WTF Facts : funny, interesting & weird facts about probability, risk

WTF Facts : funny, interesting & weird facts

The above link gives information about the probability of some events (mostly death). Cancer death is most probable among the listed events and chance of being hit by a falling satellite is the least probable.

About probability of reactor accidents based on past accidents

In an article, it is stated that the probability of contamination in severe accidents like that of Chernobyl and Fukushima will be far higher than earlier estimates. Though various conditions lead to the probability, the calculation described in the articles gives us an idea of probabilities. Numbers look absurd, but nothing is wrong in being pessimistic and try to improve safety systems.
http://cleantechnica.com/2012/05/24/likelihood-contamination-severe-nuclear-reactor-accidents-higher-expected/

Some statements on safety

Following are some of the statements in "Process Safety Analysis - An Introduction"  by Bob Skelton published by Institution of Chemical Engineers, UK.

1. A good safety culture ensures that both the spirit and the letter of the law are fulfilled.
2. Attitude to safety should be highly visible and shared at all levels within the company.
3. A well managed company is almost invariably not only a profitable company but a safe company.
4. Changes in existing plant are costlier than that introduced in design stage.
5. Design should be such that operator intervention is not needed for at least 30 minutes after an incident. Experience has shown that operators can not always be relied upon to make the correct decisions under immediate post-accident conditions.
6. Safety in design must be both proactive and reactive. Changes, once a plant is built, are very expensive compared with changes at the design stage.  It is not sufficient and cost efficient to make safety review after completing the design and then BOLT ON safety devices. It will not be cost effective. Engineered safety is BOLT ON safety. Engineered protective devices can fail and never place too much reliance on BOLT ON safety.
7. Commissioning is one of the most hazardous parts of any process plant operation. Not only do design errors which escaped previous checks manifest themselves but problems due to construction errors also become obvious. In addition commissioning generates hazards of its own as the plant moves from construction to operating status. It is essential that a formal set of checks be carried out before process fluids are introduced for the the first time.
8. Fire and explosions can be prevented  by not exceeding 25% of LEL. Flammable atmospheres can be avoided by ensuring that fuel lines and tanks are pressurized so the flammable material leaks out rather than air leaking in. good ventilation of vessels and plant areas can maintain safe working conditions.
9. Dust explosions are best prevented by good housekeeping - that is, by keeping the concentrations of dust down and perhaps keeping the dust damp. Inerting by dilution with non-combustible dust is another effective technique, frequently used in coal mines.
10. The risk is serious in case of static electricity, if the relative humidity is below about 60%.
11. Explosives manufacturing facilities are usually designed so that the buildings are separated by safe distance, surrounded by earth mounds so that any explosion will go upwards rather than affect other plants in the area. In addition there is usually a limit on the number of people allowed in a building.
12. Fire fighting water causes more damage than the fire itself, when polluted water is let into rivers. There may be a conflict between accepting the atmospheric pollution caused by letting the fire burn out and the water-borne pollution caused by fighting it.
13. Non-process hazards account more than 70% of all accidents in process plant.
14. Many of the worst accidents in the process industries are the result of bad maintenance practice. Ex: Piper Alpha and Flixborough
15. As many people die by asphyxiation as from toxic gases.
16. A good health and safety policy is always cost effective; most organisations grossly under estimate the cost of accidents, often by an order of magnitude. The organisation should be such that the attitude to safety is highly visible and shared at all levels within the company. Active participation is encouraged to promote the objectives of not just preventing accidents and industrial illness but motivating and empowering everyone to work safely.
17. A safety culture, once established, must be maintained, any any tendency to careless practices stamped out at once. Experience shows that 80% of accidents tend to happen to 20% of the workforce - the young and the old being particularly vulnerable.  Many accidents are caused by operators not fully appreciating the significance of small, but nevertheless important changes.
18. A good system of accident reporting is proactive and reactive, whereas most tend to be purely reactive.
19. Effective safety at all stages of a project - from inception to demolition - can only be achieved if there is a commitment at all levels. The senior management must see health and safety as being just as important as profitability and they must make certain that all their workers are aware of this fact.
20. A well managed company is almost invariably not only a profitable company but a safe company.
21. In hazard analysis, a distinction must be made between routine operator action and operator intervention in an emergency.  For routine operator action, the operator can usually take time and is under no great stress. Safety assessments involve the prediction of the likelihood of errors when the operator is taking corrective action against alarms. The time for corrective action may short, the operator is liable to be under some stress and so the probability of errors is greater.
22. Total elimination of human error will never be possible. Use must be made of the science of ergonomics to ensure that everything possible is done to enhance the strengths of human operators whilst at the same time allowing for the weaknesses.
23. The most important rule is, 'inherent safety is better than engineered safety', ' what you have not got can not leak'. Even elaborate safety devices can't reduce risk to zero due to the escape of a noxious substance, but replacing a noxious substance by a more benign one could well eliminate that risk altogether.

 

Risk = Probability (???) x SEVERITY

Yesterday I read a news item that a US satellite Iridium-33 in use collided with a Russian satellite Cosmos 2251 that is no longer in use on Tuesday (10.02.2009) at 0455 GMT at 790 km height above Siberia. It seems that this type of accident happened for the first time. There are more than 17000 man-made objects at present in the space. I went through internet and found that the probability of such collision is once in tens of years and the debris now generated can reduce this probability to once in a year or so as there are some more satellites in the same altitude and the total debris may hinder space craft movement in the future.

Now, the question is not about space but on the events on the earth.

In any factory, accidents keep occurring. When somebody (normally safety officer / advisor) points out about unsafe acts / unsafe conditions in the shop floor / factory premises and asks for correction, the usual reaction is, a staring look and then the reply comes, "oh, we have been doing this for the last few years / we are doing like this from the beginning / who is expert -you are me - you safety people does not know any thing other than talking / I can't do - you come and do / so on...

How true are the words of the famous safety professional Trevor Kletz -

Corporates do not have memory.

We have done this way 100 times is not acceptable unless an accident on 101st time is acceptable.

We never imagined that satellite collision is possible. But, it happened. Where the chances are remote, still it happened and where the chances are high in our activities in the shop floor, we do not want to correct our selves.

If we see the accident history in any factory, after the accident, the usual sheepish answer from the injured or his colleagues or manager is that it happened for the first time, the person is experience, skilled, safety conscious, near retirement, he doesn't want to take official leave and will take personal leave for the period away from duty due to accident, so on.

In spite of all the above qualities, still accidents occurred, then imagine what can happen to others. It is the attitude that requires correction rather than any thing else.

When somebody narrates their own experience, people listen attentively, appreciate him that he came clean and after coming out from the room the listeners do the same old things. This is why accidents keep occurring again and again, if not to the same person / or same shop floor, they will be occurring somewhere else to some body else.

We love short cuts and feel that we are above all others, accident does not occur when we are working.

One of my colleague, who retired 4 years ago, used to tell in all his training classes, that we should leave the organization with same organs as we had when we joined.

Yes, it is true that no body wants to lose their organs and suffer. But, momentary decision without thought for consequences will lead to accidents.

Rarely, does the type of accident will be new in any factory that is few years old. May be after the accident, corrective actions are taken. But after few years, the corrected systems will be replaced because people forget the reasons for safe guards in place and meddle with the systems. They want to prove to their bosses that they are inventors and soon after their will be accidents and shop floor persons will be suffered. But, the so called inventor would have got his promotion or pay rise and even would have left the organization.

So, every body should work seriously on the hazards at the shop floor, let the probability is however less. Nobody says there is no (zero) probability of occuring for an accident. In fact the word probability it self gives meaning of some uncertainty. Hence, if the severity / consequence from even from remote probable event is not acceptable, without looking for chance of occurrence, we should eliminate all those hazards and make our work place safer.

Risk assessment and actions should concentrate more on consequence rather than on probability and make life safer for persons.