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ANNEX IIU.K.ESSENTIAL HEALTH AND SAFETY REQUIREMENTS RELATING TO THE DESIGN AND CONSTRUCTION OF EQUIPMENT AND PROTECTIVE SYSTEMS INTENDED FOR USE IN POTENTIALLY EXPLOSIVE ATMOSPHERES
1. Common requirements for Equipment and protective systems U.K.
1.5. Requirements in respect of safety-related devices U.K.
1.5.1.Safety devices must function independently of any measurement and/or control devices required for operation.U.K.
As far as possible, failure of a safety device must be detected sufficiently rapidly by appropriate technical means to ensure that there is only very little likelihood that dangerous situations will occur.
The fail-safe principle is to be applied in general.
Safety-related switching must in general directly actuate the relevant control devices without intermediate software command.
1.5.2.In the event of a safety device failure, equipment and/or protective systems shall, wherever possible, be secured.U.K.
1.5.3.Emergency stop controls of safety devices must, as far as possible, be fitted with restart lockouts. A new start command may take effect on normal operation only after the restart lockouts have been intentionally reset.U.K.
1.5.4. Control and display units U.K.
Where control and display units are used, they must be designed in accordance with ergonomic principles in order to achieve the highest possible level of operating safety with regard to the risk of explosion.
1.5.5. Requirements in respect of devices with a measuring function for explosion protection U.K.
In so far as they relate to equipment used in explosive atmospheres, devices with a measuring function must be designed and constructed so that they can cope with foreseeable operating requirements and special conditions of use.
1.5.6.Where necessary, it must be possible to check the reading accuracy and serviceability of devices with a measuring function.U.K.
1.5.7.The design of devices with a measuring function must incorporate a safety factor which ensures that the alarm threshold lies far enough outside the explosion and/or ignition limits of the atmospheres to be registered, taking into account, in particular, the operating conditions of the installation and possible aberrations in the measuring system.U.K.
1.5.8. Risks arising from software U.K.
In the design of software-controlled equipment, protective systems and safety devices, special account must be taken of the risks arising from faults in the programme.