Hazard spotting

IchemE—Institution of Chemical Engineers, Hazard Spotting User s Guide, Multimedia Package, Rugby, Warwickshire, 2003. 

Examples of system safety analyses include routine hazard spotting job safety analysis hazard and operability studies design safety analysis fault-tree analysis and simulation exercises using a computer. 

As expected, new safety campaigns did havesome initial impact but the improvements were either not maintained or were disproportionately small in comparison to the efforts and expenditure involved. One of these initiatives involved a system of hazard spotting by safety committee teams, but the impact of this was minimal. 

This informal approach, by undertaking hazard spotting and taking initial preventive and protective steps on the shop floor , will have a direct effect upon the safety management within an organisation, which will reduce the overall risks. 

In support of an effective safety culture and the informal hazard spotting approach, formal proactive monitoring will be undertaken by supervisors and members of the management team. 

One of the benefits of using a VR system for hazard spotting is the abiUty to customize scenarios and apply random hazards. This is important because it means that trainees cannot necessarily learn to pass the test by repeated trial and error. Because each test can be unique, knowledge retention is assessed. 

In addition to simple hazard spotting applications, SAFE-VR also has a method for creating simulations of dynamics, procedural operations, as well as fault tree diagnosis. Any object can have a number of possible actions associated with it, actions that can initiate events within the SAFE-VR simulation (Hollands et al. 1999). 

As an example of a SAFE-VR scenario. Figure 10.18 shows an image from a hazard-spotting system that involves a preshift inspection of a surface mine haulage truck. This world consists of a single truck with about 25 different hazards associated with different components of the truck. The hazards themselves vary in apparent severity from missing securing pins to Utter arotmd the air filter. The sys-... 

Figure 10.19 is a shot from a SAFE-VR simulation of a Universal Mkll 650 drill rig. These rigs can be complex to operate and extremely hazardous if handled incorrectly. This simulation combines hazard spotting with the operational simulation of the rig. In addition to the plant itself, this simulation also includes the personnel involved in the activity, who may be acting dangerously, such as the worker in the picture failing to wear protective headgear. 

This is a brief summary of NFPA 704 which addresses hazards that maybe caused by shoii-term, acute exposure to a material during handling under conditions of fire, spill, or similar emergencies. This standard provides a simple, easily recognized, easily understood system of markings. The objective is to provide on-the-spot identification of hazardous materials. 

Vapor Density (VD) — the mass per unit volume of a given vapor/gas relative to that of air. Thus, acetaldehyde with a vapor density of 1.5 is heavier than air and will accumulate in low spots, while acetylene with a vapor density of 0.9 is lighter than air and will rise and disperse. Heavy vapors present a particular hazard because of the way they accumulate if toxic they may poison workers if nontoxic they may displace air and cause suffocation by oxygen deficiency if flammable, once presented with an ignition source, they represent a fire or explosion hazard. Gases heavier than air include carbon dioxide, chlorine, hydrogen sulfide, and sulfur dioxide. 

This chapter is not concerned with accidents on the road. Rather, it describes some of the many incidents that have occurred while tank trucks and cars (known in Europe as road and rail tankers) were being filled or emptied. Section 18.8 shows how hazard and operability studies have been used to spot potential hazards in filling systems, and Section 22.3 describes some runaway reactions in tank trucks and cars.. 

It is common in many offshore areas to encounter a shallow gas hazard. Quite often, these hazards can be spotted on seismic, and a surface location is chosen to avoid the hazard. However, there is always a risk of encountering a shallow gas flow with insufficient casing in the well to allow a shut-in. In this instance a diverter system is called on as a safety measure. The ideal function of the diverter system is to allow the well to flow and subside by natural means. In many cases the diverter system simply provides enough time to evacuate the rig. 

Safety signs of approved types, available from laboratory supply houses and safety equipment dealers, should be posted in appropriate spots. The door leading out of the laboratory should be marked EXIT, while the door to a back room should be marked NO EXIT. The location of a fire extinguisher must be clearly marked. Signs are available for every type of hazard. Homemade signs not conforming to official standards should not be considered. 

An 850 kg batch of a slightly doped form of azodicarbonamide exploded violently, with a TNT equivalence of 3.3 kg, 5 minutes after sampling at the end of drying. The probable initial temperature was 65°C, the lowest self accelerating decomposition temperature 90°C, and such decomposition is not explosive. Full explosibility tests, including detonability, had shown no hazard. Further study demonstrated that slightly contained azodicarboxamide, thermally initiated at the bottom of a column or conical vessel could explode even at the 5 kg scale. The above TNT equivalence corresponds to decomposition of 4% of the available charge. The cause of the presumptive hot spot is unknown. 

The final points to pick up here are that care needs to be exercised at every stage of the work. Even then, simple errors may creep into the most carefully made measurements, but these can usually be spotted by cross-checking. Poorly matching results of duplicate analyses may well be a clue to problems in the whole measurement system. A key part of any work is to tidy everything away afterwards, and deal yourself with any hazards you may have created. In brief, leave everything as you would hope to find it. 

Among the issue with mobile risk sources are, for example, transport of high volumes of hazardous substances through densely populated areas, parking the tanker vehicles at improper sites, passage of the tanker vehicles through the spots with the highest occurrence of car accidents etc. 

General Considerations 1 Location of people relative to the unit 2 Location of critical systems 3 Dominant wind direction 4 Climate and weather extremes earthquake, flooding, windstorms 5 Site topography 6 External hazards or threats (fire/explosion/toxic release from nearby process or facility aircraft subsidence sabotage) 7 Traffic flow patterns and clearances from process vessels and lines 8 Security and reliability of all critical feeds and utilities 9 Command center and alternate command center locations 10 Evacuation routes, emergency exits, safe rally spots... 

In a typical application, UV detectors are used in general or spot coverage locations. General coverage detectors are usually mounted in the comers and along the walls of a hazardous area. 

---