Given the state of the economy, everyone has to be more careful with their budgets. But engineers should beware of trying to save money by buying cheaper safety-related products, as it could cost them dearly.
Take the humble safety relay, for example. Two products from different manufacturers may appear to do the same job, however, the cheaper product may not offer everything that the more expensive alternative does. Diagnostic data via LEDs may seem like an unnecessary luxury to the buyer, but the engineering time saved during commissioning – or the downtime avoided in the event of an unplanned stoppage – could cost orders of more than the relay’s purchase price.
The mean time to failure (MTTF) of the cheaper product may well be shorter than the MTTF of the higher quality (and more expensive) unit, so it is more likely to cause unplanned downtime.
Maintenance engineers should also bear in mind that any change from the original equipment specification (such as switching from one safety relay to another from an alternative supplier) should be properly documented.
One of the problems that can be associated with safety-related control systems is nuisance trips. If a lens on a safety light curtain becomes dirty, the safety-related control system shuts down the machine.
However, this stoppage is costly and can also be detrimental. Nuisance trips can be triggered by any device within the safety-related control system, but it is fair to say that higher-quality products are less likely to cause nuisance trips.
Penny-pinching on safety equipment is unwise at best and unsafe at worst. Careful design of safety-related control systems can lead to cost savings. Certain multifunctional safety relays can help to cut costs by reducing stockholding and enabling a smaller control cabinet to be specified. Purpose-built models offer far better diagnostics than conventional safety relays, which benefits machine builders, system integrators and end users.
Pilz Safe Automation
03 9544 6300
www.pilz.com.au