Key Transfer Blocks

Key transfer blocks provide the mechanism by which access authority is moved from one point in a key interlock system to another. Key transfer blocks generally require that one or several keys must be present before one or more keys can be released. For example, the presence of all transformer-rectifier ground keys might be required to be present in a transfer block before access door keys are released. Likewise all the access door keys would be required to be present before the ground keys were released from the transfer block and used in the transformer-rectifiers.

This transfer mechanism is extremely useful on multi-chambered precipitators where chambers can be energized separately. For example, on a double-chambered precipitator, when the transformer-rectifier set is properly grounded, the ground keys from one chamber might be released while ground keys for the other chamber are retained. In such a situation, the released ground keys would be used in a key transfer block to release the access door keys to the grounded chamber. On the other hand, the retained ground keys for the other chamber would not be available and access door keys for that chamber would be retained in the associated transfer block, thus providing a situation where one half of the precipitator could be safely energized while service is performed on the other half.