New Dold Trapped Key Systems Faqs
A trapped key system uses a series of mechanical locks and keys to control the access of gates or doors to active equipment or machines, ensuring safe access to those machines. Systems are set up in a predefined sequence, or key transfer plan, preventing accidental access to equipment. A mechanical solution provides safety which cannot be defeated.
Here we review some of the features and answer several frequently asked questions about Trapped Key Systems.
Q: What is a Key Transfer Plan and why would I need one before I purchase a Trapped Key solution?
A: A Key Transfer Plan is a picture-based “map” of how your safety application is laid out. The more detailed the better, but it should include drawings of the doors on a machine or plant floor. Connecting these points with lines to associate a sequence of locking and unlocking help provide an overview of desired operation. For example: requiring one key at the panel to use in an exchange box to release three other keys for use in different doors is a typical use.
Q: How does a trapped key solution work with my current safety controls and PLC?
A: The Dold Trapped Key solution requires only one wiring point. The standard SX or solenoid locking ZRH base houses force guided contacts and feedback circuits similar to a standard safety switch; this is your electrical connection with your machine. Other components are mechanically related, so essentially you have a wireless safety system. This is ideal for applications where the control and the guarded gate are farther away which would be expensive to hardwire. And, if you have several machines of varying origin you can tie guarded access together on all of them.
Q: How do I specify the correct system for my machine?
A: There are several resources available on AutomationDirect’s website, including a five-step selector guide, video, and more. These tools can assist the designer in specifying and building the system as well as choosing needed accessories. Ordering a larger gate set than needed for the number of gates in a system compromises the safety integrity of that system and spare keys are not available. Assessment of the safety need in the beginning is crucial. If your system is excessively complicated you may want to seek professional advice from a safety expert. Please see: www.automationdirect.com/trapped-keys
By Andrew Waugh, Sensors & Safety Product Manager, AutomationDirect
Originally Posted: Sept. 10, 2014