H2s Manual

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 H2S. Knowing where this toxic gas usually is found will help you develop strategies to reduce your likelihood of exposure. In this section, you will learn about common locations of H2S. 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 encountered. If that happens, the gas could be released from, or accumulate 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 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 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 working around pipelines and pipeline facilities, you may find H2S in 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 knowledge, you will be better able to protect yourself from this deadly gas. In this section, 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 Slightly heavier than air (1.19 compared to 1.0 for 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 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 is hazardous and irritates the eyes and the respiratory system explosive when mixed with air, depending upon the proportions.

Odour Vapour Density

Flammability

Measurement of H2S Two different scales are commonly used to measure hydrogen sulphide concentrations. Most of us are already familiar with 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 scale that divides the total mass into much, much 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 for every 1% 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 unit we are familiar with 1,000 kilometres = 1,000,000 metres Think of some town or city 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 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 proportions. This range is called the flammable range (or explosive 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 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 Levels H2S Exposure (ppm) Less than 1 ppm 10 ppm (8-hour OEL) 20 to 200 ppm 100 ppm

500 to 700 ppm 700 to 1000 ppm

Possible Health Effects You can smell it No known adverse health effects Eye and respiratory tract irritation and loss of smell. Will also cause headache and nausea. Immediately Dangerous to Life and Health (IDLH) IDLH refers to a hazardous atmosphere where a person without adequate respiratory protection may be fatally injured or suffer immediate, irreversible or incapacitating health effects. Affects the central nervous system. After a couple of minutes, it causes loss of reasoning, loss of balance, unconsciousness and breathing to stop Immediate loss of consciousness. Permanent brain damage and DEATH will occur 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 safety and must not be ignored! For the purpose of this course, we will refer to them in terms of Alberta’s Occupational Exposure Limits (OEL). These exposure limits may be expressed differently in other jurisdictions. Your 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

Concentration 10 ppm

15 minute OEL

15 ppm

Ceiling OEL

20 ppm

OEL Descriptions 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 H2S.

Detection of H2S Detection Systems ELECTRONIC MONITORS Electronic monitors use sophisticated electronics to measure the concentration of H2S and provide very accurate readings, if functioning properly. These units are designed to continuously monitor gas levels. Some units are capable of monitoring more than one gas. The purpose of these devices is to protect your 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 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. 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 the 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 type of electronic monitor. The system consists of :

• a central control unit • remote display(s) • remote sensor(s) • alarm(s) GENERIC STEPS FOR 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 • ensure proper placement between you and

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 then positioned throughout the jobsite or plant 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 the other types of electronic monitors, the fixed monitor works on a continuous basis and will alarm at a pre-set level of H2S. This 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 incidents, fire incidents in fact in any incident where Breathing 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 panic 2. Hold your breath 3. Wear Breathing Apparatus if available 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 against the possible danger of H2S adequate 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 particular danger such as permanent tanks, open drainage or 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 required. These can be flags, wind socks or weather vanes, these are 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 you smell H2S while at the work site what is your response …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… ……………………….

2.

What are the factors to bear in mind during rescue operations …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………….

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 will practice the donning procedure for the set 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.