Hydrogen Sulphide Training Manual
Contents:
•
Origin of H2S
•
Properties of H2S
•
Human Anatomy
•
Effects of H2s
•
H2S First Aid Treatment
•
Detection of H2s
•
Breathing Apparatus
•
Safety Practice
•
Emergency Response
• Practical Exercises
Origin of H2S Origin of H2S
H2S is a naturally occurring substance. Sources of the gas include: • • •
geological formations organic material chemically produced H2S
Locations of H2S The oil and gas industry is the single largest source of H 2S. Knowing where this toxic gas usuall usually y is found found will will help help you you develo develop p strate strategies gies to reduce reduce your your likeli likelihood hood of exposur exposure. e. In this this sectio section, n, you will learn learn about about common common locations locations of H2S. General General locations linked to H2S occurrence include: • • • • • •
Drilling Operations Well Stimulation Operations Well Service Operations Production Operations Plant Operations Transportation Operations
Specific Locations Drilling Operations When drilling for oil or gas, it is possible that a formation containing H2S may be encounte encountered red.. If that happens, happens, the gas could be releas released ed from, or accumulat accumulatee in, the following areas • • • • • •
blow-out preventer (BOP) flow nipple drilling fluids at the wellbore drilling fluid piping system shale-shaker and mud tanks flare pit
• • •
under the sub-structure degasser choke manifold
Well Stimulation Operations • wellhead • circulating tanks • production tanks • circulating pumps and piping systems • production fluids • return fluids • vents • sample valves • BOP • coil tubing • flare pit • tank trunks • dismantling and repairing at maintenance facilities and on-lease Well Service Operations
Specific locations of H2S in these these operations include : • • • • • • • •
circulating tanks production tanks circulating pumps and piping systems open tanks gauge hatches wellhead wellbore and other fluids dismantling and repairing at maintenance facilities and on-lease
Field Operations
There are several specific locations in field operations where H2S will probably occur. These include : • • • • •
water, oil or emulsion storage tanks and associated manways treaters and separators processing oil, water, gas and emulsions dehydrators for removing water from gas streams pig senders and traps for cleaning pipelines p ipelines and field gathering systems flare pits and stacks used for burning off gas
•
enhanced oil recovery sites (these activities may cause a formation to become sour)
Plant Operations
In plants, H2S may be found around the following : • • • • • •
inlet separators the sweetening process process vessels compressor buildings sulphur extraction, storage and transfer facilities storage tanks
Transportation
Specific transportation facilities and areas where H2S may be found include : terminals for transferring product between trucks, railcars and ships hatches, vents and spills associated with trucks, railcars and ships tank truck maintenance and repair facilities When When work workin ing g arou around nd pipel pipelin ines es and and pipel pipelin inee faci facili liti ties es,, you you may find find H2S H2S in the the following areas : • • •
meter stations (due to operational adjustments and maintenance) pig launching and receiving stations compressors and buildings where the pressure of the gas is raised before entering the pipeline system
Properties of H2S PROPERTIES OF H2S
If you’re going to understand what H2S is and how it behaves, you need to know its properties. With proper proper knowledge, you will be better able to protect yourself yourself from this deadly gas. In this section, you you will learn about the properties of H2S, including : • • • • •
Colour Odour Vapour Density Flammability Solubility
PROPERTIES
DESCRIPTION
Colour
Colourless no visible sign of H2S to warn you of its presence Smells like “rotten eggs” impairs your sense of smell at low concentrations do not rely on your sense of smell to detect H2S Sligh lightl tly y heav heaviier than han ai air (1. (1.19 19 com compar pared to 1.0 1.0 for for air) air) in gas mixtures, it will be present wherever the gas mixture is found Gas mixtures may be heavier or lighter than air, depending on their Vapour density and temperature compared to the ambient atmosphere (i.e. usually air) in its pure state, or as a high proportion proportion of a gas mixture, it may flow or settle into low-lying area, such as pits, trenches and natural depressions Flammable burns with a blue flame and gives off sulphur dioxide gas, SO2 SO2 SO2 is haza hazard rdou ouss and and irri irrita tate tess the the eyes eyes and the the resp respir irato atory ry system explosive when mixed with air, depending upon the proportions.
Odour
Vapou apourr Dens Densit ity y
Flammability
Measurement of H2S
Two different scales are commonly used to measure hydrogen sulphide concentrations. Most of us are already already familiar with the the percentage (%) scale. It divides the total into 100 parts and tells us in “parts per hundred” how much of the total we are looking at.
When we deal with the effects of hydrogen sulphide on the human body, we have to use a measurement measurement scale scale that divides the total mass mass into much, much smaller smaller units. For this purpose, the “parts per million” or “ppm” scale is used. It divides the total into 1,000,000 parts and tells us, parts per million, the concentration of the substance we are looking at. The smallest unit we can measure is one part per million. 1% equals 10,000 ppm
As we compare the two scales, we can see that that for every 1% there there are 10,000 ppm. It is easy for most of us to picture in our minds what one part in a hundred means. However, it is much more difficult to picture how small one part in a million really is. As a mental exercise, let’s imagine what one part per million (ppm) would mean when we compare it to distance. We are all familiar with the length of a metre; about the distance of one long step 1,000 metres = one kilometre, another a nother unit we are familiar with 1,000 kilometres = 1,000,000 metres Think of some town or city approximately approximately 1,000 km from where you are right now One part per million (ppm) of that distance would be one metre, or one long step. This should give you an idea of how small one ppm really is. Flammability
H2S is usually found mixed with a variety of hydrocarbon and other gases and liquids. These products may may pose other hazards, in addition to H2S. These hazards include : Hydrocarbon Fire and Explosion All hydrocarbon vapours and gases will ignite when mixed with air within a certain range of proportio proportions. ns. This range range is called the the flammable flammable range range (or explosive explosive range). range). The flammable range for mixtures of hydrocarbon products (i.e. crude oil vapours, natural gas etc.) is variable, depending upon the proportions of hydrocarbon and other components in the mixture. The lowest amount of gas in air that will burn is the lower flammable limit, or LFL (also called the lower explosive limit, or LEL). The highest amount of gas in air that will will burn is the upper flammable limit, or UFL (also called the upper explosive limit, or UEL). Serious, potentially fatal, burns may occur as a result of exposure to the uncontrolled ignition of hydrocarbon products. Toxic Effects How much H2S does it take to make me sick or kill me? At what level can I smell it?
When do I lose my sense of smell? At what ppm will I pass out? The following table will guide you to the answers to these questions. H2S Toxicity Toxicity Levels H2S H2S Exp Expos osur uree (pp (ppm) m) Less than 1 ppm 10 ppm (8-hour OEL) 20 to 200 200 ppm
100 ppm
500 to 700 ppm
700 to 1000 ppm
Poss Possib ible le He Heal alth th Effec ffects ts You can smell it No known adverse health effects
Eye Eye and respiratory tract act irritati ation and loss of sme smell. Will also cause use headache and nausea. Immediately Dangerous to Life and Health (IDLH) IDLH refers to a hazardous atmosphere where a person without adequat adequatee respir respirato atory ry protec protectio tion n may be fatall fatally y injure injured d or suffer suffer immediate, irreversible or incapacitating health h ealth effects. Affects th the ce central ne nervous sy system. After a co couple of of mi minutes, it it causes causes loss loss of reason reasoning ing,, loss loss of balance balance,, unconsc unconsciou iousne sness ss and breathing to stop Immediate loss of consciousness. Permanent brain damage and DEATH DEATH will occur occ ur if you are not rescued immediately.
Occupational Exposure Limits (OEL)
Government agencies set limits for worker exposure to toxic substances. These levels are there for your your safety and must must not be ignored! For the purpose purpose of this course, course, we will refer to them in terms of Alberta’ Alberta’ss Occupational Exposure Limits (OEL). These exposure limits limits may be expressed expressed differently differently in other jurisdict jurisdictions. ions. Your instructor instructor will review these with you, as appropriate. As a rule-of-thumb, try to keep your exposure to H2S as low as possible. Exposure levels to H2S are normally measured in ppm. OELs for H2S are shown in the below given table. Occupational Exposure Limits for H2S Occupational Exposure Limit 8 hour OEL
Conce oncent ntra rati tion on
10 ppm
15 minute OEL
15 ppm
Ceiling OEL
20 ppm
OEL OE L Des Descr crip ipti tion onss
A time-weighted average (TWA) maximum exposure for an eight hour work day A TWA exposure limit of up to 15 minutes with a 60 minute separation between each exposure. No one should be exposed to greater than 20 ppm of H2S at any time without adequate respiratory protection.
NOTE :
The accepted practice is to wear breathing apparatus at 10 ppm and above. Good work practices should aim for zero exposure to H 2S.
Detection of H2S
Detection Systems ELECTRONIC MONITORS Electronic monitors use sophisticated electronics to measure the concentration of H2S and provide very very accurate readings, readings, if functioning properly properly.. These units are designed to continuously continuously monitor gas gas levels. Some units are capable capable of monitoring moree tha mor than n one gas. gas. Th Thee pu purp rpose ose of the these se devices devices is to protec protectt yo your ur safety safety by warning of the presence of H2S. CAUTION Electronic monitors do not think for you. You must still be alert to the dangers of Electronic H2S. In this section, you will learn about various aspects of electronic monitors including:
• • • •
Principle of Operation Major Components Personal and Portable Monitors Fixed Monitors
Principle of Operation Continuous electronic monitors use electricity to power a sensor that detects H2S. When the sensor detects the presence of H2S at a pre-set level, usually 10 ppm, it activates an alarm. The sensor may be powered by batteries or AC power. power. Major Components Whether it is a personal, portable or fixed monitor, the basic components of the unit include : • • •
a power source sensor(s) a display
an alarm
•
Personal and Portable Monitors Personal monitors are designed to be worn by by the worker. worker. They may clip onto a belt, fit in an outside pocket or be worn on a harness. Typical personal monitors are illustrated in the Figure below. Portable monitors are designed to be placed between the worker and the source of H2S or in a confined space. A typical portable monitor is ill Fixed Monitors Fixed monitors are permanently installed units and are usually found in gas plants and oil batteries. These are the most sophisticated sophisticated type of electronic monitor. monitor. The system consists of :
• • • •
a central control unit remote display(s) remote sensor(s) alarm(s) GENERIC STEPS FOR OPERATING OPERATING PERSONAL AND PORTABLE MONITORS
STEPS 1 2 3
POWER ON CALIBRATION CHECK ALARM CHECK
4 5
MONITOR MODE POSITION UNIT
DESCRIPTION Check batteries or AC power source Function test unit with calibration gas Ensure the alarm works at the pre-set level. Most units are pre-set to alarm at 10 ppm H2S Ensure the unit is set to monitor H2S For personal monitors • place the unit in an outside pocket (make sure the sensor and alarm are not covered) • clip it to your belt, or • put the harness on For portable units • ensur en suree pr prope operr pl place aceme ment nt be betwe tween en yo you u an and d
possible sources of H2S NOTE : When operating a personal or portable monitor, always follow the manufacturer’s instructions.
Fixed Monitors Cont: •
The central control unit is usually installed in the control room or a central building.. Sensors are building are then position positioned ed throughout throughout the the jobsite or plant area. area. In some cases, a number of systems are linked together to form a network. Remote sensors send signals by wire or radio waves to the central unit.
•
Like th Like thee ot othe herr ty type pess of ele elect ctro roni nicc mo moni nitor tors, s, the fix fixed ed mo monit nitor or wo work rkss on a continuous continuo us basis and will alarm at a pre-se pre-sett level of H 2S. This level level is usually 10 ppm.
Operation of Fixed Monitors •
Fixed monitors are installed by specially trained technicians who calibrate and test the units to the manufacturer’s specifications.
Note : Key points to remember for all types of electronic monitors : Always make sure that the unit has been calibrated and is properly maintained. When an alarm goes off, get out of the area immediately.
Safety Practice Emergency Response
Buddy System
Any work in a hazardous location must be carried out using the Buddy System. If one worker enters a hazardous area another person his (Buddy) will observe his work from a safe place. The buddy system is also used to ensure the safety of Breathing Apparatus wearers in H2s release release inci inciden dents, ts, fir firee inci incident dentss in fac factt in any incident incident wher wheree Bre Breathi athing ng Apparatus is required to be worn. Important At all times where Breathing Apparatus is worn a minimum of two persons will be used At no time will one Breathing Apparatus wearer be allowed to enter the effected area Emergency Procedure If while you are working, or at the worksite, you smell H2S or the detection system operates: 1. Don’t pa pan nic 2. Ho Hold ld you yourr br brea eath th 3. Wear Brea Breathin thing g Appa Apparatu ratuss if availa available ble If no BA available 4. Leave the area immediately 5. Do not attempt to rescue anyone until you have donned Apparatus 6. Report to the emergency station Remember that at least two persons should be involved in rescue Rescue Operations Assess the situation: Gather as much information as possible regarding the incident, ♦ number of casualties
Breathing
♦ ♦ ♦ ♦
available rescuers available equipment medical assistance area involved Other factors to consider
♦
Hazards Fire - Explosion
Rescue
• Don Full Duration Breathing Apparatus •Remove victim immediately to fresh air •If breathing, keep casualty at rest administer oxygen if available •If not breathing start artificial respiration immediately •Request Medical assistant •Keep casualty in the recovery position & keep warm •If eyes are affected rinse thoroughly with water • Do not leave unattended H2S Safety Practice Production workers are the people most often exposed to H2S, but we must always be aware that in inhabited areas the general population should also be made aware of the possible danger. Signs For warning warning against against the poss possible ible danger danger of H2S adeq adequate uate warning warning signs must be placed wherever there are potential hazards. As well as warning about the hazard No Smoking signs must be displayed.
Fences Areas of particul particular ar danger such such as permanent tanks, tanks, open drainage or flair flair pits and wellheads should be fenced off. The fences should be installed far enough away from the hazard area to allow air to dilute the poisonous gases to a safe concentration. If barriers are not erected adequate warning signs must be placed around the area. Wind Indicators In all area where H2S is present some form of wind direction indicator are requ re quir ired ed.. Th These ese can be fla flags gs,, wi wind nd soc socks ks or wea weathe therr van vanes, es, the these se ar aree normally in a bright high visibility. Detection Where there is a danger of H2s continual monitoring of H2s will occur. See section: H2S Monitoring Equipment H2s Emergency Response & Rescue – Self Test
1.
If yo you u sme smell ll H2 H2S S whi while le at th thee wor work k sit sitee wha whatt is is you yourr res respo pons nsee …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… ……………………….
2.
What Wh at ar aree the the fa fact ctor orss to to bea bearr in in min mind d dur durin ing g res rescu cuee ope opera rati tion onss …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………….
Practical Exercises
1. Escape set Practical Exercise (a) Donning of escape BA Set in fresh air. Trainees working in groups will have a general walk round in open air negotiating obstacles and carry out routine checks of the pressure gauge. The instructor will indicate time elapsed at regular intervals. 2. Escape Set Practical Exercise (b) Trainees to don escape BA sets in a simulated toxic environment and make their way to a place of safety.
3. Air Line / Escape set Practical session At the end of this session the trainees will fully understand the working principles of an Air line system in an H2S area.
4. MSA Ultralite Full Duration Set Practical Training At the end of this exercise the trainees will be competent and confident in donning and wearing the MSA Full Duration Set. Trainees working in groups groups will practice the donning donning proce procedure dure for the set set and and will wear the set in differing conditions open space and confined areas.
5. H2S Rescue Operations Practical Trainees will learn the principals of Rescue / Casualty Handling using available equipment that would be found at their location. Working in teams trainees will carry out a simulated exercises using Full Duration BA and live casualties.
6. Buddy System Practical (a) Working in teams of two the trainees will be given a task either H2S detection using portable monitors, rescue or systems inspection.
7. Buddy System Practical Application (b) Trainees using the skills learned in exercise 3 will set up and use the Airline trailer unit and escape sets.
8. Final Exercise Evacuation of H2S effected area rescue of casualties and stabilisation of H2S leak. Note: Exercises will be finalised after seeing the facilities available at the ASAB FTG and surrounding area.
