H2S HAZARDS

NGI TRAINING CENTRE

INTRODUCTION• All hydrocarbon bearing reservoirs encountered in the South Pars field

contain H2S

• There is therefore a major safety concern during First gas,

production ,and maintenance operations performed in the Assaluyeh

Plant

TOPIC COVEREDH2S NamesH2S NamesH2S SourcesH2S SourcesH2S PropertiesH2S PropertiesH2S EffectsH2S EffectsH2S Presence, identificationH2S Presence, identificationH2S MeasurementsH2S MeasurementsHazard ControlHazard ControlFirst aid and rescue operationsFirst aid and rescue operations

H2S IS ALSO KNOWN AS

Sulphurated hydrogenSulphurated hydrogen

Sour gas

Rotten egg gas

Swamp gasSwamp gas

Sour gasSour gas

Sewer gasSewer gas

Stink dampStink damp

Hydrosulphuric acidHydrosulphuric acid

Is the H2S gas is friend or foe ?

It can be a friend, as in sulfurous hot springs, IT HEALS BROUNCHI

When H2S reach to dangerous concentrationLEADS TO FATALLEADS TO FATAL

When H2S reach to dangerous concentrationLEADS TO FATALLEADS TO FATAL

Hydrogen Sulphide, a Chemical Combination of :

H

H

S H2SH2S

H2S is also found on earth, resulting from the decay organic matter containing sulphur.

In Volcanic activities, it often escapes from earth fissures, mixed with other gases

It also found in natural gas, many type of crude and oil fields

It also found in Industry as a result of chemical process and by products of crude oil distillation. It always found in refinery.

PHYSICALPHYSICALAND AND

CHEMICAL CHEMICAL PROPERTIESPROPERTIES

H2S is H2S is colorlesscolorless (no visible sign of (no visible sign of H2S to warn you of its presence) H2S to warn you of its presence)

COLOUR andCOLOUR and ODORODOR

Smell often described as Smell often described as rotten eggsrotten eggs

HeavierHeavier than air: Specific gravity= 1.189 than air: Specific gravity= 1.189

ThereforeThereforeH2S will collect in low areas such as, well H2S will collect in low areas such as, well

cellars, open drain ditches and excavations.cellars, open drain ditches and excavations.

It has been noticed, however, that H2S could It has been noticed, however, that H2S could also be swept along with the produced gas and also be swept along with the produced gas and

be present on high spotsbe present on high spots

WEIGHTWEIGHT

BOILINGBOILING and MELTINGand MELTING

Boiling point Boiling point - 60.3- 60.3 C (- 76.5 F), C (- 76.5 F), Melting point Melting point - 82.9- 82.9 C (- 117.2 F) C (- 117.2 F)

So in its natural state we see it asSo in its natural state we see it as GAS GAS

H2S SOLUBILITYH2S SOLUBILITY SolubleSoluble in both water, 4 in both water, 4

volume gas in 1 volume volume gas in 1 volume water at 0 degree Celsius water at 0 degree Celsius

(Produce irritable gas) (Produce irritable gas) and liquid hydrocarbonsand liquid hydrocarbons

This gas This gas can be can be releasedreleased when the when the

liquid is agitated, such liquid is agitated, such as when wading as when wading through water in through water in

excavations. excavations.

Porous matter such as iron sulphides and oxides and muddy residues, absorbs H2S in large quantities.When disturbed or when temp. gets higher, H2S gas will form.

Many incidents and accidents could be avoided if everybody would remember the fact when the equipment is opened.

EXPLOSIVEEXPLOSIVE

Forms an explosive mixture with a Forms an explosive mixture with a concentration between concentration between 4.3% and 46%4.3% and 46% by by

volumevolumeAuto ignition occurs at Auto ignition occurs at 500 F (260 C)500 F (260 C) which which

is a very low ignition temperatureis a very low ignition temperature

LEL and UEL

5

Too much

Upper Explosive

Limit

Explosive

Lower Explosive

LimitToo little

% Explosive

LimitEXPLOSIVE

0%

4.3%

46%

BURNING BURNING

Burns with a Burns with a blueblue flame and produces flame and produces Sulphur Dioxide (SO2), less toxic than Sulphur Dioxide (SO2), less toxic than

H2S but very H2S but very irritatingirritating to eyes and lungs to eyes and lungs and may cause serious injuryand may cause serious injury

Effect of H2S on Equipment

H2S combines with moisture in the air to H2S combines with moisture in the air to form corrosive acid which eats away at form corrosive acid which eats away at pipes and valves. It cause a form of pipes and valves. It cause a form of hydrogen embrittlement known as sulfide hydrogen embrittlement known as sulfide stress crackingstress cracking

IMPORTANTIMPORTANT

H2S is extremelyH2S is extremely toxictoxic

and will be present in high levels in our site.and will be present in high levels in our site.

UP TO 8000 ppm UP TO 8000 ppm

H2S EFFECTS ON H2S EFFECTS ON HUMAN BEINGSHUMAN BEINGS

• Extremely toxic (almost as toxic as Hydrogen Cyanide) and 5 to 6 times as toxic as Carbon Monoxide.

• H2S can only be smelt at low concentrations (1-50 ppm). Beyond 50ppm, the nerve endings are destroyed, you are no longer able to smell anything after about 15 minutes exposure.

Therefore,

DO NOT DEPEND ON SMELL TO DETECT H2S

H2S is dangerous in its action on the human body than in causing accidents by ignition and explosion.

H2S is worst when it reaches certain concentrations, as its paralyses the olfactory nerves

H2S Measuring unitsH2S Measuring units

In dealing with H2S several units may be used for measuring its concentration

The most common unit used in the oil and gas industry is the ppm

(part per million)

0.0001 volume % = 1ppmOR

10,000 ppm = 1%

TLV-TWAThe threshold limit value-time weighted average, TLV-TWA

Is the average airborne concentration to which a worker may be exposed for 8 hours per day without any adverse health effects.

For Hydrogen Sulphide this value is 5 ppm.

The short term exposure limit or STEL is the maximum concentration to which a worker may be exposed for a maximum period of 15 minutes, for hydrogen Sulphide this value is 10 ppm

Duration

The way in which H2S affects you depends on the following:

Frequency

intensity

Susceptibility

The length of time the individual is exposed

How often the individual has been exposed

The concentration of exposure

The individual’s physiological make-up

CONCENTRATIONCONCENTRATION H2S ppmH2S ppm EFFECTSEFFECTS1 ppm1 ppm Smell of rotten eggSmell of rotten egg

5 ppm5 ppm 8 hr.T W A Beginning eye Irritation8 hr.T W A Beginning eye Irritation

10 ppm10 ppm 15 min STEL15 min STEL

27 ppm27 ppm Strong unpleasant odorStrong unpleasant odor

100 ppm100 ppm Lose sense of smell Coughing, Eye pain Lose sense of smell Coughing, Eye pain and Drowsinessand Drowsiness

300 ppm300 ppm Loss of consciousness(approx.20 min), Loss of consciousness(approx.20 min), Make conjunctivitis and respiratory tract Make conjunctivitis and respiratory tract irritationirritation

1000 ppm1000 ppm Immediate respiratory arrest, loss of Immediate respiratory arrest, loss of consciousness, followed by deathconsciousness, followed by death

Symptoms of ExposureSymptoms of Exposure

Eye IrritationEye Irritation

SicknessSickness

DizzinessDizziness

ChokingChoking

Lack of Muscle controlLack of Muscle control

TECHNICAL PREVENTIONTECHNICAL PREVENTION

MEDICAL PREVENTIONMEDICAL PREVENTION

PREVENTION OF ACCIDENTSPREVENTION OF ACCIDENTS

( ALL ACCIDENTS ARE PREVENTABLE )

TECHNICAL PREVENTIONTECHNICAL PREVENTION AND AND CONTROLCONTROL

Permit to Work (Risk Assessment)Permit to Work (Risk Assessment)

(Safe systems of work)(Safe systems of work)

Identification of Hazardous AreasIdentification of Hazardous Areas

Measurement of ContaminatesMeasurement of Contaminates

Personnel TrainingPersonnel Training

PERMIT TO WORKPERMIT TO WORK

Permit to Work is a system of Permit to Work is a system of management controls adopted, in management controls adopted, in writing, to writing, to Ensure Ensure the safety of the safety of workers in an area which, in the workers in an area which, in the absence of such controls would expose absence of such controls would expose the worker to risk..the worker to risk..

SAFE WORKING PRACTICES

• Check the wind direction

• Monitor your working area by gas detectors

• Know at least two escape routes from your workplace

• Know the location of all emergency equipment

• Ensure your emergency training is up to date

• Carry a personal H2S monitor at every opportunity

• No smoking

• No naked flames

• No mobile phones

• Never work alone, ensure that at least one other person knows your location

• Know the companies emergency procedures

• Remain vigilant and observe all audio or visual alarms

• All electrical equipment must be approved and intrinsically safe

• You should be aware of safety equipment locations

• You should be aware of escape set locations

Types of Measurement Types of Measurement EquipmentEquipment

Fixed EquipmentFixed Equipment

Portable EquipmentPortable Equipment

Fixed Equipment

Fixed Detectors Are Installed Fixed Detectors Are Installed Around The Site And Emit an Around The Site And Emit an Audible Alarm And Audible Alarm And sometimes flashing Lights sometimes flashing Lights When Gas Levels Are When Gas Levels Are Exceeded.Exceeded.

This type of equipment This type of equipment

gives a continuous measurementgives a continuous measurement

in hazardous areasin hazardous areas

Portable/Personal EquipmentPortable/Personal Equipment

Portable Alarms Are Carried to Any Area in Which Gas Levels Are Required to be measured For Reasons of Personal or Plant Safety.

Portable Detectors usagePortable Detectors usage

You must leave the area and report your findings to your Supervisor & the HSE OFFICE

AFTER USING GAS DETECTION EQUIPMENT

If gas levels are too high

Emergency and First AidEmergency and First Aid

If we see any person we If we see any person we think may have been think may have been affected by H2S, we affected by H2S, we must help him,must help him,

BUTBUT

Before attempting to rescue a person, You Before attempting to rescue a person, You mustmust consider your own safety consider your own safety

AvoidAvoid delays in the rescue. delays in the rescue. Response must be immediate if a worker is Response must be immediate if a worker is overcomeovercomeRemember that Remember that timetime is the most important is the most important

factor for First Aidfactor for First Aid you can save a life within you can save a life within a fewa few minutes minutes

REMEMBER

RESCUE SHALL NOT BE ATTEMPTED UNLESS GAS LEVELS

ARE ACCEPTABLE

Emergency OperationsEmergency OperationsIn the event of a release of gas from other areas, personnel will In the event of a release of gas from other areas, personnel will

take the following actions:take the following actions:

1.1. Shut off all machinery and tools Shut off all machinery and tools 2.2. Quickly move upwind or crosswind, away from the leakage of Quickly move upwind or crosswind, away from the leakage of

gasgas3.3. Avoid inhaling, while seeking an area for fresh air.Avoid inhaling, while seeking an area for fresh air.4.4. Get out of the contaminated area. Get out of the contaminated area. 5.5. Do not attemptDo not attempt to rescue a worker . to rescue a worker .6.6. Never enter a suspected, contaminated area without Never enter a suspected, contaminated area without

Breathing apparatus to rescue a co-worker, or for any other Breathing apparatus to rescue a co-worker, or for any other reason. reason.

7.7. Evacuate the area in an upwind direction, using the Evacuate the area in an upwind direction, using the windsocks, flag or existing flare stacks to indicate the wind windsocks, flag or existing flare stacks to indicate the wind direction.direction.

8.8. Remember H2S is Remember H2S is heavierheavier than air and will gather in low than air and will gather in low level areas.level areas.

10-10- Sound the Sound the Alarm. Alarm.

11- 11- ReportReport to your to your SupervisorSupervisor and the and the HSE OfficeHSE Office If using a radio If using a radio repeat repeat THIS IS ANTHIS IS AN EMERGENCYEMERGENCY two or three times to clear two or three times to clear

the airways and to gain attention.the airways and to gain attention.

12- Calmly state what has happened, the location of the leak and 12- Calmly state what has happened, the location of the leak and any visible danger to people in the immediate area. any visible danger to people in the immediate area.

Have the receiver of your message alert the Have the receiver of your message alert the Project Project SuperintendentSuperintendent and and field safety office.field safety office.

13- 13- AlertAlert the local the local Fire Department, PoliceFire Department, Police and other and other Emergency Emergency

Response TeamsResponse Teams. .

14- Get 14- Get medical aidmedical aid for workers exposed to H2S. for workers exposed to H2S. Immediately wash off skin, hands and affected areas Immediately wash off skin, hands and affected areas with plenty of water and wash out eyes for at least 15 with plenty of water and wash out eyes for at least 15 minutes.minutes.

15- If other crews are nearby 15- If other crews are nearby alertalert them by radio or by them by radio or by

signaling them, keeping a clear distance up wind from signaling them, keeping a clear distance up wind from the hazard area.the hazard area.

NOTE: It may be necessary for the company to assist in NOTE: It may be necessary for the company to assist in alerting the general area for evacuation.alerting the general area for evacuation.

16- 16- Stay in a safe areaStay in a safe area (Muster Point) and act as a guide (Muster Point) and act as a guide for company personnel responding to the situation and for company personnel responding to the situation and await further instructions from your supervisor.await further instructions from your supervisor.

EvacuationEvacuationEvacuation routesEvacuation routes

Evacuation routes will be provided from every working area to Evacuation routes will be provided from every working area to muster points. These routes shall be kept free from obstruction muster points. These routes shall be kept free from obstruction and properly markedand properly marked

WindWind

An accurate wind forecast must be available and posted An accurate wind forecast must be available and posted at all times. The wind direction must be shown by TWO VISIBLE at all times. The wind direction must be shown by TWO VISIBLE WIND INDICATORS such as wind socks, illuminated at nightWIND INDICATORS such as wind socks, illuminated at night

Alarm SystemAlarm System

A dedicated alarm will be set at 5 ppm. Explosion proof horns A dedicated alarm will be set at 5 ppm. Explosion proof horns and flashing lights will be provided which will be distinct from and flashing lights will be provided which will be distinct from normal Fire and Evacuation alarmsnormal Fire and Evacuation alarms

Muster PointsMuster Points

Will be set up for all locationsWill be set up for all locations

ESCAPE FILTERESCAPE FILTER

Emergency TelephoneEmergency TelephoneNumbersNumbers

Main Characteristics of H2S-Summary:

Potentially lethal

Heavier than air

Colorless

Readily dispersed by wind or air currents

Flammable - burns with a blue flame

Odor of rotten eggs (below concentration of 100 ppm)

Highly Corrosive to certain materials (eg steel)

FACING SUCH AN INSIDIOUS AND DANGEROUS ENEMY, THE SAFEST METHOD IS TO APPLY ALL SAFETY RULES WITHOUT ANY HESITATION

THINK ABOUT THINK ABOUT YOUR SAFETY YOUR SAFETY

AND THE SAFETY AND THE SAFETY OF OTHERSOF OTHERS