How better guard switches improve safety and reduce downtime

Chris Best, Sales Director, and Mabruk Farrah, Managing Director of Mechan Controls, explain the benefits of replacing traditional magnetic reed-type safety switches with coded magnetic, solid-state safety switches, and how easy it is to perform the upgrade.

Magnetic reed safety switches definitely have a place in a factory, but certain applications do not present the right conditions for them to survive for long periods. This often leads to them needing to be replaced frequently, resulting in higher long-term costs and increases in production downtime. It is easy to blame the safety switch and its manufacturer for its unreliability without looking at the core reasons for why they fail.

Maybe the failures are due to the plastic fixings breaking, or perhaps the position of the guard results in high impact/shock loading when closing the guard. These types of failures are annoying but can be resolved simply and, more importantly, cost-effectively.

Mechan Controls' patented HE-Series switches benefit from three features that most commonly used magnetic reed switches do not offer. This article outlines why the HE-Series is a better overall product and what these switches offer in terms of functionality compared to standard reed switches.

Coded magnetic operation for medium level coding according to ISO EN ISO 14119

Mechan Controls' HE-Series uses a coded magnetic switch and actuator that cannot be defeated or tampered with by one, two or even three magnets. Unless the user knows the exact combination of magnetic strengths and polarities, the switch cannot be operated. Most reed safety switches offer no or limited coding and therefore can often be defeated using a standard magnet(s).

Solid-state design replaces reeds with transistors

The solid-state design means Mechan HE-Series safety switches are shock- and vibration-proof. Why is this useful? Standard magnetic safety switches are often mounted on machine lids or perimeter guarding, resulting in high impacts when the guards are being accessed. Operators frequently open and close guards quickly to minimise the machine's downtime but neglect the damage it causes to the safety switches in the process.

It is also common in high-vibration applications for vibrations to cause the reeds to 'chatter', tripping the safety relay/control circuit in the process. The HE-Series switches eliminate this completely, providing the vibrations do not result in the actuator moving out of operating distance from the switch.

Simultaneous switching

Reed switches with more than one contact often suffer from high hysteresis. What does this mean? If there are two normally-closed (N/C) contacts, one N/C contact will change over sooner than the other. This is often seen in applications where gate sagging has changed the angle in which the actuator approaches the safety switch.

Why is this a problem? Most magnetic reed switches have an inherent delay between the two separate safety contacts due to the construction/position of the reeds. Safety relays can detect this delay due to the time limit set between the safety input channels. This can cause interruptions to the output of the machine, consequently reducing productivity.

How do Mechan HE-Series switches differ?

HE-Series switches use solid-state outputs that do not suffer from hysteresis. This means when the actuator is within operating distance to the switch, all contacts changeover at the exact same time. The process is instantaneous and works well with modern safety circuits that are often more sensitive.

How easy is it to swap magnetic switches to Mechan HE-Series?

The answer is very easy! HE-Series switches are available in all the common housings and mounting/fixing holes. The contacts use volt-free outputs meaning they will replace traditional magnetic switches without the need to change the existing safety control circuit.

Is there a cost saving?

It depends what switch is being replaced. We often replace magnetic reed switches with the HE-Series and customers usually see a significant cost reduction. Remember, the HE-Series is a long-term solution and if we fix the main cause of your failures, the product will pay for itself.

Technical considerations

The following points should be borne in mind when specifying HE-Series safety switches:

  1. The HE-Series are electronically operated switches so they require a 24V DC supply to operate.
  2. Due to the HE-Series being electronically operated, they are not recommended for applications where temperatures exceed +70degC.
  3. A risk assessment should take place to establish that the specifications of these safety switches are suitable for the application.

Follow the link for more information about Mechan Controls' patented HE-Series non-contact safety switches.

Mechan Controls Ltd

14/16 Seddon Place
Stanley Industrial Estate

+44 (0)1695 722264

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