Interlock guarding occurs when the act of moving the guard (opening, sliding or removing) to allow access, stops the action of the hazardous mechanism. Interlock guarding works by: • disconnecting the drive mechanism mechanically (e.g. applying a brake or disengaging a clutch or geared mechanism) • isolating the power source of the drive mechanism (e.g. stopping the motor) • a combination of mechanical and power disconnection.
People operating machinery and equipment could: • be required to place their hands close to the mechanism of the machinery and equipment that does the work, and may be injured if caught or trapped by moving parts • be exposed to constant harmful noise, radiated energy or fumes being emitted from the machinery and equipment being operated, or are close to • inadvertently bump or knock poorly placed control levers or buttons • be required to make adjustments to the mechanism of machinery and equipment while the machine is in motion • be required to clear away scrap • make minor adjustments, or reach into the moving mechanism of the machinery and equipment being operated.
Accidental start-up, or movement of a machine mechanism, can occur: • if control levers or buttons are bumped or knocked • if a short circuit of the control system occurs • when hydraulic or air pressure is released • when undoing retaining bolts. The word machine is derived from the Latin word machina. The modern meaning of the word is influenced due its specialized application in the military siege engines. They are also used in the stage engines, which are used in theater.
Access may vary during each stage of the machinery and equipment life cycle. For example: • installation or removal o complete access from every area may be required and involve disconnection or connection of services, such as water, air, pipes, installation of electrical cable to switch board • operation o access for set up, operation and adjustment • maintenance, repair, cleaning, alteration or adaptation o access to remote areas may be required.