Interlocks can be used in many process or procedural systems within Ports involving the transmission of electricity, including crane movement, ship to shore power, and local substations or backup generators. For more information on trapped key interlock applications at the Ports, click HERE


We recommend our SD series for typical indoor use or HD series for use in more harsh environments. The SD series interlock is manufactured completely of brass with a 7-pin tumbler and standard key design that cannot be duplicated . The HD series is manufactured with a stainless steel housing and cylinder with a robust dowel pin key design that will withstand greater force and will not drop through standard floor grating.  

For more information of each product series, click here.

trapped key interlock
trapped key interlock
trapped key interlocks



Trapped key interlocks have a number of functions in substation switchgear applications. For example, preventing the paralleling of two energy sources, preventing particular operations until a breaker is locked open or closed, preventing disconnecting of breakers under load, and minimizing the possibility of a hazardous arc flash. These are often part of a larger trapped key interlock system.





Scheme 1 - Prevent opening of switch when breaker is closed.


Scheme 8 - Prevents operation of disconnects when breaker is closed. Permits servicing of breaker when disconnects are locked open.


Scheme 13 - Prevents paralleling of two lines - two loads, fed from either source.


Scheme 35 - Prevents paralleling of two lines - two loads, fed from either source (one tie breaker). Allows switching loads to a generator.


Scheme 39 - Prevents improper maintenance bypass of UPS equipment.


Watch the animation below to see how KIRK® safety interlocks protect life and equipment when carrying out maintenance on live equipment


For complete Scheme Book, click here.

arc flash

The application data sheet to the right explains how arc flash hazards can be reduced by incorporating KIRK® trapped key interlocks with Utility Relay Company AC-PRO® Quick Trip®

shore power

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