1. Discuss briefly the assertion that ‘investment by a company in safety procedures and training reduces the risk and probability of accidents and is good for business’. 

2. In systematic Risk Assessment when analysing a hazardous incident it is useful to answer four basic questions regarding the incident. (a) State these four relevant questions. (b) State briefly the what is meant by a ‘quantitative approach’ to safety assessment. 

3. (a) Define the terms ‘hazard’ and ‘risk’ and distinguish between the two. (b) Describe briefly what is meant by ordinary (industrial), residual, process and societal risks, giving examples of each.

4. Classify the following situations in terms of type of risk and complete the risk table by assigning probabilities between 0 (not possible) and 1 (certain) with 0.1 – 0.3 (low), 0.4 – 0.6 (average), 0.7 – 0.9 (high) for injury and equipment damage for each hazard. State concisely the reasons for your choices and any qualifications you feel are required. Factors such as weather, location and population density should be considered and stated. (i) Object falling from scaffold. (ii) Tripping over a low level pipe in a petrochemical plant whilst on nightshift. (iii) Electric shock from overhead cable/line struck by lightning.

(iv) Radioactive leak into a river from nuclear power station. (v) Electricity supply interruption in an equipment store with emergency lighting. (vi) Not replacing a walkway grating on an oil rig. (vii)Hydrogen sulphide release from pocket in the end of a blanked off pipe in a crude oil fractionation plant.

5. The sketch shows a tank which contained a highly flammable volatile liquid at a slightly higher than ambient temperature. Stirrer Scraper rod Flammable vapour and nitrogen Solid residues had formed on the stirrer shaft and required removal. The vessel was pumped out and charged with nitrogen to minimise the risk of air entering to form a flammable atmosphere of hazardous vapour and air. The manhole cover was then removed and the residues began to be cleaned off with a scraper rod. The operator, however, went for his lunch before completing the job but left the manhole cover off. Upon his return, a flash fire was caused when he generated a spark by striking the stirrer shaft with the rod. Write a short report suggesting reasons why this accident occurred.

6. Answer EITHER part (a) OR part (b). A gas scrubber on an oilrig discharged gas periodically such that an accumulation of hydrocarbon gas nearby had occurred. A contractor welder was dispatched to a job immediately adjacent to the area and it being a shift change and personnel unavailable temporarily, the welder decided to commence welding. As a consequence, an incident occurred. Describe briefly: what you imagine was the incident including any hazards existing prior to or during the incident the consequences of the incident on personnel, equipment or process emergency procedures put into practice during and immediately after the incident indications of possible cause(s) of the incident (include any breaches of safety procedures (permits to work, etc.) statutory systems, codes of practice and company safety rules that led to the incident and any other causes or contributing circumstances recommendations/suggestions that would reduce the possibility of a repetition of the incident. (This is based on a real incident.) (b) Describe briefly (as in (i) to (v) of part (a)) a hazardous incident with which you are familiar.

7. (a) Distinguish between a Hazard and Operability Study (HAZOP) and Hazard Analysis (HAZAN). (b) Explain briefly the quantities shown in the equations used for hazard analysis H = D . fdt = D ? 1 /2F . T (if F . T << 1). (c) State the units of H and D and hence determine the units of fdt if any. (d) FIGURE 1 shows an external intermediate vessel which receives a continuous mixture of hydrocarbon liquid and small variable amounts of water. The water must be separated by settlement into the sump to prevent contamination of a later hydrocarbon processing stage. The sump should be drained every 4 hours by an operator. The operation is facilitated by a sight glass and high level alarm. Under normal conditions the sump would fill in approximately 10 hours. Carry out a hazard and operability study (HAZOP) on the sump and drain line for deviation of 'No Flow' and 'More Flow' of water, listing possible causes, consequences and recommendations to avoid future

10. 10. A housing estate of 250 people is considered to be at risk from a nearby factory on the basis of a hazard analysis which yielded the following data: The 20% probability of fatalities due to the blast effects of an explosion. The 10% probability of additional fatalities due to the release of toxic gas following the explosion. The probable frequency of an explosion occurring is once in ten thousand years, i.e. 0.0001 yr–1 . Find the societal and respective average individual risks for these events. Explain why such data may be misleading if the number of people exposed to the risks is increased by, for example, the expansion of the housing estate.