BECAUSE emergency stop devices (e-stops) are everywhere, they tend to be taken for granted but the law takes them very seriously as the last line of defence in machine safety.
AS 4024 describes an emergency stop as “a device which, regardless of the power source, e.g. electrical pneumatic or hydraulic, requires deliberate action to bring a machine to rest when danger is recognised”.
While the preferred form of e-stop is a mushroom-type push button, operable by palm, other formats are wires, ropes, bars and handles, all acceptable so long as they provide equivalent levels of safety.
Each Australian state has its own plant regulations but, for simplicity’s sake, we’ll focus on the Victorian OHS (Plant) Regulations 1995 (in terms of emergency stop devices, the regulations are the same across the states).
The Plant Regulations and AS 4024.1601: Design of controls, interlocking and guarding – Emergency Stop – Principles for design overlap to some degree. Under the Plant Regulations, designers and employers must meet a number of conditions.
The device must be prominent, clearly and durably marked and immediately accessible to each operator. The actuating element of the device must be coloured red. Finally the device cannot be affected by electrical or electronic circuit malfunction.
While AS 4024 Part 1601 is not legally binding it is often relied on in court to show that reasonable steps have been taken to ensure safety. The Standard specifies that emergency stops shall override all other functions in all operating modes and that it shall not be possible for any start command to be effective until the emergency stop is reset.
It also specifies that the emergency stop shall not be used as a substitute for safeguarding, that it shall not increase the risk of injury from another source and that it shall function as either a category 0 or category 1 stop (as per AS 60204-1). The standard requires the stop to be suitably marked, prominently located and readily accessible from all operator positions.
Mushroom-head latch-in or lock-in manual reset types and push-buttons are preferred and they must be positioned at each operator control station and other locations where emergency stop is required.
Pilz Safe Automation 03 9544 6300.