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... ot to go unnoticed. As with cockpit design directly wired instruments are always present as a back up for VDU failure. I believe this principle should be applied to all complex control systems. 4. 2. 2. Working/ Long Term Knowledge The points above underline the requirement for operators to maintain their manual skills. This can be approached in two ways.
One possibility is to allow the operators hands on manual control of the process for a limited time each shift. This may prove unfeasible, however, in high-risk plants. In this case management should provide high fidelity simulators to develop these necessary fast reactions in case of emergency scenarios. 4. 2. 3. Human-Computer Collaboration Governance should ensure design processes are manipulated so that a philosophy is integrated where the human and machine should be designed together, for collaboration. This would benefit over past designs where humans were an afterthought, subsequently isolated from the system. One method to address this issue is to enforce task analyses in the design stage.
Tasks humans may be required to carry out with the machine can be broken into swim lanes where tasks are grouped for human and computers. This allows necessary interfaces between human-computer to be recognised and understood designing the human as an integral part of the system: Fig. 2 V Swim Lane Task Analysis The shaded circles indicate the HCI (Human Computer Interface) between the tasks (white boxes) and this diagrammatic form also allows designers/ operators a simple overview of the system architecture, building the all-important knowledge base. 5. Processes for Safe Operation This section will concentrate on the processes that can be adopted by organisations for safer operations. As a basis for this discussion, and personal reference, I will be using a diagram from the course lecture notes that I am sure youre familiar with! Around this I will attempt to identify the important design and monitoring issues to be recognised by organisations, where appropriate using relevant case studies to reinforce the points made. Being a Systems Engineer I will also consider the issues in a systems view of this process, that is of particular relevance to my studies.
Fig. 3 V Processes to design in disasters 5. 1 Safe Operations This diagram gives a complete overview of a generic process applied with a view to eliminating disasters. The left side demonstrates the companies knowledge management, design process and maintenance philosophy whilst the right side concentrates on operational management. Several basic principles are contained within this process that constitute the main principals of safe operation: 5. 1. 1 Hazards Recognised and Understood If hazards are not recognised and addressed early in the design process they can have catastrophic consequences in operation. An approved approach combines HAZOPS (Hazards and Operability Survey), seeking relevant user experience, and the use of standards and benchmarks.
In 1984 there was leak of radioactive material into the sea from the British Nuclear Fuels Limited (BNFL) plant at Sellafield, Cumbria. Initial reasoning was operator error, but the underlying fault was design error. Poor pipe work design meant radioactive solids managed to settle in the sea lines during pumping between tanks. These were later washed out to sea by a thought safe flow. This is a clear example of where a HAZOP analysis would have detected and subsequently prevented such environmental damage. A recommended stage after HAZOPS is to conduct FMECA (Failure Mode and Criticality Analysis) on the identified risks.
This identifies the ways in which automated systems can be designed to react to failures so as to optimise system response. Modern aircraft are a good example. With power loss the system is designed to provide power to hydraulics first to enable attitude control, then a radio to communicate the trouble etc. until all failure modes are covered in contingency (within reason). With one of the eternal goals of management to improve performance this requires experiments to develop the required improvements, with subsequent changes to processes and operation. This increases the chances of unacceptable performance and dangerous incidents due to the relatively unknown processes being applied.
This concept was simply expressed in diagrammatic form by Rasmussen J. He aptly named this concept Safety Migration. Fig. 4 V Rasmussen Safety Migration The acceptable operational environment is the central region limited by the three restrictive boundaries. To ensure the lower boundaries are not crossed due to management pressure (with the increased possibility of accidents) a shallow gradient should be applied. In order to maintain this shallow gradient Hazops should be made a priority by the governing body. This technique mainly covers new hazards.
In order to maximise current knowledge of hazards that already exist, the relative experienced entities should be consulted. Standards should be adhered to as these already define safe operating conditions. An example standard being the noise action regulations defined by the HSE. Managements should compare their organisation to leading benchmark companies in the same sector to keep an open mind and acknowledge better practices. Links can be sought and established for such, using joint ventures and projects that are increasingly common in modern evolving companies such as BAESYSTEMS (joint ventures with American and European companies) 5. 1. 2 Ensuring Equipment fit for Purpose Hazards outlined from the above processes should be fed back so safety is inherent in the design. It should be appreciated that first design will not be flawless so user reviews should ideally be conducted on prototypes.
Aside from safety issues, the cost of implementing changes increases as you progress down the system lifecycle so the earlier the better. Mock scenarios and simulations allow the equipment to be used in the correct context hopefully rising flaws that may occur in operational use. A personal example of such was working on the Nimrod WSIR (Weapon System Integration Rig) at BAE SYSTEMS Wharton. A rig with complete mock up of the avionic and mission systems exists that is extremely representative of the real aircraft. This allows each individual piece of equipment to be integrated and qualified into the system. Flaws in design are highlighted and rectified before reaching first flight, and the human factors in the cockpit can be realistically simulated.
This process all helps towards achieving a mature product that is understood and predictable. 5. 1. 3. Systems and Procedures to maintain integrity There are three main categories of processes to be considered in governance: h Operational Processes V Defines the philosophy in the physical day-to-day operation of the plant and delivery to external customers. h Support Processes V Deliver products and service to internal customers h Design & Development Process V How the systems are designed. The best design and equipment in the world still require safe operating and maintenance procedures reinforced by effective processes.
Piper Alpha was a distinctive example of failure in maintenance procedures. A valve was left open and the next shift unknowingly tried to use this backup pump to tragic effect. One method that is popular now is a permit to work system. Permit to Work System A permit-to-work system is a formal written system used to control certain types of work that are potentially hazardous. A permit-to-work is a document that specifies the work to be done and the precautions to be taken. Permits-to-work form an essential part of safe systems of work for many maintenance activities.
They allow work to start only after safe procedures have been defined and they provide a clear record that all foreseeable hazards have been considered. A permit is needed when maintenance work can only be carried out if normal safeguards are dropped or when new hazards are introduced by the work. Examples are, entry into vessels, hot work and pipeline breaking. Operational procedures should be defined for inherent safety. As discussed earlier an integral part of the procedures should be to keep humans integrated within the automation systems to maintain a knowledge base of the process within operational staff. Management should ensure operators experience little time pressure so erroneous actions...
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Research essay sample on Joint Ventures Knowledge Base
