Emergency Stops, Stop Switches - EN 13850 and EN 60947-5-5
Machines and equipment covered by the Machinery Directive (2006 / 42 / EC) should be equipped with at least one Emergency-Stop actuator with the proven ability to prevent an imminent or occurring hazard. DIN EN 13850 also states that contact separation must be a direct result of a movement of the operating part and must not depend on a spring.
For identification purposes, each positive opening contact on an E-Stop switch must be marked with an arrow symbol pointing to the right An Emergency Stop device is required on most equipment and machinery regardless of the type of energy used to control the function, except for machines for which the inclusion of an E-Stop would do nothing to lessen risk.
The difference between Emergency Stop and stop switches?
An Emergency-Stop differs from ordinary Stop switch – the operation of which merely turns the equipment off - in that they are generally designed for “fool-proof” or' trigger action' operation, and that the actuator is locked down and the switching element safely deployed immediately after the emergency actuation process has been carried out. The ‘stop’ command is given priority over the ‘sustain’ function and resetting is only possible following a deliberate switch unlocking routine. EN 60947-5-5 and the new IEN 13850 regulations also mandate that E-Stops feature a trigger action – where the switch must: latch-in past a point of no return as the contacts open; have a forced opening action to guard against contact welding; and protect against “blocking” (wanton or accidental obstruction of the actuator with foreign objects) and “contact teasing” (which could result in premature, unreliable or intermittent action).
In addition to the demanding mechanical and electrical definitions an E-Stop device fully compliant with the relevant EC, EN, or IEC directives must feature.
- Positive opening contacts
- Fool-proof latching
- Twist, pull or key release
- A red actuator head highlighted against a yellow background
- Unlocking direction arrows in the same colour as the actuator, i. e. red, if rotating the actuator unlocks the device
- No symbols or text on the actuator or back-ground, although IEC 60417-5638 does permit the use of the ISO 13850 symbol (194-2085)
A red and not a white arrow?
White arrows were often a notable feature on E-Stop actuators prior to 2016 because the DIN EN 60947-5-5 specification mandates that the direction of the twist movement in an E-Stop switch with a twist release must be clearly apparent to the operator. However, regulation bodies have since deemed that there is a risk that high-contrast white arrows on the red actuator could be misinterpreted by an operator as an indication of the direction of actuation in an emergency situation. To minimise this risk, DIN EN 13850 states that arrows indicating unlocking direction must be designed with a low-contrast colour that is preferably identical to the background.
In exceptional circumstances such as shock, excessive vibration or unmanaged cable strain relief, there is a possibility that the contact block on the rear of a Stop or Emergency-Stop switch can become detached from the actuator. Unfortunately, this would not usually cause the equipment to stop because the normally closed (NC) contact remains closed regardless of the actuation state of the switch, but should a hazardous situation arise the operator would be unable to stop the machine. EAO’s Series 04 and Series 45 E-Stops feature an optional self-monitoring 'fail-safe' NC contact that automatically opens in the event that the contact block becomes broken or detached from the switch, bringing the machine to a safe halt independent of operator actions.
E-Stops available today range from compact 16mm mount IP69K waterproof devices suitable for hand-held control boxes EAO Series 61 Compact through to the Series 84 low depth 22mm mount compact Estop and the Series 45 rugged metal body products that meet the increasingly specialised needs of technologically complex machinery and yet are resistant to harsh environments and operator abuse. EAO offers four families of E-Stop devices, comprising a total of 55 actuators. They all comply with DIN EN ISO 13850 and EN 60204-1 specifications and are rated ‘fool proof’ in full compliance with EN 60947-5-1 and EN 60947-5-5.