COLD STORES FANS
Fail safe
When humans are required to enter the refrigerated space, safety guidelines should be followed to avoid lock-in, reduce lone-working, ensure training is provided on good working practices, provide adequate PPE and minimise the time spent in the cold. Through good design at the outset, the cold store and
refrigeration system can provide assistance if the unthinkable does happen; including emergency stop buttons, ‘trapped- man’ alarms, door safety mechanisms to enable personnel to get out from inside a ‘locked’ door, emergency lighting and emergency exits. These incorporated safety elements are not all created
equally. Trapped-man buttons are mandatory on blast freezers, but they don’t always stop the refrigeration system or the fans working - it usually only raises an alarm so you hope someone comes to fi nd you quickly. We design our blast freezers so the trapped-man button turns off the system and the fans - this immediately stops the rapid fl ow of cold air that is designed to remove heat fast, to give the operative more time to survive.
And in terms of design there’s a safety aspect which maybe people don’t think about. When an emergency button is activated we design it so it’s not making a circuit but it’s breaking a circuit. This way we make sure it always fails safe; so if the switch fails, or a connecting wire breaks or indeed if the button is pressed, the circuit breaks and the alarm sounds.
These safety systems must of course be regularly checked Download the ACR News app today
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and tested to ensure correct operation. In addition, the refrigeration system itself should be monitored for safe and effi cient operation; this can potentially reduce the need for intervention or maintenance and eliminate the need for humans to enter the cold space. Monitoring functions can be incorporated into the initial design. Using customisable controllers, performance indicators can be used to analyse system trends which can help engineers diagnose problems that can be dealt with, perhaps remotely, before physical, on-site intervention is required.
Refrigerants Many refrigerants are fl ammable, toxic or both, and the
cold store and refrigeration system design should take into account any risks associated with the escape of these gases. In the case of fl ammable refrigerants, the design needs to consider the point at which the concentration of the gas in air makes it fl ammable, because of the oxygen required to support the combustion. The size of cold store is relevant; even if all the refrigerant leaked into a large cold store it may not reach the fl ammability threshold but might potentially displace air to a dangerous level. The system can incorporate a sensor that detects the gas, in parts per million (ppm), both upper and lower levels and automatically decide what to do with that information, such as sound an alarm, pump down the system or activate a mechanical extraction system.
A separate plant room allows
employers to restrict access to the equipment to authorised personnel only, as there are heightened risks
associated with
electrical machinery.
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