Given the state of the economy, it is understandable that everyone has to be more careful with their budgets than ever before. The maintenance engineers should beware of trying to save money by buying cheaper safety-related products. Pilz Australia discuss safety-related issues on using cheaper safety devices.
On the subject of downtime, the mean time to failure (MTTF) of the cheaper product may be shorter than the MTTF of the higher quality (and slightly 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.
Nuisance trips can be triggered by any device within the safety-related control system, but it is fair to say that higher-quality or higher-specification products have less chance to cause nuisance trips than lower-quality or lower-specification alternatives.
It has been assumed that all of the safety devices meet the necessary standards. However, it also needs to be emphasised that corners must not be cut by installing inadequate safety devices. For example, if a hazardous machine is protected by a physical guard with a uniquely coded electronic guard switch, in the event of the switch becoming damaged it should not be replaced by, say, a simple magnetically-operated guard switch that could be actuated by a standard actuator kept in the maintenance engineer's tool box.
Penny-pinching on safety equipment is unwise at best and unsafe at worst. Nevertheless, careful design of safety-related control systems can lead to cost savings. For example, the Pilz PNOZsigma slimline multifunctional safety relays can help to cut costs by reducing stockholding and enabling a smaller control cabinet to be specified. For more complex projects, a safety-related control system incorporating a Pilz PNOZmulti modular safety controller can be more cost-effective to design and implement than one using traditional safety relays and complex logic; savings are greater still if multiple machines are being built or planned. Both the PNOZsigma and PNOZmulti offer better diagnostics than conventional safety relays. These diagnostics benefit machine builders, system integrators and end users. Pilz Australia have engineers who can assist customers with designing cost-effective safety-related control systems, plus the company supplies an extensive range of safety devices at competitive prices.