what protective breathing equipment} must be carried/used- in H2s designated areas (Respiratory Protective Bquiprnent)

o what procedural controls are required for access/work in H2s

designated areas

(Proceduralcoot"olsandStandinglnstructions)

o what competence levels are needed. for personnel accessing/working

in H2S

designated areas (Competence in HZS procedures)

The following factors have a bearing on the type and extent of controls used:

. the tylpe of work activrty (eg sampling from H2s-containing

equipment, entering

vessels, etc)

o the level of human activity (ie degree of exertion)

' the location of work personnel reiative to potential H2S sources r t h e n u m b e r s o f w o r k p e r s o n n e l i n v o l v e d ( p a r t i c u l a r l y l a r g e n u m b e r s ) . the potential for an uncontrolled release

. the type of operations being carried. out (eg shutdown/start

up, concurrent or upsel

oPerations)

o the state of integrity of items of equi.pment (eg leaks, cracks,

effects of vibration'

etc)

o the occurl.ence of abnormal atmospheric cond.itions (eg inversion, wind still conditions [often at night]' storm' etc)

. the timing of wor-k (eg at night)

r the workplace and access cond.itions (eg where personnel have to crampedicongested cond'itions o' with poor access)'

The key requirements in devising the necessaly controls are that: . all the factors are recognised and taken into account

4

work in

o rhe risk is assessed

. the appropriate contlols are specified

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EP 95-0317 Revision 0 5 October 1995

H H S E M a n u a l EP 95-0317 H y d r o g e n S u l p h i d e ( H z S ) _{i n o p e r a t i o n s} V l) G R

4.2 HZS Area Classification

4.2.1 The basis of classification

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

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).

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.ent causing 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.

f 00 nqm HrS in the process (or 200 ppm if significant hearry vapour release is possibie) 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 a particular location remains difficult. For this reason it i.s lecomrrjrended to 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 Control and Safe Working Practices

Table 4.1 H2S concentrations and the effects on exposed victims

H25 concentration limit in gaseous Process streams (ppm) Derived maximum H2S concentration i n a i r ( p p m )

Effect on victim Required action for victim

>500 > 5 0 0

200 to 500

R a p i d u n c o n s c i o u s n e s s . Death occurs within minutes M a j o r s y m p t o m s c a u s i n g permanent physiological d a m a g e o r d e a t h . R a p i d l o s s o f

s e n s e o f s m e l l . L u n g o e d e m a after about 30 minutes' exposure and may still occur

some time after rescue

Removal to safe atmosphere. Artificial respiration Removal to safe atmosphere. Artificial respiration

<500 _{10 to 200 Minor, reversible symptoms} such as irritation of eyes, nose, throat and lungs from exposure

f o r m a x i m u m o f 1 0 m i n u t e s . A t 1 0 0 p p m s e n s e o f s m e l l l o s t w i t h i n 3 t o 1 5 m i n . A t 2 0 0 p p m sense of smell lost raoidlv.

Removal to safe atmosohere

1 0 Occupational exposure limit (for 8 hr exposure, ACGIH documentation of TLVs). Settinq on HzS alarm svstems

N o n e

< 5 0 < 1 0 _{No svmptoms N o n e}

@eference Shell Safety Committee publication 'Hydrogen Sulphide' 1986) G,ef. 1). See also Appendix V.

4.2.3 The classification

process

The sequence to be followed in determining HrS area classification is shown in F i g u r e 4 . 1 .

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

Figure 4.1 HrS area classification

ldentify H2S sources, collect and analYse praess/f acilities data,

establish release mechanisms concentration in air <10 ppm under all H2S-free zone Derived H2S conccntration in air <200 PPm? presence pcsible

during normal oPerating conditions?

As shown in Figure 4.1, all areas where the H'S concentration in air may exceed 10 pp*in"u be designated Hrs risk areas. They should be marked upon a dejicated set of drawings together with the associated risk: minor or rnajor.

Note: During d.riiling or workover operations in areas where HrS plesence is expected, the level of exposure cannot be accurately pred.icted. In that case' precautions as for the highest level of accid.ental exposure should be undertaken.

For exploration driling in new areas it should ahvays be assumed H"S may be pr:esent and precautions established accordingly'

4.3 HZS Detection

The objective in HoS detection is to provide early warning to caution personnel against entry into a kno*ri hazardous area without taking the appropriate HSE precautions' Amongst the key points in defirung a detection system are the following:

. it should exhibit fail-safe design . it should be specific for HrS

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4 Control and Safe Working Practices

. _{it should have detectors close to all potential sources of leakage.}

Only equipment specifically developed for the detection of HrS will achieve the clegree of response necessary to alert personnel.

It is important to be aware that all detector systems have an in-built delay between HrS release and its detection, due to the response time of the system and its components.

WHEN A}.I HzS ALARM IS SOUNDED THE GAS HAS ALREADY BEEN

PRESENT FOR SOME TIME AND I\{AY HA\M ALREADY REACHED

DANGEROUS CONCENTRATI ONS!

4.3.1 Fixed systems

No matter how well designed the facihty and how good the stand.ard. of operation an4 maintenance, _{the possibility of accidental release of HoS cannot be totaliy discounted..} For this reason it is recommended _{that HrS detection systems be installed. in high HoS} risk areas, defi.ned as those where:

' _{the process contains gases with HrS concentrafions in excess of 1.0 per cent} volume (10,000 _{ppm) or}

o _{liquids with HrS contents which could glve rise to comparable H"S emissions with} the resultant possibility of a major hazard occurring outside the facility bound.ary. However, consideration should also be given to installitrg HrS detection systems where such concentrations exceed _{0.1per cent volume (1,000 ppm), particularly where}

dispersion of leaked gas could be hindered or where escape is difficult, as for example offshore.

A fixed system does not in itself provide protection for personnel. It shouid. not therefore be considered a substitute for normal entry precautions to a high risk area, where tests using portable equipment and carrying of breathing apparatus should be part of

procedure for entry.

The basic requirement is a system of sensors located where HrS is most iikely to be released to the atmosphere or accumulate. For further details on the design of fixed. detection systems, refer to Appendix VI where relevant sections of SSC guid.eline 'Hydrogen

Sulphide, December 1986' (Ref. 1) have been included for easy reference. Refer also to DEP 32.3I.20.11-Gen ffi,ef. 2) for further detail concerning the selection, location, installation and calibration of fixed HrS detection systems.

It should be noted that high concentrations of H,S in small volumes mav be insufficient to trigger the HrS detection system.

4.3.2 Portable

sensors

In addition to the fixed HzS detection systems, portable sensors are used. for alerting the individual and should be availabie to designated personnel. They may be used. in locations where it is not practical to install fixed sensors and can also pror.ide back-up facilities in the event of a fixed system failure. These d.evices usually glve an aud.ibie and visual warning if a preset levei is exceeded and pro'"ide the ability to have a continuous read-out of the concentration.

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

lnventories and the aliocation of the portabie d,etectors

shoulcl be clescribed in the foliowing:

. Operating Manual

. Emergency Procedures Manual . ContingencY Plans'

The instrument provided should. be continuous and automatic

in operation and suitable for use by non-technicar p"r.orrrer. The instrument should

give " tl"ut audible (and' visual) alarm in the pr"r.rr.. "i UrS at the pre-selected

concentration'

In add-ition the instrument should:

. b e s u i t a b l e f o r u s e i n h a z a r d o u s a l . e a s ( m a n d a t o r y ) ' be robust in construction

. be capable of being easily hand.Ied and operated by one person

. have a integral power source, rechargeabre, rasting at least eight hours . have test function caPabilitY

. be easy to calibrate r alarm on failure'

4.3.3 Personal monitoring systems

personar Hrs monitoring systems are_only used to- wa.rn that a preset

level is exceeded' They are not meant to be ,i""rrrring de*ri.". ,ro, should they be

used as testers' personal monitoring ,yrt"*, are based. on the diffusion characteristics

of toxic gases and usually incorporate "r Juctrochemi.ur-J"r"ctor

which generate-s an electric current as the toxic gas passes over it. This current is converted

into an audible or visual dispray signal (or both) Th" ;"rnts to be considered in selecting

a personal H2S monitor ur" d."t.ribed in APPendix VI'

A prerequisite for using the monitors d.escribed above is that the operator

is made fully aware of the capabilities and. rimitationsof the equipment

and of what action has to be taken in the event of the alarm being tri#red lt sensing head should' never

be shieided by clothing or "ti;;it"*.. Higii*ar of HrS will quicklv

'poison' most

personal monitors'

4.3.4 Testing and calibration

AII systems and equipment shouid. be tested. in accordance

with the manufacturer's recommend.ations or the maintenance ,;;;1;$r, "rtuuii.h"d. tt"ough strict application

of

the Reliability centred rvr^irrt"nance 6cno ilethod'oiogy

depending on the particular s i t u a t i o n - B e c a u s e H o s d e t e c t i o n s y s t e m s a r e p ' i * u ' i i f * u " ' i " g d ' e v i c e s ' n o t o n l y t h e accur.acy should be verifiua urrt also the speed. of '..porr.e of the sensor'

The functioning of the system-related. parts such as visual beacons. audible warning devrces'

operator interfaces in the controt ."rrtre and. arike should also be verified

at i'egttlat intervals and before each period of ,rr". Due consid.erurron shourd. be given to access

to detectors to enabre frequent maintenance testing and calibration, til"

'estrlts of rvhich should be recolded.

For further details see Appendix VI'

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EP 95-0317

4 Control and Safe Working practices

4.4 Warning Signs

It is important that all equipment containing H"S is clearly marked, with vessels and pipelines individually identified. This is in addition to area warning notices which should be in all working languages. In some countries a national standard is available and in some legislation clearly defines the colour coding for process equipment and pipework containing HrS in hazardous concentrations.

r

_' I

fif,H:T::Tffi"ff,*H'$5;fttTilHffi::;*,:iT;:l;,m*y;

level of training should also be marked by appropriate signs and markers. Signr I

pictorial content are preferred to text only. j _{The following may be used as references:}

ISO 3864 Safety Signs and Colours equivalent to BS 5378 @efs. 3 and 4) BS 1553 Specification of graphical symbols for general engineering @ef. 5) SSC Safety Signs and Colour Coding September 1981 G,ef. 6)

\- API RP 49 Recommended _{Practice for Safe Drilling of Wells containing HoS G,ef. 7)}

4.5 Access Controls

Procedures must be in place for access, escape and movement control of personnel in HzS designated areas. These should include:

. _{inform the person in charge of the nature of your activities}

. _{all personnel should sign in and out at a central control point, outside the area,} where competency certifi.cates are checked

o _{special instructions concerning the work location, (normal access and escape} routes, wind direction)

. _{use of calibrated portable HrS detection equipment} I use of escape or BA sets

o working singly or in pails . radio communication

o _{special production supervision for non-HrS trained personnel as required, eg} construction workers. dr-ivers, etc.

The procedures may vary for different tpes of iocation (eg onshore or offshore) but should be prepared for the different activities which have to be performed.

4.6 Permit to Work (PTW)

A PTW should be issued fol any work to be carried out in H,S plant areas. As with any requilement for hazardous rvork. it is necessary- to establish the level of risk to the persons involved before defirung the necessary contlols and should address:

o _{satisfactory communication for al'ea or confined space entry} . _{p e r s o n a l H r S m o n i t o r s r o b e w o r n}

H S E M a n u a | E P 9 5 - 0 3 l T H y d r o g e n S u l p h i d e ( H z S ) i n o p e r a t i o n s

o s C C e s s c o n t r o l r e q u i r e m e n t a s d e s c r i b e d i n 4 . 5 o us€ made of personal tags and central tag board

r acld.itionar protective clothing provided for the type of environment encountered o safety equipment checked by a competent person and positioned correctly

ie compressed airrine BA; self-contained BA; portable d.etector; belts and life lines required.; positive isolation of aII lines to a piece of equipment

r eotry into a confined space (see Ref' 8)

For example: removar of pyrophoric sludge/debris_and waterwetting of any possible residues; gas testing ro, fl"*mable, to,.J and 02 levels; no entry if H2S

above L0 ppm (if escape is particularly time consumin! then lower HzS limits may be consider"at' rr"th air flow to be established if possible'

o frequency of testing for HoS and by whom

. r e t e s t i n g f o r H z S p r i o r t o r e s t a r t i n g a n y w o r k p e r i o d

. for work of an increased. time scale or greater degree of dilEculty where it cannot be guaranteed. that the average Hos level wil remain below 10 ppm' The wearing of a compressed airline breathing upp^r"tus shourd. be stipulated. (A11

possible steps to gas free the equipment ,rrorrra be und.ertaken before the extensive

usage of BA is accePted)'

NO ENTRY (except in emergency, with full Hos protection):

o if the confined space is being inerted, even if flammable vapours or H2S are not Present

. if the confined. space is known to contain 10 ppm or more of H2S vapours' In both these circumstances further ventilation should be applied'

Permit to Work generic guidelines are d'escribed in EP 95-0315'

wind,sock strategicalry sited and pointecr out to persons doing the job, together with instructions as to where to escaPe

adequate area warning signs positioned

4 Control and Safe Working Practices

4.7 Respiratory Protective Equipment

4.7.1 The types of RPE

Table 4.2 summarises respiratory protective equipment and its application. See also Table \TI.1.

Table 4.2 Respiratory protective equipment

1_{t \}

I

Type of Apparatus Description Application Self*onta ined breath i n g

apparatus wlth full face mask

Compressed air cylinders carried on wearer's back supply full face mask through flexible hose

'Positive _{pressure' mode minimises} pulling toxic vapour around seal of face mask

'Positive _{pressure' mode} recommended for

H2S-contaminated environment up to a max. 20,000 ppm (2%) H2S Duration 30 or 40 min depending on cylinder capacity

Suitable for escape Compressed airline breathing

apparatus with full fuce mask

Compressed air from remote cylinder supply or compressor fed to full face mask through flexible hose

'Positive _pressure'

mode with cylinders recommended for H2S-contaminated environment up to a max. 20,000 ppm (2%) H2S Direct supply from a compressor is less reliable and not recommended Not suitable for escaoe

Combination of self-contained and airline breathing apparatus (cascade system)

Self-contained breathing apparatus with compressed air cylinder and provision for connecting into compressed air supply

As for compressed airline above but also suitable for escaoe

Emergency escape BA sets with full face mask

Type | - Small compressed air cylinder canied in jacket pouch/ shoulder strap supplies full face mask through flexible hose'Positive pressure' mode prefened

Type ll - Clear plastic hood sealed at neck. Air supplied from cylinder through flexible hose

Duration 10 or 15 minutes depending cylinder capacity

Duration 5 to 15 minutes Easy to put on

Chem ical canister respirators Full face mask or mouth/nose assembly connected to canister (containing H2S absorbent chemical) by flexible tubing

Only to be considered for use for escape purposes subject strictly to conditions descrlbed in Appendix Vll

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

4.7.2 Protection

for normal operations

Depending on the H"S at'ea classification and the circumstances extent and level of controls (see 4.1 and 4.2), the foilowing levels are recommended:

Table 4.3 Protection level classification

Level of protection Description of protection A Monitor only

B Monitor and escape BA set to hand

c

Monitor and escape BA set mask at the ready D Monitor and BA set to hand

E Monitor and BA set mask at the readY F Monitor and BA set with mask fitted

Definitions of the terms 'at the ready' and 'to hand' are as follows: . 'at the ready'

For work close to a potential source of leakage the mask should be hangrng from the neck 'at the ready'.

. 'to hand'

For work further removed from a potential source of leakage having the mask ready, nearby and in the line of escape is sufficient.

However, a potential rescuer and/or the buddy on 'standby' should always have his mask hanging 'at the ready' and use a BA set.

In areas where HrS is normally present (refer to Figure 4.1), Ieve1 F shall always apply. In areas where HzS presence is quite possible first entry shall always be made with protection at level F. Only once the area has been made safe can the level of protection be reduced, eg to level B.

A BA set may either be self-contained, or air hose supplied. Where an escape BA set or BA is to be 'to hand', reliance may be put on strategically placed communal sets. Individual allocation of sets is, however, preferred to avoid the risk of confusion in an emergency. If appropriate, safety belts with lifelines to permit easy rescue may need to be worn.

Refer to Appendix VII and Table VII.1 for a summary of the main work scenarios and the recommended level of personal protection.

4 . 7 .3 P r o t e c t i o n i n e v e n t o f a c c i d e n t a l r e l e a s e s c e n a r i o s

The following guidelines may be used to determine personal protection for escape from, or rescue in aleas where HoS is not normaliy present but only after an acciclental release.

Where the maximum HrS concentration in air wiII not exceed. 200 ppm (< 500 ppm in process), where escape routes are sholt and the need for rescue is unlikely, it is sufficient to use a monitol Qevel A). This might apply to visitors to site, operators carrying out routine checks, or maintenance pelsonnel cioing light work. eg painting.

that influence the of personal protection

4 Control and Safe Working Practices

.1

I I

If a rescue situation might arise ol escape routes are }ong, then a BA set (essential for a rescue, Ievel D) or an escape set (endurance permitting, level B) should be 'to hand'. This might apply during maintenance work where an injury could occur preventing escape or where work is underway several levels from the ground.

In areas where the H2S concentration could exceed 200 ppm (> 500 ppm in process), compressed air full-face mask breathing apparatus with adequate endurance is necessary.

Consideration should be given to how personnel will be alerted when they are not actually breathing from their BA sets. Reliance on a warning from personal or frxed monitors can provide adequate warning for a distant source of H2S when concentrations cannot build up too quickly. For closer sources the sound or sight of a leak will provide much earlier warning. However, the employee at risk may not be alert to these

warnings if engrossed in work. Hence, the importance of a buddy on 'standby' in such HrS work situations. The 'standby' shall be positioned out of the danger area and shall have no work responsibility other than that of obsennrng the workers within the danger area and giving the alarm.

The proximity to the source of a possible release and the time it takes to reach a dangerous H2S concentration are thus important in deciding the state of read.iness for the donning of a BA set.

4.7.4 Protection in areas subject to sulphate-reducing

bacteria (SRB)

In all areas where SRB activity takes place, the presence of H2S shall be considered as Iikely but not normal and warning notices and area identification shall be applied accordingly. Access should be permit controlled. First entry shall always be made by someone wearing BA and carrying a portable gas detector (protection level F). Gas tests should include measurement of flammable gds, toxic gas and oxygen levels. When the HrS concentration is found to be below 10 ppm and instantaneous release can be discounted, entry is permitted without BA being worn (protection level B or D). Single person access should be prohibited. If the alarm of any monitor is set off all staff within the area must don the self-rescue equipment and evacuate the area without delay. If escape is particularly time consuming an ('early') alarm setting of 5 ppm may be adopted

4.8 Procedural Controls and Standing lnstructions

Local levels of exposure and the appropriate level of protection of personnel and other precautions, should be documented as standing instructions. For all normal activities these standing instructions should lay down in unambiguous terms:

o _{which areas are hazardous due to HtS}

. which jobs are/are not covered by the instruction

. rvhat precautions are mandator-v in the different situations . _{who may authorise permits for these jobs.}

Detailed guidelines on plepaling procedures fol HoS are given in Chapter 6.

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H S E Manual EP 95-0317 H y d r o g e n s u l p h i d e ( H z S ) i n o p e r a t i o n s

4.9 HZS Competence

All personnel who visit, work or carry out special (emergency) duties in an ar.ea where HzS is a potentiai hazard neecl to have a levei of com;retence _{compatible with the task-s} they are expected to carry out and must be trained.. In line with basic procedures developed _{as part of HSE management systems (see HSE Manua] Ep 95_0100}

and Ep 95-0r20), competence assurance _{requires the competencies to be identifiecl, training to} be provided and performance against requirements to be reviewed at regular intervals. only personnel who are trained. and certified to the required level of competence should. be allowed entry

11 3" HrS d.esignated. area. Training record.s an6 competence certification should be contained in an HSE personaip"r.port or similar document. Access by personnel to an Hzs area without an H2s entry permit should be prohibited., unless they are under direct control and surveill"-n." of " itoperly authorised an6

trained HrS permit holder who is accountable for the personnel for the time of exposure.

4.9.1 Competence

requirements

Sites with HtS classified areas should. have a three ievel competence scheme in place. A medical assessment should be required for personnel at levels 2 and. B to id.entify any factors which may preclude a person from wearing breathing apparatus. Local

reguiations may require more specific med.ical "rr"rr*ents. personnel with known physiological or psychological cond.itions that impair their normal respiration shall not be assigned to work involving potential exposure to HoS or sulphur dioxide

environments if use of breathing equipment o, exposure itself is likely to complicate their respiratory problems.

Level 1 - Familiarisation

AII staff and visitors to the site should. be aware that the site contains HrS classified areas' and of the hazards and risks of HoS. They should. also be aware of the emergency procedures _{in the event of a release and} -should

be informed. and where necessary instructed in the following:

o _{use of personal monitor and awareness/operation}

of detection systems o

meaning of and actions in the event of warning signais (visual and. audible) . _{what to do in case of HoS release.}

. _{u s e o f a n escape s e t .}

Level 2 - Classified area competence

AI1 staff who ale required to enter an HoS classified area as part of their normal work should understand and have demonstraied. _{the ability to respond to the following} requirements:

o _{to recognise the potential hazard} o

to be fully conversant with and capable of using all types of breathi.rg apparatus @A) as supplied at the location

I

to be fully' conversant with use of pelsonal and. portable monitoring equipment o _{to understand emergency}

requirements should the presence of H"S be detected. r _{to understand emel'genc)'requilements}

shoulcl _{a casualty situation occur.}

20

4 Control and Safe Working Practices

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.t

o to be capable of undertaking their roie in ener.'gency plans and if necessary take control of contingency and evacuation procedttres

r _{to be able to carry out first-aid for victims of H'S exposure.}

Level 3 - Staff with special duties

Staff with special duties with respect to contlol of HrS or to emergency response during a release will require specialist competence in those aspects of their duties in addition to competence at Level 2. Such staff includes emergency response teams, medics, production site supervisors, drillers and toolpushers, and safety officers.

I

,

4.g.2 Training programme

The training programme should be commensurate with the level of competence required I and may be on an individual basis or as a training course. Where the training cr

J run externally, or is not specific to the worksite, further training on the procedt detailed. arrangements for the particular worksite should be given.

I

1 Competence at Level 1 can normally be achieved as part of the general site - r \-

introduction. the essential points that must be coverecl as a minimum at this le' I

given above.

I For staff required to be cornpetent at Levels 2 or 3, a comprehensive tr: prograrnne for designated personnel should contain the following aspects I

plus any additional local requirernents: H2S introduction

. _{what is HrS}

. physical properties

I

.oncentrattons

J . occupational exposure limit for HoS o comparison with other gases

CIL\D

o characteristics o rrr€asurement of atmospheric I . sources I . _{effects on environment} . pyrophoric iron sulphide

. effects on health

. effects on equipment

ldentification

o area and risk classification . colour coding

. safety signs

Safe working practices

. access to worksite o p€rsonnel movements

. wind direction/indication . self protection

. _{buddy system} . l'escue procedure

. transportation . evacuation

. contingency plans o p€rmit-to-work system

H S E M a n u a l E P g 5 . O 3 l T H y d r o g e n S u l p h i d e ( H z S ) i n o p e r a t i o n s Detectors fixed personal positioning sensitivitY calibration

ResPiratory

Protective

equiPment

self- contained breathing app aratus escaPe sets

Iocation of breathing apparatus mask to face seal checking servicing of BA

First aid

o fesuscitation

In addition to the above, staff who are *"d,i.., drillers and HSE officers will

competencies-. detectors

The use of Portable instaliation should

servicin g recluirements portable

alarm settings Iimitations

air hose breathing apparat'us cascade sYstem

limitations of breathing apparatus wearing of breathing aPParatus working with breathing aPparatus donned

4.g.3 Specific elements of the

training programme

when providing training the fotlowing guiderines should

be adhered to in order to ensure the "ppropti"a" r".r.l of .otttpetence is achieved':

. breathing aPParatus (BA)

Training in the use of BA should require all pe'sonnel to wear

it and participate in a simulated. work ,"rri*. This shourd be of a duration sufficient to highlight any constraints which could. be d.etrimentar in a search and rescue situation'

o artificial resPiration

required' to carry out emergency response and .u"d to be trained' in their specialist

a n d o t h e r t y p e s o f H " S d ' e t e c t o r s w h i c h a r e p r o v i d e d o n t h e be practised b-v all participants'

. first aid

Training in first aid should include practical sessions on resuscitation' with actrve participarion by ail course memberr. gurr. first aicl should' also be explained if

this is not separ.ately trained for as this co,rld be beneficial in the case of injury'

4.g.4 ComPetence certification

on satisfactory compretion of the training program*:r.o*mensu'ate

with the 'equired Ievel of competence, and. on passing a test as appropriate

to the level' a per*sonal H"S entry permit .^r, u, issued,. er, "**pI" i. *ir." t, Fislr'e 4.2. The

maximum validity per-iod. or r.r.i ^ permit should, be one year.. on expiry of the permit. refr-esher

coltrses covering the s*biects describecr in 4.i.: ana 4.7.3 shoulcl be attended prio' to isstting a

t l

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EP 95-0317 Revisron

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4 Control and Safe Working practices

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new permit. Relaxation to a two-year validity is acceptable in areas of low risk or for those staff involved daily in H,S operations.

Figure 4.2 Competency certificate

Opco HrS Competency Certificate -L e v e l . . . . .

This is to certifv that HrS Competency

Certificate

has successfully completed training for entry into hydrogen sulphide designated areas Signed Date Expiry Date

I

I

\--

4.9.5 Competence

review

Proper records should be kept for each person assigned to installations, indicatinp instruction and training were received.. Competence should be reviewed regularly carrying out drills at the worksite. Experience has demonstrated that drills are extremelv effective.

1

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5 Recovery

5

RECOVERY

5 . 1 E m e r g e n c y

P l a n n i n g

I

_{- i}

5 . 1

. 1 E m e r g e n c y

e q u i p m e n t

-l _{Locations where HrS can be present in the air above the TLV-TWA of 10 ppm s} I _{6ave the following equipment in addition to that provided for normal operation}

,j

o spare self-contained BA sets + spare bottles (two additional sets against number

1 _I . being used)

. t

o spare escape sets (two additional sets against number being used)

1 o portable HrS monitor u'ith continuous read out and alarm

I

r p€rsonal HrS monitor

I r portable HrS detector suitable for sample aspiration

| -

o portable notices warning of H'S areas and portable barriers

I o mechanical resuscitation equipment

I

.l _{o diagram in control room showing location of emergency equipment.}

5.1.2 Procedure

for major HrS release

Locations where HrS can be present above the TLV-TWA of 10 ppm should have a written action pian in case of HoS release. It should be based on and include the following information:

. site of H2S risk areas

. siting of HrS emergency equipment . interpretation of the fu'ea HtS Gas Alarm

. rescue operations

o procedures and controls as necessary for people outside facility boundary . first aid treatment for HrS poisoning

r action on hearing Ar'ea HrS Gas A]arm covering, eg:

separate action for permanent staff and rnsitors/ contractors use of escape respirators

assembly points and escape gates

roll calI. accounting for visitorsicontractors

search and reseue operation. wearing BA and using HrS detection equipment road closures dou'nwind/stanclby boat actions

stopping of hot or cold work checks on builcling ventilation

informing local conl rnunitl' emergency services r,vhere appropriate

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EP 95-0317 Revision 0 5 October 1995

25

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

. action in case of fires in H"S areas action on hearing other plant gas alal'ms o methods for iocating a leak source

o methods of isolating the leak . methods of clispersing the leak o procedure for all clear and return to Emergency Response Procedures for HrS people outside facility boundaries.

work.

reiief should include controls for protecting

5 . 1 . 3 R e s c u e

P r o c e d u r e s

For every site defined as an HrS area, a rescue pian should be developed and practised as a regular check of the effecii reness of the emergency plocedures and of the

competence of the personnel involved.. The frequency of practice together with the ,..q,rirud performance criteria for the drills should be established in the HSB Case' Where local medical facilities may be called upon to treat or play a part in a rescue procedu'e it shoulcl be confirmecl that personnei are awale of the requirements for the treatment of HrS Poisoning.

The rescue proced.ures should be based. on minimum action on the part of the person sighting the victim, ie to raise the specific alarm. In other words a single action of the witness should. be sufficient to set the rescue proced.ures in action- The details of organising med.ical assistance, manpower assistance, medevac, information to the ,"Jporrribie Supervisor should be left to be organised by a central point'

This will allow the witness to take immed.iate rescue action on the spot provided they are equipped and trained to do so.

Rescue procedures should contain the follorving: . central reporting point

. r€porting code . witness actions

. _{r€Porting Point actions.}

The central reporting point should. be situated in a location which is permanently manned. and alJay. safe. ti ttti. is not possible. procedures shouid indicate alternatives. This point should be contactabie from the field r.ra dedicated manual call points, a d.ed.icated emergency phone or a dedicated lacl.io channel. This central reporting point should be the focal point for cailing in resources, ie medical assistance, experienced manpowel, transport, nr.edevac, etc.

This central reporting point should. have the requisite expertise level and be vested with the authority to call in such l'esoLu'ces rvithout, having to refer to

higher'leveis-The reporting code shouicl be sholt ancl precise, it shouid contain the location of the caller.. his name and a single catchwolcl to ind.icate the nature of the incident, eg

' HoS \riCTIM' and possibly the number of pelsons involved'

Witness actions: Before an)'resclle attempt tire witness should raise the alarm. Thereafter. the witness could tr'-v a linritecl fesctre attempt provided heishe is

l

l

5 Recovery

equipped to do so, ie when he is wearing a BA set the witness could try to isolate the

.t source of the leak.

I

-l _{Because persons tend to rescue instinctively they shoulci be trained not to do s} not properly equipped. Figure 5.1 beloq' lists first-aid actions and provides further I medical advice on rescue of an H"S vrctim.

_ t

IF A WITNESS HAS NO BA SET AVAILABLE THE WITNESS SHOULD NOT I ATTEMPT TO ENTBR THE RISK AREA

J _{The witness should evacuate to a safe area (eg upwrnd of the HoS source) and ,} sets when possible. Provided one BA set is available and the witness has given the I alarm and is familiar with the use of the BA set, the witness should try to carr 'J ' _{victim to an HoS-free area and try to resuscitate him. A single person attempti}

rescue needs to be aware of the risks. If unable to remove the person and a second BA I set were available the witness couid. try to put this set on the vrctim.

-l

Figure 5.1 Medical advice

First Aid and Medical Advice

HrS poisoning is a life threatening condition characterised by loss of consciousness and associated respiratory faiiure. Treatment must therefore be rapid to be

effective.

Remove the affected person to an HrS free area.

If breathing has stopped apply artificial respiration and continue until a mechanicai resuscitator is available to support respiration or until the victim resumes breathing. Obtain medical attention immediately.

If eye contamination is suspected flush the eyes with clean water for up to 10 minutes.

Subsequent to the resuscitation procedures described, keep the victim under observation and treat symptomatically as indicated by the patient's condition. The possibility of delayed pulmonary oedema up to 24 honrs after exposure should not be overlooked..

If the victinc is moved to a medical facility, ensure that inforrnation on HoS poisoning is supplied to the rnedical staff.

Other points

Harmful exposures only occur by inhalation. Intake via other routes is of no medical significance.

The use of 4-dimethyl amino phenol as an antidote for the systemic toxic effects of HrS is not recommended. Experience has shown that, following successful

resuscitation. recovery will usualiy be rapid and complete without the use of an antidote.

The reporting point should take all the necessary actions as iaid down in the emelgency procedure, thereby relieving the persons on site of ail organisational

reporting matrers such that thet'can dedicate their efforts to rescuing the endangered hfe.

I

I

I

H S E Manual EP g5-0317 H y d r o g e n s u r p h i d e ( H z S ) _{i n o p e r a t i o n s}

5 . 2 Firefig hting

5.2.1 Hazards

Pure HtS is a flammable gas. If burnt in the atmosphere it forms sulphur _{dioxide (refer} to 3'2'3) and water. In concentrations _{of 4.3 to 46.0 per cent by volume in the}

atmosphere it will readily burn upon ignition. In most situations Ho

with other sases which mav be light oJh"u'oy. pure Hrs;;;h;#t _{which could be} released from a rich surfinor soruiion is slighiry h;;;; _{than air.}

5.2.2 Precautions

In the event of a fire of HrS-containing material, it is usually better to let it burn under control until the source has been isolaied rather than releasl Hrs to the atmosphere. @xposure to the resultant sor, should be avoided.) The;;ffi; _{equipment should} be cooled and wherever possibie attempts mad.e to d.isperse _{the sulphur dioxjde product} of combustion by water sprays.

The decision to allow a fire to continue will d.epend. _{on the circumstances. If the escape} is small in volume and can be isolated easily then extinguishment _{could be the}

preferred course of action. A11 approaches must be from an upwind _{direction by} personnel wearing a self-contained. _{breathing apparatus.}

5.2.3 General

procedures/guidelines

The responsibilities for salvage/clean up and

firefighters are described in Ep g5-0ssi Fire the procedures _{Control and Recoverv.}for breathing apparatus for

28

l

I

6 Guidelines for the Preparation _{of H2s procedures}

6

GUIDELINES

FOR THE PREPARATION

OF HzS

, I

P R O C E D U R E S

_ l

Chapter 6 gives some specific guidance on the preparation of H"S procedur.es for typical I production, drilling and maintenance activities.

-l _{Proced.ures for operations involting HrS shoulcl be written for a specific locatior}

I

conditions prevailing locally.

I The immediate health effects for people exposed to HrS depend primarily on tht concentration of the HrS in the air. Precautions and procedures should be based on

r

_{;ilT#:: ;'ffi";::::::}

_{ffi*:l';""J.:ffi";}

_.,"uu,.bedef

all facilities where HrS may be encountered. While no risks shall be taken it is

]

_{;m:ilt'Ji" ##Ti?$:'1fffitff;'Te}

equipment

than

is reasonabrv

'

_{h'"3tumil3;i:;:;ff;n?T##ff;::ffi-":ffi"'ffiJlilffini}

' _.-

three main elements:

I

_{: ::;"j;il:ff';:H:i:,":n::."}

o _{developing standing instructions for all normal activities.}

6.1 Formulation of Work Procedures

The procedures should be based on the health risk assessment. The following elements related to personnel protection should be covered as a minimum. The requirements need to be defined for:

. work method . _{breathing apparatus} o _{detection/monitoring equipment} o wind indication . escape routes . _{rescue plan} . _{H:S warning signs.}

Depending on the work scenario and HrS concentrations involved, the wearing of

personal monitors, BA sets, escape sets, portable detectors the use of the buddy system, etc should be determined for the different stages of the job.

It should be made clear and known who is authorised to conduct the general site introduction.

A s1'sten should be set ttp to ensure that all site personnel have a valid HrS certificate. Numbers of staff on site at any given time shouid be kept to a minimum.

H S E M a n u a l EP 95-0312 Hydrogen S u r p h i d e _{( H z s ) in operations}

A "r'ork programme should be agreecl and signecl by all parties involved., ie production, maintenance, drilling, contractot's, etc. The programme shoulcl include the for.mulation of special procedures in respect of Hrs hazar.ds drring,

. _{boxing up}

o _drying

o _{line up}

. _{recommissioning}

All procedures which cover multifunctional departments should be authorised. by that authority which heads all those d.epartments, _{ie Operations Manager or Technical} Manager or by all parties concerned.

6.2 Drilling and Well Operations

Specific HrS procedures covering Driliing Operations in aleas where HrS is likely to be encountered are documented in EP 95-0210 Driliing (sub-chapter 6.b) and ApI Rp 49 @@ef' _{7)' It must be ensured. that such procedures tie-in well with the existing local} Emergency Contingency plans.

Considering the danger and. the consequences of exposure, when operating in an HrS environment, it is important to take note of the fotlowing key operational precautions which are adequately covered in the above d.ocument and inlne general sections of thisI

manuat: o

all personnel on a driJling location where HrS is anticipated. shall have available to

r t

them a certified breathing apparatus o

all BoP equipment and tubulars to be used in wells where HrS is expected. to be encountered, must compiy with metallurgical specifications suitable for sour service

'

effective fixed detection systems that activate audible and visual warning alarms must be installed at strategic locations on the well location

'

only personnel trained. to work in an HoS environment may be deployed to work on well locations where HrS is expected.

' _{there must be an ag:'eed. HrS 'd.r'i11'plocedure}

which shali be carried out once a week or more frequently until personnel on site are conver.sant with it

'

drills should be monitored. against known and agreed performance criteria.

The effectiveness of any H:S contingency pian can only be assured if all staff involved. in the operations are fully "*tu _{of the consequences of exposure to HrS. They must be} familiar with the right steps to control a hazard.ous ",r".rt *ili " _{o"tJ"tial release of} HrS and to recovel from the hazardou-s situation should. the release actually occur. Effective training ancl competence assessment ale of vrtal importance to achieve this.

6.3 Production Operations

in Appendix VIII examples of typical srep-b],-srep _{procedules al.e given (sphere} removal, sampling). . _isolation . _{spading/Olinding)} o _{opening up} r _{pr€ssure testing} r _{puf glng} . _{depressurising} o _flushing . _{vessel entrv} o _draining . _{despading/(deblinding)}

3 0

EP 95-0317 Revision O 5 October 1995