fundamentals of cryogenic safety and training rob done ceng mimeche project design engineer isis...
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Fundamentals of Cryogenic safety and
trainingRob Done CEng MIMechEProject Design Engineer
ISIS Design DivisionRutherford Appleton Laboratory
STFC Safety auditorOXETA training instructor
Health and safety Moral
o To prevent people getting hurto Minimise the risk that you or anyone else will be
injured or will suffer ill health
Health and safety Legal
o To comply with the lawo It is not acceptable for organisations to carryout their
activities in such a way that people will get hurt
Health and safety Financial
o Poor Health & Safety is expensive Cost of investigation Injured person away from work Injury claim Prosecution by the HSE Poor public relations
273 K
0 K
373 K
Freezing point of water
Boiling point of water
Absolute zero
Health and safety
HyperthermiaHottest temperature on Earth
Normal body temperature
Coldest temperature on Earth
Boiling point of liquefied gas
Hypothermia
343.7 K313 K310 K
294 K
183.8 K
120 K
Cryogenics
Humans can live
Lut Desert in Iran
Vostok - Antarctica
Health and Safety The temperature range of cryogenic technology has
potential life threatening consequences to the human body.
More and more facilities throughout the World use cryogenic materials for cooling equipment – increased likelihood of accidents happening.
Health and Safety
FatalitiesThere is an average of 8 deaths a year in the USA due to cryogenic asphyxiation.In 1981, a technician preparing for the space shuttle launch died when entering a confined space full of nitrogen gas.The use of cryogenic materials has resulted in fatalities through asphyxiation at a number of UK research establishments.In 1999, a laboratory assistant in Scotland died from asphyxiation caused by a liquid nitrogen spill.In 2012, a young woman in England had her stomach removed after ingesting a cocktail made with liquid nitrogen.
Health and Safety
Fatalities and near miss incidents
For every 1 Major injury/fatality that occurs there is an average of 640 additional incidents taking place in the working environment
Relevant LegislationThere is no specific cryogenic safety legislation.It is addressed through related general safety requirements:
Relevant Legislation The Health and Safety at Work Act – 1974
o General occupational health and safety provisiono Enforcement
Relevant Legislation The management of Health and Safety at Work
Regulations – 1999o Core measures relating to the minimum health and
safety requirements for the workplaceo Risk assessments
Relevant Legislation The Provision and Use of Work Equipment Regulations
(PUWER) – 1998o Place duties on people and companies who own,
operate or have control over work equipmento Provision of protective devices and controls
Relevant Legislation The Pressure Equipment Directive (PED)
o Meet the essential requirements covering the design, manufacture and testing of pressure vessels
o Vacuum vessels
Relevant Legislation The Pressure Systems (Safety) Regulations (PSSR) – 2000
o Minimises the risks when working with systems or equipment which contain a liquid or gas under pressure
o Installation
Relevant Legislation The Working at Height Regulations – 2005
o Avoidance of risks from working at heighto Minimise the distance and consequence of a fall
Relevant LegislationThese regulations address the specific hazards associated with cryogenic materials, but do not include the many related hazards:Lone WorkingAsphyxiationToxicity
The purpose of risk assessments is to provide a safe and healthy environment for all
employees, by assessing the chance of harm being done
Key factors of risk assessments
Identify all the hazards associated with the task.
Hazards1. Pressure build-upContinuous evaporation generates a gaseous atmosphere and an increase in pressure inside any liquid cryogen storage vessel.If not properly controlled and released by suitable measures, this can result in a significant build-up of pressure.A pressure relief valve (PRV) of suitable specification, which has been registered for statutory inspection, should be used to prevent over pressurisation of the vessel or system.
Hazards2. Expansion RatioThis is the ratio of the volume of the cryogenic liquid from the boiling point to normal ambient temperature and atmospheric pressure.
The evaporation of one litre of liquid nitrogen produces 696 litres of gas at NTP.
The evaporation of one litre of liquid helium produces 757 litres of gas at NTP.
Gas volume from liquid
Relative Density
Liquid methane 1 : 627 0.555
Liquid nitrogen 1 : 696 0.967
Liquid helium 1 : 757 0.138
Liquid hydrogen 1 : 851 0.069
Liquid oxygen 1 : 860 1.105
Liquid neon 1 : 1438 0.697
Solid carbon dioxide 1 : 554 1.520
Hazards3. Cold contact burnsLiquid or low-temperature gas from cryogenic materials will produce effects on the skin similar to burns.Contact with uninsulated pipes etc. will cause contact burns and may result in the skin freezing to the pipework.Gases released as cryogenic liquids vapourise can permanently damage delicate skin e.g. the eyes.
Hazards
4. Frostbite and exposureExposure to continuous cold will slow an individual’s reactions and capabilities and could lead to hypothermia.Continued exposure is likely to result in frostbite.
Hazards5. AsphyxiationThe atmosphere around us has an oxygen content of 21% O2 which enables us to breathe normally. The minimum safe O2 content for entry into any area is 19.5%, below this level entry should be forbidden.
Hazards
6. Embrittlement of materialsWhen materials are cooled, the Young’s modulus of the material will typically increase by around 20% down to liquid helium temperatures.This will increase the material’s strength and stiffness, but also the brittleness which could also cause failure of parts due to the change in this property.
There is a potential for hazards to be created directly by the people carrying out the task – this is known as the ‘human factor’
Hazards7. The human factor
Hazards8. Design – installationThe British Compressed Gases Association (BCGA) Codes of Practice provide guidance and a framework to assist with fulfilling the legal duties and achieving best practice. External storage tanks must have sufficient clearance on all sides to comply with BCGA CP36.The design of piped gas delivery systems for cryogenic liquids needs to conform to the Pressure Systems Safety Regulation 2000.
Hazards9. Vehicular transportation of cryogenic materials:•Transportation of cryogenic substances is covered by the Carriage of Dangerous Goods by Road (CDG Road) Regulations 1996.•These regulations come into force if the cryogenic substances are transported on public roads, for however brief a period.
How many times do I have to tell you!
Told
After 3 weeks
ExperiencedShown
10 %
70 %
32 %
72 %
65 %
85 %
Recall
After 3 months
Telling is a very limited way of aiding memory and results in poor recall.
Training
Classroom based study is the traditional route for training Consider the merits of mentoring Training as you work – in-house expertise – first hand
experience Graduate training scheme – MPDS
Training
What animal?
It’s never too late to learn something new
Learning to view things from a different angle
A frog ? A horse ?
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