Captive key systems do not provide full isolation of the power source, but may provide limited temporary access under controlled conditions.
People who install or dismantle machinery and equipment could: • work in isolation • work on machinery and equipment at height, or over machinery and equipment to connect services, such as electricity, air or water • work in low light, or with bright directional light • access machinery and equipment from the top, sides or underneath • work with or near cranes, forklifts or rigging to lift machinery and equipment • work in confined spaces • use power tools, welders, extension leads, which present electrical hazards if damaged or wet.
Interlock guarding is generally achieved via mechanical or electrical means, but may also include hydraulic or pneumatic control systems. The energy stored in moving parts (momentum) can cause the mechanism of the machinery or equipment to run on for some time after the source of driving energy has been removed.
Where access is not anticipated, a fixed guard can be permanently applied by a bonding agent, welding, or secured with one-way screws. If access is generally not required, a permanently fixed barrier is the preferred option.