GAS TESTING

1. GAS TESTING Presented by : AyatJeyraniMoghadam

2. INTRODUCTION TO GAS TESTING 2. The following abbreviations are used: AGT-Authorized Gas Tester. CH4-Methane (a flammable hydrocarbon gas). H2S-Hydrogen Sulphide (a toxic gas). LEL-Lower Explosive Limit. UEL-Upper Explosive Limit. ppm-Parts per million.

3. INTRODUCTION TO GAS TESTING • 1. An AGT must: • Be aware of (and demonstrate knowledge of) the TOTAL Permit to Work Procedure requirements relating to Gas testing.

4. INTRODUCTION TO GAS TESTING • 1. An AGT must: • Have successfully completed the TOTAL Authorised Gas Tester Training Course.

5. INTRODUCTION TO GAS TESTING • 1. An AGT must: • Be able to demonstrate the ability to survey potentially hazardous areas using the detection equipment available and be familiar with plant and limitation of Gas Test equipment.

6. 3. The following definitions are used in this course. Gas- any substance of very low density and viscosity. Vapour - mist or fumes suspended in air. Liquid- any flowing substance with little tendency to disperse.

7. 4 . Gas testing is involved with the following activities: • Hot work of any type where heat is used or generated, eg. by welding, flame cutting, grinding, etc.

8. 4. Gas testing is involved with the following activities: • Work which may generate sparks or other sources of ignition.

9. 4. Gas testing is involved with the following activities: • Work which may cause an uncontrolled release of hydrocarbons, other flammable or toxic materials.

10. 4. Gas testing is involved with the following activities: • Electrical instrumentation work which may cause sparks.

11. 4. Gas testing is involved with the following activities: • Entry into confined spaces. • Gas alarm investigation.

12. COMBUSTIBLE GASES 1. Explosive Limits All combustible gases and vapours are characterized by explosive limits between which the gas or vapour mixed with air is capable of sustaining the spread of flame.

13. COMBUSTIBLE GASES The lower explosive limit ( LEL ) refers to the lowest concentration of a gas in the atmosphere which results in a combustible mixture. For example, the LEL of Methane in Air is 5% by volume, this means that if there is less than 5% by volume of Methane in air the mixture is too lean to support combustion. Therefore, when Methane Gas Test equipment indicates 100% LEL, there is 5% by volume of Methane in the test atmosphere.

14. LEARN THIS! IMPORTANT! 20 UpperExplosiveLimit Too Rich 15 Explosive % Methane (CH4) IN Air Envelope (Explosive Range) 5 LowerExplosive Limit Too Lean 0

15. The Upper Explosive Limit ( UEL ) refers to the highest concentration of a gas in the atmosphere which results in a combustible mixture. For example, the UEL of Methane in air is 15% by volume, which means that if there is more than 15% of Methane in the air by volume the mixture is too rich to support combustion.

16. This would typically occur in a confined area such as a tank where the Methane could not disperse through the air; in this case the danger would not be combustion but asphyxiation due to insufficient Oxygen.

17. From the above it can be seen that concentrations of Methane in air between 5% and 15% are combustible. The LEL and UEL of other gases are shown later, ( the most common constituents of hydrocarbon gases are highlighted).

18. For most practical Gas Testing purposes it is theLEL which is significant. The AGT is responsible for recording the percentage of LEL for the specific flammable gas being tested on a permit.

19. Important: REMEMBER!

21. TOXIC GASES • Principal Characteristics of H2S • Long-term exposure limit.( TLV ) • (for 8 hour period) of 10 ppm. • Short-term exposure limit. • 15 ppm.

22. TOXIC GASES • - Hydrogen Sulphide gas is referred to by a variety of names: • Sour gas • Rotten egg gas • Sulphurated Hydrogen • H2S

23. - Main Characteristics of H2S: • Potentially lethal. • Colourless. • Heavier than air. • Readily dispersed by wind or air currents. • Flammable - burns with a blue flame. • Odour of rotten eggs (below concentration of 100 ppm). • Highly corrosive to certain materials (eg. steel). Effect of H2S on Personnel • - The way in which H2S affects you depends on the following: • Duration: the length of time the individual is exposed.

24. Frequency: how often the individual has been exposed. • Intensity: the concentration of exposure. • Susceptibility: the individual’s physiological make-up. TOXICITY TABLE: 0.0025 ppm Minimum concentration which produces odour. 10 - 20 ppm Eye and respiratory tract irritation, especially in vulnerable workers. 20 - 100 ppm Inflammation, blistering and opacity of the eye, loss of the sense of smell, headache, cough and nausea.

25. 100 - 300 ppm Respiratory difficulty , respiratory depression and irritation (exposures of 30 minutes to 8 hours). 300 - 600 ppm Central nervous system effects , eg tremors , weakness , numbness of extremities , unconsciousness and convulsions. 600 - 1000 ppm Rapid ( from one breath to several minutes)unconsciousness resulting 1000 ppm & greater Cessation of breathing followed by death.

26. Golden Rules Gas Testing ONLY to Be Carried Out by Authorised Gas TesterLEVEL I Open Areas & LEVEL II Confined Space Only

27. Golden Rules Report Any Defects Report Any Anomalies Know Your Permit!

28. CHECK YOUR PERMIT!

30. SIGN YOUR PERMIT

31. YOU ARE NOW! RESPONSIBLE

32. Thank you for your attention. THE END