High integrity/fail-safe control. All safety control systems should be designed and built to prevent failure or, in the event of failure, de-activate the operation of the machinery and equipment. The extent to which a safety control system should tolerate faults is a function of risk (likelihood and consequence), and is described fully in AS4024.1501 Safety Related Parts of Control Systems, which explains the categories of control required as a function of increasing risk.
Lower order machinery and equipment risk controls, such as personal protective equipment (PPE), can prevent injuries, but are generally not as effective as higher order controls, as they rely more on worker behaviour, maintenance programs and supervision.
People providing maintenance or repair services could: • work alone • work on machinery and equipment at height, or over machinery and equipment to connect services, such as electricity, air or water • access machinery and equipment from the rear or sides • be required to enter confined spaces of larger machinery and equipment • be trapped by the mechanism of the machinery and equipment through poor isolation of energy sources or stored energy, such as spring-loaded or counter-balance mechanisms, compressed air or fluids, or parts held in position by hydraulics or pneumatic (air) rams • move heavy parts when changing the set up of machinery and equipment, or repairing failed parts, such as electric motors or gear box assemblies • disable or remove normal safety systems to access the mechanism of machinery and equipment.
Where frequent cleaning is required, the guard may be constructed of mesh that prevents intrusion of body parts, but allows for hosing. Food production workplaces, that use conveyors in areas where hygiene or food safety is an integral part of the operation, use fixed mesh guarding of conveyor end rollers.