Can I use a "conventional" limit switch for safety applications?

Yes, it is possible to use a "conventional" limit switch (i.e. non-safety specific) for safety applications, as long as the switch is "positive action"

Note that although we don't sell limit switches any more, we have an offer of safety relays. Please click on the link to the right for further information on our XPSU range.
Definition of positive action:

• A limit switch is said to be positive action if its normally closed (NC) contacts can be changed to the open position with certainty
  
• The symbol indicating this type of operation is an arrow in a circle.

Contact with Positive Opening

Notes:

Other conditions may be necessary for integrating a limit switch in a safety application:

• Redundancy of contacts of NC contacts
• Integrity of the sensor, the contacts in the sensor must not be modified.

For these reasons, it may still be useful to use a specific safety switch. We used to sell a range for this purpose that could be recognised by its red colour. They had a plate that prevents access to the screws. This plate was attached using "5 lobe torque" safety screws, with a special fixing tool  supplied with the product. We no longer sell sensors and limit switches. For information on the above, please contact telemecaniquesensors.

Publicerad för: Schneider Electric Sverige