Trapped key interlocks increase safety of electrical connections in shore power applications
North Canton, Ohio (January 29, 2015) – KIRK® interlocking products provide safe electrical access during cold ironing, ensuring that ship power cables are properly coupled to shore power junction boxes before energizing. Trapped key access interlocks and key exchange units ensure that users follow a pre-determined sequence of operation when connecting to land based power while in port.
In a typical shore power interlocking scheme, a ship’s AMP cable reel is fitted with Kirk’s type DM latch bolts on the shore power plug. The corresponding type DM access interlocks are installed on the junction box’s voltage socket handles inside the quayside vault. A 3-key Kirk transfer block is also installed directly on the front of the junction box. Finally, the upstream breakers powering the junction box are fitted with a Kirk F-lock, keyed to coordinate with the transfer block.
To connect to shore power, the AMP cable is lowered to the wharf. Once both plugs are connected, the two DM latch bolts are inserted into the DM locks. This allows the locks to be engaged, securing the plugs in place and releasing a key for each socket. The two socket keys are then inserted into the transfer block, releasing the third key, used to energize the upstream power. This power key remains trapped in place the entire time the system is energized.
There is no way to circumvent the process; the junction box cannot be energized without first properly connecting the sockets. The socket connection then cannot be broken until the upstream power is shut off, releasing the key required by the transfer block in order to access the two socket release keys.
For cold ironing applications, Kirk recommends its HD Series interlocks. All lock components are manufactured entirely of 316 stainless steel for long service life in corrosive coastal environments. A gasketed flip cover further protects the keyways from salt and debris intrusion.