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GAS TESTING COURSE

INTRODUCTION : Why carry out a gas test?

Possibility of gas escaping from enclosed pipe work with a risk of explosion and/or toxic hazard.Risk from lack of oxygen leading to suffocation or incomplete burning which would lead to CO poisoning.Risk from oxygen enrichment and fire hazard.Toxicity with risk of poisoning the life support system.Risk of explosion or fire from flammable gases.To certify atmosphere is safe for personnel to work in.

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GAS TESTING COURSE SAFE ATMOSPHERE

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Air = 78% Nitrogen, 21% Oxygen, 1% Argon, etc..

Safe level 19 - 23% Oxygen.Oxygen deficiency:19% Minimum permissible oxygen level.15 - 19%Decreases ability to work.12 - 14%Respiration increased with work, pulse up10 - 12%Impaired co-ordination and judgment. 8 - 10% Mental failure, nausea and fainting 4 - 8% Respiration ceases and death occurs Oxygen enrichment enhances combustion causing materials that would not normally burn to ignite e.g. steel wool. Incomplete burning caused by oxygen deficiency during welding or cutting operations may produce toxic by-products e.g. Carbon Monoxide Gas monitoring instruments need minimum of 13 % O2.

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The temperature at which a substance will ignite when an outside ignition source is applied, i.e. methane remains

a gas at all temperatures and has no flashpoint temperature.

Propane gases off at 105°C and will ignite once an ignition source is applied.

GAS TESTING COURSE IGNITION TEMPERATURE

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FLASHPOINT

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Sometimes known as the spontaneous ignition temperature or just as the ignition temperature.

Heating a gas so that it will ignite spontaneously without an outside ignition source being applied.

Methane590°CPropane 467°C

At certain concentrations in air, all petroleum gases will ignite at normal temperatures once an outside ignition source

has been applied.Provided no ignition sources are applied

it will take extreme heating of the gas for it to spontaneously ignite.

GAS TESTING COURSE IGNITION TEMPERATURE

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AUTO IGNITION TEMPERATURE

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LEL AND UELLower Explosive Limit - Given as a percentage mixture by volume

compared to that of air the lowest percentage mixture when ignition could take place.

Upper Explosive Limit - The highest percentage mixture by volume in air when ignition could take place.

GAS TESTING COURSE RANGE OF FLAMMABILITY

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A gas will only ignite in air if it is in the correct mixture.Too Lean - Insufficient gas vapour in air to igniteToo Rich - Insufficient air for gas mixture to ignite.

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SIMPLE ASPHYIANTSGases such as Methane, Carbon Dioxide and Nitrogen

have no effect on the body in small doses.Large volumes of these gases will reduce

the oxygen content in the atmosphere to cause suffocation.

CHEMICAL ASPHYXIANTSGases such as Carbon Monoxide, Hydrogen Sulphide

can poison the life support system. These types of gases can cause sickness, paralysis or death even when in the

atmosphere in minute concentrations.

GAS TESTING COURSE TOXICITY OF A GAS

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GAS TESTING COURSE TOXICITY OF A GAS

IRRITANTSSubstances such as Sulphur Dioxide,

Chlorine and Ammonia can irritate the respiratory tract, and lungs.

BLOOD POISONS Substances such as Benzene, Arsine can damage red and white

blood cells

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OCCUPATIONAL EXPOSURE LIMITS (OEL)Limit below which no health damage can occur. i.e. dose at which a person can cope.OEL set by Health and Safety Executive (HSE) published annually in Guidance Note EH/40Maximum Exposure Limit (MEL).Occupational Exposure Standard (OES)Long term Exposure Limit (LTEL) 8 hour time weighted average.Short Term Exposure Limit (STEL)Single 10 minute exposure threshold limit Value (TLV)

GAS TESTING COURSE EXPOSURE LIMITS

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Gases that are lighter than air have a number less than 1 e.g. Methane 0.55

Gases that are heavier than air have a number greater than 1 e.g. H2S 1.2

GAS CLOUDSGases move from place to place under two influences:

Gravity and natural buoyancy, normal turbulenceIn event of a leak gases remain mixed until each component is removed by condensation, diffusion or bulk air movement.

-Natural and Mechanical ventilation affects the movement of gas/air mixtures.

GAS TESTING COURSE DENSITY

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WARNING DEVICESBoth audio and visible alarms are situated on each instrument

to alarm at a designated reading. i.e.

19%+23% for oxygen

10% LEL for flammable gases

10 ppm for Hydrogen Sulphide

GAS TESTING COURSE GAS METERS

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1. ELECTRO CHEMICAL SENSORS – O2 AND TOXIC GASES

2. CATALYTIC SENSORS – FLAMMABLE GASES

3. THERMAL CONDUCTIVITY SENSORS – O2 DEPLETED ATMOSPHERE

GAS TESTING COURSE SENSORS

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TO DETECT GAS VOLUME BY PERCENTAGE OR CONCENTRATION IN PPM

DIFFERENT TYPES OF TUBES & PUMPS

GAS TESTING COURSE DETECTOR TUBES

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MANDATORY SEQUENCE FOR GAS TESTING 1. Oxygen

2. Flammable 3. Toxic

GAS TESTING COURSE GAS TEST

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CONFINED SPACE ENTRY HOT WORK

VEHICLE ENTRY

GAS TESTING COURSE GAS TEST

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GAS TEST CERTIFICATE PERMIT TO WORK

GAS TESTING COURSE GAS TEST