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GOOD MANUFACTURING PRACTICE FOR BIOPROCESS ENGINEERING (ERT 421). Huzairy Hassan School of Bioprocess Engineering UniMAP. 4) Fault tree analysis - is a logically constructed diagram used to model the way that c ombinations of failures cause the event of interest (the top event) to occur .
School of Bioprocess Engineering
- is a logically constructed diagram used to model the way that combinations of failures cause the event of interest (the top event) to occur.
- provides valuable insights into the way that hazardous events interact even if no data is inserted for calculations (hazardous event frequencies or probabilities).
- The logical arrangement of the 'And' and 'Or' gates of the fault tree is more critical to the overall calculation of the likelihood of the top event than the accuracy of the data inserted.
- A rule of thumb is that if there are more than twenty elements in the tree then subdivision is worthwhile.
- Acceptable to whom? - to the people who will be affected.
- when the benefits seem to outweigh the perceived risk, people will tolerate a risk until it can be made acceptable.
- dominated by product security and qualityas these govern the potential consequences to the people who use the industry products.
2) Risk acceptability criteria range and precision
- 'Zero risk‘ concept – is often mentioned when the potential consequences of a particular risk are extremely severe yet extremely unlikely.
- basis of the 'precautionary principle', which is often quoted to stop particular risks from being taken.
- The industrial regulators have used upper and lower boundaries of risk with risks in between these levels controlled to be 'As low as reasonably practicable' (ALARP).
Risk ranking - based on the intuitive idea that the events with the worst consequences should have the least chance of occurrence to have an acceptable risk.
- mostly used for comparisons or for sensitivity analysis. (Sensitivity analysis is the process of testing the effects of different values of the data or assumptions made on the predictions from QRA models).
Chemical reaction hazards
1)Chemical reaction hazards assessment
- methodical assessment (described by Barton and Rogers:
- Seveso, Italy, (1976) – In a manufacturing plant of 2,4,5 trichlorophenol sodium salt by alkaline hydrolysis of tetrachlorobenzene, a chemical mixture containing dioxin, in the form of aerosol cloud escaped into the air.
A large number of animals were killed and thousands of victims of diseases including cancer, chronic dermatitis, neuropathy and deformed babies.
a- overcharging with compressed gases or liquids,
b- excessive vapour generation due to overheating, or
c- runaway reaction.
- When control is lost, the most effective way to prevent damage to the reactor is to relieve the pressure through an emergency relief system.
1- what is the maximum pressure that the vessel can contain?
2- what pressure will activate the relief system?
3- will the relieved material be a liquid, a vapour or a two- phase mixture?
When handling flammable solvents or finely divided organic powders,
used for the reactions such as hydrogenation, nitration, Grignard reaction, and oxidation in primary production processes.
1) Material fire and explosion properties
a) gases and vapours:
lower and upper explosive limit in air, critical oxygen content, density, minimum ignition energy, auto-ignition temperature, minimum flame diameter.
b) Flammable and highly flammable liquids:
flash point, boiling point, lower and upper explosive limit in air, auto-ignition temperature, vapour density.
c) finely divided powders and dusts:
dust classification, maximum dust explosion pressure, critical oxygen content, St rating (maximum rate of pressure rise during explosion), minimum ignition energy, train firing.
Area Classification (British Standard 5345)
Rules of thumb for preliminary process design and risk assessments:
1) Occupational exposure limits (OELs):
- The OELs for materials that cause chronic effects are usually based on an 8-hour time weighted average exposure. Highly active materials are allocated shorter times such as the 15-minute time weighted average exposure.
- Some materials may be allocated both long and short-term exposure limits.
- The dose-response relationship for a toxic substance is the relationship between the concentration at the site of ingress and the intensity of the effect on the recipient.
3) Occupational health systems description
4) Occupational health controls
5) Occupational health impact assessment
1) Environmental hazards in the pharmaceutical industry
a) Routine solvent emissions to air
Summarize a current issue (news) (2009 or 2010) about GMP. Make a commentary and deduction based on what have been discussed in the class.
Due date: 30 September 2010