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Doug Preddy

Doug Preddy. I started working at TRIUMF in 1982 for the experimental facilities group. In1986 I became TRIUMF’s first cryogenics operator. I have moved between the Beamlines group and the cryogenics group since then.

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Doug Preddy

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  1. Doug Preddy I started working at TRIUMF in 1982 for the experimental facilities group. In1986 I became TRIUMF’s first cryogenics operator. I have moved between the Beamlines group and the cryogenics group since then. In January of this year I took over as Group leader for the Beamlines group. This includes the Alignment and Magnet measurements groups at TRIUMF.

  2. Oxygen Deficiency Monitoring at TRIUMF April 11, 2011 Doug Preddy Beamlines Group Leader TRIUMF

  3. Oxygen Deficiency Monitoring • What are the effects of an ODH on a human body? • Why do we need a monitoring system? • Where do we need a monitoring system? • What do we expect a monitoring system to do? • How do workers respond to an alarm? • What are the maintenance and inspection requirements for a monitoring system?

  4. What is ODH There normally is 21% oxygen in the air that we breathe When the oxygen level drops below 19.5% we consider there to be an Oxygen Deficiency Hazard in the area

  5. Effects & Symptoms • (%O2 in air) • 23.5 Maximum “Safe Level” OSHA • 21 O2 level in air • 19.5 Minimum permissible O2 level – (most detectors are set at this level or just above it) • 15-19 First signs of hypoxia. Decreased ability to work strenuously. May induce early symptoms in persons with coronary, pulmonary or circulatory problems. • 12-14 Respiration rate increases with exertion, pulse up, impaired muscular coordination, perception & judgement. • 10-12 Respiration further increases in rate & depth, poor judgement, lips blue. • 8-10 Mental failure, fainting, unconsciousness, ashen face, blueness of lips, nausea, vomiting, inability to move freely. • 6-86 minutes – 50% probability of fatality 8 minutes – 100% fatal • 4-6 Coma in 40 seconds, convulsions, respiration ceases, death

  6. Common causes of an ODH • Gas release • Cryogenic liquid release • Fire

  7. Facts & Figures - Liquid Nitrogen and Helium • One litre liquid converts to ~700 litres of gas • Cold nitrogen gas is heavier than air so accumulates at ground level. • Cold helium gas is lighter than air so accumulates at ceiling level. • When liquid N2 or He is exposed to air the cloudy vapour that you see is condensed moisture, not N2 or He gas. N2 and He gas is invisible and this is the Danger!!!. • OHSA recommend at least 6 changes of air per hour when using liquid N2 or He in an enclosed space.

  8. Quick explanation of the physiology of ODH • The following slides will explain how a low oxygen atmosphere affects a worker.

  9. Transport of oxygen in the human body

  10. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. Concentration of O2 in the lungs is high Concentration of O2 in the tissues and Brain is lower. Oxygen Osmosis Oxygen is transported from the lungs to cells, tissue and brain via Osmosis.

  11. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 flows from high concentration to low concentration. O2 deficient air is inhaled O2 deficient air is inhaled O2 deficient air is inhaled O2 deficient air is inhaled O2 deficient air is inhaled O2 deficient air is inhaled Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 in the tissues and Brain is higher than the lungs Concentration of O2 equalises throughout the body. Concentration of O2 equalises throughout the body. Concentration of O2 equalises throughout the body. Breathing O2 deficient air • Reverse Osmosis • Lungs take O2 from the blood stream which in turn takes it from the brain.

  12. Why do we need a ODH system? • TRIUMF has a number of areas where large amounts of oxygen displacing gases and cryogenic liquids are stored or delivered. • While the storage vessels and pressurized piping are certified by the BC Safety Authority, there still exists the possibility of venting these gases and liquids. This may cause the oxygen concentration in the area of these systems to drop below safe levels for workers. • The oxygen deficiency alarm system is primarily in place for the safety of TRIUMF workers, while equipment safety is a secondary consideration.

  13. What happens next? • When a person enters an oxygen deprived atmosphere the oxygen level in the arterial blood drops to a low level within 5-7 seconds. • Loss of consciousness follows in 10-12 seconds. • Heart failure and death ensue if person does not receive any oxygen in 2-4 minutes. • Holding your breath causes the oxygen in your blood to be used up. If you then inhale the inert atmosphere, suffocation and death will follow in most cases very quickly.

  14. Where do we need a ODH system? • A risk hazard analysis must be completed for any area that has stored or delivered gases and/or cryogenic liquids that could be released into the area. The analysis would look at a number of criteria that would help define areas that require a fixed low oxygen monitoring system. • Is there a sufficient quantity of gas or cryogenic liquid that could be released into the area and cause a low oxygen situation? • Is this an area that has people working in it on a regular basis? • Is there a ventilation system to ensure an adequate volume of air is exchanged so that a low oxygen concentration is not likely?

  15. What do we expect the system to do? • Local alarms • A fixed low oxygen concentration alarm system would continually monitor the local area and alarm if the oxygen concentration at the sensor drops below 19.5%. The system would alarm locally with a horn/siren and a flashing light. The system would also alarm outside the entrance to each area via a two light system. • Remote alarms • The system would provide annunciation of a low oxygen alarm to the control rooms. • Ventilation • Ventilation fans could be turned on by the system to provide outside air into an area that shows a low oxygen concentration.

  16. Our first try at ODH monitoring • CET SENSORS • Hi/low sensor positions • Daisy chained sensors • Master panel with remote panel in control room • Local light and horn alarms in areas • Two light warning system outside each area

  17. Our first try at ODH monitoring We got some things right: Two light warning system outside each area Lights and horns to annunciate alarm in area.

  18. Our first try at ODH monitoring • Communication between sensors and master panel • Communication between master panel and remote panels • Sensors were not the correct type • Hazard analysis was not done well enough • The sensors were not positioned correctly We got some things wrong:

  19. How we are proceeding now • Perform an in depth hazard analysis first. • Remove sources of gases by venting dewars etc. outside • Selection of proper sensors • Build a plc based system. • Improve the communication between components • Improve the display of information on panels • Decide on the proper sensor placement • Establish what can we reuse from the old system

  20. How we are proceeding now • Provide alarms to control room(s) • Write procedures for workers to follow in case of alarms • Establish procedures for non monitored areas • Establish a training program for workers in an area where there is an oxygen deficiency hazard possible.

  21. ODH monitoring at TRIUMF • We have recognized the need for ODH monitoring at TRIUMF • Our first effort was not done well enough • A thorough hazard analysis is essential to building a properly working system • Selection of sensors that are compatible with the environment is key to a system that works well

  22. We now have a better understanding of the effects of an ODH on the workers at TRIUMF. There is a need for a proper fixed ODH monitoring system in order to provide a safe work environment for workers. A written response procedure, as well as training for workers also makes the work place safer. Ensuring the system is calibrated and functioning properly is an ongoing process.

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