The use of computer-based control systems allows modern fairground rides to perform increasingly complex functions at very high speeds. In some cases, passenger safety will depend on the correct operation of these control systems, so their failure could compromise passenger safety. As a result, it is important that the rate of potentially dangerous control-system failures is adequately low in relation to the hazard level associated with the functions that they carry out.
Quantitative risk assessment techniques are used in, for example, the process and manufacturing industries, but these techniques have been slow in moving to the fairground industry. To try and rectify this, this report sets out to illustrate how quantitative risk assessment techniques can be used to determine the target Safety Integrity Level (SIL) for the control systems of three diverse types of fairground ride, with the intention of encouraging the use of these techniques and also to indicate the expected target SIL requirements for the control systems of these typical types of ride.
Having determined the target SIL, the designer can use appropriate techniques (e.g. multiple channels, extensive internal diagnostics, etc.) to ensure that the rate of potentially dangerous control system failures is adequately low, using the guidance provided by standards such as BS EN 13849 or BS EN 61508/IEC 61508.
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