Written by Andy Maskell, Product Manager- Safety

The simple answer is yes! The difficult bit is making sure it happens and making sure we apply all of the relevant standards in the right way.

For this weeks blog I want to take a look at “Fault Masking” and some of the associated standards as well as some solutions that will help you comply.

EN ISO 14119 & ISO/TR14119

These standards apply to Interlocking devices associated with guards. In particular these standards help with design and selection as well as common issues associated with serial connection of guard safety devices. It is a common approach to series connect devices with potential free contacts back to a single safety logic device which performs the diagnostics for the overall safety of the machine or system.

Fault masking is caused by damage or interference in the device or wiring associated with the series safety circuits. This can lead to loss of the safety function and therefore create a potentially hazardous situation.

This video gives a better idea of how this looks.

https://www.youtube.com/watch?v=6VHJscVQ8BE

To make sure you comply with standards you need to ensure that fault masking does not occur. This can be achieved in several ways:

• Use additional contacts individually connected to a monitoring device in combination with appropriate diagnostic procedures to avoid fault masking.(*Additional wiring effort?)
• Avoid connecting in series of interlocking devices and use individual safety inputs for each interlocking device. (*A safety relay for each switch or use a safety controller – Additional cost?)
• Use interlocking devices with internal diagnostics and monitored outputs (*TYPE 4 ?)

The most popular solution is to use a safety device that satisfies the last option. The best device to use is classed as a Type 4. This means the device will have high coding and cannot be accidentally or intentionally defeated by surrounding objects or even a magnetic device. (See table below for switch types)

So enough about the problem of fault masking. Here is the solution….

PSR-SWITCH

PSR-SWITCH offers series connection of up to 30 switches back to one safety logic device (safety relay or controller) using our SACC range of cables and connectors to further reduce wiring effort and wiring errors.

• Up to PLe/Cat4/SIL3
• Integrated restart function
• Flexible cabling options
• IP65/IP67/IP69/IP69K
• RFID Technology
• Integrated diagnostics
• I/O Link integration (Coming very soon)

Using PSR switch will ensure you meet the necessary standards and save time and effort in the process. Keep an eye out for future developments in the PSR-SWITCH range.

If you would like further information please feel free to call me directly.

Andrew Maskell (Product Manager – Safety) Mob: 07584 235440

Email: amaskell@phoenixcontact.com