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.
Canada’s national laboratory for particle and nuclear physics
Laboratoire national canadien pour la recherche en physique nucléaire
et en physique des particules
Oxygen Deficiency Monitoring
at
TRIUMF
April 11, 2011
Doug Preddy
Beamlines Group Leader
TRIUMF
Accelerating Science for Canada
Un accélérateur de la démarche scientifique canadienne
Owned and operated as a joint venture by a consortium of Canadian universities via a contribution through the National Research Council Canada
Propriété d’un consortium d’universités canadiennes, géré en co-entreprise à partir d’une contribution administrée par le Conseil national de recherches Canada
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?
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
April 11, 2011
4
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.
6-8
6 minutes – 50% probability of fatality
8 minutes – 100% fatal
4-6
Coma in 40 seconds, convulsions, respiration ceases, death
April 11, 2011
5
Common causes of an ODH
• Gas release
• Cryogenic liquid release
• Fire
April 11, 2011
6
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.
April 11, 2011
7
Quick explanation of the physiology of
ODH
• The following slides will explain how a low
oxygen atmosphere affects a worker.
8
Transport of oxygen in the human body
Oxygen Osmosis
O2
O2flows
flowsfrom
fromhigh
highconcentration
concentrationtoto
low
lowconcentration.
concentration.
Concentration of O2
in the lungs is high
Concentration of O2 in the
tissues and Brain is lower.
Oxygen is transported from the lungs to cells, tissue and
brain via Osmosis.
Breathing O2 deficient air
O2 flows from high concentration to
O2 concentration.
flows from high concentration to
low
low concentration.
O2 deficient air is
inhaled
Concentration
Concentration of O2 equalises throughout
the body.of O2 in the tissues
and Brain is higher than the lungs
•Reverse Osmosis
•Lungs take O2 from the blood stream which in turn takes it from the brain.
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.
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.
13
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?
14
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.
15
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
April 11, 2011
16
Our first try at ODH monitoring
We got some things right:
Two light warning system
outside each area
April 11, 2011
Lights and horns to
annunciate alarm in area.
17
Our first try at ODH monitoring
We got some things wrong:
• 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
Aril11, 2011
18
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
April 11, 2011
19
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.
April 12, 2011
20
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
April 11, 2011
21
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.
April 12, 2011
22
Canada’s national laboratory for particle and nuclear physics
Laboratoire national canadien pour la recherche en physique nucléaire
et en physique des particules
Thank you!
Merci!
Questions?
Owned and operated as a joint venture by a consortium of Canadian universities via a contribution through the National Research Council Canada
Propriété d’un consortium d’universités canadiennes, géré en co-entreprise à partir d’une contribution administrée par le Conseil national de recherches Canada
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