Castell InterlocksÃ heavy-duty interlocks are designed for the safety of workers operating electrostatic precipitators. CastellÃs trapped key interlocks force workers to adhere to a step-by-step process every time they want to gain internal access to a precipitator. Each step releases a key which in turn permits activation of the next stage in the process. The locks incorporate a simple mechanism with tolerances that make them extremely forgiving and far less likely to become clogged with dirt or dust, Castell says. Should the mechanism experience some level of fouling, the robust key is capable of transmitting much more torque to the lock without bending or breaking than a standard pin tumbler key.